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  • Author or Editor: Waltram Second Ravelombola x
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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.

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Cowpea is a leguminous and versatile crop which provides nutritional food for human consumption. However, salinity unfavorably reduces cowpea seed germination, thus significantly decreasing cowpea production. Little has been done for evaluating and developing salt-tolerant cowpea genotypes at germination stage. The objectives of this research were to evaluate the response of cowpea genotypes to salinity stress through seed germination rate and to select salt-tolerant cowpea genotypes. The seed germination rates under nonsalt condition and salinity stress (150 mm NaCl) were evaluated in 151 cowpea genotypes. Four parameters, absolute decrease (AD), the inhibition index (II), the relative salt tolerance (RST), and the salt tolerance index (STI) were used to measure salt tolerance in cowpea. The results showed that there were significant differences among the 151 cowpea genotypes for all parameters (P values <0.0001). The AD in germination rate was 5.8% to 94.2%; the II varied from 7.7% to 100%; the RST ranged from 0 to 0.92; and STI varied from 0 to 0.92. A high broad sense heritability (H2) was observed for all four parameters. High correlation coefficients (r) were estimated among the four parameters. PI582422, 09–529, PI293584, and PI582570 were highly salt tolerant at germination stage. In addition, genotypes from the Caribbean and Southern Asia exhibited better tolerance to salinity, whereas those from Europe and North America were the most salt-susceptible.

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