Classification of environments to control genotypes by environment interaction with application to wheat in Rio Grande do Sul

The presence of genotype x environment interaction is the critical point in genetic improvement of cultivated plants, as wheat (Triticum aestivum L.), and regionalization is one of practical approaches used for its control. The nature of cultivar x environments interaction shows some advantages in separating locals in the three regions actually existent in the State, showing also biasedness in σ2CL estimates when data from one year is used, due to presence of cultivar x year and cultivar x local x year interactions. Clustering and principal components methods showed no consistency in locals classification during the period of years considered. Cannonical variates method was considered the best appropriate for the present case. Results derived from data showed that II, III and IV regions did not differ significantly, being considered just one region.