Morpho-agronomic, molecular characterization, and resistance to pests and diseases of cowpea genotypes in the semi-arid of Brazil

Semi-arid regions require the use of varieties adapted to local edaphoclimatic conditions. This study aimed to characterize landraces (Verde Ligeiro, Sempre Verde, Cariri, Azul, and Corujinha) and commercial cultivars (BRS-Pajeú, Novaera, and Guariba) of cowpea and evaluate the resistance to pests and diseases of the genotypes in irrigated (Lagoa Seca, PB) and non-irrigated (Esperança, PB) production fields. The genotypes were cultivated in an agroecological system, and morpho-agronomic analyses were performed according to the International Biodiversity descriptors of the species. Molecular characterization was performed by using ISSR markers. Pests and diseases were evaluated during the crop cycle. The genotypes had differences in qualitative characteristics (growth habit, flower color, seed color, seed shape, and mature pod color) and in quantitative characteristics (days to flowering, number of pods, pod length, number of seeds per pod, and yield). In irrigated field, the Corujinha landrace had the highest yield, and Cariri had the lowest. In non-irrigated field, the Sempre Verde landrace was the most productive, and the BRS-Novaera cultivar was the least. The 11 ISSR primers used for molecular characterization of the genotypes generated 123 bands, of which 65% were polymorphic. Intrapopulation genetic diversity was low, but cluster analysis separated the populations into two groups. Differences in the incidence of powdery mildew and cercospora leaf spot were found among the genotypes, as well as differences in pod bug infestation. The BRS-Novaera genotype was the most susceptible to diseases and pests in both irrigated and non-irrigated fields. It is concluded that the most productive genotypes with the lowest intensity of diseases and pests in irrigated fields were the Corujinha, Sempre Verde, and Azul landraces, and the BRS-Pajeú and BRS-Guariba commercial cultivars; and under rainfed conditions, the most adapted cultivar was the Sempre Verde landrace.