Molecular Breeding in Cowpea

Cowpea (Vigna unguiculata L. Walp.) (2n=2x=22) is an important and often a staple annual legume widely grown in Africa, Latin America, Southeast Asia, and the southern United States. It is chiefly used as a fresh or dry grain or vegetable crop for food, and can also be used as animal fodder. The objective of this project was to build a Genotyping by Sequencing (GBS) and Single Nucleotide Polymorphism (SNP) platform for molecular breeding in cowpea and to merge molecular and classical breeding to expedite genetic gain and development of new cowpea cultivars. The molecular approach includes the discovery of genome-wide SNP through GBS, analysis of genetic diversity for world-wide accessions, conducting of genome-wide association, and the identification of SNP markers associated with morphologic and agronomic traits, disease resistance, and seed quality through marker-assisted and genome-wide selection. It is expected that more than 30,000 SNPs will be discovered from 1,000 world-wide cowpea lines through GBS.  Genetic diversity is being analyzed in these 1,000 cowpea lines. Genome-wide association is being conducted for morphologic traits such as plant habit, dry pod color, pod placement, mature seed pattern, seed coat color, seed pattern color, flower color, seed protein and sugar contents. Further, agronomic traits such as grain (seed) yield, 100-seed weight and seed size,  along with abio- and biotic (disease and pest) resistance/tolerance to cowpea wilt (Fusarium oxysporum f. sp. tracheiphilum), cowpea mosaic virus (CPMV), bacterial blight (Xanthomonas axonopodis pv. vignicola), cowpea aphid, iron deficiency chlorosis (IDC), and low phosphorus uptake efficiency are being studied for associations. SNP markers are also being identified for these traits. This research will provide breeders a tool to select for these traits through marker-assisted selection in a cowpea breeding program.