Mechanisms of tolerance to water deficit and physiological responses to rehydration in cowpea

The cowpea bean is one of the main legumes grown in the Northeast region, with a purpose directed to the production of dried grains or green pods. However, this region suffers from climatic variations, with drought being the main abiotic stress factor. Therefore, the objective was to evaluate the physiological, morphological and pod production characteristics of traditional cowpea varieties in terms of drought tolerance and rehydration in the Brazilian semiarid region. The varieties were: Pingo de Ouro 1,2 (PO), Sempre Verde (SV) and Feijao de Moita (FM). The experimental design used was entirely randomized, in a 3 x 2 factorial scheme (3 genotypes x 2 soil water conditions) with 5 replicates for each treatment, totaling 30 experimental units. Growth variables, carbon metabolism, and pod production were evaluated. The results suggest that the water stress negatively affected the cowpea genotypes, especially those that had negative effects on the morphological level and pod production. In these aspects, the genotype FM was the most sensitive to the severe water stress. However, Creole genotypes showed characteristics physiology similar to the standard tolerance genotype, the PO. Also, all genotypes recovered after rehydration. In terms of pod production and characteristics, the genotype PO, in general, presented better responses under stress conditions.