Agrophisiology of TAS

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Europ. J. Agronomy 28 (2008) 526540

Agrophysiological characterisation and parametrisation ofAndean tubers: Potato (Solanum sp.), oca (Oxalis tuberosa),

isano (Tropaeolum tuberosum) and papalisa(Ullucus tuberosus)

Bruno Condori a,1, Pablo Mamani a,1, Ruben Botello a,1, Fernando Patino a,1,Andre Devaux b,2, Jean Francois Ledent c,

a

Fundacion Para la Promocion e Investigacion de Productos Andinos, Casilla 1079, La Paz, Boliviab Centro Internacional de la Papa, P.O. Box 1558, Lima 12, Peruc Unite dEcophysiologie et dAmelioration Vegetale, Universite Catholique de Louvain,

Croix du Sud, 2 bte 11, 1348 Louvain-la-Neuve, Belgium

Received 28 June 2007; received in revised form 8 December 2007; accepted 10 December 2007

Abstract

Bolivia is part of the eight most important centres of biodiversity and domestication of plants in the world, including a broad diversity of

Andean grains, roots and tubers. A study was implemented to obtain the quantitative information to develop and validate, a simple growth potential

model of Andean tubers in production areas located above 3000 m altitude, and to analyze the difference between species in growth attributes

and the resulting tuber production. Three potato species and sub-species (Solanum tuberosum ssp. andigenum and ssp. tuberosum, and Solanum

juzepczukii) as well as Oca (Oxalis tuberosa), Isano (Tropaeolum tuberosum) and Papalisa (Ullucus tuberosus) were studied. Trials were conducted

under normal field conditions prevailing in Bolivia but with the best cropping techniques available locally to obtain optimal growing conditions.Data on dry weight (of leaves, stems, tubers and roots) and leaf area were taken at several dates in five trials conducted between 1993 and 2003.

The percentage of ground cover was also measured. Beta functions were fitted to data of dry weight and leaf area to establish growth curves.

The potato groups have a smaller cycle duration than other Andean tubers. The Crop Growth Analysis indicated three important characteristics

differentiating Andean tubers: the S. juzepczukii potato has a high Relative Growth Rate (RGR) and a higher leaf mass ratio but a smaller tuber

yield, due to a smaller harvest index (HI) and a very low Net Assimilation Rate (NAR). S. tuberosum ssp. tuberosum potatoes have smaller Leaf

Area Index (LAI), and RGR than juzepczukii, but their NAR and HI are higher. S. tuberosum potatoes are quite productive for the size of their

LAI. The Tropaeolum tuberosum or Isano has a great capacity of Ground Cover (GC) or a great LAI that is not translated into a greater tubers

yield. It has low RGR, NAR and HI compared to all the other species studied. The crop growth was interpreted in Light Use Efficiency (LUE) and

evolution of light interception through a linear model. The LUE of potato group is more elevated than the LUE of the other Andean tubers. Within

each group there is no statistical difference for the LUE value. The relationship of LAI with GC or fraction of light interception was determined

with both linear and exponential relations. The low slope value for the relationship between LAI and GC characterises all Andean tubers studied

compared to results reported for potato under other latitudes.

2007 Elsevier B.V. All rights reserved.Keywords: Native potato; Andean tuber; Growth analysis; Light use efficiency

Corresponding author. Tel.: +32 10 47 34 58; fax: +32 10 47 20 21.

E-mail addresses: [email protected] (B. Condori),

[email protected] (P. Mamani), [email protected] (R. Botello),

[email protected] (F. Patino), [email protected] (A. Devaux),

[email protected](J.F. Ledent).1 Tel.: +591 22 141209.2 Tel.: +511 349 6017.

1. Introduction

Bolivia is part of the eight most important centres of biodiver-

sity and domestication of plants in the world, including a broad

diversity of Andeangrains, roots andtubers. Amongst thetubers,

the mostwidespreadthrough the Andes sincepre-Hispanic times

are oca (Oxalis tuberosa Molina), isano (Tropaeolum tubero-

sum Ruiz and Pavon), papalisa (Ullucus tuberosus Caldas) and

1161-0301/$ see front matter 2007 Elsevier B.V. All rights reserved.

doi:10.1016/j.eja.2007.12.002


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B. Condori et al. / Europ. J. Agronomy 28 (2008) 526540 527

potato (Solanum ssp. L.) (Contreras, 2001; Rea, 1998). Of these

tubers, potato is the most known and grown over the world,

followed by oca, even though oca is produced only in Mex-

ico and New Zealand (CIED, 2002) outside the Andes. The

other tubers are specific to the Andean highlands. Superficies

of Andean tubers other than potatoes are not known with preci-

sion but in the regions where potatoes are in rotation with other

Andean tubers the superficies should be approximately equal

(potatoes and other Andean tubers).

The composition and the number of varieties which consti-

tute the Andean tubers germplasm is very heterogeneous and

the quantities of seed material in collections is limited hence

a risk of loss of biodiversity. The banks of germplasm kept in

Toralapa (Bolivia) contain 1200 accesions of potato, 500 de oca,

200 de papalisa, and 80 de isano (Garcia and Cadima, 2003).

Except for isano which is mainly used for feeding pigs Andean

tubers are grown chiefly for human consumption under differ-

ent forms (fresh, boiled, fried, oven cooked, stewed, as soups,meal obtained after dehydration, etc.). There is also some use as

medicinal plants.

Some studies on the nutritional value and rusticity of Andean

tubers confirm them as alternatives to cover increasing demands

in human and animal food and in industry, however, there

is still little knowledge of the growth dynamics and poten-

tial production characteristics of such tubers (CIED, 2002). It

is a known fact that Andean tubers played a multiplicity of

roles in human activities since pre-Hispanic times; however, at

present such tubers are almost forgotten and therefore under-

used, with the exception of potato (NRC, 1989; Tapia, 1994;

Rea, 1998).

Bolivia has a broad diversity of cultivated and wild potatoes,

7 and 31 species, respectively, as noted by Ochoa (1990). But of

the seven species cultivated, three can be cited as more impor-

tant. In order of importance and market presence, the sub-specie

Solanum tuberosum ssp. andigenum with the Waycha cultivar

should be cited as one of the variety most appreciated by the

consumers, both rural and urban. It is followed by Solanum

juzepczukii with the bitter cultivar Luki and Solanum tuberosum

ssp. tuberosum with the cultivars Alpha and Desiree (Irigoyen,

2002). Due to its high concentration of glycoalkaloids, Luki has

a bitter taste when consumed fresh without processing (Ochoa,

1990). For this reason it is processed into a frozen and dehy-

drated product called chuno or tunta before consumption, usinga traditional processing method. One of its favourable attributes

is that it can be grown in the highest areas (at elevations over

3000 m) due to its tolerance to frost (Rea, 1992). Alpha is a

cultivar introduced from Europe, it is better adapted to milder

areas, with the advantage of a shorter cycle, it becomes a winter

production alternative in semi-tropical regions of Bolivia, even

though its presence in the market is relatively recent and still

small (Irigoyen, 2002).

It is noteworthy that in Bolivia compared to other Andean

countries, the yield of tuber crops, potato included, is low in

spite of the rusticity of the species and varieties used and even

though they are genetic resources from this region (OEA, 1996).This could be due to several factors, such as the technological,

socioeconomic and cultural factors. Another factor is the poor

knowledge about the growth and production processes of the

Andean tubers (Tapia, 1994; Zeballos, 2006).

Most national statistics or authors mention potato as the tuber

of reference and only in very specific occasions oca and papal-

isa are mentioned. Official reports indicate that mean domestic

yieldsof freshtubersare about 6 t/hafor potato, 3 t/hafor oca and

4 t/ha for papalisa (Montes de Oca, 1992; Tapia, 1994; Zeballos,

1997, 2006; INE, 1999). No official reports on isano yields are

available, though some studies indicate that isano yields can

be quite higher than potato yields (CIED, 2002). However, in

other research reports, values higher than the national mean can

be found: Gonzales et al. (1997) indicate means of 25 t/ha of

tubers for potato and oca, and 30 t/ha for isano in farmers plots

of the Candelaria area, a agrobiodiversity zone in Cochabamba.

