Jcea74 7
Jcea74 7
Manuscript received: September 2, 2006; Reviewed: January 29, 2007; Accepted for publication: January 29, 2007
ABSTRACT
The investigation was carried out to determine the stability and adaptability patterns of a set of 40 promising spring
wheat genotypes from Kazakhstan and Siberia evaluated in a multievironment yield trial across 22 environments. Some
of the most widely known parametric stability parameters were used as well as the less frequently cited reliability index
(I). Grain yield correlated significantly and positively with the stability parameters b and S2 and the reliability index
(I); but did not correlate with AMMI ASV. However, the stability parameters failed in detecting adaptability patterns.
In contrast, the reliability index (I) was probed to be more useful in supporting practical decisions. With regard to the
genotypes, cultivars Lutescens 54, Lutescens 30-94, Lutescens 29-94, Tertsia, Omskaya 35, and Shortandynskaya 95
showed to be the widest adapted and the most reliable cultivars.
KEYWORDS: spring bread wheat (Triticum aestivum L.), Kazakhstan, Siberia, parametric stability analysis, reliability
index
the main effects of genotypes (αi) and environments          in unfavorable cropping regions) to 0.70 for modern
(βj) and multiplicative components for the effect of the     agriculture in most favorable regions [2].
interaction (фij). Thus, the mean response of genotype i     2.3 Computer program
in an environment j is modeled by:
                                                             Calculations were performed by IRRISTAT 4.3 software
                                                             [5] using the cross site analysis procedure, which gives
Ŷ= μ + αi + βj +             λkγikδjk + ρij + εij   (3)
                                                             outputs of AMMI and joint regression models including
in which фij is represented by:
                                                             analysis of variance, regression coefficients, as well as
             λkγikδjk                                        genotypes and environments means and Biplots graphics.
                                                             For the rest of calculations as stability and reliability
                                                             index an ordinary spread sheet program was used.
where λk is the size, γik is the normalized genotype
vector of the genotype scores or sensitivities, δjk is the
normalized environmental vector of the scores describing     3. RESULTS AND DISCUSSION
environments, ρij are the AMMI residuals , and εij is the
error term.
                                                             3.1 Mean yield
As mentioned above, the AVS is the distance from the
                                                             The mean yield of the 40 genotypes across 22
coordinate point to the origin in a two dimensional
                                                             environments (location x year) ranged from 2.01 t/
scattergram of PCA1 scores against PCA2 scores.
                                                             ha to 3.16 t/ha (Table 1). The difference in the rank of
Because the PCA1 score contributes more to the GxE
                                                             the genotypes in the various environments indicated
sum of squares, a weighted value is needed. This weight
                                                             the presence of GxE interactions (Table 2), that was
is calculated according to the relative contribution of
                                                             confirmed by the significant effect of the genotype x
PCA1 to PCA2 to the interaction SS [11].
                                                             environment interaction (explaining 15.76% of the G + E
                                                             + GE) in the AMMI analysis of variance (Table 3). From
ASV = {[(SSPCA1 / SSPCA2) (GPCA1score)]2 + (GPCA2s           Table 2 and Figure 1 it is possible to see that genotype
core)}1/2   (4)                                              29 (Lutescens 54) was present in the top 5 rank in 13
                                                             out of 22 environments (being identified as dominant
                                                             cultivar in 6 environments); followed by genotype 34
where SSPCA1 / SSPCA2 is the weight given to the PCA1
                                                             (Lutescens 29-94) that appeared in the top 5 rank in 8
value by dividing the PCA1 sum of squares by the PCA2
                                                             of 22 environments, being the dominant cultivar in 3
sum of squares, GPCA1score is the PCA1 score for that
                                                             environments; genotype 35 (Lutescens 30-94) was the
specific genotype, and GPCA2score is the PCA2 score
                                                             best in 2 environments and appeared in the top 5 rank in
for that specific genotype.
