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J agric Sci Camb (1984) 103 443-458 4 4 3With 1 text-figurePrinted in Great Britain
Comparisons of growth and earlyyields of potato varieties of contrasting maturity
classification at three sites
BY R L GRIFFITH E J ALLEN SUSAN A OBRIEN AND P J OBRIENDepartment of Agriculture (Crop Husbandry) University College of Wales
Aberystwyth Dyfed
Received 17 April 1984)
SUMMARYSix experiments which compared a range of contrasting varieties are reported Two
experiments were at a very early coastal site in N Pembrokeshire (Trefin) two at a sitein South Pembrokeshire (Trefloyne) and two at a coastal site in N Norfolk (Bran-caster) No variety was in every experiment but several were in the majority ofexperiments In some experiments sprout growth was manipulated by control ofstorage temperatures A variety classified as early or second early produced the highestyields in all experiments but the yields of the best maincrop varieties were high andsubstantially better than many early varieties The highest-yielding variety at the firstharvest maintained this advantage throughout June and July At two sites (Trefin andBrancaster) the highest-yielding variety was consistent from year to year but overallthe ranking order of varieties for yields was inconsistent eg Arran Comet was thehighest-yielding variety at Trefin in both years and one of the lowest yielding atBrancaster
The results suggest that it is unwise to attempt to rank varieties for early yields byan overall score The maturity classification of varieties is not necessarily an accurateguide to the utility of a variety A consideration of the physiological age of the seed andgrowing conditions provided some explanation of these effects and their implication forbreeding are discussed
INTRODUCTION out-yielded maincrops only for a short period at thebeginning of harvesting Moreover several authors
In the United Kingdom potato varieties are have reported that the growth pattern of varietiesclassified into three maturity groups early second especially many classified as earlies (OBrien et alearly and maincrop which broadly indicate the 1983 OBrien amp Allen 1981) can be modified byappropriate time of harvesting The classification management of the seed tuber The low yields ofis not meant to be rigid but early varieties are early varieties later in the season may be primarilygenerally associated with lower yields later in the determined by the use of old seed of certain varie-season than second earlies and maincrops and to ties for OBrien et al (1983) have shown that inobtain the highest yields over a long period several some early varieties old seed leads to smaller leafchanges in variety are assumed to be necessary areas which senesce earlier than younger seedFew direct comparisons of contrasting varieties thereby reducing yields later in the seasonhave been reported and some available data suggest Such results suggest that high yields early in thethat differences between varieties are smaller than season may be achieved without prejudice to laterhitherto assumed Gunasena amp Harris (1971) found yields and this possibility has considerable impli-that Craigs Royal (second early) produced similar cations for the breeding and testing of new varie-high final yields (80 tha) to Pentland Dell (main- ties as well as the most effective use of existingcrop) and Allen (1977) reported that early varieties varieties This paper presents comparisons of con-
trasting potato varieties grown at three different Present address Department of Applied Biology sites and harvested during the first 2-3 months of
University of Cambridge the season (May-July) In some experiments sprout
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444 R L GRIFFITH AND OTHERS
Table 1 Details of varieties used in Expls 1-6
Variety
Home GuardArran CometMaria BardPentland CrownStormont EnterpriseDesireePrimuraPentland JavelinF46USpuntaRenovaJuliverDragaAmincaWiljaEstimaUlster SceptreRed Craigs RoyalMaria PiperFoxtonRecordVanessa
Origin
BritishBritiahBritishBritishBritishDutchDutchBritiahBritiahDutchDutchDutchDutchDutchDutchDutchBritishBritishBritishBritishDutchDutch
Maturityclassification
EarlyEarlyEarlyMaincropMaincropMaincropEarlyEarlyEarlySecond earlySecond earlyMaincropMaincropEarlySecond earlySecond earlyEarlySecond earlyMaincropMaincropMaincropEarly
growth of varieties was manipulated by control ofstorage temperature so as to achieve the requiredphysiological age for early harvests As the datacovered five seasons the influence of site andseason in relation to the testing of varieties couldbe assessed
THE EXPERIMENTS
Two experiments were carried out on the farmof Mr I Davies Park Court Trefin SW Dyfed onlight gravelly soil of the Arfon Series (Rudeforth ampBradley 1972) Both experiments used 66 cm rowsA fertilizer dressing of 166 kg N 107 kg P and138 kg Kha was applied by hand over the ridgesprior to planting Sampling grading and recordingtechniques were essentially as reported by Allen(1977) Details of the varieties grown are given inTable 1
Experiment 1 1976-7Treatments were five varieties Home Guard
Arran Comet Maris Bard Pentland Crown andStormont Enterprise replicated four times in arandomized-block design Plots were four rowswide and 6-1 m long Seed tubers of 55-65 65-7575-85 and 85-95 g were used for the four replicatesand spaced 30 cm apart in the row Numbers ofplants and stems were recorded on two rows on8 and 22 April and yields estimated from ten plantsper plot on 31 May 10 June and 1 July
The seed of Arran Comet Pentland Crown and
Stormont Enterprise was once-grown from mid-Wales and weighed out at University College ofWales in late January when Arran Comet hadconsiderable sprout growth The seed was placedapical end uppermost in trays and stored at 12 degCin a glasshouse with supplementary heating untilplanting The seed of the other varieties was selectedfrom the farmers own Scottish seed in his glass-house on 11 February After selection the seed wasplaced apical end uppermost in trays and left inthe farm glasshouse until planting Sprout measure-ments were made on ten tubers per seed size of eachvariety on 12 March and the experiment plantedby hand on 20 March
Experiment 2 1977-8There were six treatments comprising Home
Guard Arran Comet Maris Bard a once-grownstock (OG) and a certified stock (CC) PentlandCrown and Desiree replicated four times in arandomized-block design The once-grown stock ofMaris Bard was the progeny of the certified seedused in Expt 1 and had been multiplied in a fieldof early potatoes It had been defoliated and har-vested early (early July and mid-July respectively)and consequently had an early end to dormancywhich resulted in very long sprouts (advancedphysiological age) by planting The seed of PentlandCrown and Desiree was once-grown in mid-Waleswhile for the remaining three varieties the seed wasfrom the purchased certified stock of the farmerThe seed from Trefin was weighed out in the farmglasshouse on 22 December and only Maris Bard(certified stock) had no sprout growth Tubers wereplaced in trays as in Expt 1 and remained in thefarm store until planting Seed of Desiree and Pent-land Crown were weighed out at University Collegeof Wales on 13 January when there was some sproutgrowth Tubers were placed in trays as in Expt 1and stored at 12 degC until planting Sprout measure-ments were taken on 9 February on ten tubers ofeach size on all varieties and the experimentplanted on 3 March Plots were four rows wide and5-3 m long Seed tubers of 70-80 80-90 90-100and 110-115 g were used for the four replicates andspaced 27 cm apart in the row Numbers of plantsand stems were counted on 30 March 7 April and1 May using 10-6 m of row Growth analyses usingtwo adjacent plants per plot were carried out on4 and 18 May and yields estimated from ten plantsper plot on 30 May 7 and 16 June
Two experiments were carried out at TrefloyneField Station on Old Red Sandstone soils of thePembroke Series (Soil Survey Record No 24 1974)Both experiments used 71 cm rows and receivedfertilizer dressings of 154 kg N 66 kg P and 160 kgKha applied over the opened ridges prior toplanting
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Growth of contrasting potato varieties 445
Experiment 3 1978-9Treatments were nine varieties Primura Home
Guard Arran Comet Pentland Javelin F4611(earlies) Spunta Renova (second earlies) Juliverand Draga (maincrops) replicated three times in arandomized-block design Plots were three rowswide and 11-25 m long Seed tubers of 40-50 50-60and 60-70 g were used for the three replicates andspaced 25 cm apart in the row Number of plantsand above-ground stems were recorded on 18 Mayusing one complete row Growth analysis (twoplants per plot) and estimates of yields (ten plantsper plot) were carried out on 21 June 3 16 and31 July
All seed was once-grown in mid-Wales Seedwas selected before the onset of sprout growth andplaced in trays as in Expts 1 and 2 The seed wasstored in a frost-free glasshouse until planting(average daily temperature 84 degC) Sprout measure-ments were taken on 8 March using ten seed tubersof each size and the experiment planted by handon 19 April
Experiment 4 1979-80In this experiment 11 varieties were compared
Aminca and Maris Bard (earlies) and Wilja (secondearly) were added to those in Expt 3 and HomeGuard deleted There were three replicates plotdimensions and seed size were as in Expt 3Numbers of plants and above-ground stems werenot recorded in this experiment Growth analysisand estimates of yield were carried out as in Expt 3on 18 27 June 8 and 28 July
Seed production treatment selection and storagewere as in Expt 3 The average daily temperatureof the glasshouse was 9-9 degC Sprout measurementswere taken on 3 March using ten tubers of eachseed size and the experiment planted by hand on21 March
Two experiments were carried out at DeepdaleFarms Limited Brancaster Norfolk on light sandysoils of the Wick Series Rows were 76 cm apartand tubers spaced 20 cm apart Both sites werestone-separated prior to planting
Experiment 5 1979-80Nine varieties Home Guard Arran Comet Maris
Bard (earlies) Red Craigs Royal Wilja Estima(second earlies) Maris Piper Pentland Squire andDesiree (maincrop) were compared in three random-ized blocks Seed of 40-55 g was used for all repli-cates Plots were four rows wide and 5 m longPlant and stem emergence were recorded every3-4 days using one whole row per plot Yields wereestimated from 14 plants per plot on 24 June 8 and22 July
All seed was once-grown in mid or west Wales
Table 2 Number of day-degrees gt4C experiencedby seed from onset of sprouting (3 mmsprout) toplant-ing in three varieties
Experiment
Variety
Home GuardArran CometMaris Bard
(once grown)Maris Bard(certified)
1 5 6
640 390 890 mdash 270 mdash630 340 880 760 300 mdashmdash 740 mdash mdash mdash mdash
330 80 mdash 430 230 530
and selected in late December when all seed hadbroken dormancy The first three varieties werestored at 6 degC the next three at 8 degC and the threemaincrop varieties at 12 degC Sprout measurementswere made on 30 tubers per variety on 29 Februaryand the seed moved to Norfolk The experimentwas planted by hand on 21 March A liquid fertilizerdressing of 150 kg N 86 kg P 167 kg K and 30 kgMgha was applied at planting Four applicationsof 25 mm of water were made by rain-gun on 1422 May and 4 18 June
Experiment 6 1980-1Seven varieties Maris Bard Ulster Sceptre
Vanessa (earlies) Wilja Estima (second earlies)Record and Foxton (maincrop) were compared inthree randomized blocks Seed of 70-80 80-90 and90-100 g was used for the three replicates plotswere the same size as in Expt 5 Emergence was notrecorded and yields were estimated from 14 plantsper plot on 8 22 June and 6 July
Seed of all varieties was stored at 6 degC until mid-February when the two maincrop varieties weretransferred to 12 degC Sprout measurements weremade on ten tubers per seed size of each variety on3 March and the experiment planted by hand on5-6 March
A liquid fertilizer dressing of 145 kg N 61 kg Pand 119 kg Kha was applied at planting Threeapplications of 25 mm of water were made by rain-gun on 7 22 June and 7 July In all experimentsthe control of weeds was satisfactory and theapplication of fungicides and aphicides ensuredthat both blight (Phytophthora infestans) and virusdiseases were controlled
In all experiments the yields per hectare wereobtained by harvesting the area occupied by thestated number of plants irrespective of any missingplants From growth analysis samples on someoccasions yields are presented per plant and careshould be exercised if these values are converted toyield per hectare as the sample area was small andinappropriate for such conversion
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446 R L GRIFFITH AND OTHERS
(a) Aberporth
40
30
20
10
0
50
U 40 H
A
pound 30MU
bullvI 20O
I o
I
1977
-10
50
40 -
30-
20-
10-
0 -
-10
March April
(b) Trefloyne
1979
April
1980
May
(c) Hemsby
V
March April
40-
30-
20
i o H
o
50
40-
30-
20
10
OH
1978
-10J r
50-
40-
30-
20
- 1 0 -
March April
1980
March April
1981
March April
Fig 1 For description see opposite
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60 -i
40-
20
140 n
120 -
100 -
BO-
S 60
40-
20-
lOO-i
80-
60-
40-
20-
0
Growth of contrasting potato varieties(d) Aberporth
1978
447
1977
(e) Trefloyne1979 1980
1980Hemsby
1981
March April May June March April May June
Fig 1 Weekly number of day-degrees gt 4 degC (a-c) and total monthly rainfall (d-f) in 2 years at Aber-porth (north Pembrokeshire) Trefloyne (south Pembrokeshire) and Hemsby (Norfolk) T Time ofplanting v time of 50 plant emergence
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448 R L GBIFFITH AND OTHEBS
Table 3 Sprout growth per tuber number of emerged plants and stems Expt 1
Length of longest sprout(mm)
Total sprout length (mm)Number of sprouts gt 3 mmNumber of emerged plants
f000sha) 22 iv 77Number of above-groundstemsplant 30 v 77
Number of mainstemsplant30 v 77
HomeGuard
50-4
73-23 0
43-5
4-9
2-0
Table 4 Tuber yields
Total yield 31 v 77Yield gt 25 mm 31 v 77Total yield 10 vi 77Yield gt 25 mm 10 vi 77Total yield 1 vii 77Yield gt 25 mm 1 vii 77Yield gt 38 mm 1 vii 77Number of tubers 31 v 77
10 vi 771 vii 77
HomeGuard
8 05-2
12-610-721-520113-2
1193890780
ArranComet
27-8
6113-3
41-9
5-2
2-8
MarisBard
21-2
6014-6
311
5-7
5-2
[tha) and number of tubers
ArranComet
11-68-6
17-915-931 330-223-3
1054984790
MarisBard
9-74-8
16-513-929026-817-2
20231257979
PentlandCrown
15-7
26-92-8
28-8
5-3
1-9
(OOOsha)
PentlandCrown
5-72-5
1109 2
25-324-3180
994760696
StormontEnterprise
14-9
38-74-3
22-6
5-8
4-2
Expt 1StormontEnterprise
5-52-8
11-69-2
24823-6160
1153959815
SE
1-71
2-450-26062
0-26
0-34
SE
0-660-541-051-091-971-871-72
1016661371
From the records of temperature in storage andobservation of the end of dormancy the numbers ofday-degrees experienced by the seed of the varietiesin the majority of experiments are shown in Table2 Where no direct observation of the end of dor-mancy was made the timing of this event wasobtained from records of the same variety in otherexperiments
Only at Trefloyne in 1980 was wilting of plantsobserved in prolonged dry weather in July In allother experiments growth was not observed to beaffected by water availability The monthly rain-fall figures and weekly number of day-degreesgt 4 degC (air) are given in Fig 1
RESULTS
Experiment 1 (1977)
The early varieties produced substantially moresprout growth and emerged earlier than the main-crop varieties (Table 3) Final emergence was com-plete in all varieties and there were no effects ofvariety on number of above-ground sterna How-
ever Maris Bard and Stormont Enterprise pro-duced predominantly mainstems and had signifi-cantly more than other varieties (Table 3) PentlandCrown produced substantially more secondarystems than mainstems
At the first harvest (31 May) Arran Comet pro-duced the highest total yield and all early varietiessignificantly outyielded the maincrops (Table 4)Arran Comet had markedly higher saleable yield( gt 25 mm) than all other varieties and the other twoearlies were higher yielding than the maincrops Atthe two subsequent harvests Arran Comet producedthe highest total and graded yields although MarisBard was usually not significantly lower yieldingMaris Bard lost many of its small tubers so thatalthough it had the most tubers throughout harvest-ing the differences between varieties in number oftubers became smaller and the effects on total yieldwere also found in graded yields NonethelessArran Comet produced significantly higher yield inthe gt 38 mm grade than other varieties as a con-sequence of having the lowest number of tubers ofall varieties which resulted in increased mean
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Growth of contrasting potato varieties 449
Table 5 Sprout growth per tuber number of emerged plants (OOOsha)and number of stems per plant Expt 2
Length of longest sprout (mm)Total sprout lengthNumber of sproutsNumber of emerged
7 iv 781 v 78
(mm)gt 3 mmplants
HomeGuard
21-942-02-7
46-648-4
Number of above-ground stemsplant18 v 78
Number of mainstemsplant18 v 78
Date of sampling
4 v 7818 v 7830 v 78
7 vi 7816 vi 78
Total yield30 v 78
Yield gt 25 mm30 v 78
Total yield7 vi 78
Yield gt 25 mm7 vi 78
Total yield16 vi 78
Yield gt 25 mm16 vi 78
Number of tubersgt 25 mm30 v 78
HomeGuard
0-561-492-492-952-60
4-4
2-5
Table 6
ArranComet
0-722-434 0 14-764-84
Arran Maris Maris PentlandComet Bard (OG) Bard (CC) Crown
17-740-93-7
29-548-4
5-9
2-9
Leaf area bull
MariaBard (OG)
0-370-570-801-431-44
38-4100-9
4 1
33-540-1
1-5
1-4
5-6 11117-1 2582-8 3-7
5-6 31-449-1 47-2
5-5 8-1
50 2-4
indices Expt 2
MarisBard (CC)
0 1 81-383-283163-32
PentlandCrown
0-471-633-413 6 33-68
Desiree
11-7211
2-4
30148-8
3-8
2 0
Desiree
0-371-432-792-963-50
Table 7 Tuber yields (tha) and number of tubers (y000sha) Expt 2