Other researchers, such as Iriarte (2003, personal communica-

tion), indicate that in communities close to the area surrounding

LakeTiticaca yieldsof 2731 t/ha of oca, and 3841 t/ha of isano

can be found. Quispe et al. (1997) reports yields of 30 t/ha ofpotato, 22 t/ha of oca and 33 t/ha of isano. Reports on isano

yields are noteworthy, since yields ranging from 9 to 74 t/ha

can be found (Grau et al., 2003). Research reports on papalisa

indicated that its yield could reach 33 t/ha (Garcia and Cadima,

2003).

This gap between maximum yields and average yields shows

the necessity to consolidate a clear and accurate knowledge

based on the characterisation of Andean tubers, describing

the main agrophysiological indices to determine their growth

under average and optimal conditions, and thus understand their

functioning. This could serve to establish criteria of genetic

improvement for the development of cultivars, criteria of crop

management and parameters to be used in simulation systems

for improving the crop management and thus achieving better

yields.

Oneway in which development and growthdynamicsin plant

species can be studied and explained is through Crop Growth

Analysis, an explanatory, holistic and comprehensive approach

to interpret plant form and function (Clawson et al., 1986; Hunt,

1982; Hunt et al., 2002). Growth analysis techniques are based

on a description of the physiological performance of a species,

considering that the accumulation of carbon is determined by

the amount of foliage and their daily photosynthetic efficiency.

Some studies on the growth and production of Andean tubers

have addressed specific aspects according to the objective ofeach study, such as phenology, fertilization, and hydroponics,

both in Bolivia (Quispe et al., 1997; Valdivia et al., 1998)

and Peru (Valladolid et al., 1984; Gomez et al., 2001) using

growth analysis techniques. The above studies used different

methodologies, such as classic growth analysis (Hunt, 2003)

or functional analysis of growth according to Hunt (1979,

1982) and Hunt et al. (2002), where polynomial equations are

fitted to values of the coordinates of points measured through

time to obtaine trend values. The coefficients of these equa-

tionscannot be biologically explained; moreover, Poorter (1989)

indicates that suchgrowth curves may exhibit erratic behaviours.

A relatively recentalternative to plot growthcurves is theBetafunction proposed by Yin et al. (2003). It is presented as one of

the most versatile functions to describe growth curves and to


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528 B. Condori et al. / Europ. J. Agronomy 28 (2008) 526540

use for agronomic interpretation and characterisation purposes,

because plotting of such curves requires three parameters clearly

explainable and easily measurable in the field. This function

makes an easier description and interpretation of a crop growth

analysis (CGA).

Considering the above, this study is intended to characterise

and analyze different Andean tubers through the comparison

of their agrophysiological attributes and their growth dynamics

under their natural agroecological conditions. In another paper

the growth model for native potato species will be analyzed.

2. Materials and methods

2.1. Genetic material

For this study, three genotypes of potato, one of oca, one of

isano and one of papalisa were used. For potato, the species and

sub-species studied were: S. juzepczukii (JUZ) with the bittercultivar Luki; Solanum tuberosum ssp. andigenum (AND) with

the cultivar Waycha; Solanum tuberosum ssp. tuberosum (TUB)

with the cultivar Alpha. In oca or O. tuberosa (OXA) the cultivar

Pukanawi was used. In Isano or T. tuberosum (TRO) the cultivar

Anaranjado was used. In papalisa or U. tuberosus (ULL) the

cultivar Manzana wasused; these potato, oca, isano and papalisa

cultivars are the most widespread amongst farmers of the studied

area.

2.2. Trials

For the growth and development study of Andean tubersseveral trials were conducted in Toralapa, Candelaria and Pat-

acamaya, in Bolivia (Table 1). The trials were conducted in

experimental stations (Toralapa and Patacamaya) and in farm-

ers fields (Candelaria) but in all cases there was a cooperation

between researchers and local farmers for the cultivation and

crop management. The crops were managed according to the

best local cropping techniques. Toralapa is located at an ele-

vation of 3430 m, at 1730 SL and 6540 WL. The average

temperature in this location is 11 C, relative moisture 55%, and

annual rainfall 500 mm. Candelaria is located at an elevation of

3265 m, 1716 SL and 6566 WL. The average temperature

in this location is 11 C, relative moisture is 80%, and rainfall

950 mm (CIDETI, 1994). Patacamaya is located at an elevation

of 3800 m, at 1714 SL and 6755 WL. The average temper-

ature in this zone is 11.2 C, with relative moisture 50%, and

rainfall 385 mm (Montes de Oca, 1992). The station of Pataca-

maya closed in 2000 but it was still in activity at the time of

these trials.

In these areas the potato is usually the first crop of the rota-

tion system. In Patacamaya and Toralapa potatoes are planted

after a rest period (fallow) of 23 years, but in Candelaria,

because the cropping system is more intensive there is no fal-

low period. In the three locations, the Andean tubers come

always as third or fourth crop in the rotation after potato, quinoa,

and faba bean. During the trial implementation, cropping tech-

niques included fertilization, weeding, ridging and preventive

phytosanitary treatments to ensure plant health and obtain the

maximum yield under these conditions.

Planting density was47,600 plantsper hectare, with distances

of 0.7 m between furrows and 0.30 m between plants. For fer-tilization, 801600 to 8016060 kg/ha of N, P2O5 and K2O

were applied, based on soil requirements, and additional irriga-

tion was also used as required and as available (e.g., additional

irrigation was performed in Patacamaya). The planting dates

were the same for the different Andean tubers but the harvest

date was established according to maturity and development

cycle of the Andean tubers tested (Table 1).

Pests and diseases treatments against late blight (Phytoph-

thora infestans (Mont. de Bary) were applied using Man-

cozeb+ metalaxil (Ridomil MZ) and Clorotalonil (Bravo 500),

Andean weevil (Premnotrypes latithorax Pierce, Premnotrypes

solaniperda Kuschel, and Rigopsidius tucumanus Heller) and

moth (Phthorimaea operculella Zeller, Symetrischema tango-

lias Gyen, Paraschema detectendum Povolny) by synthetic

cipermetrine-based pyrethroids (Karate) and clorpirifos (Lors-

ban).

Experimental plots for each trial were arranged in complete

randomised blockswith three or four repetitions,the surface area

of each experimental plot ranged from 21 to 29.4 m2 (Table 1).

2.3. Data collection

Daily measurements of maximum and minimum tempera-

tures, global solar radiation and rainfall were recorded using

Table 1

Description of the trials conducted to study the growth curves of Andean tubers

Trial Elevation

(m)

Mean

temperaturea (C)

Species studied Planting date Harvest date Cycle

(days)

Number of

harvests

Plot repetition Soil typeb

Toralapa 3430 11.4 TUB, AND, JUZc 22/10/1993 13/04/1994 174 6 29.4 m2 4 SL

Patacamaya 3800 11.1 TUB, AND, JUZ 19/10/1998 20/04/1999 184 5 21.0 m2 4 SL

Toralapad 3430 11.5 OXA, TRO 18/10/1995 08/05/1996 204 9 26.3 m2 4 SL

Candelaria 3265 11.0 OXA, TRO, ULL 16/10/1998 30/05/1999 227 5 24.0 m2 3 L

Candelaria 3260 11.4 OXA, TRO, ULL 19/09/2003 27/04/2004 221 5 21.0 m2 3 SL

a Air temperature data are mean data from emergence to harvest.b SL, silty loam. L, loamy. SL, sandy loam.c Species and sub-species of potato: JUZ is Solanum juzepczukii; AND is Solanum tuberosum ssp. andigenum; TUB is Solanum tuberosum ssp. tuberosum. Other

Andean tubers: OXA is Oxalis tuberosa, TRO is Tropaeolum tuberosum and ULL is Ullucus tuberosus.d Part of the data of this trial were published by Quispe et al. (1997).


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automatic or manual weather climate measurement equip-

ment located on experimentation sites. Periodical sampling of

biomass was performed five to nine times from emergence

to final harvest, according to the availability of plants to be

destroyed (Table 1). Harvests or samplings were determined

based on four phenological macro-stages. Thus, the first harvest

was determined at the onset of foliage formation upon com-

pletion of plant emergence; the second harvest was made at

the onset of tuberisation and flowering whereas the third one

occurred at the maximum development of foliage and physio-

logical maturity. The last harvest took place when plants had at

least half of their foliage in senescence and their tuber skin fully

set.

