An empirical method of grouping genotypes based on a linear function of the genotype-environment interaction.

The regression approach for analysing genotype-environmental interaction is extended to include the grouping of genotypes. An unweighted pair-group cluster analysis was applied to a special dissimilarly index, derived from the test statistic for differences among regressions. The resulting groups reflect the general pattern of response to the various environments. The data of Yates and Cochran (1938) were used to illustrate the clustering process.