Mega-Environmental Design: Using Genotype x Environment Interaction to Optimize Resources for Cultivar Testing

The efficient use of testing resources is one of the key factors for successful plant breeding programs. Controlling micro- and macro-environmental variability is an effective way of improving the testing efficiency and the selection of superior genotypes. Common experimental designs in genotypic testing usually use replicated or augmented experiments at each location, but they are balanced across locations. Some studies suggest that the increase in population size even at the expense of balanced experiments might be beneficial if genotype x environment interaction (GEI) is modeled. The objective of this study was to compare strategies for micro and macro-environmental variability control that include GEI information to optimize resource allocation in multi-environment trials (METs). Six experimental designs combined with four spatial correction models were compared for efficiency under three experimental sizes using simulations under a real yield variability map. Additionally, six resource allocation strategies were evaluated in terms of accuracy and the expected response to selection. The a-lattice (ALPHA) experimental design was the best one at controlling micro-environmental variability. The moderate mega-environmental design (MED) strategy had the largest response to selection. This strategy uses historical mega-environments (MEs) to unbalance genotypic testing within MEs while modeling GEI. The MED was the best resource allocation strategy and could potentially increase selection response up to 43% in breeding programs when genotypes are evaluated in METs.