Identification of candidate genes controlling red seed coat color in cowpea (Vigna unguiculata[L.] Walp)

Abstract

Seed coat color is an important consumer-related train in cowpea (Vigna unguiculata[L.] Walp.) and has been a subject of study for over a century. Utilizing newly available resources, including mapping populations, a high-density genotyping platform, and several genome assemblies, red seed coat color has been mapped to two loci,Red-1(R-1) andRed-2(R-2), on Vu03 and Vu07, respectively. A gene model (Vigun03g118700) encoding a dihydroflavonol 4-reductase, a homolog of anthocyanidin reductase 1, which catalyzes the biosynthesis of epicatechin from cyanidin, has been identified as a candidate gene forR-1. Possible causative variants have been also identified forVigun03g118700. A gene model on Vu07 (Vigun07g118500), with predicted nucleolar function and high relative expression in the developing seed, has been identified as a candidate forR-2. The observed red color is believed to be the result of a buildup of cyanidins in the seed coat.