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Transcript of ATTONAL TRIALS - International Sunflower...
GENETIC RESEMBLANCE
A. V. VRÂNCEANU and F. M. STOENESCUResearch Institute for Cereals and IndustrialCrops, 8264 Fundulea, Romania
INTRODUCTION
Genetic diversity is considered one of themost important factor securing crop stabiiity.A large genetic diversity would reduce theyield fluctuation in a certain area because dif-ferent genotypes react differently to the envi-ronmental variation. Also, it is well known thatthe appearance and spreading of the new,more virulent races of the pests are positivelycorrelated with the area occupied by the cor-responding genes for resistance.
A greater genetic diversity at territorial Ie-vel may be achieved in sunflower by meansof a higher number of different hybrids butthe numbey per se does not constitute an ade-quate solution, taking into account that certainhybrids could be genetically related and thecultivation of more alike genotypes may beequivalent to the extension of a single one.
Presently sunflower breeders seeking yieldimprovement are generally faced with a rela-tive vast array of potential parent genotypesamong which only a limited number of crossescan be made in order to obtain new valuableinitial breeding material. The choice is usuallybased on a combination of yield data, visualassessment of agronomic characteristics andpest resistance, and very seldom the pedigreeknowledge. Genetic investigations based onlestcrosses are costly and so quite rare. It is gene-rally assumed that maximum improvement ofthe initial material can be obtained from cros-ses which release the maximum amount ofvariations between parents which are geneti-cally diverse.
From this point of view, our attempts toevaluate the genetic relationship among hy-brids, which constitute the aim of this paper,could be of a certain usefulness.
MATERIALS AND METHODS
Thc identification of the genotype structuresfitting properly the ecological conditions ofdifferent regions has been one of the mainpurposes of the F.A.O. Research Network onSunflower. All sunflower eultivars tested since
OF SUNT'I.,OWER CT]LTIYARS TESTEI)11\ INTBR]\ATTONAL TRIALS
the Network's establishment have representedthe latest achievements of the main sunflowerbreeding centres from all over the world(Annex 1). Trials have been conducted with101 Fl hybrids and 13 open pollinated varie-ties (OPV) in four biennial cycles, startingfrom 1976, under a wide range of environmentsfrom Europe, Near and Middle East, Africa,Latin America and U.S.A. and their resultswere published in the Information BulletinHELIA, numbers I, 2, 3, 5 and 7.
The estimation of the relationship degree ofsunflower cultivars on genealogy basis requiresthe knowledge of parental genetic origin, whichis not always accessible. Such an approach hasalso the inconvenience that divergent inbredscould be often selected from the same sourcematerial, while similar ones mav arise fromdistinct origins.
The genetic resemblance estimation on thebasis of common allele percentage is also diffi-cult and relative for this study, because thenumber of the identified genes in sunflower isstill small and the existence of their alleles inthe tested genotypes has been only approxi-mately investigated.
A more complete assessment of the geneticresemblance has been done for some groups ofcereal cultivars, on the basis of their vield res-ponse to a large range of environments.. {ohnson (1977), working with corn hy-brids, elaborated a model which providêsweighted estimates of hybrid means, coeffi-cients of the regression of each hybrid on anenvironmental index and coefficients of ther:egression of each hybrid on a set of ortho-gonal residu,al vectors. Genotypic similaritywas defined as the euclidian distance betweengenotypes in the space whose coordinate axeswere the locations. A claster analysis arrangedthe hybrids into groups that were differeniia-ble in terms of means and stabilitv.
Habgood (19?7) proposed a method ofestimating the genetic diversity of self-fertili-zing cereal cultivars based on genotype-envi-ronment interactions. The degree of similarityor diversity between each pair of genotypes inan array is estimated by the correlation over
Sunflower cultivars tested intrials in the period
Supplyingcountry
Argentina(Continental)
Bulgaria(GeneralToshevo)
France(INRA)
Hungary(Iregszemcse
andSzeged)
Italy
Poland(Poznan)
Romania(Fundulea)
Spain(INTA)
Biennialcycles
1980-1981
1976-1977
1978-19?9
1982-1983
1976-1977
1978-1979
1980-1981
1982-1983
1978-1979
1980-1981
1982-1983
1978-19?9
1980-1981
1982-1983
1978-1979
1980-1981
1976-19?7
1976-1977
1978-1979
1980-1981
1982-1983
1976-197?
