2019 ASHS Annual Conference

Cowpea is a legume offering good quality nutrition to the human’s diet. Cowpea is cultivated on more than 14 million hectares worldwide. However, drought stress has been shown to have devastating impacts on cowpea production. Developing drought-tolerant cowpea cultivars could be an alternative to alleviate drought-related issues in cowpea. Therefore, this study aimed to conduct a genome-wide association study (GWAS), identify single marker polymorphism (SNP) markers, perform genomic selection (GS), and evaluate GS accuracy for drought-related traits in cowpea. The experiment involved a total of 331 cowpea genotypes, which were phenotyped in a greenhouse using 3 blocks (time). Of the 331 accessions, 234 were genotyped using a total of 1,006 high quality SNPs postulated from genotyping-by-sequencing (GBS). Phenotypes were collected before applying drought stress, at the time where 50% of the susceptible control displayed chlorotic unifoliate leaves, and when all plants for the susceptible control were completely dead. Soil moisture was recorded weekly. Phenotypic data consisted of plant height, stem diameter, chlorophyll content, plant greenness score, number of plants showing chlorotic unifoliate leaves, number of plants showing first chlorotic trifoliate leaves, average ratio between green trifoliate leaves and chlorotic trifoliate leaves, number of dead plants, number of plants showing dead growing points, and wilting dynamics of the genotype. A large variation in these phenotypic data is expected among the association panel. GWAS will be conducted using TASSEL, GAPIT, FarmCPU, and BLINK. Significant SNPs (LOD>3) and overlapping SNPs between traits will be identified. GS will be conducted using rrBLUP, gBLUP, BLR, RF, and SVMs. We expect that GS accuracy will depend on the trait and GS models. These results can be used in cowpea breeding for drought tolerance.