Grain Protein Content and Yield of Cowpea Genotypes Subjected to Drought

In this study, we aimed to evaluate the protein and amino acid contents in grain and the yield of four cowpea genotypes grown in a greenhouse under drought stress at the pollination stage, considered the most sensitive stage to water stress. The four genotypes were two landraces, EPACE 10 and Paulistinha, and two commercial cultivars, Novaera and BR 17 Gurguéia. Water deficit was imposed for eight days, until leaf water potential (Ψa) was close to -2.0 MPa, and then the plants were rehydrated until maturation. On the last day of stress, EPACE 10 and Paulistinha had higher Ψa values than the other two genotypes. When irrigated, landraces had higher grain protein content (GPC) than the commercial cultivars. Under drought, total GPC was reduced only in EPACE 10, while it remained unchanged in BR 17 Gurguéia. In this condition, EPACE 10 exhibited a notably higher grain amino acid content (GAC), with methionine levels peaking. In addition, SDS-PAGE was successfully used to discriminate the genotypes. Under irrigation, the commercial genotypes (BRS Novaera and BR 17 Gurguéia) yielded more than the two landraces. Still, BRS Novaera had lower methionine and cysteine contents. However, under drought, EPACE 10 and BR 17 Gurguéia had the highest yields. In contrast, EPACE 10 had the best amino acid profile, especially for methionine and cysteine, but with slightly lower lysine content. Therefore, EPACE 10 may serve as a potential genotype for improving food security in low-input agriculture, and BR 17 Gurguéia for irrigated farming. However, more studies are needed, especially in the field, to confirm these results.