HomeGuard
19-2
17-8
24-8
23-8
27-3
26-4
450
ArranComet
20-6
19-3
30-5
29-2
351
341
592
MarisBard (CC)
16-8
14-1
24-7
220
3 2 0
29-8
440
MarisBard (OG)
11-6
10-4
16-8
15-6
21-4
20-4
222
PentlandCrown
16-7
14-6
25-9
24-5
30-9
299
451
Desiree
17-8
15-9
22-4
21-1
28-8
27-4
548
SE
0-701-740-26
2-281-35
0-55
0-38
SE
004701390-2030-2670-353
SE
0-93
0-98
0-95
0-95
1-53
1-49
304
tuber size At the second harvest the yields of themaincrop varieties were not significantly lowerthan Home Guard and at the final harvest the twomaincrops exceeded Home Guard although notsignificantly Thus by the end of June the main-crop varieties appeared to have surpassed theyields of the most popular early variety but notthose of two less widely-grown varieties
15
Experiment 2 (1978)The growth of the once-grown stock of Maris
Bard was quite different from all other varietiesSprout growth commenced in October and byplanting the length of the longest sprout was sub-stantially greater than that of all other varietiesEmergence commenced earlier than other varieties
AGS 103
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en O
Tab
le 8
Sp
rout
gr
owth
per
tub
er (
9 M
arch
) n
umbe
r of
em
erge
d pl
ants
an
d st
ems
(O
OO
sha
) E
xpt
3
Len
gth
of l
onge
st s
prou
t (m
m)
Tot
al s
prou
t le
ngth
(m
m)
Num
ber
of s
prou
ts gt
3 n
unN
o o
f em
erge
d pl
ants
18 v
79
No
of
abov
e-gr
ound
ste
ms
21
v 7
9N
o o
f m
ain
stem
sp
lan
t21
v
79N
o o
f se
cond
ary
stem
sp
lan
t21
v 7
9N
o o
f ab
ove-
grou
nd s
tem
sp
lan
t21
v
79
Dat
e of
sam
plin
g P
rim
ura
21 v
i 7
9 4-
23
vii
79
4-
716
vii
79
4-7
31 v
ii
79
0-6
c
hang
e pe
ak L
87
to 3
1 v
ii 7
9
Pri
mu
ra
12-2
27-6 3-3
39-8
272 1-
7
2-6
4-3
Juli
ver
2-8
3-9
41
2-3
44
Juli
ver
10
024
-5 3-6
42-3
172 2-
3
0-9
3-2
Spu
nta
19-9
36-8 2-8
25-4
124 1-
8
0-7
2-5
Ren
ova
11-6
24
03
0
22-9
210 1-
3
20
3-3
Dra
ga
5-7
14
02-
5
2-5
124 1-
8
0-5
2-3
Tab
le 9
L
eaf
area
indi
ces
Exp
t 3
Spu
nta
2-4
3-9
3-4
2-8
28
Ren
ova
2-5
3-7
4-3
31
28
Dra
ga
2-9
4-0
6-2
31
40
Ho
me
Gu
ard
20
2-3
2-6
1-5
42
Hom
eG
uard
57-4
60-8 1-3
14-4
176 2-
2
11
3-3
Arr
anC
omet
33-8
38-8 1-4
30-1
199 1
1
2-4
3-5
Pen
tlan
dJa
vel
in
12-7
25-3 30
51-2
189 2
1
1-2
3-3
Arr
an
Fen
tlan
d
F4
61
1
8-9
21-4 3-2
45-3
219 3-
2
10
4-2
Com
et
Jav
elin
F
46
11
30
4-2
3-7
1-8
57
2-7
3-8
3-3
0-4
89
2-8
3-7
3-7
1-8
51
SE
1-30
1-91
0-24
3-66
17-7 0-80
0-32
0-31
SE
0-31
0-33
0-36
03
8
mdash
bull 9 BIT tT r hgt O o s W
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Growth of contrasting potato varieties 451but approximately 20 of plants failed to emergeowing to little potato disorder The emergedplants were smaller than those of other varietiesand produced lower leaf area indices (L) Thenumber of tubers was less than in all other varietiesand yield was also less than other varieties Thedata for this seed stock of Maris Bard were ana-lysed with all other varieties and are presented butfurther reference to this stock is limited to theimplications of little potato disorder in assessingvarieties
At planting sprout lengths in Home Guard andcertified Maris Bard Arran Comet and PentlandCrown were less than in Expt 1 (Table 5) As inExpt 1 Arran Comet and Home Guard emergedearlier than the maincrop varieties but Maris Bard(CC) emerged later than the maincrop varietiesThe growth of the leaf surface was extremely rapidin Arran Comet and it had the highest leaf areaindices throughout the experiment (Table 6) ItsL value exceeded 4 before the end of May andthroughout June was significantly greater than allother varieties (Table 6) Initially Home Guardhad larger leaf area indices than the remainingvarieties but by 18 May there were no significantdifferences between these varieties During Juneleaf area indices increased in the maincrops andMaris Bard but decreased in Home Guard and on16 June Pentland Crown had significantly largerL than Home Guard
At the first harvest on 30 May yield was highthe mean yield for the experiment was 17-1 thaand Arran Comet produced the highest total yieldand yield in the grade gt 25 mm and these yieldswere significantly higher than all varieties exceptHome Guard (Table 7) Home Guard was notsignificantly higher yielding in these grades thanany other variety but it produced significantlygreater yields in the grade gt 38 mm than themaincrop varieties At the second harvest (7 June)Arran Comet produced significantly larger yields intotal and in the grade gt 32 mm than all othervarieties There were no significant differences inthese yields between Home Guard Maris Bard andPentland Crown but Desiree produced significantlylower yields than Pentlond Crown Home Guardand Arran Comet did not differ significantly inyield of tubers gt 38 mm but both outyielded othervarieties At the final harvest Arran Comet still hadthe highest total and graded yields but these werenot significantly greater than Pentland Crown andMaris Bard Home Guard and Ddsiree producedsimilar yields which were not significantly differentfrom Pentland Crown and Maris Bard (Table 7)Yield at the final harvest was high in relation tothe length of the growing season Although tuberinitiation was not recorded accurately it is un-likely to have occurred before mid-April in any
variety and therefore a total bulking period of nomore than 8 weeks produced an average rate of4-5 thaweek Rate of bulking may have beenrelated to the size of the leaf surface since the twovarieties with the smallest leaf areas (Home Guardand Desiree) had the lowest rates of bulking
As in Expt 1 Arran Comet produced the highestyields throughout the period of harvesting In con-trast Maris Bard (CC) approached the yield ofArran Comet only at the final harvest and was notsignificantly different from the maincrops
Experiment 3 (1979)There were large differences between varieties in
all aspects of sprout growth (Table 8) Arran Cometand Home Guard produced only one or two sproutsof greater length than other varieties There werefew differences between the remaining varietiesexcept that Draga had very short sprouts Emerg-ence did not seem to be determined by sproutlength at planting as Pentland Javelin and F4611were the first varieties to complete emergence andHome Guard was especially slow This delay inemergence in Home Guard (and Arran Comet) wasassociated with coiled sprouts and in Home Guardsome plants failed to emerge owing to little potatodisorder
There were considerable differences between thevarieties in number of above-ground stems and inthe composition of this population (Table 8) Pri-mura and F4611 produced the most above-groundstems but in the former most were secondary stemsand in the latter main stems Only Home Guardfailed to produce a leaf area index of 3 (Table 9)and the largest peak L values were produced byPrimura (early) and Draga (maincrop) Thesepeak values occurred at different times Primuraproduced its leaf surface very rapidly and its Lexceeded 4 in mid-June Draga was much later inproducing its leaf area and reached its peak in JulyAll varieties decreased in leaf area in the later partof July as a consequence of increasing moisturestress in a prolonged period of dry sunny weatherPrimura and Pentland Javelin were close to com-plete senescence by the end of July while Spuntaand Renova lost relatively little leaf area at thistime
At the first and second harvests Primura andthe four British earlies produced the highest totalyields and most were significantly higher than theother Dutch varieties (Table 10) At the thirdharvest Primura was the highest-yielding varietyand significantly better than all varieties exceptF4611 Pentland Javelin and Renova Betweenthe third and fourth harvests four varieties bulkedlittle (Juliver F4611 Arran Comet and PentlandJavelin) and at the final harvest Primura was still
15-2
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
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444 R L GRIFFITH AND OTHERS
Table 1 Details of varieties used in Expls 1-6
Variety
Home GuardArran CometMaria BardPentland CrownStormont EnterpriseDesireePrimuraPentland JavelinF46USpuntaRenovaJuliverDragaAmincaWiljaEstimaUlster SceptreRed Craigs RoyalMaria PiperFoxtonRecordVanessa
Origin
BritishBritiahBritishBritishBritishDutchDutchBritiahBritiahDutchDutchDutchDutchDutchDutchDutchBritishBritishBritishBritishDutchDutch
Maturityclassification
EarlyEarlyEarlyMaincropMaincropMaincropEarlyEarlyEarlySecond earlySecond earlyMaincropMaincropEarlySecond earlySecond earlyEarlySecond earlyMaincropMaincropMaincropEarly
growth of varieties was manipulated by control ofstorage temperature so as to achieve the requiredphysiological age for early harvests As the datacovered five seasons the influence of site andseason in relation to the testing of varieties couldbe assessed
THE EXPERIMENTS
Two experiments were carried out on the farmof Mr I Davies Park Court Trefin SW Dyfed onlight gravelly soil of the Arfon Series (Rudeforth ampBradley 1972) Both experiments used 66 cm rowsA fertilizer dressing of 166 kg N 107 kg P and138 kg Kha was applied by hand over the ridgesprior to planting Sampling grading and recordingtechniques were essentially as reported by Allen(1977) Details of the varieties grown are given inTable 1
Experiment 1 1976-7Treatments were five varieties Home Guard
Arran Comet Maris Bard Pentland Crown andStormont Enterprise replicated four times in arandomized-block design Plots were four rowswide and 6-1 m long Seed tubers of 55-65 65-7575-85 and 85-95 g were used for the four replicatesand spaced 30 cm apart in the row Numbers ofplants and stems were recorded on two rows on8 and 22 April and yields estimated from ten plantsper plot on 31 May 10 June and 1 July
The seed of Arran Comet Pentland Crown and
Stormont Enterprise was once-grown from mid-Wales and weighed out at University College ofWales in late January when Arran Comet hadconsiderable sprout growth The seed was placedapical end uppermost in trays and stored at 12 degCin a glasshouse with supplementary heating untilplanting The seed of the other varieties was selectedfrom the farmers own Scottish seed in his glass-house on 11 February After selection the seed wasplaced apical end uppermost in trays and left inthe farm glasshouse until planting Sprout measure-ments were made on ten tubers per seed size of eachvariety on 12 March and the experiment plantedby hand on 20 March
Experiment 2 1977-8There were six treatments comprising Home
Guard Arran Comet Maris Bard a once-grownstock (OG) and a certified stock (CC) PentlandCrown and Desiree replicated four times in arandomized-block design The once-grown stock ofMaris Bard was the progeny of the certified seedused in Expt 1 and had been multiplied in a fieldof early potatoes It had been defoliated and har-vested early (early July and mid-July respectively)and consequently had an early end to dormancywhich resulted in very long sprouts (advancedphysiological age) by planting The seed of PentlandCrown and Desiree was once-grown in mid-Waleswhile for the remaining three varieties the seed wasfrom the purchased certified stock of the farmerThe seed from Trefin was weighed out in the farmglasshouse on 22 December and only Maris Bard(certified stock) had no sprout growth Tubers wereplaced in trays as in Expt 1 and remained in thefarm store until planting Seed of Desiree and Pent-land Crown were weighed out at University Collegeof Wales on 13 January when there was some sproutgrowth Tubers were placed in trays as in Expt 1and stored at 12 degC until planting Sprout measure-ments were taken on 9 February on ten tubers ofeach size on all varieties and the experimentplanted on 3 March Plots were four rows wide and5-3 m long Seed tubers of 70-80 80-90 90-100and 110-115 g were used for the four replicates andspaced 27 cm apart in the row Numbers of plantsand stems were counted on 30 March 7 April and1 May using 10-6 m of row Growth analyses usingtwo adjacent plants per plot were carried out on4 and 18 May and yields estimated from ten plantsper plot on 30 May 7 and 16 June
Two experiments were carried out at TrefloyneField Station on Old Red Sandstone soils of thePembroke Series (Soil Survey Record No 24 1974)Both experiments used 71 cm rows and receivedfertilizer dressings of 154 kg N 66 kg P and 160 kgKha applied over the opened ridges prior toplanting
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Growth of contrasting potato varieties 445
Experiment 3 1978-9Treatments were nine varieties Primura Home
Guard Arran Comet Pentland Javelin F4611(earlies) Spunta Renova (second earlies) Juliverand Draga (maincrops) replicated three times in arandomized-block design Plots were three rowswide and 11-25 m long Seed tubers of 40-50 50-60and 60-70 g were used for the three replicates andspaced 25 cm apart in the row Number of plantsand above-ground stems were recorded on 18 Mayusing one complete row Growth analysis (twoplants per plot) and estimates of yields (ten plantsper plot) were carried out on 21 June 3 16 and31 July
All seed was once-grown in mid-Wales Seedwas selected before the onset of sprout growth andplaced in trays as in Expts 1 and 2 The seed wasstored in a frost-free glasshouse until planting(average daily temperature 84 degC) Sprout measure-ments were taken on 8 March using ten seed tubersof each size and the experiment planted by handon 19 April
Experiment 4 1979-80In this experiment 11 varieties were compared
Aminca and Maris Bard (earlies) and Wilja (secondearly) were added to those in Expt 3 and HomeGuard deleted There were three replicates plotdimensions and seed size were as in Expt 3Numbers of plants and above-ground stems werenot recorded in this experiment Growth analysisand estimates of yield were carried out as in Expt 3on 18 27 June 8 and 28 July
Seed production treatment selection and storagewere as in Expt 3 The average daily temperatureof the glasshouse was 9-9 degC Sprout measurementswere taken on 3 March using ten tubers of eachseed size and the experiment planted by hand on21 March
Two experiments were carried out at DeepdaleFarms Limited Brancaster Norfolk on light sandysoils of the Wick Series Rows were 76 cm apartand tubers spaced 20 cm apart Both sites werestone-separated prior to planting
Experiment 5 1979-80Nine varieties Home Guard Arran Comet Maris
Bard (earlies) Red Craigs Royal Wilja Estima(second earlies) Maris Piper Pentland Squire andDesiree (maincrop) were compared in three random-ized blocks Seed of 40-55 g was used for all repli-cates Plots were four rows wide and 5 m longPlant and stem emergence were recorded every3-4 days using one whole row per plot Yields wereestimated from 14 plants per plot on 24 June 8 and22 July
All seed was once-grown in mid or west Wales
Table 2 Number of day-degrees gt4C experiencedby seed from onset of sprouting (3 mmsprout) toplant-ing in three varieties
Experiment
Variety
Home GuardArran CometMaris Bard
(once grown)Maris Bard(certified)
1 5 6
640 390 890 mdash 270 mdash630 340 880 760 300 mdashmdash 740 mdash mdash mdash mdash
330 80 mdash 430 230 530
and selected in late December when all seed hadbroken dormancy The first three varieties werestored at 6 degC the next three at 8 degC and the threemaincrop varieties at 12 degC Sprout measurementswere made on 30 tubers per variety on 29 Februaryand the seed moved to Norfolk The experimentwas planted by hand on 21 March A liquid fertilizerdressing of 150 kg N 86 kg P 167 kg K and 30 kgMgha was applied at planting Four applicationsof 25 mm of water were made by rain-gun on 1422 May and 4 18 June
Experiment 6 1980-1Seven varieties Maris Bard Ulster Sceptre
Vanessa (earlies) Wilja Estima (second earlies)Record and Foxton (maincrop) were compared inthree randomized blocks Seed of 70-80 80-90 and90-100 g was used for the three replicates plotswere the same size as in Expt 5 Emergence was notrecorded and yields were estimated from 14 plantsper plot on 8 22 June and 6 July
Seed of all varieties was stored at 6 degC until mid-February when the two maincrop varieties weretransferred to 12 degC Sprout measurements weremade on ten tubers per seed size of each variety on3 March and the experiment planted by hand on5-6 March
A liquid fertilizer dressing of 145 kg N 61 kg Pand 119 kg Kha was applied at planting Threeapplications of 25 mm of water were made by rain-gun on 7 22 June and 7 July In all experimentsthe control of weeds was satisfactory and theapplication of fungicides and aphicides ensuredthat both blight (Phytophthora infestans) and virusdiseases were controlled
In all experiments the yields per hectare wereobtained by harvesting the area occupied by thestated number of plants irrespective of any missingplants From growth analysis samples on someoccasions yields are presented per plant and careshould be exercised if these values are converted toyield per hectare as the sample area was small andinappropriate for such conversion
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446 R L GRIFFITH AND OTHERS
(a) Aberporth
40
30
20
10
0
50
U 40 H
A
pound 30MU
bullvI 20O
I o
I
1977
-10
50
40 -
30-
20-
10-
0 -
-10
March April
(b) Trefloyne
1979
April
1980
May
(c) Hemsby
V
March April
40-
30-
20
i o H
o
50
40-
30-
20
10
OH
1978
-10J r
50-
40-
30-
20
- 1 0 -
March April
1980
March April
1981
March April
Fig 1 For description see opposite
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60 -i
40-
20
140 n
120 -
100 -
BO-
S 60
40-
20-
lOO-i
80-
60-
40-
20-
0
Growth of contrasting potato varieties(d) Aberporth
1978
447
1977
(e) Trefloyne1979 1980
1980Hemsby
1981
March April May June March April May June
Fig 1 Weekly number of day-degrees gt 4 degC (a-c) and total monthly rainfall (d-f) in 2 years at Aber-porth (north Pembrokeshire) Trefloyne (south Pembrokeshire) and Hemsby (Norfolk) T Time ofplanting v time of 50 plant emergence
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448 R L GBIFFITH AND OTHEBS
Table 3 Sprout growth per tuber number of emerged plants and stems Expt 1