                                                             7 of 22 environments; genotype 36 (Lutescens 53-95),
                                                             was the dominant cultivar in 3 environments and was
2.2.4 The reliability index (I)                              inside the top 5 rank in 6 environments; genotype 21
The reliability index as proposed by Kataoka [7] for         (Tertsia), was the dominant cultivar in 2 environments
economic analysis can be used for estimating, on the         and in 6 environments appeared within the top 5 rank;
basis of the distribution of yield values observed across    genotype 15 (Udacha), was winner in 3 environments
test environments, the lowest yield expected for a given     and was within the top 5 rank in 5 environments; and
genotype and a specified probability of negative events       genotype 39 (Aktube 32), that was the dominant cultivar
[3]. It can be calculated by the following expression:       in 3 environments. Other genotypes that, although were
                                                             not dominant cultivars in more than one environment,
Ii = mi - Z(P) Si         (5)                                but appeared consistently in the top 5 rank across 22
                                                             environments were: genotype 27 (Shortandynskaya 95),
                                                             genotype 2 (Omskaya 35), and genotype 5 (Sonata), (7, 7
where mi = mean yield, Si = square root of the
                                                             and 5 times inside the top 5 rank respectively).
environmental variance (S2), and Z(P) = percentile from
                                                             Table 4 serves to illustrate the importance of recommending
the standard normal distribution for which the cumulative
                                                             the right genotype for each environment. In our case, an
distribution function reaches the value P. Z(P) can assume
                                                             improvement of 0.893 t/ha could be achieved across the
the following values depending on the chosen P level:
                                                             22 environments if only the dominant cultivar for each
0.675 for P = 0.75; 0.840 for P = 0.80; 1.040 for P =
                                                             environment had been sown.
0.85; 1.280 for P = 0.90; and 1.645 for P = 0.95. P values
may vary between 0.95 (for subsistence agriculture
            Table 2. Environments grouped by their winning genotypes, including the first 5 recommended
                           cultivars for each environment, based on the AMMI2 estimates.
               Environments                Dominant cultivar                AMMI2 cultivar recommendations
                       yield                         yield
             Codea                         Code                       1st        2nd         3rd        4th         5th
                       (t/ha)                        (t/ha)
              B         4.63                36        5.58            36          29          34        41          37
              H         2.74                36         3.7            36          28          42        35          34
              R         2.14                36         2.9            36          42          21         2          29
               A        4.46                35        5.73            35          23          29        34          27
              L         4.40                35        5.8             35          20           5        21          2
              O         3.02                29        4.57            29          35          25         2          34
              Q         2.67                29        4.19            29          17           2        24          25
              G         2.54                29        3.42            26          29          34        11          36
              U         1.48                29        2.29            29          18          21        27          28
              T         0.75                29        1.03            28           7          29        27           6
              V         1.99                29        2.47            11           5          27        29           2
               S        2.99                15         4.5            15           5          21         8           9
               J        1.85                15         2.4            27          26          17        15          25
              N         2.29                15        3.12            15          35           2        42          36
              M         2.43                21         3.2            21          27           2        29          15
               P        2.07                21        3.15            21           5          24        15          29
               F        1.87                39        2.27            39          29          37        38           7
              K         1.86                39        2.29            39          25          18        35          27
              E         1.85                39        2.32            24          39          18        37          17
              C         3.86                34        4.59            37          38          20        34          41
              D         3.46                34        5.22            41          34          35        40          29
               I        2.44                34        2.69            8           31          36        5           34
          a
            The full name of the environments are: A = Barnaul 2004, B = Chelyabinsk 2004, C = Kurgan 2004, D = Omsk 2004, E
          = Aktube 2004, F = Karabalyk 2004, G = Shortandy 2004, H = Almaty 2004, I = Pavlodar 2004, J = Petropavlovsk 2004,
          K = Karaganda 2004, L = Barnaul 2003, M = Chelyabinsk 2003, N = Kurgan 2003, O = Omsk 2003, P = Aktube 2003, Q
          = Karabalyk 2003, R = Shortandy 2003, S = Almaty 2003, T = Pavlodar 2003, U = Petropavlovsk 2003, V = Karaganda
          2003.