In each experimental unit and in each sampling, the fresh and

dry weights of four plants fractioned in leaves (L), stems (S) and

tubers (T) were measured. The sum of L plus S gives foliage

weight (Sh). The sum of Sh plus T is the total biomass (W).

Leaf Area Index (LAI) was measured using an area meter (LI-COR, model LI-3000A, Lincoln, USA). The LAI is the ratio

of the foliar surface per unit of soil surface. Root (R) weight

was measured but not included in the total plant weight, due to

its variability caused by the difficulty of separating roots from

the soil. Root growth is only taken into account to calculate its

proportion in the total biomass. The ideal size of potato sam-

ples has been reported to be of six to nine plants for studies

on nitrogen concentration (Goffart et al., 2000), a coefficient

of variation (CV) from 4 to 8% being obtained in that case. In

this study, the plant samples were only used to determine the dry

matter concentration. The ground cover (GC) of leaf canopy was

also measured. This corresponds to the portion of soil surface

hidden by the canopy when seen from above. These readings

were made periodically, every 15 days, from emergence to a

short time before the harvest, using a mesh grid of 100 rectan-

gles of 7 cm 9 cm, obtained from the multiple of the distance

between furrows and the distance between plants, respectively.

The ground cover data was taken to estimate directly the crop

capacity to intercept light during the vegetative cycle (Haverkort

et al., 1991).

2.4. Data analysis

2.4.1. Final yield of total biomass and tubers

The last harvests of each cropping cycle were used to cal-culate the fresh tuber yields (FTY in t/ha). The dry tuber yield

(DTY in kg/ha) was determined from the fresh yield using the

percentage of dry matter in tubers (DMT in %). The Harvest

Index (HI) was determined by the ratio of DTY to total dry

matter (TDM in kg/ha).

2.4.2. Crop growth analysis

In Crop Growth Analysis, three main aspects will be pre-

sented: the accumulation of biomass in the different plantorgans;

the distribution of assimilates generated by each part of the plant

(stems and leaves versus tubers); the estimates of the different

absolute and relative rates and indices of the CGA itself. A sum-mary of the parameters and variables of this study is described

in Table 2.

Table 2

Abreviations, list of variables and parameters used in the growth analysis

Abbreviation Description Units

A Leaf area m2/m2

AGR Absolute growth rate g/day, Eq. (3)CGA Crop growth analysis

Cm Maximum value of the absolute

growth rate

g/m2, Eq. (2)

DMT Dry matter concentration in tubers %

DTY Dry tuber yield kg/ha

FTY Fresh tuber yields t/ha

GC Ground cover Fraction

HI Harvest index %

L Leaf weight g/m2

LAI Leaf area index m2/m2

LAR Leaf area ratio m2/g, Eq. (6)Eq. (7)

LMR Leaf mass rate g/g, Eq. (7)

LUE Light use efficiency g/MJ

NAR Net assimilation rate g m2 day1, Eq. (5)

PAR Photosynthetically active radiation MJ/m2

R Root weight g/m2

RGR Relative growth rate g g1 day1, Eq. (4)

S Stem weight g/m2

Sh Shoot weight g/m2

SLA Specific leaf area m2/g, Eq. (6)

T Tuber weight g/m2

TDM Total dry matter kg/ha

W Total plant weight (with out roots) g/m2

Y Any growth parameter (W, T, Sh, R) g/m2, Eq. (1)

Insideparenthesisis thenumber of referenceattributedin thetextto theequation

used for calculating the parameter or variable.

To construct the Beta-curves of accumulated biomass, we

started with primary yield data (W, T, Sh,R) measured over timein several intermediate harvests, as described in data collection.

Every data set (W, T, Sh,R) was subjected to a non-linear regres-

sion analysis to obtain the growth curves over time expressed in

days on a surface area of 1 m2 of soil. The regression was based

on the Beta function (Yin et al., 1995, 2003), a more versatile

and explanatory equation than a polynomialequation commonly

used for CGA. The Beta function is of a sigmoid type with three

clearly explanatory parameters, and based on two fundamental

equations (Eqs. (1) and (2)):

Y= Ymax

1+

te t

te tm

t

te

te/(tetm),

with0 tm < te (1)

Cm = Ymax

2te tm

te (te tm)

tm

te

tm/(tetm)(2)

Yis any growth parameter; tis the time in days after emergence;

tm is the time when the maximum growth rate of Yis reached; teis the time when the growth period ends. Ymax is the maximum

value ofYreached at te time (Eq. (1)). Cm is the maximum value

of the absolute growth rate reached at tm time (Eq. (2)).

The Beta regression was calculated with the Sigma Plot

software (Evaluation Version 8.02) that calculates non-linearregression through iterations, and requires an initial approximate

value for each parameter of the function.


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Assimilates distribution, was characterised by the proportion

of dry matter allocated in the different organs, leaves, stems and

tubers, and its evolution through time was determined using the

Beta-curves.

The CGA (crop growth analysis) was based on the curves

fitted to the Beta function: with total plant weight (W in g/m2),

leaf area (A in m2/m2), or leaf weight (L in g/m2) as dependent

variable. Using these curves the following growth parameters

were determined: the Absolute Growth Rate (AGR) based on

Eq. (3): the Relative Growth Rate (RGR) based on Eq. (4); the

Net Assimilation Rate (TAN) by Eq. (5); the Specific Leaf Area

(SLA) by Eq. (6); the Leaf Mass Rate (LMR) by Eq. (7). The

Leaf Area Ratio (LAR) can also be determined by the product

of Eqs. (6) and (7). These parameters have been discussed in

several research works conducted since the turn of the century

and are still used nowadays. Hunt (1982), Clawson et al. (1986)

and Hunt et al. (2002) discuss their limitations and scope in

detail.

AGR =dW

dt(g/day) (3)

RGR =

1

W

dW

dt

(g g1 day1) (4)

NAR =

1

A

dW

dt

(g m2 day1) (5)

SLA =A

L(m2 /g) (6)

LMR =L

W(g/g) (7)

2.4.3. Measurement of the photosynthetic mechanisms and

light use efficiency of the plant

Evident relationships between LAI and GC exist for potato

crop, and these range from a linear relationship to an exponen-

tial relationship (Haverkort et al., 1991; Tourneux et al., 2003;

Jefferies and Mackerron, 1989; Kooman, 1995). To determine

whether or not the different species of Andean tubers show a

relation to LAI, which is consistent with the models determined

for potato, we conducted regression analyses on LAI and GC,

pairing the data observed throughout the whole growth cycle ofthe crops.

On the other hand, we determined light use efficiency (LUE)

for each species of Andean tubers. This was performed by a

linear regression analysis of the amount of intercepted photo-

synthetically active radiation (PAR) and the total dry biomass

produced over time. The PAR was calculated from global radia-

tion data. The light interception fraction is measured directly by

GC and can serve to estimate the accumulated value of the inter-

cepted PAR, as explained by Haverkort et al. (1991). Studies

conducted on potato all over the world demonstrate an average

value of 2.8 g of dry matter for each MJ of intercepted light (Stol

et al., 1991). TheLUE value for the other Andean tubers remainsunknown to this day. The program used for these analyses was

also Sigma Plot (Evaluation Version 8.02).

3. Results and discussion

Fig. 1(A) shows the final yield for the fresh tubers (FTY)

of various Andean species. In general, isano (TRO) shows the

highest yield (55 t/ha) of all species, whereas papalisa (ULL)

shows the lowest one (26 t/ha). Oca (OXA) has an average yield

of 31 t/ha similar to potato. Amongst potatoes,the yieldsofandi-

genum (AND) with 35 t/ha, and tuberosum (TUB) with 34 t/ha,

do not differ significantly among them but both are statistically

higher than the yield ofjuzepczukii (JUZ), with 31 t/ha.