1978-19?9
1980-1981
10
Annex I
the F.A.O. internationalof 19?6-1983
Cultivars (SH:single hybrids,'IH:three-way hybrids,
)PV:open pollinated varieties)
Contiflor (SH)
Helios 322 (SH)
Hemus (OPV), HB-451(SH), Peredovik (OPV)
HB-?83 (SH)
Airelle (SH), Relax (SH),Remil (SH) Issanka (OPV)
Remil (SH), Luciole (SH),rNRA-7702 (SH)
Primasol (SH)
H9P1(SH),H9P2(TH),H9P4(1H)Sorex (SH), Olga II (SH)
H-27-77 (SH), Marika (SH),Vera r(SH)
G 9-76 (SH), G 19-?7G 24-77 (SH)
IH-10 (OPV), Iregi(OPV), Iregi Csikôs
Gahib 6 (SH)
(SH),
816 B(oPv)
HNK-81 (SH), HNK-84(SH), Koflor 1 (SH), IH-56(SH), IH-155 (SH), Gahib ?(SH), Citosol 2 (SH), Cito-sol 3 i(SH)
Argentario (OPV)
Ala (OPV)lffielkopolski (OPV)
Romsun 52 ,(SH), Romsun53 (SH), Romsun 59 (SH),Sorem B0 (SH), Sorem Bz(SH), Sorem HT-64 (TH)RO-18 (SH), RO-20 (SH),Romsun 301 (SH).
Record (OPV), Romsun 59(SH), Sorem HT-111 (TH),Sorem HT-116 (TH), So-rem HT-117 (TH), Romsun90 (sH).
RO-18 (SH), RO-19 (SH),RO-33 (SH), RO-26 (SH),RO-27 (TH), RO-34 (SH),RO-29 (TH), RO-40 (SH),RO-45 (SH), RO-46 (SH),Ro-loo (SH), RO-130 (SH)
RO-25 (SH), RO-36 (SH),RO-70 (SH), RO-44 (SH),RO-131 (SH), RO-134 (SH),RO-141 (TH), RO-150 (SH)
H-23 (SH)
Sepasol (OPV), HS-1161(sH), HS-72 M (SH)
Halcon (SH), Pinzon (SH),sH-s-690 (sH), sH-3000x2(HT), SH-72 MX1161(HT)
U.S.A.
Yugoslavia(Novi Sad)
P.O.I. 301 A(sH), H-2413BO A (SH)
H-894Sungro
Sunbred 265 (SH), Interst.77?5 (SH), DO-704 (SH)
Sunbred 254 (SH), Cargill205 (SH), Seedtec S-315(SH), Stauffer 3101 (SH)
YU-NS-65 (SH), YU-NS-I(SH)
Novi Sad 20 (OPV), NoviSad 61 (OPV), VNIIMK8931 (OPV), NS-H-27 (SH),NS-H-34 (SH), NS-H-63RM (SH)
NS-H-10 (SH), NS-H-l1(sH), NS-H-13 (SH), NS-H-17 (SH), NS-H-33 (SH),NS-H-36 (SH),
NS-H.3 (SH), NS-H-4 (SH),NS-H-5 (SH), NS-H-40(sH), NS-H-42 (SH), NS-H-43 (SH).
a range of environments of their respectivedeviations from the mean yield of aII genoty-pes in each environment.
Sàulescu et 41. (1981) used the coeffi-cient of correlation (r) and the coefficient ofdetermination (r2) between the yields of eachcultivar pair in two large sets of winter wheatyield tests. The coefficient of correlation hasthe advantage of indicating directly the pairsof genotypes with the highest yield stability.It is known that the mean variance of twovariables depends not only on the variance ofeach of them but also on the magnitude of thecoéfficient of correlation between them :
' s,f"+I]:ls1*ls?.1-l'.S* Sv. so, ast2l4."^4*r2
"rrr.U", than 1 is the correlation coefficient (r)
between the yields of two cultivars, the betteris compensated their yield variation in diffe-rent environments and the variance of the ave-rage yields is smaller.
