Genetic diversity of farmer-preferred cowpea (Vigna unguiculata L. Walp) landraces in Turkey and evaluation of their relationships based on agromorphological traits

Cowpea (Vigna unguiculata L. Walp) is one of the important vegetable, grain, and fodder legume species grown in the tropics and subtropics. Cowpea is grown on small farms, and locally adapted landraces or populations are cultivated, and genetic improvements are limited by the lack of knowledge of genetic diversity of the indigenous and cultivated germplasm. Characterization and classification of diversity of the germplasm is valuable for both plant breeders and germplasm curators in the development of conservation strategies and identification of plant genetic resources. In the present study, 36 qualitative and quantitative agromorphological traits were used to characterize and assess the genetic diversity of 32 farmer preferred cowpea genotypes collected from diverse cultivated locations. Genetic variation was highly significant, and phenotypic diversity was observed for agromorphological traits. Agromorphological traits were classified by principal components analysis (PCA) into 10 components, which explained 81.18% of the total variation. PCA revealed that seed properties such as weight, diameter, width, length, eye color and immature pod pigmentation, leaf and pod color properties were the primary characteristics to discriminate cowpea genotypes. The hierarchical analysis grouped the genotypes into five clusters, and significant association was not apparent between geographic origin and agromorphological traits. The promising germplasm was identified to improve the landraces for fresh pod, grain, and fodder.