Dry matter concentration in the tuber (DMT) (Fig. 1(B)),

differs significantly amongst the species. Broadly speaking, the

potato group has the highest dry matter concentration (over

23%), JUZ has the highest DMT value in the group, 33%,

whereas for AND the intermediate DMT value of 26% is

reached. Amongst the other Andean tubers, ULL has a percent-

age of 18% dry matter, OXAhas a valueof 15% and TRO shows

the lowest dry matter concentration in the tuber (8%). A higherconcentration of dry matter is known to be associated with better

quality for processing or industrial uses.

JUZ and AND have the highest dry matter yield (TDM),

followed by TUB (Fig. 1(C)). Other Andean tubers, TRO and

OXA have higher dry yields than ULL, but these three tubers

have lower yields than the potato group. A trend in the total yield

(TDM) and dry tuber yield (DTY) is found in the potato group,

where differences, are found between JUZ, AND and TUB (in

decreasing order of yield). In the other tubers, dry yield of OXA,

ULL and TRO do not differ significantly (Fig. 1(C)). In this case

too, the yield of these three Andean tubers is quite lower than in

the potato group. These loweryields may be due to the capability

of translocation of assimilates to the tuber characteristic of each

species and expressed by the Harvest Index.

Theabove statement can be explained by the harvest index HI

(DTY/TDM ratio), which differs significantly among species. In

the potato group, TUB shows the highest HI value, with 86%,

followed by JUZ with 78% and AND with 67%. HI values of

70% and 61% are observed for ULL and OXA, respectively,

and the lowest value is found in TRO, with 42% ( Fig. 1(D)).

Potatoes and other Andean tubers have been found to be highly

productive species, meaning that the largest portion of the entire

production of biomass, goes to tuber production, except in TRO.

IndeedtheirHIs areover 61%. This is higherthan in other species

of worldwide importance for food, such as grains (about 50%)or oil-seeds (about 35%) as Kooman (1995) mentions.

The results for these five agronomic variables may be close

to optimal or potential levels for the production systems where

the trials were implemented. Indeed these data were gath-

ered in trials minimizing stress caused by factors that can be

affected by crop management (moisture, pests and soil fertil-

ity) and under low population density with 100% emergence

(47,600 plants/ha). In actual conditions of field production, the

first factor that affects yields negatively is the seedheterogeneity,

both in size and quality that results in an emergence rate below

the planting density, crop heterogeneity and causes direct losses

in the final yield. Climatic constraints affect plant performancein general and this applies also to emergence. In the trials con-

ducted, the average emergence was 80%, even though selected


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Fig. 1. Agronomic behaviour of Andean potatoes: S. t. ssp. tuberosum (TUB), S. juzepckzukii (JUZ) and S. t. ssp. andigenum (AND); other Andean tubers: Oxalis

tuberosa (OXA), Tropaeolum tuberosum (TRO) and U. tuberosus (ULL); in (A) fresh tuber yield in t/ha (FTY); (B) percentage of dry matter in tubers (DMT); (C)

total dry matter and dry tuber yield in kg/ha (TDM and DTY); (D) harvest yield (HI). Mean of the values observed in the final harvest, error bars were determined

by all trials for each species. S. t. is Solanum tuberosum.

seed of certified quality had been used. Our plots appeared more

homogeneous (compared to some farmers plots) but we are

aware that in field plots of homogenous appearance the samples

corresponding to smallsurface areascan generate an overestima-

tion up to 30% (Ledent, 2005 personal communication). Despite

this possible overestimation our results show that a more rigor-

ous management allows achieving yields several times higher

than the yields reported in statistics and bibliography (Table 3).

Relative yield was obtained by dividing the value of these poten-

tial yields (Fig. 1(A)) by the domestic mean (Montes de Oca,

1992; Tapia, 1994; Zeballos, 1997; INE, 1999) or by the mean

of local data or trials conducted for research purposes (Garcia

and Cadima, 2003).

Our results allowed deducing some relations or ratiosbetween total dry biomass (TDM) and dry tuber yield (DTY)

and between dry tuber yield (DTY) and fresh tuber yield. These

ratios were obtained across environments and cultivars. These

ratios although approximate may be useful to estimate biomass

or dry tuber yield when only fresh tuber yield is available.

3.1. Dry biomass accumulation

The means observed for biomass (g/m2), i.e., total

dry weight without roots (W= T+ Sh), tubers (T), shoots

(Sh = leaves+ stems) and roots (R) were subjected to a non-

linear regression analysis over time (days) by the Beta function.

The three parameters of this function are descriptive, because

they provide the value of the maximum growth rate at different

times. They help us interpret the duration of the cropping cycle(Table 4). Determination coefficients r2 show a high fit of the

Table 3

Final yield on the trials for each Andean tuber, relative yields vis a vis potential yield, and two constants of production units transformation

Andean tuber species Final yield (t/ha) Relative yields Transformations

On the national mean On mean local data From TDM to DTY From DTY to FTY

TUB 34.4 6.88 1.64 0.86 4.30

JUZ 31.3 6.26 1.49 0.78 3.00

AND 34.9 6.98 1.66 0.67 3.88

OXA 30.5 10.17 2.03 0.61 6.63

TRO 56.2 4.01 0.42 12.99

ULL 25.3 6.25 1.67 0.70 5.78No official reports on the national yield of isano (TRO) are available. See Fig. 1 for abbreviations. TDM is total dry matter, DTY is dry tuber yield and FTY is fresh

tuber yield.


8/16



Table 4

Beta parameters and coefficients of determination for biomass accumulation in diverse organs of Andean tubers fitted by the Beta function

TUB S.E. JUZ S.E. AND S.E. OXA S.E. TRO S.E. ULL S.E.

Total weight (W= T+Sh)

Cm 17.70 1.3 17.41 0.9 18.48 2.3 9.00 0.7 10.81 0.3 8.43 0.5Wm 1071.00 11.6 1007.82 8.02 1102.76 26.5 662.27 73.2 873.64 32.0 557.55 51.6

tm 67 0.6 70 1.2 68 1.6 95 5.9 100 2.6 75 9.0

te 104 0.9 104 1.9 104 2.3 137 17.0 147 1.5 115 15.9

r2 0.96 ** 0.94 ** 0.90 ** 0.88 ** 0.86 ** 0.94 **

Tubers (T)

Cm 19.67 0.4 23.33 0.1 18.53 0.2 10.38 0.2 7.81 0.2 9.74 0.1

Tm 951.34 3.8 659.01 14.9 792.83 21.6 460.86 18.9 401.77 16.3 431.27 15.3

tm 74 0.2 90 0.6 78 1.4 118 1.9 115 2.1 95 1.5

te 104 0.3 104 1.2 104 2.3 137 4.9 147 2.8 115 3.8

r2 0.94 ** 0.90 ** 0.86 ** 0.88 ** 0.86 ** 0.83 **

Shoots (Sh =L + S)

Cm 4.16 0.3 8.24 0.8 7.16 0.5 3.88 0.2 8.81 0.2 3.64 0.1

Shm 211.24 19.4 435.85 52.4 385.25 33.8 259.12 17.4 573.96 17.6 206.13 5.9

tm 35 7.4 45 20.1 45 6.5 70 19.7 85 4.6 55 3.4te 75 2.9 82 13.9 83 2.6 112 11.9 122 2.1 92 1.4

r2 0.79 ** 0.77 ** 0.79 ** 0.72 ** 0.69 ** 0.71 **

Roots (R)

Cm 0.16 0.53 0.53 0.18 0.70 0.21

Rm 10.12 29.48 30.76 11.44 39.56 11.10

tm 40 45 40 70 90 55

te 90 85 85 110 120 89

r2 0.42 ns 0.40 ns 0.35 ns 0.30 ns 0.38 ns 0.23 ns

Where S.E. is the Standard Error; ns is r2 not significant. Wis the total weight of the plant, Tis the weight of the tubers, Sh is foliage weight, and R is root weight;

all expressed in dry weight and g/m2. tis the time in days after emergence; tm is the time when the maximum growth rate of W(T, Sh or R) is reached; te is the time

when the growth period ends. Wmax is the maximum value of W (T, Sh or R) reached at te time. Cm is the maximum growth rate reached at time tm expressed in

g m2 day1.** r2 highly significant.

Beta function for the different parts of the plants, except the

roots.

