Analysis and Handling of G × E in a Practical Breeding Program.
Genotype by environment interaction (GE) is a reality in plant breeding and crop production, and has to be dealt with. There are but two viable options to deal with GE: to utilize it or to avoid it, depending on whether it is repeatable. Repeatable GE can be selected for (utilized) whereas unrepeatable GE has to be selected against (avoided). To utilize GE involves identifying repeatable GE, dividing the target region into subregions or megaenvironments (ME) based on the repeatable GE pattern, and selecting within ME. By definition, GE within ME is unrepeatable and has to be avoided. To avoid unrepeatable GE is to test in a sufficient number of environments (locations and years) representing the target ME and to select both high mean performance and high stability. My preferred analytic tool for identifying repeatable GE, ME analysis, representative test locations, and superior genotypes is GGE (genotypic main effect plus GE) biplots, which was demonstrated using oat (Avena sativa L.) yield data from multilocation multiyear trials. Some important issues on GE study, in relation to genotype evaluation, were discussed. These included the framework of multiyear multilocation trials, the distinction between repeatable and nonrepeatable components of GE, the need to consider both genotypic main effect (G) and GE, and the relative importance of mean performance (G) vs. stability (GE) in genotype evaluation.
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