MODELING EXPECTATION AND VARIANCE FOR GENOTYPE BY ENVIRONMENT DATA

An integration of mio types of models for the analysis of genotype by environment interaction is presented. On the one hand. the expectation of G x E interaction is frequently modelled by regression models; on the other hand, for deviations from these regressions, either separate stability parameters are defined or extra components of variance are introduced. A class of mixed models is described that contains facilit ies for modelling expectation by regression and, in addition, has exte nsive possibilities for dealing with heteroscedasticity. Practical asp ects of the use of these mixed models are illustrated on a data set in volving sugar yield in beet.