2018 ASHS Annual Conference

Cowpea (Vigna unguiculata (L.) Walp) is a legume crop grown worldwide to provide protein for human consumption and animal feed. The objective of this research is to estimate the cowpea seed protein content and at the same time conduct association mapping and SNP marker identification for seed protein content in USDA cowpea germplasm. A total of 173 USDA cowpea germplasm accessions were evaluated for their seed protein contents, including 18 accessions with black seed coat color, 26 blackeye, 29 browneye, 12 cream, 8 pinkeye, 15 red, 19 red holstein, 26 tan, and 20 varied color. The field experiment was conducted in two locations within Arkansas State (Fayetteville and Alma) in 2016. A randomized complete block design (RCBD) with three blocks was used for the experiment in each location. In each plot, cowpea accessions were planted in four rows 10 feet long, with three feet between rows. The seed protein content averaged 25.6%, with a range from 19.6% to 31.0%, and had a standard deviation (Std) of 1.82% with 0.06% Std Error, indicating the seed protein content had large variation in the 173 cowpea accessions. The seed protein content showed difference among the seed coat color: cream and pinkeye seed types had the highest seed protein content with 27.2% and 26.7% respectively; black, blackeye, and browneye second highest with 25.9%, 26.0%, and 26.0% respectively; then, red and tan with 25.3% and 25.3%, respectively; and finally the red Holstein with 23.7%. Association analysis was conducted with the single marker regression (SMR) without structure and without kinship, the regression linear model (GLM), and the mixed linear model (MLM) methods as described in TASSEL 5. Eight SNP markers, C35058883_723, C35069896_1985, C35074656_2002, C35084640_31, Scaffold40268_5600, Scaffold72747_120, Scaffold75749_1913, and Scaffold94454_419 were founded to be associated with seed protein content in the panel of 173 cowpea accessions. This study will provide a tool for breeders how to use USDA cowpea resource and to select high seed protein contents in cowpea breeding program through marker-assisted selection.