Identification of Loci Controlling Domestication-Related Traits in Cowpea (Vigna unguiculata L. Walp)

Cowpea (Vigna unguiculata L. Walp) is a major source of protein, folic acid and several vitamins for many people in sub-Saharan Africa and other parts of the developing word. Cowpea was domesticated in Africa, most likely from the wild form V. unguiculata ssp dekindtiana, and several domestication locales have been proposed including West and Southeast Africa. Cultivated and wild cowpeas differ in various characters collectively designated as “domestication syndrome”. However, the genetic control of these domestication traits remains largely unknown. This lack of domestication-related knowledge in cowpea has limited the utilization of wild germplasm for crop improvement. To gain new insights into the genetic basis of cowpea domestication, nine domestication-related traits including ‘pod shattering’, ‘seed weight’, ‘seed number per pod’, ‘pod length’, and ‘days to flowering’ have been analyzed in a biparental mapping population. This population consists of 215 RILs derived from a cross between IT99K-573-1-1 (cultivated cowpea) and TVNu-1158 (wild cowpea), and it was genotyped with the Cowpea iSelect Consortium Array (51,128 SNPs). A genetic map containing 17,739 SNPs mapped to 1,825 bins has been developed and used for QTL mapping of the aforementioned traits. A total of 15 QTL were identified for the nine domestication-related traits on linkage groups 1, 2, 3, 4, 5, 6 and 8. These QTL could potentially be useful for cowpea breeding to more efficiently develop improved cultivars. Future studies will include identifying candidate genes underlying those QTL regions.