In the present paper, the genetic resem-blance of sunflower cultivars was estimatedin accordance \Mith their seed yields in diffe-rent years and locations, using the square-ofthe càrlelation coefficients between seed yieldsof each pair of cultivars, i.e. the coefficient ofdetermination (12'100), which can be conside-red a weighted estimation for the percentageof identical alleles for aII genes controlling theyield in the given set of environments." Three replications of each trial were usedin calculatiôn and the assessment of the sig-nificance of differences between correlationcoefficients and further between the coeffi-cients of determination lvvas performed by
computing the value, Z: : 1 n (lfr) - t n
(1-r), where 1 n is the na-tural logarithm andr the correlation coefficient.
1978-1979
1980-1981
1982-1983
1976-197?
1978-1979
1980-1981
1982-1983
RESULTS AND DISCUSSION
Data from Tables 1 to B give the coefficientsof determination (12.100) calculated for eachof the eight biennial trials conducted co-ope-ratively in the seasons 1976_1977, lgTB-1g?g,1980-1981 and 1982-1983. Taking into ac-count the similarities in seed yields of eachpair of cultivars under various environmentalconditions (16-41 locations), one could observea large amplitude of the estimations of geneticresemblance, going from 8-84% in the firstbiennial cycle to 52-gï0lo in the fourth bien-nial cycle.
Both similar responses and therefore a grea-ter genetic resemblance and uncorrelated res-ponses and therefore great genetic differencesamong the pairs of cultivars can be establis-hed. An important number of cultivars fallsinto an intermediate group of a less strikingresemblance.
It should be noted that almost all values ofthe coefficients of determination were signi-ficantly different from 100, meaning that anypair of cultivars will give more stable averageyields than each cultivar taken individually.
Diagram representation of the coefficients ofdetermination, in which their magnitude isconventionally marked by the thickness of thelines, allows to obtain a better image of thegenetic relationships among the cultivars tested(Figures 1 to B). Values of the coefficients ofdetermination less than 7b were considered asindicating uncorrelated responses and there-fore more or less distinct genotypes.
Helros 3 2 2Sorpm HT- 64
Sorem 82 o' r Airetle
R0-59 o
R0-s3R0-52
lssonkoa
Romsun 301 ?-_ Wietkopolski
i
R0-?0i/
YU- NS -1
oR0-18
Geretic simitority:
tovt ('/5 <r.2, 100<gO)
Fig. 2 - Diagram representation of genetic relation_ship of sunflorver cultivars from Trial No. 2, 19?6-19??
NS-61
Argenlorio
Gerntic simitority:
low (75<rZ . 100<80)
-
rædrum ^(01 a 72 . rcg < g5J, high (r2 . loo > 86t --r
F-iq. 3 -- Diagram representation of genetic relation-ship of sunflower open pollinated varieties from Trial
No. 1, 1978-19?9
Surgro380 A
H-2t a
H-094
Fig. 4 - Diagramship of sunflower
HS-1161CrerPiic sinrilority,
..-.--.-,-- low (75 < f2 . ilo< 80]
-,
medium {81< f 2 100 < 85}
-
high ( 12. 100>86)
representation of genetic relation-hybrids from Trial No. 1. 19?8-19?9
Genefic simitorify,
___-_..--._ low (75<r2 100<g0l._--.-- medrum (81 <12.100<B5l
Fig. 1 - Diagram representation of genetic relation-ship of sunflower hybrids from Trial No. 1, 19?6-19??
HB -1s1
R0- 22:"'-------:i;*o./-\" NS-H-13
R0-26 1t:::-'!""--'--'
R0-34
NS-H-10 iNS - r1-17
oerntic similoriiy:
--..------. low (?S < f2, 100 <90 )
-
medium (81 <r'. 100<85)
-
hrgh (1. 100>86)
îig, 5 - Diagram representation of genetic relation-ship of sunflower cultivars from Trial No. 1' 1980-1981
d 265
NS-H-36
lnierst 77?5
R0-46m'701+
-sH-3000 x2
'1161 6enetic simitority:_ f;ilïî,,i;d3;'l*."'îig, 6 * Diagram representation of genetfc relation-ship of sunflower hybrids from Trial No. 2, 1980-1981
A similar response and 'therefore a greatergenetic resemblance showed the following pairsand groups of cultivars :
Trial No. 1 (19?6-19?7) :
YU-NS-65/Relax, Romsun 52lRomsun 53, Rom-sun 53/Sorem HT-64 (Table 1).
Trial No. 2 (1976-7977) :
YU-NS-1/H-23, Wielkopolski/RO-30 (labie 2).