Length of longest sprout(mm)
Total sprout length (mm)Number of sprouts gt 3 mmNumber of emerged plants
f000sha) 22 iv 77Number of above-groundstemsplant 30 v 77
Number of mainstemsplant30 v 77
HomeGuard
50-4
73-23 0
43-5
4-9
2-0
Table 4 Tuber yields
Total yield 31 v 77Yield gt 25 mm 31 v 77Total yield 10 vi 77Yield gt 25 mm 10 vi 77Total yield 1 vii 77Yield gt 25 mm 1 vii 77Yield gt 38 mm 1 vii 77Number of tubers 31 v 77
10 vi 771 vii 77
HomeGuard
8 05-2
12-610-721-520113-2
1193890780
ArranComet
27-8
6113-3
41-9
5-2
2-8
MarisBard
21-2
6014-6
311
5-7
5-2
[tha) and number of tubers
ArranComet
11-68-6
17-915-931 330-223-3
1054984790
MarisBard
9-74-8
16-513-929026-817-2
20231257979
PentlandCrown
15-7
26-92-8
28-8
5-3
1-9
(OOOsha)
PentlandCrown
5-72-5
1109 2
25-324-3180
994760696
StormontEnterprise
14-9
38-74-3
22-6
5-8
4-2
Expt 1StormontEnterprise
5-52-8
11-69-2
24823-6160
1153959815
SE
1-71
2-450-26062
0-26
0-34
SE
0-660-541-051-091-971-871-72
1016661371
From the records of temperature in storage andobservation of the end of dormancy the numbers ofday-degrees experienced by the seed of the varietiesin the majority of experiments are shown in Table2 Where no direct observation of the end of dor-mancy was made the timing of this event wasobtained from records of the same variety in otherexperiments
Only at Trefloyne in 1980 was wilting of plantsobserved in prolonged dry weather in July In allother experiments growth was not observed to beaffected by water availability The monthly rain-fall figures and weekly number of day-degreesgt 4 degC (air) are given in Fig 1
RESULTS
Experiment 1 (1977)
The early varieties produced substantially moresprout growth and emerged earlier than the main-crop varieties (Table 3) Final emergence was com-plete in all varieties and there were no effects ofvariety on number of above-ground sterna How-
ever Maris Bard and Stormont Enterprise pro-duced predominantly mainstems and had signifi-cantly more than other varieties (Table 3) PentlandCrown produced substantially more secondarystems than mainstems
At the first harvest (31 May) Arran Comet pro-duced the highest total yield and all early varietiessignificantly outyielded the maincrops (Table 4)Arran Comet had markedly higher saleable yield( gt 25 mm) than all other varieties and the other twoearlies were higher yielding than the maincrops Atthe two subsequent harvests Arran Comet producedthe highest total and graded yields although MarisBard was usually not significantly lower yieldingMaris Bard lost many of its small tubers so thatalthough it had the most tubers throughout harvest-ing the differences between varieties in number oftubers became smaller and the effects on total yieldwere also found in graded yields NonethelessArran Comet produced significantly higher yield inthe gt 38 mm grade than other varieties as a con-sequence of having the lowest number of tubers ofall varieties which resulted in increased mean
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Growth of contrasting potato varieties 449
Table 5 Sprout growth per tuber number of emerged plants (OOOsha)and number of stems per plant Expt 2
Length of longest sprout (mm)Total sprout lengthNumber of sproutsNumber of emerged
7 iv 781 v 78
(mm)gt 3 mmplants
HomeGuard
21-942-02-7
46-648-4
Number of above-ground stemsplant18 v 78
Number of mainstemsplant18 v 78
Date of sampling
4 v 7818 v 7830 v 78
7 vi 7816 vi 78
Total yield30 v 78
Yield gt 25 mm30 v 78
Total yield7 vi 78
Yield gt 25 mm7 vi 78
Total yield16 vi 78
Yield gt 25 mm16 vi 78
Number of tubersgt 25 mm30 v 78
HomeGuard
0-561-492-492-952-60
4-4
2-5
Table 6
ArranComet
0-722-434 0 14-764-84
Arran Maris Maris PentlandComet Bard (OG) Bard (CC) Crown
17-740-93-7
29-548-4
5-9
2-9
Leaf area bull
MariaBard (OG)
0-370-570-801-431-44
38-4100-9
4 1
33-540-1
1-5
1-4
5-6 11117-1 2582-8 3-7
5-6 31-449-1 47-2
5-5 8-1
50 2-4
indices Expt 2
MarisBard (CC)
0 1 81-383-283163-32
PentlandCrown
0-471-633-413 6 33-68
Desiree
11-7211
2-4
30148-8
3-8
2 0
Desiree
0-371-432-792-963-50
Table 7 Tuber yields (tha) and number of tubers (y000sha) Expt 2
HomeGuard
19-2
17-8
24-8
23-8
27-3
26-4
450
ArranComet
20-6
19-3
30-5
29-2
351
341
592
MarisBard (CC)
16-8
14-1
24-7
220
3 2 0
29-8
440
MarisBard (OG)
11-6
10-4
16-8
15-6
21-4
20-4
222
PentlandCrown
16-7
14-6
25-9
24-5
30-9
299
451
Desiree
17-8
15-9
22-4
21-1
28-8
27-4
548
SE
0-701-740-26
2-281-35
0-55
0-38
SE
004701390-2030-2670-353
SE
0-93
0-98
0-95
0-95
1-53
1-49
304
tuber size At the second harvest the yields of themaincrop varieties were not significantly lowerthan Home Guard and at the final harvest the twomaincrops exceeded Home Guard although notsignificantly Thus by the end of June the main-crop varieties appeared to have surpassed theyields of the most popular early variety but notthose of two less widely-grown varieties
15
Experiment 2 (1978)The growth of the once-grown stock of Maris
Bard was quite different from all other varietiesSprout growth commenced in October and byplanting the length of the longest sprout was sub-stantially greater than that of all other varietiesEmergence commenced earlier than other varieties
AGS 103
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en O
Tab
le 8
Sp
rout
gr
owth
per
tub
er (
9 M
arch
) n
umbe
r of
em
erge
d pl
ants
an
d st
ems
(O
OO
sha
) E
xpt
3
Len
gth
of l
onge
st s
prou
t (m
m)
Tot
al s
prou
t le
ngth
(m
m)
Num
ber
of s
prou
ts gt
3 n
unN
o o
f em
erge
d pl
ants
18 v
79
No
of
abov
e-gr
ound
ste
ms
21
v 7
9N
o o
f m
ain
stem
sp
lan
t21
v
79N
o o
f se
cond
ary
stem
sp
lan
t21
v 7
9N
o o
f ab
ove-
grou
nd s
tem
sp
lan
t21
v
79
Dat
e of
sam
plin
g P
rim
ura
21 v
i 7
9 4-
23
vii
79
4-
716
vii
79
4-7
31 v
ii
79
0-6
c
hang
e pe
ak L
87
to 3
1 v
ii 7
9
Pri
mu
ra
12-2
27-6 3-3
39-8
272 1-
7
2-6
4-3
Juli
ver
2-8
3-9
41
2-3
44
Juli
ver
10
024
-5 3-6
42-3
172 2-
3
0-9
3-2
Spu
nta
19-9
36-8 2-8
25-4
124 1-
8
0-7
2-5
Ren
ova
11-6
24
03
0
22-9
210 1-
3
20
3-3
Dra
ga
5-7
14
02-
5
2-5
124 1-
8
0-5
2-3
Tab
le 9
L
eaf
area
indi
ces
Exp
t 3
Spu
nta
2-4
3-9
3-4
2-8
28
Ren
ova
2-5
3-7
4-3
31
28
Dra
ga
2-9
4-0
6-2
31
40
Ho
me
Gu
ard
20
2-3
2-6
1-5
42
Hom
eG
uard
57-4
60-8 1-3
14-4
176 2-
2
11
3-3
Arr
anC
omet
33-8
38-8 1-4
30-1
199 1
1
2-4
3-5
Pen
tlan
dJa
vel
in
12-7
25-3 30
51-2
189 2
1
1-2
3-3
Arr
an
Fen
tlan
d
F4
61
1
8-9
21-4 3-2
45-3
219 3-
2
10
4-2
Com
et
Jav
elin
F
46
11
30
4-2
3-7
1-8
57
2-7
3-8
3-3
0-4
89
2-8
3-7
3-7
1-8
51
SE
1-30
1-91
0-24
3-66
17-7 0-80
0-32
0-31
SE
0-31
0-33
0-36
03
8
mdash
bull 9 BIT tT r hgt O o s W
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Growth of contrasting potato varieties 451but approximately 20 of plants failed to emergeowing to little potato disorder The emergedplants were smaller than those of other varietiesand produced lower leaf area indices (L) Thenumber of tubers was less than in all other varietiesand yield was also less than other varieties Thedata for this seed stock of Maris Bard were ana-lysed with all other varieties and are presented butfurther reference to this stock is limited to theimplications of little potato disorder in assessingvarieties
At planting sprout lengths in Home Guard andcertified Maris Bard Arran Comet and PentlandCrown were less than in Expt 1 (Table 5) As inExpt 1 Arran Comet and Home Guard emergedearlier than the maincrop varieties but Maris Bard(CC) emerged later than the maincrop varietiesThe growth of the leaf surface was extremely rapidin Arran Comet and it had the highest leaf areaindices throughout the experiment (Table 6) ItsL value exceeded 4 before the end of May andthroughout June was significantly greater than allother varieties (Table 6) Initially Home Guardhad larger leaf area indices than the remainingvarieties but by 18 May there were no significantdifferences between these varieties During Juneleaf area indices increased in the maincrops andMaris Bard but decreased in Home Guard and on16 June Pentland Crown had significantly largerL than Home Guard
At the first harvest on 30 May yield was highthe mean yield for the experiment was 17-1 thaand Arran Comet produced the highest total yieldand yield in the grade gt 25 mm and these yieldswere significantly higher than all varieties exceptHome Guard (Table 7) Home Guard was notsignificantly higher yielding in these grades thanany other variety but it produced significantlygreater yields in the grade gt 38 mm than themaincrop varieties At the second harvest (7 June)Arran Comet produced significantly larger yields intotal and in the grade gt 32 mm than all othervarieties There were no significant differences inthese yields between Home Guard Maris Bard andPentland Crown but Desiree produced significantlylower yields than Pentlond Crown Home Guardand Arran Comet did not differ significantly inyield of tubers gt 38 mm but both outyielded othervarieties At the final harvest Arran Comet still hadthe highest total and graded yields but these werenot significantly greater than Pentland Crown andMaris Bard Home Guard and Ddsiree producedsimilar yields which were not significantly differentfrom Pentland Crown and Maris Bard (Table 7)Yield at the final harvest was high in relation tothe length of the growing season Although tuberinitiation was not recorded accurately it is un-likely to have occurred before mid-April in any
variety and therefore a total bulking period of nomore than 8 weeks produced an average rate of4-5 thaweek Rate of bulking may have beenrelated to the size of the leaf surface since the twovarieties with the smallest leaf areas (Home Guardand Desiree) had the lowest rates of bulking
As in Expt 1 Arran Comet produced the highestyields throughout the period of harvesting In con-trast Maris Bard (CC) approached the yield ofArran Comet only at the final harvest and was notsignificantly different from the maincrops
Experiment 3 (1979)There were large differences between varieties in
all aspects of sprout growth (Table 8) Arran Cometand Home Guard produced only one or two sproutsof greater length than other varieties There werefew differences between the remaining varietiesexcept that Draga had very short sprouts Emerg-ence did not seem to be determined by sproutlength at planting as Pentland Javelin and F4611were the first varieties to complete emergence andHome Guard was especially slow This delay inemergence in Home Guard (and Arran Comet) wasassociated with coiled sprouts and in Home Guardsome plants failed to emerge owing to little potatodisorder
There were considerable differences between thevarieties in number of above-ground stems and inthe composition of this population (Table 8) Pri-mura and F4611 produced the most above-groundstems but in the former most were secondary stemsand in the latter main stems Only Home Guardfailed to produce a leaf area index of 3 (Table 9)and the largest peak L values were produced byPrimura (early) and Draga (maincrop) Thesepeak values occurred at different times Primuraproduced its leaf surface very rapidly and its Lexceeded 4 in mid-June Draga was much later inproducing its leaf area and reached its peak in JulyAll varieties decreased in leaf area in the later partof July as a consequence of increasing moisturestress in a prolonged period of dry sunny weatherPrimura and Pentland Javelin were close to com-plete senescence by the end of July while Spuntaand Renova lost relatively little leaf area at thistime
At the first and second harvests Primura andthe four British earlies produced the highest totalyields and most were significantly higher than theother Dutch varieties (Table 10) At the thirdharvest Primura was the highest-yielding varietyand significantly better than all varieties exceptF4611 Pentland Javelin and Renova Betweenthe third and fourth harvests four varieties bulkedlittle (Juliver F4611 Arran Comet and PentlandJavelin) and at the final harvest Primura was still
15-2
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
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Growth of contrasting potato varieties 445
Experiment 3 1978-9Treatments were nine varieties Primura Home
Guard Arran Comet Pentland Javelin F4611(earlies) Spunta Renova (second earlies) Juliverand Draga (maincrops) replicated three times in arandomized-block design Plots were three rowswide and 11-25 m long Seed tubers of 40-50 50-60and 60-70 g were used for the three replicates andspaced 25 cm apart in the row Number of plantsand above-ground stems were recorded on 18 Mayusing one complete row Growth analysis (twoplants per plot) and estimates of yields (ten plantsper plot) were carried out on 21 June 3 16 and31 July
All seed was once-grown in mid-Wales Seedwas selected before the onset of sprout growth andplaced in trays as in Expts 1 and 2 The seed wasstored in a frost-free glasshouse until planting(average daily temperature 84 degC) Sprout measure-ments were taken on 8 March using ten seed tubersof each size and the experiment planted by handon 19 April
Experiment 4 1979-80In this experiment 11 varieties were compared
Aminca and Maris Bard (earlies) and Wilja (secondearly) were added to those in Expt 3 and HomeGuard deleted There were three replicates plotdimensions and seed size were as in Expt 3Numbers of plants and above-ground stems werenot recorded in this experiment Growth analysisand estimates of yield were carried out as in Expt 3on 18 27 June 8 and 28 July
Seed production treatment selection and storagewere as in Expt 3 The average daily temperatureof the glasshouse was 9-9 degC Sprout measurementswere taken on 3 March using ten tubers of eachseed size and the experiment planted by hand on21 March
Two experiments were carried out at DeepdaleFarms Limited Brancaster Norfolk on light sandysoils of the Wick Series Rows were 76 cm apartand tubers spaced 20 cm apart Both sites werestone-separated prior to planting
Experiment 5 1979-80Nine varieties Home Guard Arran Comet Maris
Bard (earlies) Red Craigs Royal Wilja Estima(second earlies) Maris Piper Pentland Squire andDesiree (maincrop) were compared in three random-ized blocks Seed of 40-55 g was used for all repli-cates Plots were four rows wide and 5 m longPlant and stem emergence were recorded every3-4 days using one whole row per plot Yields wereestimated from 14 plants per plot on 24 June 8 and22 July
All seed was once-grown in mid or west Wales
Table 2 Number of day-degrees gt4C experiencedby seed from onset of sprouting (3 mmsprout) toplant-ing in three varieties
Experiment
Variety
Home GuardArran CometMaris Bard
(once grown)Maris Bard(certified)
1 5 6
640 390 890 mdash 270 mdash630 340 880 760 300 mdashmdash 740 mdash mdash mdash mdash
330 80 mdash 430 230 530
and selected in late December when all seed hadbroken dormancy The first three varieties werestored at 6 degC the next three at 8 degC and the threemaincrop varieties at 12 degC Sprout measurementswere made on 30 tubers per variety on 29 Februaryand the seed moved to Norfolk The experimentwas planted by hand on 21 March A liquid fertilizerdressing of 150 kg N 86 kg P 167 kg K and 30 kgMgha was applied at planting Four applicationsof 25 mm of water were made by rain-gun on 1422 May and 4 18 June
Experiment 6 1980-1Seven varieties Maris Bard Ulster Sceptre
Vanessa (earlies) Wilja Estima (second earlies)Record and Foxton (maincrop) were compared inthree randomized blocks Seed of 70-80 80-90 and90-100 g was used for the three replicates plotswere the same size as in Expt 5 Emergence was notrecorded and yields were estimated from 14 plantsper plot on 8 22 June and 6 July
Seed of all varieties was stored at 6 degC until mid-February when the two maincrop varieties weretransferred to 12 degC Sprout measurements weremade on ten tubers per seed size of each variety on3 March and the experiment planted by hand on5-6 March
A liquid fertilizer dressing of 145 kg N 61 kg Pand 119 kg Kha was applied at planting Threeapplications of 25 mm of water were made by rain-gun on 7 22 June and 7 July In all experimentsthe control of weeds was satisfactory and theapplication of fungicides and aphicides ensuredthat both blight (Phytophthora infestans) and virusdiseases were controlled
In all experiments the yields per hectare wereobtained by harvesting the area occupied by thestated number of plants irrespective of any missingplants From growth analysis samples on someoccasions yields are presented per plant and careshould be exercised if these values are converted toyield per hectare as the sample area was small andinappropriate for such conversion
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446 R L GRIFFITH AND OTHERS
(a) Aberporth
40
30
20
10
0
50
U 40 H
A
pound 30MU
bullvI 20O
I o
I
1977
-10
50
40 -
30-
20-
10-
0 -
-10
March April
(b) Trefloyne
1979
April
1980
May
(c) Hemsby
V
March April
40-
30-
20
i o H
o
50
40-
30-
20
10
OH
1978
-10J r
50-
40-
30-
20
- 1 0 -
March April
1980
March April
1981
March April
Fig 1 For description see opposite
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60 -i
40-
20
140 n
120 -
100 -
BO-
S 60
40-
20-
lOO-i
80-
60-
40-
20-
0
Growth of contrasting potato varieties(d) Aberporth
1978
447
1977
(e) Trefloyne1979 1980
1980Hemsby
1981
March April May June March April May June
Fig 1 Weekly number of day-degrees gt 4 degC (a-c) and total monthly rainfall (d-f) in 2 years at Aber-porth (north Pembrokeshire) Trefloyne (south Pembrokeshire) and Hemsby (Norfolk) T Time ofplanting v time of 50 plant emergence
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448 R L GBIFFITH AND OTHEBS
Table 3 Sprout growth per tuber number of emerged plants and stems Expt 1
Length of longest sprout(mm)
Total sprout length (mm)Number of sprouts gt 3 mmNumber of emerged plants
f000sha) 22 iv 77Number of above-groundstemsplant 30 v 77
Number of mainstemsplant30 v 77
HomeGuard
50-4
73-23 0
43-5
4-9
2-0
Table 4 Tuber yields
Total yield 31 v 77Yield gt 25 mm 31 v 77Total yield 10 vi 77Yield gt 25 mm 10 vi 77Total yield 1 vii 77Yield gt 25 mm 1 vii 77Yield gt 38 mm 1 vii 77Number of tubers 31 v 77
