Genetic and QTL Analysis for Hilum-Eye Types in Cowpea (Vigna Unguiculata L. Walp)

Abstract Cowpea is an important food legume widely grown in the semi-arid tropics and serves as a main source of dietary protein, minerals, and vitamins. However, varieties differ from region to region based on the consumer’s preference for seed types determined by seed size, seed coat texture, seed color, and hilum-eye types. The genetics of seed size, seed color, and seed coat texture have been well documented, but the hilum-eye types have not been studied well because they represent seven different types with complex interactions. We studied the genetic segregation for hilum-eye types and determined the number of genes involved in a recombinant inbred line (RIL) population derived from a cross between a small eye parent ‘GEC’ and a Watson eye parent ‘IT98K-476-8’. The results demonstrated a three-gene model, W (Watson), S (small), and R (large), for cowpea seed hilum-eye type pattern and the interaction of these three genes, W, S, and R, resulted in five phenotypes, viz. self, Watson, small, large, and ring hilum-eye types. Moreover, we also mapped the RILs for hilum-eye types, identified three quantitative trait loci (QTLs), and aligned to the cowpea reference genome as QTL qHilum7.1, qHilum9.1, and qHilum10.1, corresponding to these three genes, Ring type (R), Watson type (W), and Small type (S) hilum-eye type patterns, respectively. Therefore, there was a complete agreement between the genetic analysis and QTL mapping for the number of genes controlling the hilum types in cowpea.