Can tepary bean be a model for improvement of drought resistance in common bean?

Common bean (Phaseolus vulgaris L.) is the most important grain legume for human consumption and drought stress affects over 60% of dry bean production worldwide. Field studies were conducted over two seasons at Centro Internacional de Agricultura Tropical (CIAT), Palmira, Colombia to (i) evaluate phenotypic differences in drought resistance; and (ii) identify adaptive traits that can be used in on-going breeding programmes of common bean for developing drought resistant genotypes. A total of 36 genotypes, including elite inbred and interspecific lines and landraces of common bean and tepary bean were evaluated under field conditions with two levels of water supply (irrigated and rainfed). Results showed that two accessions of tepary bean, P. acutifolius (G 40159 and G 40068) and two elite lines (RAB 650, SEA 23) of common bean were outstanding in their adaptation to terminal drought stress. The superior performance of these genotypes under drought stress was associated with their ability to mobilise photosynthates from leaves and stems to developing grain. Tepary bean was superior to common bean in combinig several desirable traits that contribute to greater level of adaptation to terminal drought stress. Canopy biomass, pod partitioning index, stem biomass reduction and pod harvest index could serve as useful traits to improve the efficiency of breeding programmes to select superior genotypes of common bean under terminal drought stress.Keywords: Abiotic stress, harvest index, water stressAfrican Crop Science Journal, Vol. 21, No. 4, pp. 265 - 28