10 vi 771 vii 77
HomeGuard
8 05-2
12-610-721-520113-2
1193890780
ArranComet
27-8
6113-3
41-9
5-2
2-8
MarisBard
21-2
6014-6
311
5-7
5-2
[tha) and number of tubers
ArranComet
11-68-6
17-915-931 330-223-3
1054984790
MarisBard
9-74-8
16-513-929026-817-2
20231257979
PentlandCrown
15-7
26-92-8
28-8
5-3
1-9
(OOOsha)
PentlandCrown
5-72-5
1109 2
25-324-3180
994760696
StormontEnterprise
14-9
38-74-3
22-6
5-8
4-2
Expt 1StormontEnterprise
5-52-8
11-69-2
24823-6160
1153959815
SE
1-71
2-450-26062
0-26
0-34
SE
0-660-541-051-091-971-871-72
1016661371
From the records of temperature in storage andobservation of the end of dormancy the numbers ofday-degrees experienced by the seed of the varietiesin the majority of experiments are shown in Table2 Where no direct observation of the end of dor-mancy was made the timing of this event wasobtained from records of the same variety in otherexperiments
Only at Trefloyne in 1980 was wilting of plantsobserved in prolonged dry weather in July In allother experiments growth was not observed to beaffected by water availability The monthly rain-fall figures and weekly number of day-degreesgt 4 degC (air) are given in Fig 1
RESULTS
Experiment 1 (1977)
The early varieties produced substantially moresprout growth and emerged earlier than the main-crop varieties (Table 3) Final emergence was com-plete in all varieties and there were no effects ofvariety on number of above-ground sterna How-
ever Maris Bard and Stormont Enterprise pro-duced predominantly mainstems and had signifi-cantly more than other varieties (Table 3) PentlandCrown produced substantially more secondarystems than mainstems
At the first harvest (31 May) Arran Comet pro-duced the highest total yield and all early varietiessignificantly outyielded the maincrops (Table 4)Arran Comet had markedly higher saleable yield( gt 25 mm) than all other varieties and the other twoearlies were higher yielding than the maincrops Atthe two subsequent harvests Arran Comet producedthe highest total and graded yields although MarisBard was usually not significantly lower yieldingMaris Bard lost many of its small tubers so thatalthough it had the most tubers throughout harvest-ing the differences between varieties in number oftubers became smaller and the effects on total yieldwere also found in graded yields NonethelessArran Comet produced significantly higher yield inthe gt 38 mm grade than other varieties as a con-sequence of having the lowest number of tubers ofall varieties which resulted in increased mean
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Growth of contrasting potato varieties 449
Table 5 Sprout growth per tuber number of emerged plants (OOOsha)and number of stems per plant Expt 2
Length of longest sprout (mm)Total sprout lengthNumber of sproutsNumber of emerged
7 iv 781 v 78
(mm)gt 3 mmplants
HomeGuard
21-942-02-7
46-648-4
Number of above-ground stemsplant18 v 78
Number of mainstemsplant18 v 78
Date of sampling
4 v 7818 v 7830 v 78
7 vi 7816 vi 78
Total yield30 v 78
Yield gt 25 mm30 v 78
Total yield7 vi 78
Yield gt 25 mm7 vi 78
Total yield16 vi 78
Yield gt 25 mm16 vi 78
Number of tubersgt 25 mm30 v 78
HomeGuard
0-561-492-492-952-60
4-4
2-5
Table 6
ArranComet
0-722-434 0 14-764-84
Arran Maris Maris PentlandComet Bard (OG) Bard (CC) Crown
17-740-93-7
29-548-4
5-9
2-9
Leaf area bull
MariaBard (OG)
0-370-570-801-431-44
38-4100-9
4 1
33-540-1
1-5
1-4
5-6 11117-1 2582-8 3-7
5-6 31-449-1 47-2
5-5 8-1
50 2-4
indices Expt 2
MarisBard (CC)
0 1 81-383-283163-32
PentlandCrown
0-471-633-413 6 33-68
Desiree
11-7211
2-4
30148-8
3-8
2 0
Desiree
0-371-432-792-963-50
Table 7 Tuber yields (tha) and number of tubers (y000sha) Expt 2
HomeGuard
19-2
17-8
24-8
23-8
27-3
26-4
450
ArranComet
20-6
19-3
30-5
29-2
351
341
592
MarisBard (CC)
16-8
14-1
24-7
220
3 2 0
29-8
440
MarisBard (OG)
11-6
10-4
16-8
15-6
21-4
20-4
222
PentlandCrown
16-7
14-6
25-9
24-5
30-9
299
451
Desiree
17-8
15-9
22-4
21-1
28-8
27-4
548
SE
0-701-740-26
2-281-35
0-55
0-38
SE
004701390-2030-2670-353
SE
0-93
0-98
0-95
0-95
1-53
1-49
304
tuber size At the second harvest the yields of themaincrop varieties were not significantly lowerthan Home Guard and at the final harvest the twomaincrops exceeded Home Guard although notsignificantly Thus by the end of June the main-crop varieties appeared to have surpassed theyields of the most popular early variety but notthose of two less widely-grown varieties
15
Experiment 2 (1978)The growth of the once-grown stock of Maris
Bard was quite different from all other varietiesSprout growth commenced in October and byplanting the length of the longest sprout was sub-stantially greater than that of all other varietiesEmergence commenced earlier than other varieties
AGS 103
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en O
Tab
le 8
Sp
rout
gr
owth
per
tub
er (
9 M
arch
) n
umbe
r of
em
erge
d pl
ants
an
d st
ems
(O
OO
sha
) E
xpt
3
Len
gth
of l
onge
st s
prou
t (m
m)
Tot
al s
prou
t le
ngth
(m
m)
Num
ber
of s
prou
ts gt
3 n
unN
o o
f em
erge
d pl
ants
18 v
79
No
of
abov
e-gr
ound
ste
ms
21
v 7
9N
o o
f m
ain
stem
sp
lan
t21
v
79N
o o
f se
cond
ary
stem
sp
lan
t21
v 7
9N
o o
f ab
ove-
grou
nd s
tem
sp
lan
t21
v
79
Dat
e of
sam
plin
g P
rim
ura
21 v
i 7
9 4-
23
vii
79
4-
716
vii
79
4-7
31 v
ii
79
0-6
c
hang
e pe
ak L
87
to 3
1 v
ii 7
9
Pri
mu
ra
12-2
27-6 3-3
39-8
272 1-
7
2-6
4-3
Juli
ver
2-8
3-9
41
2-3
44
Juli
ver
10
024
-5 3-6
42-3
172 2-
3
0-9
3-2
Spu
nta
19-9
36-8 2-8
25-4
124 1-
8
0-7
2-5
Ren
ova
11-6
24
03
0
22-9
210 1-
3
20
3-3
Dra
ga
5-7
14
02-
5
2-5
124 1-
8
0-5
2-3
Tab
le 9
L
eaf
area
indi
ces
Exp
t 3
Spu
nta
2-4
3-9
3-4
2-8
28
Ren
ova
2-5
3-7
4-3
31
28
Dra
ga
2-9
4-0
6-2
31
40
Ho
me
Gu
ard
20
2-3
2-6
1-5
42
Hom
eG
uard
57-4
60-8 1-3
14-4
176 2-
2
11
3-3
Arr
anC
omet
33-8
38-8 1-4
30-1
199 1
1
2-4
3-5
Pen
tlan
dJa
vel
in
12-7
25-3 30
51-2
189 2
1
1-2
3-3
Arr
an
Fen
tlan
d
F4
61
1
8-9
21-4 3-2
45-3
219 3-
2
10
4-2
Com
et
Jav
elin
F
46
11
30
4-2
3-7
1-8
57
2-7
3-8
3-3
0-4
89
2-8
3-7
3-7
1-8
51
SE
1-30
1-91
0-24
3-66
17-7 0-80
0-32
0-31
SE
0-31
0-33
0-36
03
8
mdash
bull 9 BIT tT r hgt O o s W
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Growth of contrasting potato varieties 451but approximately 20 of plants failed to emergeowing to little potato disorder The emergedplants were smaller than those of other varietiesand produced lower leaf area indices (L) Thenumber of tubers was less than in all other varietiesand yield was also less than other varieties Thedata for this seed stock of Maris Bard were ana-lysed with all other varieties and are presented butfurther reference to this stock is limited to theimplications of little potato disorder in assessingvarieties
At planting sprout lengths in Home Guard andcertified Maris Bard Arran Comet and PentlandCrown were less than in Expt 1 (Table 5) As inExpt 1 Arran Comet and Home Guard emergedearlier than the maincrop varieties but Maris Bard(CC) emerged later than the maincrop varietiesThe growth of the leaf surface was extremely rapidin Arran Comet and it had the highest leaf areaindices throughout the experiment (Table 6) ItsL value exceeded 4 before the end of May andthroughout June was significantly greater than allother varieties (Table 6) Initially Home Guardhad larger leaf area indices than the remainingvarieties but by 18 May there were no significantdifferences between these varieties During Juneleaf area indices increased in the maincrops andMaris Bard but decreased in Home Guard and on16 June Pentland Crown had significantly largerL than Home Guard
At the first harvest on 30 May yield was highthe mean yield for the experiment was 17-1 thaand Arran Comet produced the highest total yieldand yield in the grade gt 25 mm and these yieldswere significantly higher than all varieties exceptHome Guard (Table 7) Home Guard was notsignificantly higher yielding in these grades thanany other variety but it produced significantlygreater yields in the grade gt 38 mm than themaincrop varieties At the second harvest (7 June)Arran Comet produced significantly larger yields intotal and in the grade gt 32 mm than all othervarieties There were no significant differences inthese yields between Home Guard Maris Bard andPentland Crown but Desiree produced significantlylower yields than Pentlond Crown Home Guardand Arran Comet did not differ significantly inyield of tubers gt 38 mm but both outyielded othervarieties At the final harvest Arran Comet still hadthe highest total and graded yields but these werenot significantly greater than Pentland Crown andMaris Bard Home Guard and Ddsiree producedsimilar yields which were not significantly differentfrom Pentland Crown and Maris Bard (Table 7)Yield at the final harvest was high in relation tothe length of the growing season Although tuberinitiation was not recorded accurately it is un-likely to have occurred before mid-April in any
variety and therefore a total bulking period of nomore than 8 weeks produced an average rate of4-5 thaweek Rate of bulking may have beenrelated to the size of the leaf surface since the twovarieties with the smallest leaf areas (Home Guardand Desiree) had the lowest rates of bulking
As in Expt 1 Arran Comet produced the highestyields throughout the period of harvesting In con-trast Maris Bard (CC) approached the yield ofArran Comet only at the final harvest and was notsignificantly different from the maincrops
Experiment 3 (1979)There were large differences between varieties in
all aspects of sprout growth (Table 8) Arran Cometand Home Guard produced only one or two sproutsof greater length than other varieties There werefew differences between the remaining varietiesexcept that Draga had very short sprouts Emerg-ence did not seem to be determined by sproutlength at planting as Pentland Javelin and F4611were the first varieties to complete emergence andHome Guard was especially slow This delay inemergence in Home Guard (and Arran Comet) wasassociated with coiled sprouts and in Home Guardsome plants failed to emerge owing to little potatodisorder
There were considerable differences between thevarieties in number of above-ground stems and inthe composition of this population (Table 8) Pri-mura and F4611 produced the most above-groundstems but in the former most were secondary stemsand in the latter main stems Only Home Guardfailed to produce a leaf area index of 3 (Table 9)and the largest peak L values were produced byPrimura (early) and Draga (maincrop) Thesepeak values occurred at different times Primuraproduced its leaf surface very rapidly and its Lexceeded 4 in mid-June Draga was much later inproducing its leaf area and reached its peak in JulyAll varieties decreased in leaf area in the later partof July as a consequence of increasing moisturestress in a prolonged period of dry sunny weatherPrimura and Pentland Javelin were close to com-plete senescence by the end of July while Spuntaand Renova lost relatively little leaf area at thistime
At the first and second harvests Primura andthe four British earlies produced the highest totalyields and most were significantly higher than theother Dutch varieties (Table 10) At the thirdharvest Primura was the highest-yielding varietyand significantly better than all varieties exceptF4611 Pentland Javelin and Renova Betweenthe third and fourth harvests four varieties bulkedlittle (Juliver F4611 Arran Comet and PentlandJavelin) and at the final harvest Primura was still
15-2
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
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446 R L GRIFFITH AND OTHERS
(a) Aberporth
40
30
20
10
0
50
U 40 H
A
pound 30MU
bullvI 20O
I o
I
1977
-10
50
40 -
30-
20-
10-
0 -
-10
March April
(b) Trefloyne
1979
April
1980
May
(c) Hemsby
V
March April
40-
30-
20
i o H
o
50
40-
30-
20
10
OH
1978
-10J r
50-
40-
30-
20
- 1 0 -
March April
1980
March April
1981
March April
Fig 1 For description see opposite
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
60 -i
40-
20
140 n
120 -
100 -
BO-
S 60
40-
20-
lOO-i
80-
60-
40-
20-
0
Growth of contrasting potato varieties(d) Aberporth
1978
447
1977
(e) Trefloyne1979 1980
1980Hemsby
1981
March April May June March April May June
Fig 1 Weekly number of day-degrees gt 4 degC (a-c) and total monthly rainfall (d-f) in 2 years at Aber-porth (north Pembrokeshire) Trefloyne (south Pembrokeshire) and Hemsby (Norfolk) T Time ofplanting v time of 50 plant emergence
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448 R L GBIFFITH AND OTHEBS
Table 3 Sprout growth per tuber number of emerged plants and stems Expt 1
Length of longest sprout(mm)
Total sprout length (mm)Number of sprouts gt 3 mmNumber of emerged plants
f000sha) 22 iv 77Number of above-groundstemsplant 30 v 77
Number of mainstemsplant30 v 77
HomeGuard
50-4
73-23 0
43-5
4-9
2-0
Table 4 Tuber yields
Total yield 31 v 77Yield gt 25 mm 31 v 77Total yield 10 vi 77Yield gt 25 mm 10 vi 77Total yield 1 vii 77Yield gt 25 mm 1 vii 77Yield gt 38 mm 1 vii 77Number of tubers 31 v 77
10 vi 771 vii 77
HomeGuard
8 05-2
12-610-721-520113-2
1193890780
ArranComet
27-8
6113-3
41-9
5-2
2-8
MarisBard
21-2
6014-6
311
5-7
5-2
[tha) and number of tubers
ArranComet
11-68-6
17-915-931 330-223-3
1054984790
MarisBard
9-74-8
16-513-929026-817-2
20231257979
PentlandCrown
15-7
26-92-8
28-8
5-3
1-9
(OOOsha)
PentlandCrown
5-72-5
1109 2
25-324-3180
994760696
StormontEnterprise
14-9
38-74-3
22-6
5-8
4-2
Expt 1StormontEnterprise
5-52-8
11-69-2
24823-6160
1153959815
SE
1-71
2-450-26062
0-26
0-34
SE
0-660-541-051-091-971-871-72
1016661371
From the records of temperature in storage andobservation of the end of dormancy the numbers ofday-degrees experienced by the seed of the varietiesin the majority of experiments are shown in Table2 Where no direct observation of the end of dor-mancy was made the timing of this event wasobtained from records of the same variety in otherexperiments
Only at Trefloyne in 1980 was wilting of plantsobserved in prolonged dry weather in July In allother experiments growth was not observed to beaffected by water availability The monthly rain-fall figures and weekly number of day-degreesgt 4 degC (air) are given in Fig 1
RESULTS
Experiment 1 (1977)
The early varieties produced substantially moresprout growth and emerged earlier than the main-crop varieties (Table 3) Final emergence was com-plete in all varieties and there were no effects ofvariety on number of above-ground sterna How-
ever Maris Bard and Stormont Enterprise pro-duced predominantly mainstems and had signifi-cantly more than other varieties (Table 3) PentlandCrown produced substantially more secondarystems than mainstems
At the first harvest (31 May) Arran Comet pro-duced the highest total yield and all early varietiessignificantly outyielded the maincrops (Table 4)Arran Comet had markedly higher saleable yield( gt 25 mm) than all other varieties and the other twoearlies were higher yielding than the maincrops Atthe two subsequent harvests Arran Comet producedthe highest total and graded yields although MarisBard was usually not significantly lower yieldingMaris Bard lost many of its small tubers so thatalthough it had the most tubers throughout harvest-ing the differences between varieties in number oftubers became smaller and the effects on total yieldwere also found in graded yields NonethelessArran Comet produced significantly higher yield inthe gt 38 mm grade than other varieties as a con-sequence of having the lowest number of tubers ofall varieties which resulted in increased mean
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Growth of contrasting potato varieties 449
Table 5 Sprout growth per tuber number of emerged plants (OOOsha)and number of stems per plant Expt 2
Length of longest sprout (mm)Total sprout lengthNumber of sproutsNumber of emerged
7 iv 781 v 78
(mm)gt 3 mmplants
HomeGuard
21-942-02-7
46-648-4
Number of above-ground stemsplant18 v 78
Number of mainstemsplant18 v 78
Date of sampling
4 v 7818 v 7830 v 78
7 vi 7816 vi 78
Total yield30 v 78
Yield gt 25 mm30 v 78
Total yield7 vi 78
Yield gt 25 mm7 vi 78
Total yield16 vi 78
Yield gt 25 mm16 vi 78
Number of tubersgt 25 mm30 v 78
HomeGuard
0-561-492-492-952-60
4-4
2-5
Table 6
ArranComet
0-722-434 0 14-764-84
Arran Maris Maris PentlandComet Bard (OG) Bard (CC) Crown
17-740-93-7
29-548-4
5-9
2-9
Leaf area bull
MariaBard (OG)
0-370-570-801-431-44
38-4100-9
4 1
33-540-1
1-5
1-4
5-6 11117-1 2582-8 3-7
5-6 31-449-1 47-2
5-5 8-1
50 2-4
indices Expt 2
MarisBard (CC)
0 1 81-383-283163-32
PentlandCrown
0-471-633-413 6 33-68
Desiree
11-7211
2-4
30148-8
3-8
2 0
Desiree
0-371-432-792-963-50
Table 7 Tuber yields (tha) and number of tubers (y000sha) Expt 2
HomeGuard
19-2
17-8
24-8
23-8
27-3
26-4
450
ArranComet
20-6
19-3
30-5
29-2
351
341
592
MarisBard (CC)
16-8
14-1
24-7
220
3 2 0
29-8
440
MarisBard (OG)
11-6
10-4
16-8
15-6
21-4
20-4
222
PentlandCrown
16-7
14-6
25-9
24-5
30-9
299
451
Desiree
17-8
15-9
22-4
21-1
28-8
27-4
548
SE
0-701-740-26
2-281-35
0-55
0-38
SE
004701390-2030-2670-353
SE
0-93
0-98
0-95
0-95
1-53
1-49
304
tuber size At the second harvest the yields of themaincrop varieties were not significantly lowerthan Home Guard and at the final harvest the twomaincrops exceeded Home Guard although notsignificantly Thus by the end of June the main-crop varieties appeared to have surpassed theyields of the most popular early variety but notthose of two less widely-grown varieties
15
Experiment 2 (1978)The growth of the once-grown stock of Maris
Bard was quite different from all other varietiesSprout growth commenced in October and byplanting the length of the longest sprout was sub-stantially greater than that of all other varietiesEmergence commenced earlier than other varieties
AGS 103
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en O
Tab
le 8
Sp
rout
gr
owth
per
tub
er (
9 M
arch
) n
umbe
r of
em
erge
d pl
ants
an
d st
ems
(O
OO
sha
) E
xpt
3
Len
gth
of l
onge
st s
prou
t (m
m)
Tot
