GGE biplot analysis of yield associations with root traits in a Mesoamerican bean diversity panel

Common bean production is subject to prolonged and crop-failure-threatening drought events worldwide. One of the best approaches in identifying parents and progeny with local adaptation to a target environment is the characterization of multiple environments. In this study, we used genotype + genotype x environment (GGE) biplot analysis to examine the informativeness of the testing environments used by the bean breeding program at Michigan State University to select for drought tolerance. A group of 96 diverse Mesoamerican common bean (Phaseolus vulgaris L.) genotypes assembled from breeding programs and germplasm collections across the US were tested in two Michigan locations for three years. GGE biplots were used to rank genotypes according to environments and treatments (irrigated and rainfed) within environments. A genotype-by-trait analysis was also used to identify traits relevant to yield under rainfed and irrigated environments. Significant differentiation and non-redundancy was found among the environments suggesting that resource use is efficient. Rainfed environments were better at discriminating high performing genotypes in Michigan. A number of root architecture traits such as taproot diameter were independent or associated with yield in common bean under different environments. Genotype by trait analysis showed a significantly negative correlation between growth habit and seed yield. A common feature of the better adapted and higher yielding genotypes under Michigan conditions was the upright type II growth habit. Genotypes with contrasting traits associated with yield under rainfed and irrigated conditions were identified and could be used in the development of improved drought tolerance in future common bean cultivars.