     Table 3. AMMI analysis of variance for the yield (t/ha) of 40 spring wheat genotypes in 22 environments.
                                                                                                              Explained
                         Source                         Df                  SS                 MS
                                                                                                                 (%)
                   Environment                          21              854.539             40.6923             77.76
                     Genotype                           39              71.0508              1.82182             6.46
              Genotype X Environment                   819              173.217             0.211498            15.76
                AMMI component 1                       59               43.7750             0.741948            25.27
                AMMI component 2                       57               28.3835             0.497956            16.38
                       Total                           879              1098.81
                  Table 4. Yield improvement on the trial if only the first AMMI2 recommendation
                                        was planted at each environment.
                                        Environment         Dominant         Cultivar
                     Environmenta                                                             improvement
                                         yield (t/ha)        cultivar       yield (t/ha)
                          B                 4.63               36              5.58               0.953
                          H                 2.74               36               3.7               0.960
                          R                 2.14               36               2.9               0.759
                           A                4.46               35              5.73               1.272
                           L                4.40               35               5.8               1.397
                          O                 3.02               29              4.57               1.551
                          Q                 2.67               29              4.19               1.525
                          G                 2.54               29              3.42               0.884
                          U                 1.48               29              2.29               0.807
                           T                0.75               29              1.03               0.279
                          V                 1.99               29              2.47               0.478
                           S                2.99               15               4.5               1.512
                           J                1.85               15               2.4               0.549
                          N                 2.29               15              3.12               0.834
                          M                 2.43               21               3.2               0.773
                           P                2.07               21              3.15               1.079
                           F                1.87               39              2.27               0.405
                          K                 1.86               39              2.29               0.427
                           E                1.85               39              2.32               0.465
                          C                 3.86               34              4.59               0.726
                          D                 3.46               34              5.22               1.764
                           I                2.44               34              2.69               0.251
                        Average             2.63                               3.52               0.893
                    a
                      The full name of the environments are: A = Barnaul 2004, B = Chelyabinsk 2004, C = Kurgan
                    2004, D = Omsk 2004, E = Aktube 2004, F = Karabalyk 2004, G = Shortandy 2004, H =
                    Almaty 2004, I = Pavlodar 2004, J = Petropavlovsk 2004, K = Karaganda 2004, L = Barnaul
                    2003, M = Chelyabinsk 2003, N = Kurgan 2003, O = Omsk 2003, P = Aktube 2003, Q =
                    Karabalyk 2003, R = Shortandy 2003, S = Almaty 2003, T = Pavlodar 2003, U = Petropavlovsk
                    2003, V = Karaganda 2003.
3.2 The Finlay and Wilkinson’ (b) regression                       Genotypes 29 (Lutescens 54), 35 (Lutescens 30-94) and
coefficient                                                         34 (Lutescens 29-94) ranked as the three best yielding
Table 5 showed genotypes 9 (Irgina), 31 (Nadezhda), 32             cultivars (the only three with mean yield over 3 t/ha), but
(No. 18), 19 (Altaiskaya 50), and 13 (Novosibirskaya               genotype 29 (Lutescens 54) adapted better by having the
15) as the cultivars with the greatest stability because of        best mean yield (rank 1) and lower regression coefficient
their b value significantly lower than 1.0. However, as all         (rank 33 versus 39 and 40 respectively).
of them were within the cultivars with the lowest yield
mean, the conclusion is that they were poorly adapted to           3.3 The environmental variance (S2)
the test environments.                                             The environmental variance (S2) gave almost the same
Genotypes 17 (Lutescens 574), 4 (Chernyava 13), 27                 rank of the cultivars as the regression coefficient. This
(Shortandynskaya 95), and 2 (Omskaya 35) possesses                 near perfect correlation is confirmed by the Spearman
average stability due to their regression coefficient near          correlation coefficient r = 0.97*** (Table 6). Genotypes
to 1.0, and can be consider as well adapted cultivars              31(Nadezhda), 9 (Irgina), and 32 (No. 18) with the lowest
across the environments because their good mean yield,             (S2) values (the most stable cultivars), were also within the
except for cultivar 4 (Chernyava 13).                              lowest yielding, and thus performed as the least adapted
                   Table 5. Rank and estimation of stability and reliability measures, and grain yield for
                                           40genotypes across environments.