al s
prou
t le
ngth
(m
m)
Num
ber
of s
prou
ts gt
3 n
unN
o o
f em
erge
d pl
ants
18 v
79
No
of
abov
e-gr
ound
ste
ms
21
v 7
9N
o o
f m
ain
stem
sp
lan
t21
v
79N
o o
f se
cond
ary
stem
sp
lan
t21
v 7
9N
o o
f ab
ove-
grou
nd s
tem
sp
lan
t21
v
79
Dat
e of
sam
plin
g P
rim
ura
21 v
i 7
9 4-
23
vii
79
4-
716
vii
79
4-7
31 v
ii
79
0-6
c
hang
e pe
ak L
87
to 3
1 v
ii 7
9
Pri
mu
ra
12-2
27-6 3-3
39-8
272 1-
7
2-6
4-3
Juli
ver
2-8
3-9
41
2-3
44
Juli
ver
10
024
-5 3-6
42-3
172 2-
3
0-9
3-2
Spu
nta
19-9
36-8 2-8
25-4
124 1-
8
0-7
2-5
Ren
ova
11-6
24
03
0
22-9
210 1-
3
20
3-3
Dra
ga
5-7
14
02-
5
2-5
124 1-
8
0-5
2-3
Tab
le 9
L
eaf
area
indi
ces
Exp
t 3
Spu
nta
2-4
3-9
3-4
2-8
28
Ren
ova
2-5
3-7
4-3
31
28
Dra
ga
2-9
4-0
6-2
31
40
Ho
me
Gu
ard
20
2-3
2-6
1-5
42
Hom
eG
uard
57-4
60-8 1-3
14-4
176 2-
2
11
3-3
Arr
anC
omet
33-8
38-8 1-4
30-1
199 1
1
2-4
3-5
Pen
tlan
dJa
vel
in
12-7
25-3 30
51-2
189 2
1
1-2
3-3
Arr
an
Fen
tlan
d
F4
61
1
8-9
21-4 3-2
45-3
219 3-
2
10
4-2
Com
et
Jav
elin
F
46
11
30
4-2
3-7
1-8
57
2-7
3-8
3-3
0-4
89
2-8
3-7
3-7
1-8
51
SE
1-30
1-91
0-24
3-66
17-7 0-80
0-32
0-31
SE
0-31
0-33
0-36
03
8
mdash
bull 9 BIT tT r hgt O o s W
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Growth of contrasting potato varieties 451but approximately 20 of plants failed to emergeowing to little potato disorder The emergedplants were smaller than those of other varietiesand produced lower leaf area indices (L) Thenumber of tubers was less than in all other varietiesand yield was also less than other varieties Thedata for this seed stock of Maris Bard were ana-lysed with all other varieties and are presented butfurther reference to this stock is limited to theimplications of little potato disorder in assessingvarieties
At planting sprout lengths in Home Guard andcertified Maris Bard Arran Comet and PentlandCrown were less than in Expt 1 (Table 5) As inExpt 1 Arran Comet and Home Guard emergedearlier than the maincrop varieties but Maris Bard(CC) emerged later than the maincrop varietiesThe growth of the leaf surface was extremely rapidin Arran Comet and it had the highest leaf areaindices throughout the experiment (Table 6) ItsL value exceeded 4 before the end of May andthroughout June was significantly greater than allother varieties (Table 6) Initially Home Guardhad larger leaf area indices than the remainingvarieties but by 18 May there were no significantdifferences between these varieties During Juneleaf area indices increased in the maincrops andMaris Bard but decreased in Home Guard and on16 June Pentland Crown had significantly largerL than Home Guard
At the first harvest on 30 May yield was highthe mean yield for the experiment was 17-1 thaand Arran Comet produced the highest total yieldand yield in the grade gt 25 mm and these yieldswere significantly higher than all varieties exceptHome Guard (Table 7) Home Guard was notsignificantly higher yielding in these grades thanany other variety but it produced significantlygreater yields in the grade gt 38 mm than themaincrop varieties At the second harvest (7 June)Arran Comet produced significantly larger yields intotal and in the grade gt 32 mm than all othervarieties There were no significant differences inthese yields between Home Guard Maris Bard andPentland Crown but Desiree produced significantlylower yields than Pentlond Crown Home Guardand Arran Comet did not differ significantly inyield of tubers gt 38 mm but both outyielded othervarieties At the final harvest Arran Comet still hadthe highest total and graded yields but these werenot significantly greater than Pentland Crown andMaris Bard Home Guard and Ddsiree producedsimilar yields which were not significantly differentfrom Pentland Crown and Maris Bard (Table 7)Yield at the final harvest was high in relation tothe length of the growing season Although tuberinitiation was not recorded accurately it is un-likely to have occurred before mid-April in any
variety and therefore a total bulking period of nomore than 8 weeks produced an average rate of4-5 thaweek Rate of bulking may have beenrelated to the size of the leaf surface since the twovarieties with the smallest leaf areas (Home Guardand Desiree) had the lowest rates of bulking
As in Expt 1 Arran Comet produced the highestyields throughout the period of harvesting In con-trast Maris Bard (CC) approached the yield ofArran Comet only at the final harvest and was notsignificantly different from the maincrops
Experiment 3 (1979)There were large differences between varieties in
all aspects of sprout growth (Table 8) Arran Cometand Home Guard produced only one or two sproutsof greater length than other varieties There werefew differences between the remaining varietiesexcept that Draga had very short sprouts Emerg-ence did not seem to be determined by sproutlength at planting as Pentland Javelin and F4611were the first varieties to complete emergence andHome Guard was especially slow This delay inemergence in Home Guard (and Arran Comet) wasassociated with coiled sprouts and in Home Guardsome plants failed to emerge owing to little potatodisorder
There were considerable differences between thevarieties in number of above-ground stems and inthe composition of this population (Table 8) Pri-mura and F4611 produced the most above-groundstems but in the former most were secondary stemsand in the latter main stems Only Home Guardfailed to produce a leaf area index of 3 (Table 9)and the largest peak L values were produced byPrimura (early) and Draga (maincrop) Thesepeak values occurred at different times Primuraproduced its leaf surface very rapidly and its Lexceeded 4 in mid-June Draga was much later inproducing its leaf area and reached its peak in JulyAll varieties decreased in leaf area in the later partof July as a consequence of increasing moisturestress in a prolonged period of dry sunny weatherPrimura and Pentland Javelin were close to com-plete senescence by the end of July while Spuntaand Renova lost relatively little leaf area at thistime
At the first and second harvests Primura andthe four British earlies produced the highest totalyields and most were significantly higher than theother Dutch varieties (Table 10) At the thirdharvest Primura was the highest-yielding varietyand significantly better than all varieties exceptF4611 Pentland Javelin and Renova Betweenthe third and fourth harvests four varieties bulkedlittle (Juliver F4611 Arran Comet and PentlandJavelin) and at the final harvest Primura was still
15-2
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
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60 -i
40-
20
140 n
120 -
100 -
BO-
S 60
40-
20-
lOO-i
80-
60-
40-
20-
0
Growth of contrasting potato varieties(d) Aberporth
1978
447
1977
(e) Trefloyne1979 1980
1980Hemsby
1981
March April May June March April May June
Fig 1 Weekly number of day-degrees gt 4 degC (a-c) and total monthly rainfall (d-f) in 2 years at Aber-porth (north Pembrokeshire) Trefloyne (south Pembrokeshire) and Hemsby (Norfolk) T Time ofplanting v time of 50 plant emergence
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448 R L GBIFFITH AND OTHEBS
Table 3 Sprout growth per tuber number of emerged plants and stems Expt 1
Length of longest sprout(mm)
Total sprout length (mm)Number of sprouts gt 3 mmNumber of emerged plants
f000sha) 22 iv 77Number of above-groundstemsplant 30 v 77
Number of mainstemsplant30 v 77
HomeGuard
50-4
73-23 0
43-5
4-9
2-0
Table 4 Tuber yields
Total yield 31 v 77Yield gt 25 mm 31 v 77Total yield 10 vi 77Yield gt 25 mm 10 vi 77Total yield 1 vii 77Yield gt 25 mm 1 vii 77Yield gt 38 mm 1 vii 77Number of tubers 31 v 77
10 vi 771 vii 77
HomeGuard
8 05-2
12-610-721-520113-2
1193890780
ArranComet
27-8
6113-3
41-9
5-2
2-8
MarisBard
21-2
6014-6
311
5-7
5-2
[tha) and number of tubers
ArranComet
11-68-6
17-915-931 330-223-3
1054984790
MarisBard
9-74-8
16-513-929026-817-2
20231257979
PentlandCrown
15-7
26-92-8
28-8
5-3
1-9
(OOOsha)
PentlandCrown
5-72-5
1109 2
25-324-3180
994760696
StormontEnterprise
14-9
38-74-3
22-6
5-8
4-2
Expt 1StormontEnterprise
5-52-8
11-69-2
24823-6160
1153959815
SE
1-71
2-450-26062
0-26
0-34
SE
0-660-541-051-091-971-871-72
1016661371
From the records of temperature in storage andobservation of the end of dormancy the numbers ofday-degrees experienced by the seed of the varietiesin the majority of experiments are shown in Table2 Where no direct observation of the end of dor-mancy was made the timing of this event wasobtained from records of the same variety in otherexperiments
Only at Trefloyne in 1980 was wilting of plantsobserved in prolonged dry weather in July In allother experiments growth was not observed to beaffected by water availability The monthly rain-fall figures and weekly number of day-degreesgt 4 degC (air) are given in Fig 1
RESULTS
Experiment 1 (1977)
The early varieties produced substantially moresprout growth and emerged earlier than the main-crop varieties (Table 3) Final emergence was com-plete in all varieties and there were no effects ofvariety on number of above-ground sterna How-
ever Maris Bard and Stormont Enterprise pro-duced predominantly mainstems and had signifi-cantly more than other varieties (Table 3) PentlandCrown produced substantially more secondarystems than mainstems
At the first harvest (31 May) Arran Comet pro-duced the highest total yield and all early varietiessignificantly outyielded the maincrops (Table 4)Arran Comet had markedly higher saleable yield( gt 25 mm) than all other varieties and the other twoearlies were higher yielding than the maincrops Atthe two subsequent harvests Arran Comet producedthe highest total and graded yields although MarisBard was usually not significantly lower yieldingMaris Bard lost many of its small tubers so thatalthough it had the most tubers throughout harvest-ing the differences between varieties in number oftubers became smaller and the effects on total yieldwere also found in graded yields NonethelessArran Comet produced significantly higher yield inthe gt 38 mm grade than other varieties as a con-sequence of having the lowest number of tubers ofall varieties which resulted in increased mean
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Growth of contrasting potato varieties 449
Table 5 Sprout growth per tuber number of emerged plants (OOOsha)and number of stems per plant Expt 2
Length of longest sprout (mm)Total sprout lengthNumber of sproutsNumber of emerged
7 iv 781 v 78
(mm)gt 3 mmplants
HomeGuard
21-942-02-7
46-648-4
Number of above-ground stemsplant18 v 78
Number of mainstemsplant18 v 78
Date of sampling
4 v 7818 v 7830 v 78
7 vi 7816 vi 78
Total yield30 v 78
Yield gt 25 mm30 v 78
Total yield7 vi 78
Yield gt 25 mm7 vi 78
Total yield16 vi 78
Yield gt 25 mm16 vi 78
Number of tubersgt 25 mm30 v 78
HomeGuard
0-561-492-492-952-60
4-4
2-5
Table 6
ArranComet
0-722-434 0 14-764-84
Arran Maris Maris PentlandComet Bard (OG) Bard (CC) Crown
17-740-93-7
29-548-4
5-9
2-9
Leaf area bull
MariaBard (OG)
0-370-570-801-431-44
38-4100-9
4 1
33-540-1
1-5
1-4
5-6 11117-1 2582-8 3-7
5-6 31-449-1 47-2
5-5 8-1
50 2-4
indices Expt 2
MarisBard (CC)
0 1 81-383-283163-32
PentlandCrown
0-471-633-413 6 33-68
Desiree
11-7211
2-4
30148-8
3-8
2 0
Desiree
0-371-432-792-963-50
Table 7 Tuber yields (tha) and number of tubers (y000sha) Expt 2
HomeGuard
19-2
17-8
24-8
23-8
27-3
26-4
450
ArranComet
20-6
19-3
30-5
29-2
351
341
592
MarisBard (CC)
16-8
14-1
24-7
220
3 2 0
29-8
440
MarisBard (OG)
11-6
10-4
16-8
15-6
21-4
20-4
222
PentlandCrown
16-7
14-6
25-9
24-5
30-9
299
451
Desiree
17-8
15-9
22-4
21-1
28-8
27-4
548
SE
0-701-740-26
2-281-35
0-55
0-38
SE
004701390-2030-2670-353
SE
0-93
0-98
0-95
0-95
1-53
1-49
304
tuber size At the second harvest the yields of themaincrop varieties were not significantly lowerthan Home Guard and at the final harvest the twomaincrops exceeded Home Guard although notsignificantly Thus by the end of June the main-crop varieties appeared to have surpassed theyields of the most popular early variety but notthose of two less widely-grown varieties
15
Experiment 2 (1978)The growth of the once-grown stock of Maris
Bard was quite different from all other varietiesSprout growth commenced in October and byplanting the length of the longest sprout was sub-stantially greater than that of all other varietiesEmergence commenced earlier than other varieties
AGS 103
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en O
Tab
le 8
Sp
rout
gr
owth
per
tub
er (
9 M
arch
) n
umbe
r of
em
erge
d pl
ants
an
d st
ems
(O
OO
sha
) E
xpt
3
Len
gth
of l
onge
st s
prou
t (m
m)
Tot
al s
prou
t le
ngth
(m
m)
Num
ber
of s
prou
ts gt
3 n
unN
o o
f em
erge
d pl
ants
18 v
79
No
of
abov
e-gr
ound
ste
ms
21
v 7
9N
o o
f m
ain
stem
sp
lan
t21
v
79N
o o
f se
cond
ary
stem
sp
lan
t21
v 7
9N
o o
f ab
ove-
grou
nd s
tem
sp
lan
t21
v
79
Dat
e of
sam
plin
g P
rim
ura
21 v
i 7
9 4-
23
vii
79
4-
716
vii
79
4-7
31 v
ii
79
0-6
c
hang
e pe
ak L
87
to 3
1 v
ii 7
9
Pri
mu
ra
12-2
27-6 3-3
39-8
272 1-
7
2-6
4-3
Juli
ver
2-8
3-9
41
2-3
44
Juli
ver
10
024
-5 3-6
42-3
172 2-
3
0-9
3-2
Spu
nta
19-9
36-8 2-8
25-4
124 1-
8
0-7
2-5
Ren
ova
11-6
24
03
0
22-9
210 1-
3
20
3-3
Dra
ga
5-7
14
02-
5
2-5
124 1-
8
0-5
2-3
Tab
le 9
L
eaf
area
indi
ces
Exp
t 3
Spu
nta
2-4
3-9
3-4
2-8
28
Ren
ova
2-5
3-7
4-3
31
28
Dra
ga
2-9
4-0
6-2
31
40
Ho
me
Gu
ard
20
2-3
2-6
1-5
42
Hom
eG
uard
57-4
60-8 1-3
14-4
176 2-
2
11
3-3
Arr
anC
omet
33-8
38-8 1-4
30-1
199 1
1
2-4
3-5
Pen
tlan
dJa
vel
in
12-7
25-3 30
51-2
189 2
1
1-2
3-3
Arr
an
Fen
tlan
d
F4
61
1
8-9
21-4 3-2
45-3
219 3-
2
10
4-2
Com
et
Jav
elin
F
46
11
30
4-2
3-7
1-8
57
2-7
3-8
3-3
0-4
89
2-8
3-7
3-7
1-8
51
SE
1-30
1-91
0-24
3-66
17-7 0-80
0-32
0-31
SE
0-31
0-33
0-36
03
8
mdash
bull 9 BIT tT r hgt O o s W
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Growth of contrasting potato varieties 451but approximately 20 of plants failed to emergeowing to little potato disorder The emergedplants were smaller than those of other varietiesand produced lower leaf area indices (L) Thenumber of tubers was less than in all other varietiesand yield was also less than other varieties Thedata for this seed stock of Maris Bard were ana-lysed with all other varieties and are presented butfurther reference to this stock is limited to theimplications of little potato disorder in assessingvarieties
At planting sprout lengths in Home Guard andcertified Maris Bard Arran Comet and PentlandCrown were less than in Expt 1 (Table 5) As inExpt 1 Arran Comet and Home Guard emergedearlier than the maincrop varieties but Maris Bard(CC) emerged later than the maincrop varietiesThe growth of the leaf surface was extremely rapidin Arran Comet and it had the highest leaf areaindices throughout the experiment (Table 6) ItsL value exceeded 4 before the end of May andthroughout June was significantly greater than allother varieties (Table 6) Initially Home Guardhad larger leaf area indices than the remainingvarieties but by 18 May there were no significantdifferences between these varieties During Juneleaf area indices increased in the maincrops andMaris Bard but decreased in Home Guard and on16 June Pentland Crown had significantly largerL than Home Guard
At the first harvest on 30 May yield was highthe mean yield for the experiment was 17-1 thaand Arran Comet produced the highest total yieldand yield in the grade gt 25 mm and these yieldswere significantly higher than all varieties exceptHome Guard (Table 7) Home Guard was notsignificantly higher yielding in these grades thanany other variety but it produced significantlygreater yields in the grade gt 38 mm than themaincrop varieties At the second harvest (7 June)Arran Comet produced significantly larger yields intotal and in the grade gt 32 mm than all othervarieties There were no significant differences inthese yields between Home Guard Maris Bard andPentland Crown but Desiree produced significantlylower yields than Pentlond Crown Home Guardand Arran Comet did not differ significantly inyield of tubers gt 38 mm but both outyielded othervarieties At the final harvest Arran Comet still hadthe highest total and graded yields but these werenot significantly greater than Pentland Crown andMaris Bard Home Guard and Ddsiree producedsimilar yields which were not significantly differentfrom Pentland Crown and Maris Bard (Table 7)Yield at the final harvest was high in relation tothe length of the growing season Although tuberinitiation was not recorded accurately it is un-likely to have occurred before mid-April in any
variety and therefore a total bulking period of nomore than 8 weeks produced an average rate of4-5 thaweek Rate of bulking may have beenrelated to the size of the leaf surface since the twovarieties with the smallest leaf areas (Home Guardand Desiree) had the lowest rates of bulking
As in Expt 1 Arran Comet produced the highestyields throughout the period of harvesting In con-trast Maris Bard (CC) approached the yield ofArran Comet only at the final harvest and was notsignificantly different from the maincrops
Experiment 3 (1979)There were large differences between varieties in
all aspects of sprout growth (Table 8) Arran Cometand Home Guard produced only one or two sproutsof greater length than other varieties There werefew differences between the remaining varietiesexcept that Draga had very short sprouts Emerg-ence did not seem to be determined by sproutlength at planting as Pentland Javelin and F4611were the first varieties to complete emergence andHome Guard was especially slow This delay inemergence in Home Guard (and Arran Comet) wasassociated with coiled sprouts and in Home Guardsome plants failed to emerge owing to little potatodisorder
