Analysis of the environmental component of genotype × environment interaction in crop adaptation evaluation

Cluster analysis has been useful in summarizing patterns of genotypic performance and environmental productivity when there is a significant amount of genotype × environment (G × E) interaction confounding the plant breeder. There has, however, been little emphasis on analysing the enviromental component of G × E interaction or identifying environments which elicit similar patterns of yield response across genotypes. Grouping environments on the basis of genotype mean has been relatively uninformative, because it has largely ignored the G × E interation. The method discussed here groups environments in such a way that the relative, not the actual, genotype performance is similar within environment groups. The use of genotype yield deviations from environment mean yield as a measure of the G × E effect in pattern analysis (the combined use of numerical classification and ordination), and their representation in bar graphs as a relative genotype ranking index ( RGRI), is shown to be very effective in separating differential soybean line responses in different environments in Thailand. Recommendations of cultivars can then be made to farmers in particular regions.