A procedure to assess the relative merit of classification strategies for grouping environments to assist selection in plant breeding regional evaluation trials

• Published in: Field crops research 1993-10, Vol.35 (1), p.63-74
• Main Authors: Cooper, M., Byth, D.E., DeLacy, I.H.
• Format: Article
• Language: English
• Subjects: AMELIORATION DES PLANTES; AUSTRALIA; AUSTRALIE; Breeding; Classification; CROP YIELD; ENVIRONMENTS; ENVIRONNEMENT; Evaluation trial; FITOMEJORAMIENTO; GENOTIPOS; GENOTYPE; GENOTYPES; Indirect selection; MEDIO AMBIENTE; PLANT BREEDING; RENDEMENT DES CULTURES; RENDIMIENTO DE CULTIVOS; SELECCION; SELECTION; TRITICUM; Wheat
• ISSN: 0378-4290; 1872-6852
• DOI: 10.1016/0378-4290(93)90137-C

Classification methodology is widely used by plant breeders to group environments on the results of regional evaluation trials to assist in selection among genotypes. To be effective, this strategy must be integrated with the theory of indirect selection. Environments which group together should reflect commonality of genotypic discrimination and therefore give rise to similar selection among genotypes. Four strategies for classifying environments were compared. These were based on untransformed and three forms of transformed data (coded, standardised and rank). The comparison assessed how effectively the groups of environments formed by using each transformation maximised the opportunity for exploiting indirect selection between environments within the same group relative to environments in other groups. The objective in this study was to identify groups of international environments, used by CIMMYT in its international nursery program, which gave high indirect response to selection for grain yield in six Australian environments. Generally the four classification strategies identified subsets of international environments for which selection gave a greater indirect response than that for selection on average performance across all of the international environments (35% to 94% on average over all Australian environments). Environmental classifications based on the standardised and rank transformations were generally superior to those based on the untransformed and coded transformations (46% on average over all Australian environments). The magnitude of this advantage differed between the Australian environments but was substantial for the two environments which expressed the greatest opportunity for exploiting indirect selection. These results have obvious and large implications for the use of classification methodology to structure regional testing regimes for plant breeding programs.