                                                                      Regression
    Rank        ASV stability              S2 stability               coefficient              Reliability index        Mean yield
              Genotype     ASV          Genotype        S2        Genotype        b           genotype        I     Genotype    Yield
       1         17       0.112            31        0.617           9         0.669*            29         2.115      29        3.16
       2         21       0.189            9         0.669           31        0.685*            28         1.988      35        3.11
       3         38       0.205            32        0.715           32        0.716*            35         1.967      34        3.01
       4         20       0.232            13        0.756           19        0.740*            17         1.939      21        2.97
       5         7        0.263            14        0.783           13        0.755*            21         1.935      28        2.92
       6         3        0.289            22        0.818           8         0.785             27         1.931      2         2.86
       7         28       0.294            19        0.848           24        0.805             25         1.888      41        2.85
       8         1        0.308            10        0.919           14        0.808*            15         1.884      27        2.85
       9         27       0.328            25        0.940           22        0.827*            24         1.862      20        2.85
      10         14       0.380            8         0.949           10        0.862             5          1.854      5         2.85
      11         33       0.388            24        0.950           25        0.893             34         1.847      37        2.82
      12         25       0.399            1         0.988           11        0.948             26         1.843      17        2.81
      13         39       0.405            11        1.033           18        0.948             2          1.842      15        2.79
      14         26       0.409            18        1.049           15        0.954             20         1.809      36        2.78
      15         11       0.450            6         1.065           6         0.956             11         1.788      42        2.77
      16         15       0.464            17        1.086           1         0.970             18         1.785      39        2.76
      17         6        0.490            26        1.119           26        0.976             39         1.784      26        2.73
      18         18       0.494            15        1.175           23        0.983             6          1.739      7         2.71
      19         23       0.533            23        1.198           17        0.996             37         1.730      25        2.70
      20         12       0.585            33        1.199           4         1.006             36         1.729      24        2.68
      21         22       0.597            27        1.201           27        1.007             41         1.725      18        2.65
      22         4        0.622            28        1.223           2         1.010             14         1.692      11        2.64
      23         37       0.724            4         1.240           33        1.028             42         1.686      38        2.62
      24         2        0.738            3         1.274           3         1.037             1          1.682      6         2.61
      25         13       0.767            38        1.318           28        1.050             4          1.666      4         2.60
      26         32       0.791            12        1.328           5         1.051             23         1.664      23        2.58
      27         40       0.841            39        1.346           38        1.082             7          1.657      40        2.58
      28         36       0.842            5         1.404           12        1.104             38         1.654      12        2.57
      29         29       0.853            2         1.466           39        1.120             33         1.633      33        2.55
      30         31       0.891            21        1.529           20        1.129             12         1.602      1         2.52
      31         5        0.910            20        1.535           36        1.137             31         1.525      14        2.44
      32         10       0.910            29        1.545           21        1.142             8          1.519      3         2.38
      33         35       0.978            7         1.561           29        1.145             13         1.517      8         2.34
      34         24       0.997            36        1.568           7         1.164             40         1.505      10        2.26
      35         8        1.040            40        1.623           42        1.174             10         1.453      13        2.25
      36         19       1.113            42        1.659           40        1.181             32         1.440      31        2.18
      37         42       1.188            37        1.694           41        1.248*            3          1.433      32        2.15
      38         41       1.215            41        1.804           37        1.257*            19         1.332      19        2.11
      39         34       1.262            35        1.858           35        1.291*            9          1.324      22        2.04
      40         9        1.346            34        1.913           34        1.313*            22         1.275      9         2.01
    *indicates coefficients significantly different from the overall regression coefficient which is 1.
