Abstract
Cowpea (Vigna unguiculata [L.] Walp., diploid, 2n = 22) is a major crop used as a protein source for human consumption as well as a quality feed for livestock. It is drought and heat tolerant and has been bred to develop varieties that are resilient to changing climates. Plant adaptation to new climates and their yield are strongly affected by flowering time. Therefore, understanding the genetic basis of flowering time is critical to advance cowpea breeding. The aim of this study was to perform genome-wide association studies (GWAS) to identify marker trait associations for flowering time in cowpea using single nucleotide polymorphism (SNP) markers. A total of 368 accessions from a cowpea mini-core collection were evaluated in Ft. Collins, CO in 2019 and 2020, and 292 accessions were evaluated in Citra, FL in 2018. These accessions were genotyped using the Cowpea iSelect Consortium Array that contained 51,128 SNPs. GWAS revealed seven reliable SNPs for flowering time that explained 8–12% of the phenotypic variance. Candidate genes including FT, GI, CRY2, LSH3, UGT87A2, LIF2, and HTA9 that are associated with flowering time were identified for the significant SNP markers. Further efforts to validate these loci will help to understand their role in flowering time in cowpea, and it could facilitate the transfer of some of this knowledge to other closely related legume species.
Highlights
Cowpea (Vigna unguiculata [L.] Walp., diploid, 2n = 22) is a major crop grown worldwide for food and nutritional security (Lonardi et al, 2019)
Range of flowering was shorter in Florida as compared to Colorado
We identified 30 Marker trait association (MTA) corresponding to 20 unique single nucleotide polymorphism (SNP) for days to flowering that explained 8–12% of phenotypic variance in the genome-wide association studies (GWAS) conducted using four software in the three datasets (Table 2)
Summary
Cowpea (Vigna unguiculata [L.] Walp., diploid, 2n = 22) is a major crop grown worldwide for food and nutritional security (Lonardi et al, 2019). Annual cowpea production is estimated at 7 million tons of dry grain harvested on about 14 million hectares worldwide (Singh, 2020). It is a major source of protein for human consumption (Phillips et al, 2003), fodder for livestock. Cowpea forms a symbiotic association with root nodulating bacteria and fixes nitrogen directly to the soil (Martins et al, 2003) This biological nitrogen fixation improves crop growth and grain production without increasing production costs associated with application of nitrogen fertilizers. Crop rotation including cowpea helps to decrease instances of Striga hermonthica, a parasitic weed of cereals (Berner et al, 1996)
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