Canonical variate analysis of genotype x environment interactions

The additive main effects and multiplicative interaction (AMMI) model is us ed to investigate genotype x environment interactions often encountered in variety trials. Interaction effects are accounted for by several multiplica tive terms in the model, with each consisting of a genotypic and an environ mental parameter. These effects are estimated using principal-component ana lysis. An alternative method is presented to estimate the genotypic and env ironmental parameters in the multiplicative terms of the AMMI model by cano nical variate analysis. The number of significant interactive terms can be easily determined using the chi(2) test. Each of the multiplicative terms i nclude a unitless coefficient measuring genotypic response and an environme ntal effect in terms of the physical unit of the concerned trait. Biplots c an be used with the scores of both genotypes and environments for graphic e xamination of analytic results. Total tuber-yield data from potato genotype s tested in a series of international trials are used to illustrate the new analytic procedure.