cultivars across the test environments. Between the top                               3.4 AMMI model and the AMMI Stability Value
yielding genotypes, cultivar 29 (Lutescens 54) performed                              (ASV)
as the widest adapted by having a lower (S2) value,                                   The PCA scores of a genotype in the AMMI analysis
and being the top one yielding genotype. Conversely,                                  are an indicator of the stability of a genotype over
genotypes 35 (Lutescens 30-94) and 34 (Lutescens 29-                                  environments. The greater the PCA scores, either negative
94) were the two least stable cultivars and although                                  or positive, the more specifically adapted a genotype
wide adapted, they showed some specific adaptation to                                  is to certain environments. The more the PCA scores
locations Barnaul and Omsk respectively (Table 2).                                    approximate zero (0), the more stable the genotype is
                                                                    S2                b          ASV             I
                                           Yield            0.75***              0.73***         -0.12       0.87***
                                                2
                                            S                                    0.97***         0.01        0.40**
                                            b                                                    -0.08        0.38*
                                           ASV                                                                -0.26
                                       * Indicates significance at P = 0.05
                                       ** Indicates significance at P = 0.01
                                       *** Indicates significance at P = 0.001
                                                                                                     D
                  A= Barnaul 2004,
                  B= Chelyabinsk 2004,
                  C= Kurgan 2004,
                  D= Omsk 2004,
                  E= Aktube 2004,
                  F= Karabalyk 2004,
                  G= Shortandy 2004,
                  H= Almaty 2004,
                  I= Pavlodar 2004,
                  J= Petropavlovsk 2004,                                                                                        A
                  K= Karaganda 2004,
                  L=Barnaul 2003,                                                                                                   B
                  M= Chelyabinsk 2003,
                  N= Kurgan 2003,                                                                                    35
                  O= Omsk 2003,
                  P= Aktube 2003,
                  Q= Karabalyk 2003,
                  R= Shortandy 2003,
                  S= Almaty 2003,                                            G
                  T= Pavlodar 2003,
                  U= Petropavlovsk 2003,
                  V= Karaganda 2003
                                           29                                                   36
                                                                R                 H                                         L
                                                                                                               C
                                                                                 Q
                                      U                                                    O
                                                    F                N
                                                    K   V
                                           39       E
              T                                                          I            15
                                                            P   21       M
  Figure 1. Grouping of environments according to the superior cultivar as determined by theAMMI2 estimates at
each environment. Note that according to the information provided in Table 2, environments I, C, and D and can join
   the genotype’s 34 group; environment J, the genotype’s 15 group; and environment V, the genotype’s 29 group.
       Figure 2. AMMI2 genotype x environment biplot for 40 genotypes and 22 environments. Genotypes and
                          environments names correspond to those in Tables 1 and 2.