Trial No. 1 (i978-1979) :
Argentario/Sepasol/Record, NS-61/Peredovik/Argentario, NS-2O/Argentario/Sepasol (Table 3).
Trial No. 2 (1978-1979) :
H-894/Romsun 90/NS-H-63/HS-1161/P.O.I. 301
A, Sorex/Olga II, Sorem HT-l1?/Sorem HT-l16/HB-451, NS-H-34/Sungro-80 A (table 4).
Trial No. 1 (1980-1981) :
Citosot
Genetk simltority:
- rnedium^(80<r2' t00<85)
- high (rz 100>861
Fig,7 - Diagram representation of genetic relation-ship of sunflower hybrids from Trial No. 1, 1982-1983
NS-H-Il
NS.H.3
Stouffer 3101
Seedtec S-31
Corgill
HNK- 81
citosot 2
6enetic srmitoritY'
- ffiiïpl,'&ïl;i*'u''
Fig. I - Diagram representation of genetic relation-ship of sunflower hybrids from Trial No. 2' 1982-1983
Marika/Ver a/RO-27 / Ala/}J-27 -7 7, NS-H-I 0/NS-H-1?, NS-H-11/RO-34, RO-22/ALa/RO-19, RO-26lPrimasol, RO-18/RO-26 (Table 5).Trial No. 2 (1980-1981) :
IH-10/Iregi 816 B/Halcon/Gahib 6, HaIcon/SH-3000 X 2/Pinzon/SH-?2 M X 1161/SH-S-690/RO-l 30/Do-704/Interst. 7775, Sunbred 265/Pin'zon/DO-704/Interst. 7775, RO-46/SH-3 000 X 2'RO-29/SH-S-690 (Table 6).Trial No. 1 (1982-1983) :
H9-P2/KofIor 1/NS-H-4/NS-H-5/HNK-81, G9-76lGr\-77 /HNK-81/HNK-84, RO-36/G19-77 /G24-77, NS-H-3/CitosoI 3/Koflor l/NS-H-4/NS-H-5, RO-25/HNK-84 (Tab1e ?).Triai No. 2 (1982-1988) :
H I P 4/NS-H-42/NS-H-40/Cargill 205/Sunbred254lCitosol 2, IH-56/CargiII 205/Gahib 7, HB-783/Seedtec S-315/Gahib 7, Seedtec S-315/IH-155 (Table B).
R0-29 . R0-40
R0-150 R0- 141
Toble 1
Éstimation of genetic resemblance (r2.100) among 11 sunflower medium-late hybrids (F.A.O. Trial
Cultivars(rt
1. Helios 322
2. YU-NS-653. Airelle4. Relax5. Remil6. Romsun 52
7. Romsun 53
B. Romsun 59
9. Sorem B0
1.0. Sorem 82
11. Sorem HT-64
47
100
63
16
100
^a
B4
36
100
15
42
15
)l
60
100
62
49
49
57
44
4B
57
100
33
78
11
79
7B
59
76
53
100
37
50
15
39
55
56
67
47
100
33
I69
61
54
83
76
60
100
35
66
15
6B
64
82
100
Table 2
Estimation of genetic resemblance (12'100) among7 sunflower early cultivars (F.A.O. Trial No. 2,
L.S.D. 0.05:9
19?6-19??, 23 locations)
cultivârs(oPv+Fd 1 , 4 7
1. Issanka
2. Wielkopolski
3. YU-NS-1
4. H-23
5. RO-18
6. RO-20
7. Romsun 301
100 53
100
36
61
100
28
69
B6
100
52
63
66
66
100
5B
B4
72
65
62
100
68
79
70
73
66
80
100
A general look over the diagrams of geneticrelationships permits to appreciate that the ge-netic diversity of the present sunflower hy-brids is quite limited and has even decreasedin the last trials, indicating thai many hybridsmay have one inbred line in common or theirparents could originate from the same or simi-lar sources of germplasm such as high oil vari-eties or closely related pollen fertility restorers.
Making a connection between the correla-tions presented in this study and {ata on mor-pho-physiological traits of the respective sun-flower cultivars published in HELIA, numbers\,2,3,5 and 7, one can observe that, contraryto expectation the similitude of reaction toenvironment was not always gre4ter betweengenotypes with similar maturity and plantheight, suggesting that other iharacterlsticscould play an equal important role in the res-ponse of sunflower cultivars to the variationsof soil and climate factors.
