Evaluation of Seed Protein Content in USDA Cowpea Germplasm

Cowpea [Vigna unguiculata (L.) Walp] is an annual legume crop grown worldwide to provide protein for human consumption and animal feed. The objective of this research was to evaluate the seed protein content in U.S. Department of Agriculture (USDA) cowpea germplasm for use in cowpea breeding programs. A field experiment was conducted with a randomized complete block design (RCBD) with three duplications in two locations, Fayetteville and Alma, in Arkansas, United States. A total of 173 USDA cowpea accessions were evaluated with the Elementar Rapid N analyzer III for their seed protein contents. The results showed that there was a wide range of seed protein content among the 173 cowpea genotypes, ranging from 22.8% to 28.9% with an average of 25.6%. The broad-sense heritability for seed protein among the 173 cowpea genotypes was 50.8%, indicating that seed protein content was inheritable and can be selected in breeding processing. The top five cowpea accessions with the highest seed protein contents were USDA accession PI 662992 originally collected from Florida (28.9%), PI 601085 from Minnesota (28.5%), and PI 255765 and PI 255774 from Nigeria and PI 666253 from Arkansas (28.4% each). PI 339587 from South Africa had the lowest protein content with 21.8%. The were also significant differences in seed protein contents observed among different seedcoat colors; the accessions with cream color exhibited higher protein content (27.2%) than others. This research could provide information for breeders to develop cowpea cultivars with higher seed protein content in a cowpea breeding program.