Improving adaptation to drought stress in small red common bean: phenotypic differences and predicted genotypic effects on grain yield, yield components and harvest index

Common bean ( Phaseolus vulagaris L.) is mainly produced in Latin America, and Eastern and Southern Africa where seasonal rainfall is erratic and soil moisture deficit often limits its production. The objectives of this study were to identify superior advanced small red common bean lines with better grain yield under drought, and to identify plant traits that could serve as selection criteria for evaluating drought resistance. Thirty four advanced inbred lines were developed through triple cross and evaluated with two commercial checks (Nasir and Red Wolayita) under drought and irrigated field conditions in two seasons (2009 and 2010) and at two locations (Melkassa and Doni Kumbi Farm) in Ethiopia. Grain yield, pods/plant, seeds/plant and 100 seed weight were reduced by 47, 19, 15, and 9 %, respectively, under the drought conditions compared to the irrigated conditions. Seven genotypes (L62, L5, L20, L79, L12, L41, and L83) had better yield under drought compared to the standard check. Similarly, these genotypes had better predicted genotypic effects, suggesting that they would also be useful as drought resistant donors in common bean cultivar development program. Genotypic variance expressed as proportions to phenotypic variance was higher compared to genotype × environment interaction effects for all traits under drought conditions, suggesting that these genotypes can be used to further improve drought-resistance regardless of environments. Strong correlation between grain yield, canopy biomass and harvest index across environments suggested that canopy biomass and harvest index are repeatable and reliable plant traits to determine drought resistance in common bean.