Fig.2 provides thegrowth curves foreach Andeantuberorgan

and species. By way of example, we show the points observed

for the total dry matter (W), where we have a high r2 (over 0.86

in all species). This analysis allows a more accurate descrip-

tion of the cropping cycle duration, both in days and in thermal

time (base 0 C, Squire, 1995), considering a daily mean tem-

perature of 11 C, accumulated as from emergence. This figure

shows root growth, which is very reduced relative to the growth

of other parts of the plant. Total root extraction was limited ineach sampling due to: sample extraction depth, involuntary cuts

or breaking of roots due to the presence of gravel in the soil,

losses during sample washings; for that reason R data was not

considered in the total biomass sum.

Fig. 2 shows the bars of Standard Error (S.E.) that compare

the sampling of the species inside potato group and the other

Andean tubers. To avoid filling the figure, and to make a simple

presentation we showed the S.E. at three stages, at the begin-

ning of the accumulation of biomass, at the maximal velocity of

growth and in the final phase of accumulation of biomass. These

stages are reached at 62, 102 and 144 DAP for the potato group

and at 90, 133 and 177 DAP for the other Andean tubers (withslight variations of days). The S.E. bars are are given for these

dates in the figures presenting CGA (Figs. 4 and 5).

Four macro-stages or phenological phases (Kooman and

Haverkort, 1995) were identified by the values of the parameters

of the Beta function and the fitted curves (Table 5).

Phase 0 of emergence, covers the period of time from plant-

ing to emergence, determined by direct periodical counts of

the population emerged over the total plants planted. This

phase is considered reached when half of the population has

emerged and takes 4060 days, depending on the species

(Table 5).

Phase 1, of onset of tuberisation goes from emergence to the

onset of tuberisation when the biomass of tubers reaches 1 g/m2as calculated by the Beta function. Leaf development occurs

mainly in this phase, that lasts 2265 days depending on the

species and includes the onset of tuberisation, which requires

253726 C days (base temperature of 0 C) depending on the

species (Table 5).

Phase 2, of maximum total growth rate goes from the onset

of tuberisation to the maximum growth rate of total biomass,

which coincides with the maximum accumulation of dry matter

in foliage, which phase is reached from 748 to 1056 C days or

from 107 to 150 days after planting (Table 5).

Phase 3, of senescence goes from the maximum growth rate

of foliage to the end of the cropping cycle or to senescence,and corresponds to 11441628 Cdays (Table 5). This phase

is reached when at least half of the foliage is senescent and


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Fig. 2. Dynamic of dry matter accumulation; observed values (circles) and curves fitted to observed values with Beta function in total biomass plant (solid line),

tubers (dotted line), shoots (dashed line) and roots (dasheddotdot line). Andean potatoes: S. t. ssp. tuberosum (A; TUB), S. juzepckzukii (B; JUZ) and S. t. ssp.

andigena (C; AND) and the other Andean tubers: Oxalis tuberosa (D; OXA), Tropaeolum tuberosum (E; TRO) and Ullucus tuberosus (F; ULL). DAP is days after

planting. Tt0 is thermal time with a base temperature of 0C; Tt0 is accumulated of mean temperatures (11

C per day) from emergence.

when the total growth and tuber curve reaches its asymptote

plateau (Fig. 2). The final harvest usually takes place after an

additional lag period following that phase, because at that timethe tuber skin is not yet well fixed This tuber maturity period

allows the formation of a periderm which helps to prevent losses

due to physical damages during harvest and storage. Such wait-

ing period can involve 30 additional days for potatoes ( Tavares,2002).

Table 5

Phenological phases duration of the diverse species of Andean tubers in days after planting, days after emergence and in thermal time (base 0 C)

Species Emergence Onset of tuberisation Maximum total growth rate Senescence

DAP (E.S.) DAP (S.E.) [DAE] C day DAP (S.E.) [DAE] C day DAP (S.E.) [DAE] Cday

TUB 40 (0.142) 62 (1.453) [22] 253 107 (0.577) [67] 748 144 (1.392) [104] 1144

JUZ 40 (0.055) 76 (1.732) [36] 407 110 (0.882) [70] 781 144 (0.581) [104] 1144

AND 40 (1.732) 70 (2.309) [30] 341 108 (1.155) [68] 759 144 (2.485) [104] 1144

OXA 55 (1.155) 120 (1.590) [65] 726 150 (0.667) [95] 1056 192 (1.392) [137] 1518

TRO 45 (2.309) 105 (1.155) [60] 671 145 (1.738) [100] 1001 192 (2.028) [147] 1628

ULL 60 (1.444) 105 (2.603) [45] 505 135 (0.945) [75] 891 175 (2.887) [115] 1276

Values based on the Beta-fitted curves in Fig. 2. DAP is days after planting and, S.E. is Standard Error, [DAE] is days after emergence. C day is the thermal time

based on 0 C.


10/16



Fig. 3. Proportion of dry matter distributed daily between tubers, stems and leaves. Values obtained from Beta-curves. DAP is days after planting. Tt0 is thermal

time wit h a base temperature of 0 C; Tt0 is accumulated of mean temperatures (11C per day) from emergence.

3.2. Distribution of assimilates

Fig. 3 shows the model of daily distribution of assimilates

between the different organs such as leaves, stems and tubers

relatively to the total. This model was based on the values fittedwith the Beta function and the phenological phases described

above. In general, the distribution of assimilates to the tubers

in OXA, TRO and ULL takes longer and is slower (100 DAP)

than in potatoes (TUB, JUZ, and AND at 60 DAP). In potatoes,

TUB is the first to start the process of translocation to the tubers,

which is sustained over time. In all cases but OXA, leaves make

up most of the plant fraction in the initial phenological phase,

whereas in OXA the proportion of leaves and stems is almost

the same during the initial phase.

3.3. Crop growth analysis

Several absolute and relative growth rates or growth attributes

in Andean tuber species were obtained with CGA, includ-

ing AGR, LAI, SLA (Fig. 4) and RGR, LMR and NAR

(Fig. 5).

In the first place, the general trends of curves of AGR and

LAI present similarities in all cases and they differ little among

species (Fig. 4(A, B and D, E) although there are some differ-ences as explained below.

No differences in the maximum value of AGR were observed

in potato, whereas in JUZ and AND LAI values higher than in

TUB were found. Even though TUB has a lower LAI, the value

of its AGR is not the lowest (Fig. 4(A and B)). This could be

indicative of a greater efficiency of allocation of assimilates per

leafareaforTUBcomparedtotheothertwospecies.Inthepotato

species the maximum values of AGR and LAI are reached at the

same time.

Among the other Andean tubers, TRO has a higher AGR and

a markedly higher LAI value than OXA and ULL. By contrast,

ULL has the lowest LAI value, but its AGR is not very differentfrom the AGR in OXA. Again, this could be explained by a

lower light use efficiency in TRO and OXA, and a better light


11/16



Fig. 4. Functional CropGrowth Analysis for Andean potatoes(AC): S.t. ssp. tuberosum (TUB,solid lines), S. juzepckzukii (JUZ,dotted lines) and S.t. ssp. andigena

(AND, dashed lines); the other Andean tubers (DF): Oxalis tuberosa (OXA, solid lines), Tropaeolum tuberosum (TRO, dotted lines) and Ullucus tuberosus (ULL,

dashed lines). Absolute Growth Rate (AGR, g/day), Leaf Area Index (LAI, m 2/m2), and Specific Leaf Area (SLA, m2/day). Values obtained from dry weight and

leaf area data fitted with Beta function. DAP is days after planting. Tt0 is thermal time with a base of 0C; Tt0 is accumulated of mean temperatures (11

C per day)

from emergence.

use by ULL. The maximum values of AGR and LAI are reachedat different times in each species (Fig. 4(D and E)).

As compared to the potato group the other Andean tubers

appear in general, to require a longer time to reach the maxi-

mum AGR and LAI values. Only TRO reaches a maximum LAI

similar to that of JUZ and AND potatoes; OXAhas a LAI similar

to that of TUB. However, all AGR values of the other Andean

tubers are much lower than those of the potato group ( Fig. 4(A,

B and D, E)).