There were considerable differences between thevarieties in number of above-ground stems and inthe composition of this population (Table 8) Pri-mura and F4611 produced the most above-groundstems but in the former most were secondary stemsand in the latter main stems Only Home Guardfailed to produce a leaf area index of 3 (Table 9)and the largest peak L values were produced byPrimura (early) and Draga (maincrop) Thesepeak values occurred at different times Primuraproduced its leaf surface very rapidly and its Lexceeded 4 in mid-June Draga was much later inproducing its leaf area and reached its peak in JulyAll varieties decreased in leaf area in the later partof July as a consequence of increasing moisturestress in a prolonged period of dry sunny weatherPrimura and Pentland Javelin were close to com-plete senescence by the end of July while Spuntaand Renova lost relatively little leaf area at thistime
At the first and second harvests Primura andthe four British earlies produced the highest totalyields and most were significantly higher than theother Dutch varieties (Table 10) At the thirdharvest Primura was the highest-yielding varietyand significantly better than all varieties exceptF4611 Pentland Javelin and Renova Betweenthe third and fourth harvests four varieties bulkedlittle (Juliver F4611 Arran Comet and PentlandJavelin) and at the final harvest Primura was still
15-2
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
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448 R L GBIFFITH AND OTHEBS
Table 3 Sprout growth per tuber number of emerged plants and stems Expt 1
Length of longest sprout(mm)
Total sprout length (mm)Number of sprouts gt 3 mmNumber of emerged plants
f000sha) 22 iv 77Number of above-groundstemsplant 30 v 77
Number of mainstemsplant30 v 77
HomeGuard
50-4
73-23 0
43-5
4-9
2-0
Table 4 Tuber yields
Total yield 31 v 77Yield gt 25 mm 31 v 77Total yield 10 vi 77Yield gt 25 mm 10 vi 77Total yield 1 vii 77Yield gt 25 mm 1 vii 77Yield gt 38 mm 1 vii 77Number of tubers 31 v 77
10 vi 771 vii 77
HomeGuard
8 05-2
12-610-721-520113-2
1193890780
ArranComet
27-8
6113-3
41-9
5-2
2-8
MarisBard
21-2
6014-6
311
5-7
5-2
[tha) and number of tubers
ArranComet
11-68-6
17-915-931 330-223-3
1054984790
MarisBard
9-74-8
16-513-929026-817-2
20231257979
PentlandCrown
15-7
26-92-8
28-8
5-3
1-9
(OOOsha)
PentlandCrown
5-72-5
1109 2
25-324-3180
994760696
StormontEnterprise
14-9
38-74-3
22-6
5-8
4-2
Expt 1StormontEnterprise
5-52-8
11-69-2
24823-6160
1153959815
SE
1-71
2-450-26062
0-26
0-34
SE
0-660-541-051-091-971-871-72
1016661371
From the records of temperature in storage andobservation of the end of dormancy the numbers ofday-degrees experienced by the seed of the varietiesin the majority of experiments are shown in Table2 Where no direct observation of the end of dor-mancy was made the timing of this event wasobtained from records of the same variety in otherexperiments
Only at Trefloyne in 1980 was wilting of plantsobserved in prolonged dry weather in July In allother experiments growth was not observed to beaffected by water availability The monthly rain-fall figures and weekly number of day-degreesgt 4 degC (air) are given in Fig 1
RESULTS
Experiment 1 (1977)
The early varieties produced substantially moresprout growth and emerged earlier than the main-crop varieties (Table 3) Final emergence was com-plete in all varieties and there were no effects ofvariety on number of above-ground sterna How-
ever Maris Bard and Stormont Enterprise pro-duced predominantly mainstems and had signifi-cantly more than other varieties (Table 3) PentlandCrown produced substantially more secondarystems than mainstems
At the first harvest (31 May) Arran Comet pro-duced the highest total yield and all early varietiessignificantly outyielded the maincrops (Table 4)Arran Comet had markedly higher saleable yield( gt 25 mm) than all other varieties and the other twoearlies were higher yielding than the maincrops Atthe two subsequent harvests Arran Comet producedthe highest total and graded yields although MarisBard was usually not significantly lower yieldingMaris Bard lost many of its small tubers so thatalthough it had the most tubers throughout harvest-ing the differences between varieties in number oftubers became smaller and the effects on total yieldwere also found in graded yields NonethelessArran Comet produced significantly higher yield inthe gt 38 mm grade than other varieties as a con-sequence of having the lowest number of tubers ofall varieties which resulted in increased mean
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Growth of contrasting potato varieties 449
Table 5 Sprout growth per tuber number of emerged plants (OOOsha)and number of stems per plant Expt 2
Length of longest sprout (mm)Total sprout lengthNumber of sproutsNumber of emerged
7 iv 781 v 78
(mm)gt 3 mmplants
HomeGuard
21-942-02-7
46-648-4
Number of above-ground stemsplant18 v 78
Number of mainstemsplant18 v 78
Date of sampling
4 v 7818 v 7830 v 78
7 vi 7816 vi 78
Total yield30 v 78
Yield gt 25 mm30 v 78
Total yield7 vi 78
Yield gt 25 mm7 vi 78
Total yield16 vi 78
Yield gt 25 mm16 vi 78
Number of tubersgt 25 mm30 v 78
HomeGuard
0-561-492-492-952-60
4-4
2-5
Table 6
ArranComet
0-722-434 0 14-764-84
Arran Maris Maris PentlandComet Bard (OG) Bard (CC) Crown
17-740-93-7
29-548-4
5-9
2-9
Leaf area bull
MariaBard (OG)
0-370-570-801-431-44
38-4100-9
4 1
33-540-1
1-5
1-4
5-6 11117-1 2582-8 3-7
5-6 31-449-1 47-2
5-5 8-1
50 2-4
indices Expt 2
MarisBard (CC)
0 1 81-383-283163-32
PentlandCrown
0-471-633-413 6 33-68
Desiree
11-7211
2-4
30148-8
3-8
2 0
Desiree
0-371-432-792-963-50
Table 7 Tuber yields (tha) and number of tubers (y000sha) Expt 2
HomeGuard
19-2
17-8
24-8
23-8
27-3
26-4
450
ArranComet
20-6
19-3
30-5
29-2
351
341
592
MarisBard (CC)
16-8
14-1
24-7
220
3 2 0
29-8
440
MarisBard (OG)
11-6
10-4
16-8
15-6
21-4
20-4
222
PentlandCrown
16-7
14-6
25-9
24-5
30-9
299
451
Desiree
17-8
15-9
22-4
21-1
28-8
27-4
548
SE
0-701-740-26
2-281-35
0-55
0-38
SE
004701390-2030-2670-353
SE
0-93
0-98
0-95
0-95
1-53
1-49
304
tuber size At the second harvest the yields of themaincrop varieties were not significantly lowerthan Home Guard and at the final harvest the twomaincrops exceeded Home Guard although notsignificantly Thus by the end of June the main-crop varieties appeared to have surpassed theyields of the most popular early variety but notthose of two less widely-grown varieties
15
Experiment 2 (1978)The growth of the once-grown stock of Maris
Bard was quite different from all other varietiesSprout growth commenced in October and byplanting the length of the longest sprout was sub-stantially greater than that of all other varietiesEmergence commenced earlier than other varieties
AGS 103
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en O
Tab
le 8
Sp
rout
gr
owth
per
tub
er (
9 M
arch
) n
umbe
r of
em
erge
d pl
ants
an
d st
ems
(O
OO
sha
) E
xpt
3
Len
gth
of l
onge
st s
prou
t (m
m)
Tot
al s
prou
t le
ngth
(m
m)
Num
ber
of s
prou
ts gt
3 n
unN
o o
f em
erge
d pl
ants
18 v
79
No
of
abov
e-gr
ound
ste
ms
21
v 7
9N
o o
f m
ain
stem
sp
lan
t21
v
79N
o o
f se
cond
ary
stem
sp
lan
t21
v 7
9N
o o
f ab
ove-
grou
nd s
tem
sp
lan
t21
v
79
Dat
e of
sam
plin
g P
rim
ura
21 v
i 7
9 4-
23
vii
79
4-
716
vii
79
4-7
31 v
ii
79
0-6
c
hang
e pe
ak L
87
to 3
1 v
ii 7
9
Pri
mu
ra
12-2
27-6 3-3
39-8
272 1-
7
2-6
4-3
Juli
ver
2-8
3-9
41
2-3
44
Juli
ver
10
024
-5 3-6
42-3
172 2-
3
0-9
3-2
Spu
nta
19-9
36-8 2-8
25-4
124 1-
8
0-7
2-5
Ren
ova
11-6
24
03
0
22-9
210 1-
3
20
3-3
Dra
ga
5-7
14
02-
5
2-5
124 1-
8
0-5
2-3
Tab
le 9
L
eaf
area
indi
ces
Exp
t 3
Spu
nta
2-4
3-9
3-4
2-8
28
Ren
ova
2-5
3-7
4-3
31
28
Dra
ga
2-9
4-0
6-2
31
40
Ho
me
Gu
ard
20
2-3
2-6
1-5
42
Hom
eG
uard
57-4
60-8 1-3
14-4
176 2-
2
11
3-3
Arr
anC
omet
33-8
38-8 1-4
30-1
199 1
1
2-4
3-5
Pen
tlan
dJa
vel
in
12-7
25-3 30
51-2
189 2
1
1-2
3-3
Arr
an
Fen
tlan
d
F4
61
1
8-9
21-4 3-2
45-3
219 3-
2
10
4-2
Com
et
Jav
elin
F
46
11
30
4-2
3-7
1-8
57
2-7
3-8
3-3
0-4
89
2-8
3-7
3-7
1-8
51
SE
1-30
1-91
0-24
3-66
17-7 0-80
0-32
0-31
SE
0-31
0-33
0-36
03
8
mdash
bull 9 BIT tT r hgt O o s W
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Growth of contrasting potato varieties 451but approximately 20 of plants failed to emergeowing to little potato disorder The emergedplants were smaller than those of other varietiesand produced lower leaf area indices (L) Thenumber of tubers was less than in all other varietiesand yield was also less than other varieties Thedata for this seed stock of Maris Bard were ana-lysed with all other varieties and are presented butfurther reference to this stock is limited to theimplications of little potato disorder in assessingvarieties
At planting sprout lengths in Home Guard andcertified Maris Bard Arran Comet and PentlandCrown were less than in Expt 1 (Table 5) As inExpt 1 Arran Comet and Home Guard emergedearlier than the maincrop varieties but Maris Bard(CC) emerged later than the maincrop varietiesThe growth of the leaf surface was extremely rapidin Arran Comet and it had the highest leaf areaindices throughout the experiment (Table 6) ItsL value exceeded 4 before the end of May andthroughout June was significantly greater than allother varieties (Table 6) Initially Home Guardhad larger leaf area indices than the remainingvarieties but by 18 May there were no significantdifferences between these varieties During Juneleaf area indices increased in the maincrops andMaris Bard but decreased in Home Guard and on16 June Pentland Crown had significantly largerL than Home Guard
At the first harvest on 30 May yield was highthe mean yield for the experiment was 17-1 thaand Arran Comet produced the highest total yieldand yield in the grade gt 25 mm and these yieldswere significantly higher than all varieties exceptHome Guard (Table 7) Home Guard was notsignificantly higher yielding in these grades thanany other variety but it produced significantlygreater yields in the grade gt 38 mm than themaincrop varieties At the second harvest (7 June)Arran Comet produced significantly larger yields intotal and in the grade gt 32 mm than all othervarieties There were no significant differences inthese yields between Home Guard Maris Bard andPentland Crown but Desiree produced significantlylower yields than Pentlond Crown Home Guardand Arran Comet did not differ significantly inyield of tubers gt 38 mm but both outyielded othervarieties At the final harvest Arran Comet still hadthe highest total and graded yields but these werenot significantly greater than Pentland Crown andMaris Bard Home Guard and Ddsiree producedsimilar yields which were not significantly differentfrom Pentland Crown and Maris Bard (Table 7)Yield at the final harvest was high in relation tothe length of the growing season Although tuberinitiation was not recorded accurately it is un-likely to have occurred before mid-April in any
variety and therefore a total bulking period of nomore than 8 weeks produced an average rate of4-5 thaweek Rate of bulking may have beenrelated to the size of the leaf surface since the twovarieties with the smallest leaf areas (Home Guardand Desiree) had the lowest rates of bulking
As in Expt 1 Arran Comet produced the highestyields throughout the period of harvesting In con-trast Maris Bard (CC) approached the yield ofArran Comet only at the final harvest and was notsignificantly different from the maincrops
Experiment 3 (1979)There were large differences between varieties in
all aspects of sprout growth (Table 8) Arran Cometand Home Guard produced only one or two sproutsof greater length than other varieties There werefew differences between the remaining varietiesexcept that Draga had very short sprouts Emerg-ence did not seem to be determined by sproutlength at planting as Pentland Javelin and F4611were the first varieties to complete emergence andHome Guard was especially slow This delay inemergence in Home Guard (and Arran Comet) wasassociated with coiled sprouts and in Home Guardsome plants failed to emerge owing to little potatodisorder
There were considerable differences between thevarieties in number of above-ground stems and inthe composition of this population (Table 8) Pri-mura and F4611 produced the most above-groundstems but in the former most were secondary stemsand in the latter main stems Only Home Guardfailed to produce a leaf area index of 3 (Table 9)and the largest peak L values were produced byPrimura (early) and Draga (maincrop) Thesepeak values occurred at different times Primuraproduced its leaf surface very rapidly and its Lexceeded 4 in mid-June Draga was much later inproducing its leaf area and reached its peak in JulyAll varieties decreased in leaf area in the later partof July as a consequence of increasing moisturestress in a prolonged period of dry sunny weatherPrimura and Pentland Javelin were close to com-plete senescence by the end of July while Spuntaand Renova lost relatively little leaf area at thistime
At the first and second harvests Primura andthe four British earlies produced the highest totalyields and most were significantly higher than theother Dutch varieties (Table 10) At the thirdharvest Primura was the highest-yielding varietyand significantly better than all varieties exceptF4611 Pentland Javelin and Renova Betweenthe third and fourth harvests four varieties bulkedlittle (Juliver F4611 Arran Comet and PentlandJavelin) and at the final harvest Primura was still
15-2
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
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Growth of contrasting potato varieties 449
Table 5 Sprout growth per tuber number of emerged plants (OOOsha)and number of stems per plant Expt 2
Length of longest sprout (mm)Total sprout lengthNumber of sproutsNumber of emerged
7 iv 781 v 78
(mm)gt 3 mmplants
HomeGuard
21-942-02-7
46-648-4
Number of above-ground stemsplant18 v 78
Number of mainstemsplant18 v 78
Date of sampling
4 v 7818 v 7830 v 78
7 vi 7816 vi 78
Total yield30 v 78
Yield gt 25 mm30 v 78
Total yield7 vi 78
Yield gt 25 mm7 vi 78
Total yield16 vi 78
Yield gt 25 mm16 vi 78
Number of tubersgt 25 mm30 v 78
HomeGuard
0-561-492-492-952-60
4-4
2-5
Table 6
ArranComet
0-722-434 0 14-764-84
Arran Maris Maris PentlandComet Bard (OG) Bard (CC) Crown
17-740-93-7
29-548-4
5-9
2-9
Leaf area bull
MariaBard (OG)
0-370-570-801-431-44
38-4100-9
4 1
33-540-1
1-5
1-4
5-6 11117-1 2582-8 3-7
5-6 31-449-1 47-2
5-5 8-1
50 2-4
indices Expt 2
MarisBard (CC)
0 1 81-383-283163-32
PentlandCrown
0-471-633-413 6 33-68
Desiree
11-7211
2-4
30148-8
3-8
2 0
Desiree
0-371-432-792-963-50
Table 7 Tuber yields (tha) and number of tubers (y000sha) Expt 2
HomeGuard
19-2
17-8
24-8
23-8
27-3
26-4
450
ArranComet
20-6
19-3
30-5
29-2
351
341
592
MarisBard (CC)
16-8
14-1
24-7
220
3 2 0
29-8
440
MarisBard (OG)
11-6
10-4
16-8
15-6
21-4
20-4
222
PentlandCrown
16-7
14-6
25-9
24-5
30-9
299
451
Desiree
17-8
15-9
22-4
21-1
28-8
27-4
548
SE
0-701-740-26
2-281-35
0-55
0-38
SE
004701390-2030-2670-353
SE
0-93
0-98
0-95
0-95
1-53
1-49
304
tuber size At the second harvest the yields of themaincrop varieties were not significantly lowerthan Home Guard and at the final harvest the twomaincrops exceeded Home Guard although notsignificantly Thus by the end of June the main-crop varieties appeared to have surpassed theyields of the most popular early variety but notthose of two less widely-grown varieties
15
Experiment 2 (1978)The growth of the once-grown stock of Maris
Bard was quite different from all other varietiesSprout growth commenced in October and byplanting the length of the longest sprout was sub-stantially greater than that of all other varietiesEmergence commenced earlier than other varieties
AGS 103
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en O
Tab
le 8
Sp
rout
gr
owth
per
tub
er (
9 M
arch
) n
umbe
r of
em
erge
d pl
ants
an
d st
ems
(O
OO
sha
) E
xpt
3
Len
gth
of l
onge
st s
prou
t (m
m)
Tot
al s
prou
t le
ngth
(m
m)
Num
ber
of s
prou
ts gt
3 n
unN
o o
f em
erge
d pl
ants
18 v
79
No
of
abov
e-gr
ound
ste
ms
21
v 7
9N
o o
f m
ain
stem
sp
lan
t21
v
79N
o o
f se
cond
ary
stem
sp
lan
t21
v 7
9N
o o
f ab
ove-
grou
nd s
tem
sp
lan
t21
v
79
Dat
e of
sam
plin
g P
rim
ura
21 v
i 7
9 4-
23
vii
79
4-
716
vii
79
4-7
31 v
ii
79
0-6
c
hang
e pe
ak L
87
to 3
1 v
ii 7
9
Pri
mu
ra
12-2
27-6 3-3
39-8
272 1-
7
2-6
4-3
Juli
ver
2-8
3-9
41
2-3
44
Juli
ver
10
024
-5 3-6
42-3
172 2-
3
0-9
3-2
Spu
nta
19-9
36-8 2-8
25-4
124 1-
8
0-7
2-5
Ren
ova
11-6
24
03
0
22-9
210 1-
3
20
3-3
Dra
ga
5-7
14
02-
5
2-5
124 1-
8
0-5
2-3
Tab
le 9
L
eaf
area
indi
ces
Exp
t 3
Spu
nta
2-4
3-9
3-4
2-8
28
Ren
ova
2-5
3-7
4-3
31
28
Dra
ga
2-9
4-0
6-2
31
40
Ho
me
Gu
ard
20
2-3
2-6
1-5
42
Hom
eG
uard
57-4
60-8 1-3
14-4
176 2-
2
11
3-3
Arr
anC
omet
33-8
38-8 1-4
30-1
199 1
1
2-4
3-5
Pen
tlan
dJa
vel
in
12-7
25-3 30
51-2
189 2
1
1-2
3-3
Arr
an
Fen
tlan
d
F4
61
1
8-9
21-4 3-2
45-3
219 3-
2
10
4-2
Com
et
Jav
elin
F
46
11
30
4-2
3-7
1-8
57
2-7
3-8
3-3
0-4
89
2-8
3-7
3-7
1-8
51
SE
1-30
1-91
0-24
3-66
17-7 0-80
0-32
0-31
SE
0-31
0-33
0-36
03
8
mdash
bull 9 BIT tT r hgt O o s W
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Growth of contrasting potato varieties 451but approximately 20 of plants failed to emergeowing to little potato disorder The emergedplants were smaller than those of other varietiesand produced lower leaf area indices (L) Thenumber of tubers was less than in all other varietiesand yield was also less than other varieties Thedata for this seed stock of Maris Bard were ana-lysed with all other varieties and are presented butfurther reference to this stock is limited to theimplications of little potato disorder in assessingvarieties
At planting sprout lengths in Home Guard andcertified Maris Bard Arran Comet and PentlandCrown were less than in Expt 1 (Table 5) As inExpt 1 Arran Comet and Home Guard emergedearlier than the maincrop varieties but Maris Bard(CC) emerged later than the maincrop varietiesThe growth of the leaf surface was extremely rapidin Arran Comet and it had the highest leaf areaindices throughout the experiment (Table 6) ItsL value exceeded 4 before the end of May andthroughout June was significantly greater than allother varieties (Table 6) Initially Home Guardhad larger leaf area indices than the remainingvarieties but by 18 May there were no significantdifferences between these varieties During Juneleaf area indices increased in the maincrops andMaris Bard but decreased in Home Guard and on16 June Pentland Crown had significantly largerL than Home Guard