Table S
Estimation of genetic resemblance(r2.100)among 11 sunflower open potlinated yarieties (F.A.O.
No. I, 19?6-19??, l9 locations)
Trial No I, 19?8-19?9, 38 locations)
Cultivars(oPv) 2 t I o 10 11
1. Peredovik2. Hemus
3. IH-104. Iregi 816 B
5. Iregi Csik6s6. Argentario7. RecordB. Sepasol
9. Novi Sad 20
10. Novi Sad 61
11. VNTIMK 8931
100 lt
100
72
69
100
76
67
7l100
63
60
6B
61
100
B4
di
'/D
66
67
100
B3
66
tl
63
66
B9
100
B5
60
7l65
60
BB
91
100
B4
63
65
64
63
B9
82
8B
100
B9
tt
53
4B
40
B9
BO
82
82
100
74
82
5B
47
66
74
76
76
'lD
77
100
I,.S.D. 0.05:9
T3
19?8-1979, 41 locations)
Cultivars(l'1) I 4 5 ,l
B o 10 11 1' 15 16 L7 18 19
1. HB-4512. Remil3. Luciole4. INRA-7?025. Sorex6. Olga II7. Sorem HT-1l1B. Sorem HT-1169. Sorem HT-117
10. Romsun 9011. HS-116112. HS-?2 M13. P.O.I. 301 A14. H-89415. H-24116. Sirngro 380 A1?. NS-H-2718. NS.H.3419. NS-H-63 RM
100 66100
.IÔ
7B100
827069
100
657B7674
100
'/D
lalô?386
100
786665776767
100
807l63657T7072
100
B3706B76656963B4
100
7463647l4751157074
100
727l736854It47646678
100
74747l7356725970597781
100
73787866
75:t+7376667L72
100
7572727554525B74.IU
86817983
100
a^
5865
52644966736673616B66
100
?11 661 ool zr641 661 70l 63631 4el 631 66?Bl 6sl ztl zo37i| 47 | 50l 55551 531 431 514el 4Bl 4el 66641 60l 611 6?6el 70l 5el 6B
641 711751e2511 67174178b8l 68l ozl ze73l| 7r | 65 | 637rl 72 | ?6 | 8266 | T2 | 63.i 75
lool 711 831 68
1100 | 65 | 63| 11001 64
| | lloo
fable 4
Estlmation ol genetic resemblance 11b.fOÔ) âmong 1Ô sunflower meilium-iate hybrids (F.A.O. Trial No. 2,
L.S.D. 0.05:8
Table 5
Estimation of genetic resemblance (12.100) among 15 sunflower medium early cultivars (F.A.O. Trial No 1,
Cultlvars(F1+OPV)
1. RO-222. H-27-773. NS-H-134. Marika5. Vera6. NS-H-l?7. NS-H-1l8. PrimasolL RO-19
10. RO-2?11. Ala12. NS-H-1013. RO-3414. RO-2615. RO-18
4869
100
7g100
6179617966
76100
778755
100
B45B28tltti)t344L
100
4l7682505364BB7924614566
100
7L76777767B51269617L74
100
BBB4499088615B6490B6
100
79B45386B667626476
100
J'49594845484650456646645886
100
6277797l667672B5537B677Btt
100
Table 6
Estimation of genetic resemblance among l8 sunflower medium-late hybrids (F.A.O. Trial No. 2, 1980-1981'
1980-1981, 16 locations)
L.S.D. 0.05:?