SLA values (Fig. 4(C)) tend to remain constant (plateau) dur-

ing a major part of the cropping cycle, it changes only at the

beginning (when it increases) and at the end of growth (when it

decreases); the SLA values are higher for JUZ and AND than forTUB, ranging from 0.023 to 0.020 m2/g. In comparative terms,

all tubers species other than potatoes reach SLA values lower

than those of potatoes. The maximum SLA values in speciesother than potatoes are reached by OXA and ULL, with 0.020

and 0.018m2/g, the lower SLA value being found in TRO, with

a maximum value of 0.013 m2/g.

Fig. 5 shows the evolution of RGR, LMR and NAR, through

time. No major differences between species canbe found, except

for differences in the times at which they reach their highest val-

ues. These values drop at first abruptly andthen slowly. In potato,

this drastic drop is reached 60 days after emergence whereas in

the other tubers the drop occurs at 80 DAE. Difference in the

RGR value among species at the beginning of the growth cycle

(Fig. 5(D)) is observed only among the Andean tubers other than

potatoes. There are no significant statistical differences betweenthe potatoes, however among other Andean tubers TRO shows

the lowest RGR (Fig. 5(A and D)).


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Fig.5. Functional CropGrowth Analysis for Andean potatoes (AC): S.t. ssp. tuberosum (TUB, solid lines), S. juzepckzukii (JUZ, dotted lines) and S.t. ssp. andigena

(AND, dashed lines); the other Andean tubers (DF): Oxalis tuberosa (OXA, solid lines), Tropaeolum tuberosum (TRO, dotted lines) and Ullucus tuberosus (ULL,

dashed lines). Relative growth rate (RGR, g g1 day1), Leaf mass ratio (LMR, g/g) and Net assimilation rate (NAR, g m2 day1). Values obtained from dry weight

and leaf area data fitted with Beta function. DAP is days after planting. Tt0 is thermal time with a base of 0C; Tt0 is accumulated of mean temperatures (11

C per

day) from emergence.

LMR is considered as the capacity of the plant to invest in

potentially photosynthetic parts (leaves). Among the potatoes

JUZ has a higher LMR value and therefore invests in more foliar

mass, contrary to TUB and AND (Fig. 5(B)) which invest more

in tubers. Other tubers do not differ in LMR at the beginning

of the cycle but as the cycle advances differences occur TRO

is presenting more foliage for the production of the same given

total biomass (Fig. 5(E)).

NAR relates to the capability of mass production by unit of

leaf surface area. In terms of NAR the potato TUB is the most

efficient although the differences with the other tubers are not

always clearly marked (Fig. 5(C)). Potatoes evolution of NARfollows a similar tendency as the other tubers but with a greater

duration of evolution through the time (Fig. 5(F)).

A global analysis including several parameters (growth rates,

etc.) obtained from CGA, shows that rates change according to

the moment and the species. Comparison of their values can be

done at given fixed moments such as at the end (final value) or

at a point near the maximum (at 102 DAP for potatoes and 133

DAP for other Andean tubers) (Table 6).

The potato TUB has a greater capacity for biomass produc-

tion per surface unit area (NAR) than JUZ and AND. A lower

proportion of foliar biomass in the total plant mass is found

for TUB compared to JUZ and AND. The thickness of leaves

(1/SLA) is lower for TUB (P < 0.05) than for AND and JUZ.

These characteristics (lower NAR, smaller SLA) are associatedwith a lower RGR resulting in a lower efficiency in the gen-

eration of total biomass. However, JUZ presents a high RGR


13/16



Table 6

Comparison of the values of the Relative Growth Rate (RGR), Net Assimilation

Rate (NAR), Leaf Mass Ratio (LMR) andSpecific Leaf Area (SLA),for the102

DAP in potatoes and 133 DAP for other Andean tubers

Species RGR (g/g) =NAR (g/m2)LMR (g/g)SLA (m2/g)

TUB 0.032 6.65 0.23 0.021

JUZ 0.035 4.39 0.35 0.023

AND 0.033 5.04 0.28 0.024

E.S. (0.0010) (1.67) (0.03) (0.0007)

OXA 0.031 4.27 0.34 0.022

TRO 0.026 3.57 0.54 0.013

ULL 0.027 4.67 0.30 0.019

S.E. (0.0018) (0.32) (0.07) (0.0024)

The data come from the curves of Figs. 4 and 5. S.E. is the Standard Error

between the species of potato and other Andean tubers, respectively.

but with a greater allocation of assimilates to the leaves (LMR),

which could affect negatively the tuber yields. TRO presents asmaller NAR than the others (OXA and ULL) but with a very

high LMR, a low SLA and a low RGR similar to ULL. In spite

of having a high LAI, TRO allocates more assimilates to the

foliage that to the tubers (Table 6).

4. Measurements of the photosynthetic mechanisms of

the plant and light use efficiency

4.1. Relationship between LAI and GC

The relationships between LAI and GC (ground cover) have

beenstudied by several authors. Exponential type functions,pro-posed by Jefferies and Mackerron (1989), Kooman (1995), are

presented for reference purposes in Fig. 6. Other researchers

such as Haverkort et al. (1991) and Tourneux et al. (2003) estab-

lished a linear relationship between LAI and GC, determining

that GC equals one-third of LAI (for LAI values 3). The frac-

tion of intercepted light was found to be equal to GC obtained

by measurements of the ground cover with a grid or leaf canopy

Table 7

Mean values of the coefficients of the exponential function resulting from the

regression between LAI and GC proposed by Jefferies and Mackerron (1989),

and Kooman (1995)

Species Coefficients of the function y = a c exp(bx)

and coefficient of determinationa c b R2

TUB 0.50 (0.13) 0.51 (0.12) 0.96 (0.78) 0.88

JUZ 0.70 (0.35) 0.75 (0.32) 0.45 (0.46) 0.90

AND 0.85 (0.44) 0.90 (0.40) 0.38 (0.37) 0.87

OXA 0.70 (0.49) 0.73 (0.46) 0.40 (0.46) 0.81

TRO 1.00 (0.25) 1.01 (0.23) 0.36 (0.19) 0.90

ULL 0.50 (0.33) 0.54 (0.31) 1.18 (1.41) 0.89

General 1.00 (0.21) 1.01 (0.20) 0.29 (0.10) 0.86

Standard Error values appear in brackets.

intercepting light (Haverkort et al., 1991). The purpose of these

relationships is to determine, by LAI measurements or sim-ple measurements of GC the fraction of light intercepted, with

which we can subsequently find the amount of photosyntheti-

cally active radiation intercepted by the plants.

Table 7 shows the coefficients obtained by regression when

fitting the exponential function y = a c exp(bx) where: y

is GC; a is the maximum value of GC; c is the intercept of the

relation log(ya) onx; b is the curves slope or the coefficient of

extinction;x is the LAI. In broad terms, it can be established that,

of the values of coefficients a and c are quite close to each other,

as also indicated in the bibliography (Jefferies and Mackerron,

1989). Such a result is also quite logical since we expect y = 0

for x = 0.The value of a (maximum value reached by GC) is consid-

ered to be a characteristic of each species. Thus, TRO reaches a

maximum GC value of 1, whereas the lowest of these values is

found in the TUB potato and in ULL, with a maximum GC value

of 0.5. The highest values of b, are found for ULL (1.18) and

TUB (0.96), i.e., their coefficient of extinction related to LAI

(bLAI) is lower than in the other species where it ranges

Fig. 6. Relationship between ground cover (GC) and LAI (leaf area index) Exponential relationship (dotted line with GC = 11.021 exp0.29LAI) and linear

relationship (dashed line with GC = 1/5LAI, R2 = 0.87) between GC and LAI from observed values in Andean tubers. Relationship obtained by Kooman (1995)

is GC= 11 exp1LAI and by Jefferies and Mackerron (1989) is GC=0.931.03 exp0.746LAI.


14/16



Fig. 7. Relationship between intercepted PAR (MJ/m2) and total dry matter (kg/ha). Dashed line corresponds to LUE for Andean potatoes (2.69 g/MJ) and dotted

line to LUE for the other Andean tubers (1.52g/MJ).

from 0.36 to 0.45, the lowest value of b being observed for TRO

and potato AND. The coefficients of determination correspond-

ing to these regressions reach values higher than 0.81. When we

ceasetoapplytheGClimitperspecies,thatis a =1,andmergeall

the species in a single data cloud, we obtain the general function

shown in Table 7 and applicable to all Andean tubers.