At the first harvest on 30 May yield was highthe mean yield for the experiment was 17-1 thaand Arran Comet produced the highest total yieldand yield in the grade gt 25 mm and these yieldswere significantly higher than all varieties exceptHome Guard (Table 7) Home Guard was notsignificantly higher yielding in these grades thanany other variety but it produced significantlygreater yields in the grade gt 38 mm than themaincrop varieties At the second harvest (7 June)Arran Comet produced significantly larger yields intotal and in the grade gt 32 mm than all othervarieties There were no significant differences inthese yields between Home Guard Maris Bard andPentland Crown but Desiree produced significantlylower yields than Pentlond Crown Home Guardand Arran Comet did not differ significantly inyield of tubers gt 38 mm but both outyielded othervarieties At the final harvest Arran Comet still hadthe highest total and graded yields but these werenot significantly greater than Pentland Crown andMaris Bard Home Guard and Ddsiree producedsimilar yields which were not significantly differentfrom Pentland Crown and Maris Bard (Table 7)Yield at the final harvest was high in relation tothe length of the growing season Although tuberinitiation was not recorded accurately it is un-likely to have occurred before mid-April in any
variety and therefore a total bulking period of nomore than 8 weeks produced an average rate of4-5 thaweek Rate of bulking may have beenrelated to the size of the leaf surface since the twovarieties with the smallest leaf areas (Home Guardand Desiree) had the lowest rates of bulking
As in Expt 1 Arran Comet produced the highestyields throughout the period of harvesting In con-trast Maris Bard (CC) approached the yield ofArran Comet only at the final harvest and was notsignificantly different from the maincrops
Experiment 3 (1979)There were large differences between varieties in
all aspects of sprout growth (Table 8) Arran Cometand Home Guard produced only one or two sproutsof greater length than other varieties There werefew differences between the remaining varietiesexcept that Draga had very short sprouts Emerg-ence did not seem to be determined by sproutlength at planting as Pentland Javelin and F4611were the first varieties to complete emergence andHome Guard was especially slow This delay inemergence in Home Guard (and Arran Comet) wasassociated with coiled sprouts and in Home Guardsome plants failed to emerge owing to little potatodisorder
There were considerable differences between thevarieties in number of above-ground stems and inthe composition of this population (Table 8) Pri-mura and F4611 produced the most above-groundstems but in the former most were secondary stemsand in the latter main stems Only Home Guardfailed to produce a leaf area index of 3 (Table 9)and the largest peak L values were produced byPrimura (early) and Draga (maincrop) Thesepeak values occurred at different times Primuraproduced its leaf surface very rapidly and its Lexceeded 4 in mid-June Draga was much later inproducing its leaf area and reached its peak in JulyAll varieties decreased in leaf area in the later partof July as a consequence of increasing moisturestress in a prolonged period of dry sunny weatherPrimura and Pentland Javelin were close to com-plete senescence by the end of July while Spuntaand Renova lost relatively little leaf area at thistime
At the first and second harvests Primura andthe four British earlies produced the highest totalyields and most were significantly higher than theother Dutch varieties (Table 10) At the thirdharvest Primura was the highest-yielding varietyand significantly better than all varieties exceptF4611 Pentland Javelin and Renova Betweenthe third and fourth harvests four varieties bulkedlittle (Juliver F4611 Arran Comet and PentlandJavelin) and at the final harvest Primura was still
15-2
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
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en O
Tab
le 8
Sp
rout
gr
owth
per
tub
er (
9 M
arch
) n
umbe
r of
em
erge
d pl
ants
an
d st
ems
(O
OO
sha
) E
xpt
3
Len
gth
of l
onge
st s
prou
t (m
m)
Tot
al s
prou
t le
ngth
(m
m)
Num
ber
of s
prou
ts gt
3 n
unN
o o
f em
erge
d pl
ants
18 v
79
No
of
abov
e-gr
ound
ste
ms
21
v 7
9N
o o
f m
ain
stem
sp
lan
t21
v
79N
o o
f se
cond
ary
stem
sp
lan
t21
v 7
9N
o o
f ab
ove-
grou
nd s
tem
sp
lan
t21
v
79
Dat
e of
sam
plin
g P
rim
ura
21 v
i 7
9 4-
23
vii
79
4-
716
vii
79
4-7
31 v
ii
79
0-6
c
hang
e pe
ak L
87
to 3
1 v
ii 7
9
Pri
mu
ra
12-2
27-6 3-3
39-8
272 1-
7
2-6
4-3
Juli
ver
2-8
3-9
41
2-3
44
Juli
ver
10
024
-5 3-6
42-3
172 2-
3
0-9
3-2
Spu
nta
19-9
36-8 2-8
25-4
124 1-
8
0-7
2-5
Ren
ova
11-6
24
03
0
22-9
210 1-
3
20
3-3
Dra
ga
5-7
14
02-
5
2-5
124 1-
8
0-5
2-3
Tab
le 9
L
eaf
area
indi
ces
Exp
t 3
Spu
nta
2-4
3-9
3-4
2-8
28
Ren
ova
2-5
3-7
4-3
31
28
Dra
ga
2-9
4-0
6-2
31
40
Ho
me
Gu
ard
20
2-3
2-6
1-5
42
Hom
eG
uard
57-4
60-8 1-3
14-4
176 2-
2
11
3-3
Arr
anC
omet
33-8
38-8 1-4
30-1
199 1
1
2-4
3-5
Pen
tlan
dJa
vel
in
12-7
25-3 30
51-2
189 2
1
1-2
3-3
Arr
an
Fen
tlan
d
F4
61
1
8-9
21-4 3-2
45-3
219 3-
2
10
4-2
Com
et
Jav
elin
F
46
11
30
4-2
3-7
1-8
57
2-7
3-8
3-3
0-4
89
2-8
3-7
3-7
1-8
51
SE
1-30
1-91
0-24
3-66
17-7 0-80
0-32
0-31
SE
0-31
0-33
0-36
03
8
mdash
bull 9 BIT tT r hgt O o s W
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Growth of contrasting potato varieties 451but approximately 20 of plants failed to emergeowing to little potato disorder The emergedplants were smaller than those of other varietiesand produced lower leaf area indices (L) Thenumber of tubers was less than in all other varietiesand yield was also less than other varieties Thedata for this seed stock of Maris Bard were ana-lysed with all other varieties and are presented butfurther reference to this stock is limited to theimplications of little potato disorder in assessingvarieties
At planting sprout lengths in Home Guard andcertified Maris Bard Arran Comet and PentlandCrown were less than in Expt 1 (Table 5) As inExpt 1 Arran Comet and Home Guard emergedearlier than the maincrop varieties but Maris Bard(CC) emerged later than the maincrop varietiesThe growth of the leaf surface was extremely rapidin Arran Comet and it had the highest leaf areaindices throughout the experiment (Table 6) ItsL value exceeded 4 before the end of May andthroughout June was significantly greater than allother varieties (Table 6) Initially Home Guardhad larger leaf area indices than the remainingvarieties but by 18 May there were no significantdifferences between these varieties During Juneleaf area indices increased in the maincrops andMaris Bard but decreased in Home Guard and on16 June Pentland Crown had significantly largerL than Home Guard
At the first harvest on 30 May yield was highthe mean yield for the experiment was 17-1 thaand Arran Comet produced the highest total yieldand yield in the grade gt 25 mm and these yieldswere significantly higher than all varieties exceptHome Guard (Table 7) Home Guard was notsignificantly higher yielding in these grades thanany other variety but it produced significantlygreater yields in the grade gt 38 mm than themaincrop varieties At the second harvest (7 June)Arran Comet produced significantly larger yields intotal and in the grade gt 32 mm than all othervarieties There were no significant differences inthese yields between Home Guard Maris Bard andPentland Crown but Desiree produced significantlylower yields than Pentlond Crown Home Guardand Arran Comet did not differ significantly inyield of tubers gt 38 mm but both outyielded othervarieties At the final harvest Arran Comet still hadthe highest total and graded yields but these werenot significantly greater than Pentland Crown andMaris Bard Home Guard and Ddsiree producedsimilar yields which were not significantly differentfrom Pentland Crown and Maris Bard (Table 7)Yield at the final harvest was high in relation tothe length of the growing season Although tuberinitiation was not recorded accurately it is un-likely to have occurred before mid-April in any
variety and therefore a total bulking period of nomore than 8 weeks produced an average rate of4-5 thaweek Rate of bulking may have beenrelated to the size of the leaf surface since the twovarieties with the smallest leaf areas (Home Guardand Desiree) had the lowest rates of bulking
As in Expt 1 Arran Comet produced the highestyields throughout the period of harvesting In con-trast Maris Bard (CC) approached the yield ofArran Comet only at the final harvest and was notsignificantly different from the maincrops
Experiment 3 (1979)There were large differences between varieties in
all aspects of sprout growth (Table 8) Arran Cometand Home Guard produced only one or two sproutsof greater length than other varieties There werefew differences between the remaining varietiesexcept that Draga had very short sprouts Emerg-ence did not seem to be determined by sproutlength at planting as Pentland Javelin and F4611were the first varieties to complete emergence andHome Guard was especially slow This delay inemergence in Home Guard (and Arran Comet) wasassociated with coiled sprouts and in Home Guardsome plants failed to emerge owing to little potatodisorder
There were considerable differences between thevarieties in number of above-ground stems and inthe composition of this population (Table 8) Pri-mura and F4611 produced the most above-groundstems but in the former most were secondary stemsand in the latter main stems Only Home Guardfailed to produce a leaf area index of 3 (Table 9)and the largest peak L values were produced byPrimura (early) and Draga (maincrop) Thesepeak values occurred at different times Primuraproduced its leaf surface very rapidly and its Lexceeded 4 in mid-June Draga was much later inproducing its leaf area and reached its peak in JulyAll varieties decreased in leaf area in the later partof July as a consequence of increasing moisturestress in a prolonged period of dry sunny weatherPrimura and Pentland Javelin were close to com-plete senescence by the end of July while Spuntaand Renova lost relatively little leaf area at thistime
At the first and second harvests Primura andthe four British earlies produced the highest totalyields and most were significantly higher than theother Dutch varieties (Table 10) At the thirdharvest Primura was the highest-yielding varietyand significantly better than all varieties exceptF4611 Pentland Javelin and Renova Betweenthe third and fourth harvests four varieties bulkedlittle (Juliver F4611 Arran Comet and PentlandJavelin) and at the final harvest Primura was still
15-2
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
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Growth of contrasting potato varieties 451but approximately 20 of plants failed to emergeowing to little potato disorder The emergedplants were smaller than those of other varietiesand produced lower leaf area indices (L) Thenumber of tubers was less than in all other varietiesand yield was also less than other varieties Thedata for this seed stock of Maris Bard were ana-lysed with all other varieties and are presented butfurther reference to this stock is limited to theimplications of little potato disorder in assessingvarieties
At planting sprout lengths in Home Guard andcertified Maris Bard Arran Comet and PentlandCrown were less than in Expt 1 (Table 5) As inExpt 1 Arran Comet and Home Guard emergedearlier than the maincrop varieties but Maris Bard(CC) emerged later than the maincrop varietiesThe growth of the leaf surface was extremely rapidin Arran Comet and it had the highest leaf areaindices throughout the experiment (Table 6) ItsL value exceeded 4 before the end of May andthroughout June was significantly greater than allother varieties (Table 6) Initially Home Guardhad larger leaf area indices than the remainingvarieties but by 18 May there were no significantdifferences between these varieties During Juneleaf area indices increased in the maincrops andMaris Bard but decreased in Home Guard and on16 June Pentland Crown had significantly largerL than Home Guard
At the first harvest on 30 May yield was highthe mean yield for the experiment was 17-1 thaand Arran Comet produced the highest total yieldand yield in the grade gt 25 mm and these yieldswere significantly higher than all varieties exceptHome Guard (Table 7) Home Guard was notsignificantly higher yielding in these grades thanany other variety but it produced significantlygreater yields in the grade gt 38 mm than themaincrop varieties At the second harvest (7 June)Arran Comet produced significantly larger yields intotal and in the grade gt 32 mm than all othervarieties There were no significant differences inthese yields between Home Guard Maris Bard andPentland Crown but Desiree produced significantlylower yields than Pentlond Crown Home Guardand Arran Comet did not differ significantly inyield of tubers gt 38 mm but both outyielded othervarieties At the final harvest Arran Comet still hadthe highest total and graded yields but these werenot significantly greater than Pentland Crown andMaris Bard Home Guard and Ddsiree producedsimilar yields which were not significantly differentfrom Pentland Crown and Maris Bard (Table 7)Yield at the final harvest was high in relation tothe length of the growing season Although tuberinitiation was not recorded accurately it is un-likely to have occurred before mid-April in any
variety and therefore a total bulking period of nomore than 8 weeks produced an average rate of4-5 thaweek Rate of bulking may have beenrelated to the size of the leaf surface since the twovarieties with the smallest leaf areas (Home Guardand Desiree) had the lowest rates of bulking
As in Expt 1 Arran Comet produced the highestyields throughout the period of harvesting In con-trast Maris Bard (CC) approached the yield ofArran Comet only at the final harvest and was notsignificantly different from the maincrops
Experiment 3 (1979)There were large differences between varieties in
all aspects of sprout growth (Table 8) Arran Cometand Home Guard produced only one or two sproutsof greater length than other varieties There werefew differences between the remaining varietiesexcept that Draga had very short sprouts Emerg-ence did not seem to be determined by sproutlength at planting as Pentland Javelin and F4611were the first varieties to complete emergence andHome Guard was especially slow This delay inemergence in Home Guard (and Arran Comet) wasassociated with coiled sprouts and in Home Guardsome plants failed to emerge owing to little potatodisorder
There were considerable differences between thevarieties in number of above-ground stems and inthe composition of this population (Table 8) Pri-mura and F4611 produced the most above-groundstems but in the former most were secondary stemsand in the latter main stems Only Home Guardfailed to produce a leaf area index of 3 (Table 9)and the largest peak L values were produced byPrimura (early) and Draga (maincrop) Thesepeak values occurred at different times Primuraproduced its leaf surface very rapidly and its Lexceeded 4 in mid-June Draga was much later inproducing its leaf area and reached its peak in JulyAll varieties decreased in leaf area in the later partof July as a consequence of increasing moisturestress in a prolonged period of dry sunny weatherPrimura and Pentland Javelin were close to com-plete senescence by the end of July while Spuntaand Renova lost relatively little leaf area at thistime
At the first and second harvests Primura andthe four British earlies produced the highest totalyields and most were significantly higher than theother Dutch varieties (Table 10) At the thirdharvest Primura was the highest-yielding varietyand significantly better than all varieties exceptF4611 Pentland Javelin and Renova Betweenthe third and fourth harvests four varieties bulkedlittle (Juliver F4611 Arran Comet and PentlandJavelin) and at the final harvest Primura was still
15-2
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
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Tab
le 1
0 T
uber
yie
lds
(th
a)
Exp
t 3
Tot
al y
ield
Yie
ld gt
25
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
38
mm
Len
gth
of l
onge
stsp
rout
(mm
)T
otal
spr
out
leng
th(m
m)
No
of
spro
uts
gt 3
mm
Dat
eof
sam
plin
g
21 v
i21
vi
3 v
ii
3 v
ii
16 v
ii
16 v
ii
31 v
ii
31 v
ii
Pri
mur
a
7-9
19-3
3-2
79 79 79
79
79
79
79
79
Pri
mur
a
10- 7- 31-
28-
45-
43-
49-
44-
Juliv
er
4-8
15-9
30
2 7 7 9 2 7 8 3
Juliv
er
Spun
ta
Ren
ova
7 5- 23 21 35 33 35 32
2 bull7 1 bull4 0 9 bull5 bull4
Tab
le 1
1
Spun
ta
16
0
30-8
2-7
71
50
25-4
22
1
37-6
35-5
45-4
39
1
7-8
5-7
22-3
20-3
42-6
41-4
48
043
-8
Spro
ut
grow
th p
er t
uber
1
Dra
ga
2-2
11
14-6
12
-5
31-4
30-5
41
13
90
[3 i
ii
80)
Mar
iaA
min
ca
Ren
ova
Dra
ga
Bar
d
16-9
10
-2
25-6
16
-4
21
1-9
2-7
6-3
0-9
15
1
23-6 2-3
Hom
eG
uard
11-5
10-6
26-5
24-9
35-4
33-5
40-2
36
0
Exp
t 4 Arr
anC
omet
18-3
27-1 1-7
Arr
an
Pen
tlan
dC
omet
Ja
veli
n
10-3 98
28-8
27-8
36-9
36-4
39-7
37
1 Pen
tlan
dJa
veli
n
10-3
19-6 2-7
13-9
12-8
31-7
29-9
41
040
-1
40-8
36
0
IF
46
11
11-5
28
1
3-7
F46
11
10 9 28
27
419 9 6 bull0 2
40-3
41 37bull0 bull8
Wil
ja
10-7
21-6 2-6
SE
1 1 1 1 1 1 2 1bull02
bull15
bull72
bull75
bull87
bull93
bull02
bull97
SE
0-92
1-38
0-22
bull t1
Q e i gtbull o a CO
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Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
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Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
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Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
