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  • Separability  (2)
  • Shifted multiplicative model  (2)
  • Adaptation  (1)
  • Composites  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Heterosis among populations of maize (Zea mays L.) with different levels of exotic germplasm (1987)
    Springer
    Theoretical and applied genetics 73 (1987), S. 445-450 
    Details
    ISSN: 1432-2242
    Keywords: Unadapted germplasm ; Adapted germplasm ; Heterotic patterns ; Gardner-Eberhart model ; Composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Thirteen maize (Zea mays L.) populations including five adapted, five adapted x exotic, two composites of adapted and exotic, and one exotic selected for adaptability were crossed in a diallel mating system. The parents and 78 crosses and nine check hybrids were evaluated for grain yield and plant height in five environments. The Gardner-Eberhart model Analysis II indicated that additive and nonadditive gene effects accounted for 60 and 40% of the total variation among populations, respectively, for grain yield and 86% and 14% of the total variation, respectively, for plant height. Components of heterosis were significant in the combined analysis for both traits. Adapted Corn Belt populations tended to have higher performance in crosses and greater values of variety heterosis than 50% adapted populations. ‘Nebraska Elite Composite’, ‘Corn Belt’ x ‘Mexican’, and ‘Corn Belt’ x ‘Brazilian’ showed high mean yields in crosses, however, they were not among those with high estimates of variety heterosis. One exotic population (‘Tuxpeno’ x ‘Antigua Grupo 2’) and three adapted populations [‘307 Composite’, ‘NB(S1)C-3’, and ‘NK(S1)C-3’] might be combined together to form a high-yielding population. It may be possible to synthesize two useful populations for reciprocal recurrent selection by grouping ‘Tuxpeno’ x ‘Antiqua Grupo 2’, ‘NB(S1)C-3’, and ‘NS(FS)LFW-8’ into one population and ‘NK(S1)C-3’, ‘Krug’x‘Tabloncillo’, and ‘307 Composite’ in the other one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262514
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  • 2
    Electronic Resource
    Electronic Resource
    A shifted multiplicative model cluster analysis for grouping environments without genotypic rank change (1993)
    Springer
    Theoretical and applied genetics 85 (1993), S. 577-586 
    Details
    ISSN: 1432-2242
    Keywords: Genotype-environment interaction ; Crossover interaction ; Separability ; Shifted multiplicative model ; Distance measure ; Cluster analysis ; Zea mays L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The shifted multiplicative model (SHMM) is used with a cluster method to identify subsets of sites in an international maize (Zea mays L.) trial without genotypic rank-change. For cluster analysis, distance between two sites is defined as the residual sum of squares after fitting SHMM with one multiplicative term (SHMM1) if SHMM1 does not show genotypic rank-change. However, if SHMM1 does show genotypic rank-change, the distance between two sites is defined as the smaller of the sums of squares owing to genotypes within each of the two sites. Calculation of distance between two sites is facilitated by using the site regression model with one multiplicative term (SREG1), which can be reparameterized as SHMM1 when only two sites are considered. The dichotomous splitting procedure, used on the dendrogram obtained from cluster analysis, will first perform SHMM analyses on each of the last two cluster groups to join (end of the dendrogram). If SHMM1 does not give an adequate fit, the next step is to move down the branches of the tree until groups of sites (clusters) are found to which SHMM1 provides an adequate fit and primary effects of sites are all of the same sign. Five final groups of sites to which SHMM1 provides an adequate fit and primary effects of sites are all of the same sign were obtained. The procedure appears to be useful in identifying subsets of sites in which genotypic rank-change interactions are negligible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00220916
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  • 3
    Electronic Resource
    Electronic Resource
    Using the shifted multiplicative model to search for “separability” in crop cultivar trials (1992)
    Springer
    Theoretical and applied genetics 84 (1992), S. 161-172 
    Details
    ISSN: 1432-2242
    Keywords: Genotype x environment interaction ; Shifted multiplicative model ; Separability ; Concurrent regression model ; Crossover interaction ; Qualitative interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The shifted multiplicative model (SHMM) is used in an exploratory step-down method for identifying subsets of environments in which genotypic effects are “separable” from environmental effects. Subsets of environments are chosen on the basis of a SHMM analysis of the entire data set. SHMM analyses of the subsets may indicate a need for further subdivision and/or suggest that a different subdivision at the previous stage should be tried. The process continues until SHMM analysis indicates that a SHMM with only one multiplicative term and its “point of concurrence” outside (left or right) of the cluster of data points adequately fits the data in all subsets. The method is first illustrated with a simple example using a small data set from the statistical literature. Then results obtained in an international maize (Zea mays L.) yield trial with 20 sites and nine cultivars is presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00223996
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  • 4
    Electronic Resource
    Electronic Resource
    The area under the function: an index for selecting desirable genotypes (1993)
    Springer
    Theoretical and applied genetics 87 (1993), S. 409-415 
    Details
    ISSN: 1432-2242
    Keywords: Genotype x environment interaction ; Adaptation ; Stability ; Desirability index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The linear regression approach has been widely used for selecting high-yielding and stable genotypes targeted to several environments. The genotype mean yield and the regression coefficient of a genotype's performance on an index of environmental productivity are the two main stability parameters. Using both can often complicate the breeder's decision when comparing high-yielding, less-stable genotypes with low-yielding, stable genotypes. This study proposes to combine the mean yield and regression coefficient into a unified desirability index (D i). Thus, D i is defined as the area under the linear regression function divided by the difference between the two extreme environmental indexes. D i is equal to the mean of the i th genotype across all environments plus its slope multiplied by the mean of the environmental indexes of the two extreme environments (symmetry). Desirable genotypes are those with a large D i. For symmetric trials the desirability index depends largely on the mean yield of the genotype and for asymmetric trials the slope has an important influence on the desirability index. The use of D i was illustrated by a 20-environments maize yield trial and a 25-environments wheat yield trial. Three maize genotypes out of nine showed values of D i 's that were significantly larger than a hypothetical, stable genotype. These were considered desirable, even though two of them had slopes significantly greater than 1.0. The results obtained from ranking wheat genotypes on mean yield differ from a ranking based on D i .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215085
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