Fig.6 shows thedistribution of the observationspoints of LAI

and GC used to fit the general function for all species. Coeffi-

cients a and c tend to the value of 1, coinciding with Kooman

(1995) and to what is logically expected as mentioned above.

By contrast the slope is lower than the value of 1 reported for

instance by Kooman (1995), reaching a value of 0.29. Large

differences occur between this general value and the values

obtained separately by species.

The slope of the relationship between LAI and GC is lower

than in Kooman (1995) or Jefferies and Mackerrons (1989)

theoretical function. This may be explained by the mean tem-

perature at which the trials were conducted (11 C daily mean),

which is significantly different from the ttemperatures between

17 and 25 C under which the work of these other researchers

was conducted. These temperatures may have promoted a faster

leaf development, something that does not occur in the areas

of production of Andean tubers. This faster development may

have influenced plant architecture and favoured more horizon-tal leaves, more opened plants (leaning stems) and therefore

a higher extinction coefficient. In our conditions the opposite

could have occurred resulting in lower extinction coefficient

and lower ground cover for a given LAI. Such differences in

architecture are also observed among species in our trials. For

instance, TUB and ULL have a low LAI but the same GC value

as species with a higher LAI in the initial part of the curve and

they appear to have an angle of foliar insertion more horizontal

but in absence of precise determination of canopy architecture

features this remains speculative. When all species were sub-

jected to a linear regression analysis, the simple relationship

GC = LAI/5 with R2

= 0.87 was found, which is different fromthe relation GC= LAI/3 (Fig. 6) found by Haverkort et al. (1991)

and Tourneux et al. (2003).

4.2. Light use efficiency

The relation between accumulated data of intercepted PAR

and total dry matter produced was studied by a linear regression

analysis, as shown in Fig. 7. The intercepted PAR was deter-

mined by the product of GC by PAR and accumulated through

the cropping cycle (Haverkort et al., 1991). The slope of the

regression line corresponds to light use efficiency. The slopes

for each species were compared; few variations among potatoes

or among the other Andean tubers were found, but there was

a marked superiority of potatoes relatively to the other species

(potatoes presented higher slope). Thus, data were grouped and

two new different regression lines were calculated: one for the

potato group and the other one for the other tubers. The LUE

value for the potato group was 2.69 g/MJ and the LUE for oca,

papalisa and isano was found to be 1.51 g/MJ (expressed on the

basis on dry matter). The LUE found for potatoes is close to

values reported by other researchers (Stol et al., 1991; Kooman

and Haverkort, 1995). Thus, compared to potatoes, the other

Andean tubers have a lower LUE, a smaller maximum GC and

GC values close to the maximum values are maintained only

for a short duration of time Maximum GC values were 0.6 and

0.4 for OXA and ULL, respectively. All of them but TRO fail

to achieve complete GC (GC values do not reach 1), their NARis low (Fig. 5(F) and Table 6) and the resulting productivity is

small.

5. Conclusions

We characterised the agrophysiological behaviour of Andean

tubers and quantitatively determined their growth dynamics

under the climatical constraints encountered in the different sites

of experiment which can be considered as representative of the

typical zones where Andeantubers are grown. Our objective was

not to study in details the impact of variations in these climatical

constraints or the effects of specific events such as frosts or (asin Tourneux et al., 2003) water stress. Significant differences

between species were found for their agronomic characteris-


15/16



tics such as yield, harvest index and dry matter concentration

in tubers. Tuber yields were clearly above the national figures

commonly reported; this is due to the optimum management

conditions of the trials. Isano has a higher fresh tuber yield than

the other Andean tubers, including potato, however, it should

be mentioned that this apparent advantage results from the large

amount of water that isano accumulates in its tubers with only

8% of dry matter. When the tuber dry yields of isano and of other

Andean tuber species such as oca and papalisa, are compared

they do not differ despite the lower harvest index of isano. The

tuber dry yield of isano is lower than in the potato species ana-

lyzed. Isano has presented the lowest harvest index. The potato

group has the highest harvest index; the S. juzepczukii potato is

the highest in terms of total dry matter yield. The Beta function

proved to be useful for fitting and analyzing growth curves. In

general, the growth of potatoes and other Andean tubers present

similar trends; the specific difference is the longer time taken by

the other Andean tubers in each phenological phase.The Crop Growth Analysis indicated three important char-

acteristics differentiating the Andean tubers: the S. juzepczukii

potato compared to other tubers species has a higher relative

growth rate but a smaller tuber yield, due to a smaller har-

vest index associated to a high leaf mass ratio and a very low

net assimilation rate (NAR). The S. tuberosum sp. tuberosum

potato has a smaller leaf area index (LAI), an higher tuber yield

although their RGR is lower, and their NAR is very high. With

a smaller utilisation of assimilates in foliage and a high harvest

index S. tuberosum sp. tuberosum is the most productive sub-

specie in relation to its relatively low LAI. Differences among

thesespeciesmayberelatedtotheirorigin;the tuberosum used in

this study is an improved variety selected for its yield capacity in

higher latitudes and temperate conditions while the juzepczukii

is a native crop that adapted itself over the years to the adverse

climatic conditions of the Andes (frost and drought). T. tubero-

sum or Isano has a great capacity of ground cover by foliage

and a great LAI that is not translated in a greater tubers yield,

it has low RGR, NAR and harvest index as compared to all the

other species studied. In addition its allocation of biomass to the

leaves is high as indicated by its leaf mass ratio.

A linear and exponencial relationship were determinated; the

coefficients of the fitted equations vary especially on the slopes

among the species of Andean tubers. The slopes of the equation

describing the relationship between LAI and GC (light inter-ception fraction) values are lower in the tubers grown in the

Andes as compared to the values reported for potato elsewhere

due to lower local temperatures (11 C average), and probably

to the architecture of the Andean tuber plants (high stems and

horizontal dispositions of leaves).

The value of light use efficiency, found for the potato variety

used in this study was similar to those reported in the bibliog-

raphy for potatoes. The other Andean tubers have lower LUE

values. A high tuber yield is not only determined by a high LUE.

The lower HI values found for Andean tubers contributed also to

their lower yield. Duration of light interception or maintenance

of maximum LAI values tended to be lesser in our conditions,characters of the foliar system such as high LAI, low SLA and

LMR). also playeda role in some cases to explain the differences

of yield obtained but not systematically (higher LAI were not

necessarily associated with higher yields and vice versa).

Thischaracterisation of agrophysiological parametersand the

development of growth of Andean tubers will be useful for a

better knowledge, to improve their management and to build a

simple model of these traditional crops for the region. Testing

the behaviour of the different tubers under the stress conditions

commonly found in the regions of cultivation remains to be

conducted.

Acknowledgements

The field experiments in Bolivia were conducted with the

team of researchers of Foundation Proinpa. The Universite

catholique de Louvain, UCL, Belgium attributed a fellowship

to B. Condori. The International Potato Centre CIP contributed

through the projects Papa Andina y ALTAGRO to the finalisa-

tion and revision of this paper. The authors thank all those who

made this work possible.

References

CIDETI, 1994. Diagnostico socioeconomicode la Microregion de Tiraque. Vol-

umen 1. Poblacion, Historia social y organizacion. Comite Interinstitucional

para el desarrollo de Tiraque, Cochabamba-Bolivia.

CIED (Centro de investigacion educacion y desarrollo), 2002. Productos Andi-

nos potenciales. Online at: http://www.ciedperu.org/productos/fraprod.htm.

Clawson, K.L., Spetch, J.L., Blad, B.L., 1986. Growth analysis of soybean

isolines differing in pubescence density. Agron. J. 78, 164172.

Contreras, A., 2001. Ecofisiologia del rendimiento de la planta de papa. Fac-

uldad de Ciencias Agrarias de la Un iversidad Austral de Chile. Online at:http://www.agrarias.uach.cl/webpapa/pag04.html.

Garcia, W., Cadima, X. (Eds.), 2003. Manejo sostenible de la agrobiodiversidad

detuberculos andinos: Sntesis de investigaciones y experiencias en Bolivia.