over all environments sampled [15].                           and 21 (Tertsia) appeared as the most stable genotypes
From Figure 2, it is possible to visualize some interesting   as they were located very close to the origin point (zero
patterns. For genotypes, the GVK cultivars (genotypes         PCA scores), and genotype 19 as the most instable (and
40, 41, and 42) were very in close relation to each           also the least adapted due to its low yield mean across
other indicating similar germplasm. The same situation        the environments). However, when analyzed together the
happens to genotypes 11 and 12 (Sibirskaya 12 and             PCA scores with the mean yield, genotype 21 (Tertsia)
Sibirskaya 123) and some of the Lutescens cultivars           emerges not only as very stable cultivar, but also as a
(genotypes 29, 34, 35 and 36). This group of Lutescens        cultivar with wide adaptation pattern. The AMMI ASV
cultivars (Lutescens 54, Lutescens 29-94, Lutescens 30-       stability value confirms what it can be seen graphically
94, and Lutescens 53-95) fell into the upper-right side       in the biplot. However, the ASV ranked genotype 34
quadrant of the AMMI2 biplot, indicating their good           (Lutescens 29-94) as the second most instable cultivar,
yield potential, especially in high yielding environments     and genotype 9 (Irgina) as the most instable one (and one
as A, B and L (Barnaul 2004, Chelyabinsk 2004, and            of the least adapted to the testing environments because
Barnaul 2003 respectively). Cultivars 17 (Lutescens 574)      of its low mean yield). The fact that one high yielding
cultivar (genotype 34), and one low yielding cultivar         In regard to the genotypes, cultivars 29, 35, 34, 21, 2,
(genotype 9) were the two most instable cultivars serves      and 27 (Lutescens 54, Lutescens 30-94, Lutescens 29-
to demonstrate the importance of analyzing both stability     94, Tertsia, Omskaya 35, and Shortandynskaya 95
and yield performance to determine also the adaptability      respectively) showed to be the widest adapted and the
patterns for cultivar recommendations.                        most reliable cultivars. Many of the Lutescens cultivars
                                                              (genotypes 29, 35, 34, 36) and cultivar Omskaya 35
3.5 The reliability index (I)                                 (genotype 2) dominated the reliability and mean yield
Making assumption that the technological level of             ranks. It can be explained by the fact that they possess
agriculture in Kazakhstan and Siberia falls between           in their pedigrees blood from the landrace Poltavka, a
the subsistence agriculture and modern agriculture, we        very broad adapted genotype due to its ability to tolerate
took (P) = 0.8, which corresponds to a Z(p) = 0.84 to be      abiotic stresses and present in more than 76% of the
inserted in equation 5 (see section 2.2.4). The reliability   modern spring wheat varieties released in Kazakhstan
index (I) ranked the genotypes according to the lowest        [13].
average yield one can expect for each cultivar across         In summary, the following cultivars were identified
the test environments. Table 5 shows that the top 5           as promising for practical recommendations at the
reliable genotypes were: genotype 29 (Lutescens 54), 28       different spring wheat producing regions in Kazakhstan
(Lutescens 13), 35 (Lutescens 30-94), 17 (Lutescens 574)      and Siberia, according to their performance across 22
and 21 (Tertsia), which agrees in grand extent to the top 5   environments:
yielding genotypes (Spearman correlation coefficient r =       •         Cultivar 29 (Lutescens 54): Chelyabinsk,
0.87***). It is not surprising that genotype 17 (Lutescens    Shortandy, Barnaul, Omsk, Karabalyk, Petropavlosk,
574) appeared as one of the most reliable genotypes           Pavlodar and Karaganda.
because from the regression coefficient analysis it was        •         Cultivar 35 (Lutescens 30-94): Barnaul,
identified as one with average adaptation (b coefficient        Karaganda, Omsk and Kurgan.
close to 1.0), and from the biplot graphic and AMMI           •         Cultivar 27(Shortandynskaya 95): Petropavlosk,
ASV value, as the most stable cultivar; all this plus its     Karaganda and Almaty.
good yield potential (although not being the best) placed     •         Cultivar 34 (Lutescens 29-94): Pavlodar, Omsk
it as 4th in the reliability rank.                            and Chelyabinsk
                                                              •         Cultivar 36 (Lutescens 53-95): Pavlodar and
3.6 Comparisons and concluding remarks                        Shortandy.
No one of the three stability parameters (b, S2, and          •         Cultivar 21 (Tertsia): Almaty and Aktube.
AMMI ASV) was sufficiently accurate in its own to be           •         Cultivar 24(Chebarkulskaya): Aktube.
considered of practical interest for genotype selection and   •         Cultivar 15 (Udacha): Almaty.
recommendation as it was manifested by the Spearman
correlation coefficient between them and the mean yield
rank (Table 6). For instance, b and S2 values, although       ACKNOWLEDGEMENTS
with a middle-high correlation coefficients (0.73***           The authors are grateful with all institutions, scientist
and 0.74*** respectively) with respect to yield, failed       and technicians involved in the Kazakhstan-Siberian
in detecting more yielding and wider adapted genotypes        Network on Spring Wheat Improvement (KASIB) that in
as Lutescens 29-94 (genotype 34), and Lutescens 30-           excellent manner conducted the trials and collected the
94 (genotype 35). Similarly, the AMMI ASV value did           data used in this paper.
not correlate with the yield of the genotypes (r = -0.12).
