Evaluation of bean cultivars to drought resistance based on water stress days in soil

Abstract

"Preto" and “Mulatinho" bean cultivars (Phaseolus vulgaris L.) were evaluated to drought resistance based on water stress days in soil. Yield experiments were installed on six planting dates using eight "Preto" cultivars: P-730, GO-3836, Iguaçu, Rio Tibagi, P-729, Rico 23, Tambó, Cuva 168-N; and six “Mulatinho" cultivars: Mulatinho Paulista, Favinha, Vila Nova, IPA-7419, Mulatinho Vagem Roxa and Mulatinho lrecê, in blocks delineated at random. Water stress days in soil were measured for all cultivars of each planting through a water balance, using a computer model. Water stress days were those days when the total extractable soil water was 25% below the storage capacity until 1 m depth level. Simple linear regression studies were made between production and number of water stress days, in all six experiments, during the flowering stage also, the productivity of each cultivar was compared with the group's general average. Grain yield decreased as number of water stress days in soil increased in all “Preto" and "Mulatinho" cultivars. Yield general average WSS higher in the "Mulatinho" cultivars than in the "Preto" cultivars, under water stress in soil. Among "Preto" cultivars. “P-730” was the most steady and 'Rio Tibagi' had the highest production, with 24.15% more than the group's general average, under zero, five, ten and fifteen degrees of water stress days in soil. Among 'Mulatinho' cultivars, 'Favinha' was the most steady and ‘IPA-7419' had the highest production, with 13.61% more than the group's general average, under the same degrees of water stress days. The advantage of this method of evaluating drought resistance based on water stress days in soil is that it permits comparing yields of different flowering stage cultivars directly, which may be subject to different water stress degrees in soil.