Drought resistance of tropical dry black bean lines and cultivars

The objectives of this research were to classify black seeded dry bean genotypes for their drought tolerance and to identify those with the highest seed yield efficiency under irrigated and drought stressed conditions. During the 2008 Winter-Spring growing season two experiments were carried out at Medellín de Bravo, Veracruz; one was irrigated during the whole growing cycle, whereas in the other one, irrigation was withheld from the onset of flowering. Nine lines, six improved cultivars and the 'Arbolito' landrace (local control) were evaluated using a randomized complete block design with three replications. Data recorded included days to physiological maturity, seedless aerial dry biomass production, number of pods per plant, weight of 100 seeds and seed yield. Analysis of variance for the irrigated and drought stressed conditions, as well as combined analysis were performed. The drought susceptibility index (DSI) and the relative efficiency index (REI) were used as efficiency criteria. Under irrigated conditions, Negro INIFAP, 82L-17-18, Negro Tacaná and Negro Veracruz were the most productive genotypes with more than 1.0 t ha-1. Under drought conditions, the last two genotypes along with line DOR 448 were the most productive with a seed yield higher than 400 kg ha-1. On average, the yield obtained under drought conditions was 37.7% of that under irrigation. With DSI values of 0.71, 0.85 and 0.87, lines DOR-448, NGO 17-99 and Icta Ju-97-1, respectively, were considered as drought tolerant. Under both moisture conditions, Negro Tacaná and Negro Veracruz with REI values of 1.67 and 1.47, respectively, showed the highest seed yield efficiency.