Physiological traits associated with drought resistance in Andean and Mesoamerican genotypes of common bean (Phaseolus vulgaris L.)

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 and rainout shelter studies were conducted at the International Center for Tropical Agriculture (CIAT), Palmira, Colombia to (i) evaluate phenotypic differences in drought resistance in Andean and Mesoamerican gene pools, (ii) identify genotypes of both Andean and Mesoamerican with superior drought resistance, and (iii) identify phenotypic traits that may be useful for breeding to improve drought resistance in common bean. A total of 24 bean genotypes, twelve genotypes belonging to Mesoamerican gene pool and twelve to Andean gene pool were evaluated under field with two levels of water supply (irrigated and rainfed) and managed drought under rainout shelter conditions. Results showed that five Mesoamerican lines SEA 5, SEA 15, SER 22, SER 16, SER 8 and one Andean line SEQ 1003 have superior resistance to drought. The superior performance of these lines under drought stress was associated with better canopy biomass at mid-pod filling that could be related to deeper root system and effective use of water, combined with efficient remobilization of photosynthates from vegetative structures to pod development (pod partitioning index, PPI) and grain filling (pod harvest index, PHI). Pod harvest index could be a useful selection criteria for drought resistance, to improve the efficiency of breeding programs for selecting superior genotypes of common bean.