Only when they were combined with the yield data and
assisted by a table of mean yield of environments and         REFERENCES
genotypes and cultivars ranks for each environment (as            [1] Akçura M., Kaya Y., Taner S., Genotype-
Table 2 in the present study), the use of these stability     environment interaction and phenotypic stability analysis
parameters take a more practical application for selection    for grain yield of durum wheat in the Central Anatolian
and recommendation. Conversely, the reliability index         region, Turk. J. Agric. For. (2005) 29: 369-375.
(I), due to its nature of combining a derived stability           [2] Annicchiarico P., Genotype X environment
measure (the Si value) and yield data, gave more useful       interactions. Challenges and opportunities for plant
information for selection and recommendation. It was          breeding and cultivar recommendations, FAO, Rome,
confirmed by its correlation with yield (r = 0.87***).         2002.
    [3] Eskridge K.M., Selection of stable cultivars using       [12] Lin C.S., Binns M.R., Lefkovitch L.P., Stability
a safety-first rule, Crop Sci. (1990) 30: 369-374.            analysis: where do we stand?, Crop Sci. (1986) 26: 894-
    [4] Finlay K.W., Wilkinson G.N., The analysis of         900.
adaptation in a plant-breeding programme, Aust. J. Agric.        [13] Martynov S.P., Dobrotvorskaya T.V.,
Res. (1963) 14: 742-754.                                     Morgounov A.I., Urazaliev R.A., Absattarova A.S.,
    [5] International Rice Research Institute, IRRISTAT      Genealogical analysis of diversity of spring bread wheat
4.0 for windows. Tutorial manual, IRRI, Manila, 2003.        cultivars released in Kazakhstan from 1929-2004, Acta
                                                             Agronomica Hungarica (2005) 53(3): 261-272.
    [6] Kang M.S., Pham H.N., Simultaneous selection
for high yielding and stable crop genotypes, Agron. J.           [14] Purchase J.L., Parametric analysis to describe
(1991) 83: 161-165.                                          genotype x environment interaction and yield stability in
                                                             winter wheat, (Ph.D. Thesis), University of Free State,
    [7] Kataoka S., A stochastic programming model,
                                                             Bloemfontein, 1997.
Econometrika (1963) 31: 181-196.
                                                                 [15] Schoeman L.J., Genotype x environment
    [8] Kokhmetova A., Analysis of genotype-
                                                             interaction in sunflower (Helianthus annuus) in South
environment interaction in wheat breeding for drought
                                                             Africa, (M.Sc. Thesis), University of Free State,
resistance, Annual Wheat Newsletter (2000) 46: 69-69.
                                                             Bloemfontein, 2003.
    [9] Kokhmetova A., Genotype-environment
                                                                 [16] Shukla G.K., Some statistical aspects of
interaction and yield stability in wheat varieties, Annual
                                                             partitioning genotype-environmental components of
Wheat Newsletter (2001) 47: 91-93.
                                                             variability, Heredity (1972) 29: 237-245.
    [10] Kokhmetova A., Genotypic structure of winter
                                                                 [17] Wricke G. Über eine Methode zur Erfassung
wheat variety Progress, Agromeridian (2005) 1: 59-66.
                                                             der ökologischen Streubreite in Feldversuchen, Z.
    [11] Leeuvner D.V., Genotype x environment               Pflanzenzüchtg (1962) 47: 92-96.
interaction for sunflower hybrids in South Africa, (M.Sc.
Thesis), University of Pretoria, Pretoria, 2005.