Conservacion y uso de la biodiversidad de races y tuberculos andinos: Una

decada de investigacion para el desarrollo (19932003). Fundacion para

la Promocion e Investigacion de Productos Andinos (PROINPA). Alcalda

de Colomi, Centro Internacional de la Papa (CIP). Agencia Suiza para el

Desarrollo y Cooperacion (COSUDE), Cochabamba, Bolivia, 208 pp.

Goffart, J.P., Olivier, M., MacKerron, D.K.L., Postma, R., Johnson, P., 2000.

Spatial and temporal aspects of sampling of potato crops for nitrogen analy-

sis. In: Haverkort, A.J.,MacKerron, D.K.L.(Eds.), Management of Nitrogen

and Water in Potato Production. Wageningen Pers, Wageningen, pp. 83

102.

Gomez, D., Rodriguez-Delfin, A., Fernandez, E., 2001. Analisis de crecimiento

de plantas de Mashua (Tropaeolum tuberosum) sometidas a condicionesnutricionales marginales. Anales cientficos de la UNALM. Lima, Peru 47,

280296.

Gonzales, S., Almanza, J., Devaux, A., Condori, P., 1997. Zonas productoras de

tuberculos andinos, identificacion e investigacion de factores limitantes de

producciony conservacionen Cochabamba.In: UniversidadNacional de San

Antonio Abad del Cusco (UNSAAC), Centro de Investigacion en cultivos

Andinos (CICA), Asociacion Arariwa (Eds.), IX Congreso Internacional de

Cultivos Andinos. Cochabamba, Bolivia, p. 21.

Grau, A., Ortega Duenas, R., Nieto Cabrera, C., Hermann, M., 2003. Mashua

(Tropaeolum tuberosum Ruiz & Pav.). Promoting the Conservation and

Use of Under-utilized and Neglected Crops, vol. 25. International Potato

Center/International Plant Genetic Resources Institute, Lima, Peru/Rome,

Italy.

Haverkort, A.J., Uenk, D., Veroude, H., Van de Waart, M., 1991. Radiation

interception by potato canopy: relations between ground cover, interceptedsolarradiation,leaf areaindexand infrared reflectanceof potato crops. Potato

Res. 34, 113121.


16/16



Hunt, R., 1979. Plant growth analysis: the rationale behind the use of the fitted

mathematical function. Ann. Bot. 43, 245249.

Hunt, R., 1982. PlantGrowth Curves: The Functional Approach to Plant Growth

Analysis. E. Arnold, London.

Hunt, R., 2003. Growth analysis, individual plants. In: Thomas, B., Murphy,

D.J.,Murray, D. (Eds.), Encyclopaediaof Applied Plant Sciences.Academic

Press, London, pp. 579588.

Hunt, R., Causton,D.R., Shipley, B., Askew,P., 2002. A modern toolfor classical

plant growth analysis. Ann. Bot. 90, 485488.

INE (Instituto Nacional de Estadstica), 1999. Estadsticas agropecuarias. La

Paz, Bolivia.

Irigoyen, X., 2002. Estudio de mercado de papas nativas en dos ciudades

de Bolivia. Cochabamba y La Paz. Reporte de Consultoria. Cochabamba,

Bolivia.

Jefferies, R.A., Mackerron, D.K.L., 1989. Radiation interception and growth of

irrigated and droughted potato (Solanum tuberosum). Field Crop Res. 22,

101112.

Kooman, P.L., 1995. Yielding ability of potato crops as influenced by tem-

perature and daylength. Ph.D. Thesis. Wageningen Agricultural University,

Wageningen.

Kooman, P.L., Haverkort, A.J., 1995. Modelling development and growth of thepotato crop influencedby temperatureand daylength:LINTUL-POTATO. In:

Haverkort, A.J., Mackerron, D.K.L. (Eds.), Potato Ecology and Modelling

of Crops Under Conditions Limiting Growth. Kluwer Academic Publishers,

Dordrecht, pp. 4160.

Montes de Oca, I., 1992. Sistemas de riego y agricultura en Bolivia. Taller de

analisis del Riego. Ministerio de Asuntos Campesinos y Agropecuarios, La

Paz.

NRC (National Research Council), 1989. Lost Crops of the Incas: Little-known

Plants of the Andes with Promise for Worldwide Cultivation. National

Academy Press, Washington, DC, pp. 82113, Online at: http://www.

nap.edu/books/030904264X/html/R1.html .

Ochoa, C.M., 1990. Las papas de Sudamerica. Bolivia, Plural Editores/CID, La

Paz.

OEA, 1996. Diagnostico ambiental del sistema Titicaca- esaguadero-Poopo-

Salar Coipasa (Sistema TDPS), Bolivia-Peru. Organizacion de los EstadosAmericanos. Washington DC, USA.

Poorter, H., 1989.Plantgrowth analysis:towardsa synthesisof theclassical and

the functional approach. Physiol. Plant. 75, 237244.

Quispe, C., Devaux, A., Gonzales, S., Tourneux, C., Hijmans, R., 1997. Eval-

uacion comparativa del desarrollo y crecimiento de Papa, Oca e Isano en

Cochabamba, Bolivia. Revista Latinoamericana de la Papa 9/10, 140155.

Rea, J., 1992. Vigencia de las papas nativas en Bolivia. In: Rea, J., Vacher, J.J.

(Eds.), La Papa Amarga. Primera mesa redonda: Peru, Bolivia. ORSTOM,

La Paz, pp. 1523.

Rea, J., 1998. Manejo y conservacion comunitaria de recursos geneticos

agrcolas en Bolivia. Online at: http://www.grain.org/sp/publications/

biodiv175-sp.cfm.

Squire, G.R., 1995. Linkages between plant and weather in models of crop pro-

duction. In:Kabat, P., Marshall, B., Broek,B.J., van den, Vos,J., Keulen, H.,

van. (Eds.), Modelling and Parameterization of the SoilPlantAtmosphere

System. Wageningen Pers, Wageningen, pp. 5776.

Stol, W., De Koning, G.H.J., Kooman, P.L., Haverkort, A.J., Van Keulen,

H., Penning de Vries, F.W.T., 1991. Agro-ecological characterisation for

potato production. A simulation study at the request of the International

Potato Center (CIP), Lima, Peru. CABO-DLO, Report 155. CABO-DLO,

Wageningen.

Tapia, G., 1994. La agricultura en Bolivia. Quimera del Desarrollo. Editorial los

Amigos del Libro, La Paz.

Tavares, S., 2002. Tuberizacion. Asociacion Brasilera de la Papa, ABBA.

Revue Batata Show, Ano 2, No. 5. Brasil. Online at: http://www.

abbabatatabrasileira.com.br/revista05 015.htm.

Tourneux, Ch., Devaux, A., Camacho, M.R., Mamani, P., Ledent, J.F., 2003.Effects of water shortage on six potato genotypes in the highlands of Bolivia

(I): morphological parameters, growth and yield. Agronomie 23, 169

179.

Valdivia, G., Devaux,A., Gonzales,S., Herbas, J., Hijmans,R., 1998. Desarrollo

y producciondeOca(Oxalis tuberosa)eIsano (Tropaeolum tuberosum) bajo

dos niveles de fertilizacion. Revista Latinoamericana de la Papa 11, 121

135.

Valladolid, J., Barrantes, F., Prado, A., Zambrano, L., Villantoy, A., 1984.

Analisis de crecimiento de tres especies de plantas tuberosas andinas bajo

condiciones de cultivo de secano en Allpachaca (3600 msnm) Ayacucho.

Centro de Investigaciones Universidad Nacional de San Cristobal de Hua-

manga, Ayacucho. Peru 2 (2), 3748.

Yin, X., Kropff, M.J., McLaren, G., Visperas, R.M., 1995. A nonlinear model

for crop development as a function of temparature. Agri. Forest Meteorol.

77, 116.Yin, X., Goudrian, J., Lantinga, E.A., Vos, J., Spiertz, H.J., 2003. A flexible

sigmoid function to determinate growth. Ann. Bot. 91, 361371.

Zeballos, H., 1997. Aspectos Economicos de la Produccion de Papa en Bolivia.

Centro Internacional de la Papa (CIP), Lima.

Zeballos, H., 2006. Agricultura y desarrollo sostenible. SIRENARE, COSUDE

and PLURAL. La Paz, 226230.

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