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458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Tab
le 1
2
Tub
er y
ield
s t
ha)
and
num
ber
of
tube
rs (
OO
Os
ha)
Exp
t 4
To
tal
yie
ld18
v
i 8
0Y
ield
gt
2
5 m
m18
v
i 8
0
To
tal
yie
ld27
v
i 8
0Y
ield
gt
32
mm
27
vi
80
To
tal
yie
ld8
vii
80
Yie
ld
gt
32 m
m8
vii
80
To
tal
yie
ld28
v
ii
80Y
ield
gt
32
mm
28
vii
80
Nu
mb
er o
f tu
ber
s18
v
i 8
0
Pri
mu
ra
Juli
ver
S
pu
nta
A
min
ca
Ren
ov
a
20-7
19
-8
23-9
26
-3
24-3
19-9
27-5
26-2
35-1
33-9
40-3
39-3
655
19-2
25-4
24-6
35
0
34-3
44-4
43-6
558
22-6
31
1
29
1
38-7
36-8
45-7
43-8
710
25-3
31-4
29-7
42
0
40-6
49-8
48-6
739
23-3
31-6
30-2
43-9
42-7
58-1
57-0
676
Dra
ga
9-6
8-3
15-3
13-7
29-3
28-4
47-2
46-7
510
Mar
iaB
ard
24-9
24
0
31
0
30
0
43-5
42-4
59-7
58-7
568
Arr
an
Pen
tlan
dC
omet
Ja
vel
in
F4
61
1
23
0
22-3
29
0
27-4
35-6
34-2
41-8
40-5
478
25-0
24-2
29-6
28-2
37-3
35-8
43-3
41-9
720
28-4
27-3
36-6
35-2
47
1
45-8
59-9
59-2
781
Wil
ja
21-1
20-8
30-4
28-2
38-5
37
0
46-7
45-3
628
SE
1-27
1-23
1-52
1-56
2-31
2-24
2-59
2-57
55
0I S
Tab
le 1
3
Spro
ut g
row
th p
er t
uber
on
29
Feb
ruar
y 19
80 a
nd
num
ber
of
emer
ged
plan
ts
(00
0sh
a)
Exp
t 5
Len
gth
of lo
nges
t sp
rout
(m
m)
Tot
al s
prou
t le
ngth
(m
m)
No
of
spro
uts
gt 3
mm
Num
ber
of e
mer
ged
plan
ts 2
1 i
v 8
0N
umbe
r of
em
erge
d pl
ants
24
iv 8
0
Arr
anC
omet
10
130
-3 4-2
62-3
64-5
Hom
eG
uard
15-8
33
13
059
-263
-6
Mar
iaB
ard
6-8
23
14-
554
-863
-6
Red
Cra
igs
Ro
yal
7-2
20-2 3-6
3-5
12-3
Wil
ja
Est
ima
5-3
14-4 2-9
16-7
43-4
4-7
14
03
026
-839
-5
Mar
isP
iper
8-3
22-5 3-6
57-8
62-3
Pen
tlan
dS
quir
e
10
124
-4 3-7
51-3
55-7
Des
iree
12-2
19-6 2-3
54-0
62-3
SE
0-22
1-07
0-22
4-82
4-34
CO
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Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
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456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Tab
le 1
4 T
uber
yie
lds
(th
a) a
nd n
umbe
r of
tub
ers
(O
OO
sha
) E
xpt
5
Tot
al y
ield
24
vi 8
0Y
ield
gt
32
mm
24 v
i 8
0T
otal
yie
ld8
vii
80
Yie
ld gt
32
mm
8 v
ii 8
0T
otal
yie
ld22
vii
80
Yie
ld gt
32
mm
22 v
ii 8
0N
umbe
r of
tub
ers
24
vi 8
0
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Tot
al y
ield
Yie
ld gt
32
mm
Arr
anC
omet
18-7
13-6
25-6
20-8
29-2
24-9
85
6
Num
ber
of t
ub
ers
Dat
e
Hom
eG
uard
11
1
7-4
15-7
13
0
20-9
18-0
632 Tab
le
ofsa
mpl
ing
8 8 22
22
6 6
22
vi
vi
vi
vi
vii vii
vi
81 81 81 81 81
81
81
Mar
isB
ard
20-3
15-3
31-4
28-2
39-6
36-3
817
15
Tub
er
Est
ima
16-5
13-6
22-3
20-7
29-3
27-9
548
Red
Cra
igs
Roy
al
17-8
12
1
23-3
21-3
32-6
30-8
61
7
yiel
ds (
tha
)
Wil
ja
12-8
4-5
18-3
15
0
21-3
17-4
625
Wil
ja
18-1
14-5
27-2
24-8
35-9
33-9
339
and
num
ber
Mar
isB
ard
14-9 8-9
18-0
14-8
21-2
17-8
669
Est
ima
21-6
18-3
36
1
33-9
47-6
46-3
624
Mar
isP
iper
20-0
15-2
32
1
29
1
41-2
38-7
896
of t
uber
s (
000s
ha)
E
xpt
Van
essa
12-7 9-6
21-5
20-4
21-0
19-5
435
Uls
ter
Scep
tre
11-3 6-5
13-9
11-3
15-3
12-2
529
Pen
tlan
dS
quir
e
18
1
16-3
27-7
25-8
37-4
36
1
501
6 Fox
ton
8-6
01
16-7
10
1
18-9
11-9
919
Des
iree
15-9
12-2
26-4
24-5
32-8
31-3
537
Rec
ord
6-7
2-8
13-6
12-2
17-9
16-4
500
s 0- 0- 1- 1- 1- 2- 52-
SE
0-83
0-73
1-22
1-33
1-42
1-46
30
1
B
66 65 45 55 94 08 4
t1 t OTHE
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Growth of contrasting potato varieties 455
gt gtmdash copy -H -H copy - I
oH
the highest-yielding variety although not signifi-cantly higher than Renova and Spunta
Primura had more tubers than most varietiesand the ranking order of varieties for graded yieldswas not the same as for total yields The fourBritish earlies produced similar yields in the gradegt 32 mm at the first harvest and all significantlyout-yielded other varieties (Table 10) AlthoughDraga was significantly lower yielding than othervarieties at the second and third harvests therewere few other significant differences betweenvarieties At the final harvest Primura producedthe highest graded yields and as in total yieldsRenova and Spunta were not significantly different
In this experiment the variety with the highesttotal yield again remained constant throughout(Primura) although the ranking of varieties forsaleable yields was more variable than in Expts 1and 2 Arran Comet produced high early yields butwas not outstanding and no higher yielding thanHome Guard throughout the rest of the season Itsyield relative to most other varieties decreasedwith delay in harvesting and was modest by finalharvest
Experiment 4 (1980)Table 11 shows that sprouts were shorter than in
Expt 3 but the relative values of varieties commonto both experiments were unchanged Arran Comethad much shorter sprouts than in Expt 3 F4611produced the highest total yield at all harvests andwas significantly higher yielding than most varie-ties (Table 12) The ranking order of varieties foryield did not change much during the seasonRenova Aminca and Maris Bard were the closestto F4611 throughout and at the final harvestdifferences between F4611 Renova and MarisBard were small Arran Comet produced signifi-cantly lower yields than F4611 at the first harvestand its yields decreased relative to other varietiesduring the season Draga had very low yieldsthroughout
Experiment 5 (1980)The reduced storage temperatures for the early
varieties reduced their sprout lengths comparedwith previous experiments and only Home Guardproduced substantially longer sprouts than themaincrop varieties (Table 13) The maincrop varie-ties emerged as early as the earlies and several daysin advance of Wilja and Estima The emergence ofRed Craigs Royal was severely delayed by coiledsprouts Final emergence was complete in all varie-ties Despite its slightly later emergence Estimaproduced the highest yields throughout the seasonand differences were significant for all comparisonsat the second and third harvests Maris Piper (main-crop) and Maris Bard (early) produced similar yields
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
456 R L GRIFFITH AND OTHERS
throughout ranked second to Estima and weresignificantly higher yielding than all other varieties(Table 14) The other maincrops were significantlyhigher yielding than Home Guard throughout Therelative yield of Home Guard and Arran Cometdecreased as harvesting was delayed and HomeGuard was the lowest-yielding variety throughoutthe season
Experiment 6 (1981)As in Expt 5 Estima produced the highest total
and saleable yields at all dates of harvesting(Table 15) Differences between other early varie-ties were small although Maris Bard was again thesecond highest yielding at the first harvest Thetwo maincrop varieties were very low yieldinginitially but at the final harvest not significantlylower yielding than any variety except Estima
DISCUSSION
The experiments covered five seasons with a widerange of yields and may be taken as a small butrepresentative sample of the environments in whichcrops are grown for harvesting before the end ofJuly The coefficients of variation (Table 16) wereof similar size as those reported in many otherexperiments and only large differences achieve theusual levels of significance In spite of this it ispossible to detect some remarkable variations indifferences between specific varieties at the differ-ent sites and at the different times of harvestingwithin a site Of the varieties present in mostexperiments Arran Comet ranged from clearly thehighest yielding (Expts 1 and 2) through themoderate (Expts 3 and 4) to the low yielding (Expt5) Its yields in Expts 3-5 decreased relative to theother varieties as harvesting was delayed Therewere however some consistent features in thedata In all experiments the variety with thehighest initial yield maintained its position through-out although the magnitude of the advantageusually decreased with delay in harvesting InExpts 4 and 5 the final harvest was in late July andat this time the highest-yielding varieties had largeleaf surfaces and high bulking rates so it 3eems un-likely that they would lose their advantage muchbefore the end of the growing season The resultssuggest that in general high early yields are notprejudicial to high yields later in the season Theimpression that high early yields are prejudicial tolater yields is the consequence of experimentsusing early varieties such as Home Guard in whichold seed is planted and its inadequate leaf coverreduces bulking rates and yields later in the season
When assessing the differences in effects of treat-ments such as varieties shown by individual experi-ments there is usually confounding of the physical
characteristics of the site seasonal weather andvarious aspects of source and management of theseed Nonetheless consideration of the three earlyvarieties Arran Comet Home Guard and MarisBard which were in most experiments providessome evidence of how these factors interact AtTrefin Arran Comet produced a growth patternwhich was almost ideal for producing high earlytuber yields This was the earliest environmentand although planting was early emergence occur-red quickly as a consequence of long sprouts andsufficiently high soil temperatures The advantagesof using old seed for rapid emergence were noteroded by any subsequent disadvantages in size orlongevity of the leaf surface This growth patternwould ensure the superiority of yields of ArranComet for the whole of the harvesting period Incontrast at Trefloyne and Brancaster in sub-sequent years Arran Comet produced more modestyields At Trefloyne the seed was physiologicallyolder mainly as a consequence of later planting andemergence was delayed as a consequence of coiledsprouts and Arran Comet was lower yielding thanseveral varieties throughout harvesting At Bran-caster quite young seed was similarly affected bycoiled sprouts and emergence was also delayed andyields poor Temperatures after planting weresometimes lower at these sites than at Trefin(Fig 1) and soil conditions rather cloddier on theheavier soils at Trefloyne Of greater significance forNorfolk in 1981 was the period of low temperature(mean soil temperature at 10cm 3-1 degC for 2 days)shortly after planting and the period of cold frostyweather in late April (mean soil temperature at10 cm 4-3 degC for 5 days) just as emergence was be-ginning The available temperature data are notextensive but suggest that small differences in meansoil temperature (1 or 2 degC) may markedly affectemergence and subsequent growth of some potatovarieties In such conditions the potential advan-tages of increased physiological age can be negatedby delay in emergence Arran Comet always pro-duced a complete plant stand and a full leaf coverbut away from Trefin so did several other varietieswhich emerged more or as quickly Jones (1981)showed that the rate of post-planting sprout elonga-tion decreased above a certain sprout length insome varieties and in adverse circumstances (lowtemperature and poor soil conditions) this wasassociated with coiling of stems and little potatodisorder The Brancaster experiment shows that inArran Comet coiling of very short sprouts canoccur Similar more dramatic effects were foundin Home Guard Only at Trefin did this varietyyield nearly as much as the highest-yielding earlyand at this site the old seed emerged quickly andcompletely and produced a full leaf cover Howeverthe leaf area began to decrease in June and the
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
Growth of contrasting potato varieties 457yield of Home Guard decreased relative to the othervarieties as harvesting was delayed As in ArranComet the old seed of Home Guard at Trefloynedid not emerge quickly but additionally failed toproduce a complete plant stand Consequently leafarea indices were lower than on other varieties andyields were initially high but decreased relative toother varieties as harvesting was delayed Theseeffects were even more marked at Brancaster wheredespite using younger seed emergence was de-layed leaf area indices were low and yields werethe lowest at the first harvest and remained sothroughout the season
The results for Maris Bard illustrate the effectsof age directly The home-produced seed in Expt 2was too old and produced incomplete emergence ofsmall plants whilst the certified stock was physio-logically much younger and produced higher yieldsthough not significantly greater than some main-crop varieties In the previous year the Maris Bardseed was older than in Expt 2 and emerged quicklyand produced yields almost as high as Arran CometAt Trefloyne (Expt 4) and Brancaster seed ofgreater age than that planted in Expt 1 emergedquickly and produced high yields throughout as acomplete leaf cover was achieved
It seems clear that the maximum benefit of in-creasing age of seed in some early varieties can beobtained only in environments in which rapid andcomplete emergence occurs and a large leaf surfaceis produced Thus only environments such asTrefin with mild temperatures and light soils arelikely to grow old seed of Arran Comet and par-ticularly Home Guard successfully in most or allseasons At harsher sites the advanced age of seedis likely to be disadvantageous because coiledsprouts andor little potato disorder will delayemergence and reduce leaf cover and thereby re-duce tuber bulking As these varieties have only ashort dormant period considerable ageing of seedwill usually occur by planting In early varietieswith longer dormancies there will be considerablevariation in age (ie sprout length) by planting asa consequence of variation in temperatures andearly yields will usually increase with age as inMaris Bard in these experiments and others atTrefloyne (OBrien et al 1983) The temperaturesduring January and February are crucial to theage of such varieties for if they are low (lt 5 degC)little or no ageing will occur and seed will emergeslowly Such effects will also occur in maincropswhich do not usually have much sprout growth atplanting but which can clearly emerge and yield aswell as earlies at some sites Increasing the age of
seed of such varieties by increasing storage tempera-ture as in Expts 2 and 5 can improve their earlyyields considerably However this is still in-adequate for some varieties such as Record andFoxton which both produced poor early yields inExpt 6
The inference from this interpretation of theresults is that the yield estimates of varieties fromexperiments can be markedly affected by the ageof seed planted and the environmental conditionsafter planting These effects are however moreexplicable than hitherto accepted The consequencesof this analysis for the testing of varieties are thatthere is little justification for attempting an overallscore for earliness and the present maturity classi-fication is not necessarily a good guide to the useful-ness of varieties for specific environments andmanagement practices
For breeders the results suggest that there islittle justification in breeding for earliness throughvarieties which achieve advanced physiological ageby the time of planting since such seed may besuitable in only a minority of sites used for theearly crop The greatest opportunity exists forvarieties which have reasonably long dormantperiods (and consequently do not achieve advancedage before planting) but emerge and expand theirleaf surface more rapidly in the prevailing tempera-tures than existing varieties In this respect theobjectives of early and maincrop breeding are notreally different as illustrated by the success ofF4611 (maincrop x maincrop) in these experi-ments The major limitation to the use of main-crop varieties very early in the season is often theirpropensity to produce larger numbers of tubers butthe character can be altered through selectionConsidering all varieties sprout length at plantingwas not closely related to emergence as found byJones (1981) so there may be some prospect ofproducing varieties which achieve reasonably ad-vanced age with short sprouts and still emergerapidly Such varieties would be suited to mech-anical planting and allow commercial exploitationof the advantages of ageing
The authors thank the collaborating farmersMr I Davies Park Court Trefin Dyfed and Greensof Soham Soham Cambs for the provision of sitesand help in carrying out the experiments and MissJ Amies for help in preparing the manuscript Theseed of the Dutch varieties was supplied by Beesonamp Wiskar Ltd The first two experiments were partof a research programme funded by the PotatoMarketing Board
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available
458 R L GRIFFITH AND OTHERS
REFERENCESALLEN E J (1977) Effects of date of planting on
growth and yield of contrasting potato varieties inPembrokeshire Journal of Agricultural Science Cam-bridge 89 711-735
GUNASENA H P M amp HARRIS P M (1971) The effectof CCC nitrogen and potassium on the growth andyield of two varieties of potatoes Journal of Agricul-tural Science Cambridge 76 33-52
JONES J L (1981) Effect of date of planting on con-trasting potato varieties PhD thesis UniversityCollege of Wales Aberystwyth
OBRIEN P J amp ALLEN E J (1981) The concept andmeasurement of physiological age Proceedings of the
Sth Triennial Conference of the European Associationfor Potato Research Munich pp 64-66
OBRIEN P J ALLEN E J BEAN J N GRIFFITHR L JONES SUSAN A amp JONES J L (1983)Accumulated day-degrees as a measure of physio-logical age and the relationships with growth andyield in early potato varieties Journal of AgriculturalScience Cambridge 101 113-131
RUDEFORTH C C amp BRADLEY R U (1972) Soils landclassification and land use in West and Central WalesSpecial Soil Survey No 6 Soil Survey Rothamsted
SOIL SURVEY RECORD No 24 (1974) 1 Soils in Dyfed II(PembrokeHaverfordwest)
at httpwwwcambridgeorgcoreterms httpdxdoiorg101017S0021859600047420Downloaded from httpwwwcambridgeorgcore Faculty of Classics University of Cambridge on 24 Nov 2016 at 154851 subject to the Cambridge Core terms of use available