741 49?61 77?61 B37Ll 64691 61
100 I 6e| 100
22 locatlons)
cultivars(F1) 1 3 4 o 6 B
q l0 ll 1' 13 14 IO 16117118
1. RO-292. RO-403. RO-1304. Sunbred 2655. NS-H-366. Interst. 7?757. DO-?048. NS-H-33L RO-100
10. sH-s-69011. SH-72 MX 116112. Pinzon13. sH-3000x214. RO-4615. RO-4516. Contiflor17. Gahib 618. Halcon
100 64100
7969
100
736279
100
7667867600
77698386B3
100
7966B5908692
100
5B66628261797S
100
67B4797678lt7674
100
8761B469828582627L
100
745882BO
8188B87l7L90
100
1976s2B6B5B89219BO
B1B4
100
7l7287BO
8B85BB778085B692
100
567l76597266675972626476B8
100
3B
5045564944567634355966
100
48l66l6B76170174?01541835Bl?Bl7e7218418568l72l8B68168186661741747715216870l78l84?21?61s87217618770l7elel63163180B4l4Bl51
1ool63l?1lloo I B6| 1100
L.S.D, 0.05:8
L4
îable Ihstimation of geneilc resemblance (r'.roo) among 15 meitlum-early hybrirls (F.a.ô. Trial No. t, toSz-t988,
L.S.D. 0.05:6
Estimation of genetic resemblance 6r.100) among 18 medium-late hybritts (F.A.O. TrialTable I
No. 2, 1982-1983,
36 locations)
Cultivars(F1) 1 2 4 6 I I 10 l1 t2 13
1.H9P12.}I9P23. G 9-76
4. G t9-77
5. G 24-77
6. HNK-817. HNK-84B. Koflor 1
9. Citosol 3
r0. Ro-2511. RO-36
12. RO-?0
13. NS-H-314. NS-H-415. NS-H-5
100 79
100 78
100
?0
81
ot
100
70
lc
B3
BB
100
7B
B5
86
85
79
100
79
75
85
B3
7B
8B
100
79
87
78
82
76
89
76
100
BO
B1
79
78
/b
81
74
BB
100
B1
tt
75
73
68
79
87aÀ
62
100
67
81
B3
92
92
79
75
7B
76
72
100
78175711 B0
761 81
rol 7s
?41 B0
rrl B0
trl 7e
761 88
,nlB76el ??
7sl B0
100 | 5e
| 100
"lBrrtl 85
rnl 75
81l7e80l 83
uul 87
B3l 83
871 86
url B3
rnl B1
821 81
661 70
85l 88
100 |
B6
| 100
39 locations)
CuItivârs(Fr) 1 , 3 4 7 B o l0 ll L2 l4 IO r7ll8
1. HB-783
2.Il9P 4
3. IH-564. IH-155
5. Gahib 7
6. Citosol 2
7. RO-448. RO-131
9. RO-134
10. RO-141
11. RO-150
12. Sunbred 254
13. Cargill 205
14. Seedtec 5-315
15. Stauffer 3101
16. NS-H-4017. NS-H-4218. NS-H-43
100 BO
100
B2
94
100
70
79
79
100
92
BO
91
67
100
75
91
90
74
76
00
62
B3
B5
d^
63
B1
100
BO
82
79
73
87
B3
BO
100
BO
B4
90
B3
90
B1
86
B5
100
7418083152801816e16776
l8777 l7B80176e3l8382
174100
| 77
| 100
82
s4
85
BO
B6
91
BO
97
B4
93
82
00
B5
90
B8
80
9B
94
B3
76
93
B2
80
86
100
92
B1
66
8B
90
74
B3
68
77
69
73
7S
90
100
73
B3
82
73
IL
93
BO
to
77
94
7l93
90
78
00
90
81
70
80
94
80
B3
81
91
7B
93
94
BO
92
00
7L 17787l83
?71867Ll7e7r
177B2lB07r
174Blls+7718383lB27017e7118078l6B?31?078174e2
l7s00167| 100
CONCLUSIONS
Although some groups of sunflower cultivarsdiffering genetically could be established fromthis study, the genetic diversity of the presentcultivated hybrids seems to be quite limitedto fit all environmental variations ànd to mini-mize the genetic vulnerability of sunflower
crops. The limiting factors are connected pri-marily with the utilization of the same type-of cytoplasmic male sterility, the genetic simi-larity of many of the female pàrents ôrigi-nating from high oil varieties and the reducédnumber of pollen fertility restorer lines.
In- order _to, enlarge the genetic diversity ofsunflower hybrids, breeders have to dev-elop
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sôurce-populations with various genetic back-ground:which would serve as selfing genepoolsand to'identify new c?zr.s and Rf sources frominterspecific crosses.
The ipignificant variability existing amongvarious pairs of hybrids from the standpointof the magnitude of the coefficients of deter-mination allows to choose those couples ofhybrids with the best reciprocal compensationof the yield variations and so to achieve anappropriate structure of hybrids which mightassure a better stability of high average yield1evels.
As it becomes apparent, beside high yieldingcapacity, sunflower hybrids should also be im-proved for their different reaction to the en-vironmental factors.
REFERENCES
H a b g o o d R. M., L977, Estimation of genetic d'ioer'sita of sel!-fertilizing cereal cultitsars based' onggnotgpe-èntsironment interactions, Euphytica,26,2, 485*489.
J o h n s o n G. R., 19?7, Analgsis of genotgpic simi-laritg in terms ol mean gield and stabilitg otenuironmental response in a set of maize hg-brids, Crop Sci., 17, 6, 837-842.
Sàulescu N. N., Tapu C., Ittu Gh., 1981, Ge-netic ilioersitg ol utinter wheat oarietal assort'ment cultitsoted at present in Rom'ania (in Ro-manian), Probleme de geneticà teoreticà çi apli-catà, XIII (2), 65-80.
LA SIMILITUDE GÉNÉTIQUE DES CULTIVARS DETOURNESOL EXPÉRIMENTES DANS LES ESSAIS
INTERNATIONAUX
Résumé
La similitude génétique de 101 hybrides et 13 cul-tivars de tournesol a été étudiée, ceux-ci étant testésdans le cadrg du Réseau de recherches de Ia F.A.O.pour le tqurnesol pendant 1976-1983, dans un grandnombre de tqcalités d'Europe et hors Europe. La si-militude génétique a été estimée en utilisant le carrédes coefffpients de corrélation entre les rendementsen graind$ de chaque paire de cultivars, c'est-à-direle coefficient de détermination (12.100). En considé-rant la similitude des rendements de chaque pairede cultivars en conditions très variées de milieu (16-41 localités), une large amplitude des coefficients dedétermination a été observée, allant de B à 9B%.
Bien que certaines groupes de cuitivars différantgénotypiquement peuvent être établies, la diversitégénétique des hybrides actuels de tournesol est assezlimitée, pour correspondre à toutes les variations dumilieu et pour réduire au minimum la vulnerabilitégénétique des .cultures de tournesol. Les facteurs limi-tatifs sont liés à l'utilisation du même type de sté-rilité mâle cytoplasmique, ainsi qu'à la similitudegénétique de beaucoup de formes parentales femelles,provenant des cultivars à teneur élevée d'huile et aunombre réduit de Iignées restauratrices de la ferti-lité du pollen.
Afin d'élargir la diversité génétique des hybridesde tournesol, il est nécessaire de créer des sources-populations à base génétique différente, pour servircomme matériel initiel pour l'autofécondation, et d'i-dentifier des nouvelles sources de stérilité mâle cyto-plasmique et de restauration de la fertilité du pollen,lors des croisements interspécifiques.
SEMEJANZA GENÉTICA DE LOS CULTIVARESDE GIRASOL TESTADOS EN LOS CULTIVOS
COMPARATIVOS INTERNACIONALES
Res{tmen
Se ha estudiado la semejanza genética de un nû-merp de 101 hibridos y 13 variedades de girasol testa-dos en la Red de investigaciones F.A.O. para elgirasol en el periodo 1976-1983 en gran nûmero delocalidades de Europa y fuera de Europa. La seme-janzâ genética fue estimada empleândose el cuadradode los coeficientes de correlaci6n entre las produccio-nes de semillas de cada pareja de cultivares, esto esel coeficiente de determinaci6n (r2.100). Tomando enconsideraciôn la similitud de las producciones de cadapareja de cultivares en condiciones variadas de me-dio, se nota una gran amplitud de los coeficientes dedeterminaci6n comprendida entre B y 98 por ciento.
A pesar de que se pueden establecer algunos gruposde cultivares que difieren genotipicamente, la diver-sidad genética de los hibridos actuales de girasol esbastante limitada para corresponder a todas la varia-ciones de medio y para minimalizar la vulnerabilidadgenétlca de los cultivos de girasol. Los factores limi-tativos estân relacionados al êmpleo de un mismotipo de androesterilidad citoplasmâtica, asi como a Iasimilitud genética de muchas formas parentales feme-las provinientes de las variedades con contenido ele-vado de aceite y del nrimero reducido de lineas res-tauradoras de la fertilidad del poleno.
Para ampliar la diversidad genética de los hibridosde girasol hace falta crearse fuentes-poblaciones conbase genética diferente que sirvan como. material ini-cial para autofecundaciôn y que identifiquen nuevasfuentas de androesterilidad citoplasmâtica y restaura-ci6n de la fertilidad del poleno dentro de los crucesinterspecificos.