Association analysis of cowpea bacterial blight resistance in USDA cowpea germplasm.

Cowpea bacterial blight (CoBB, Xanthomonas axonopodis pv. vignicola, Xav) is the most important bacterial disease of cowpea ( Vigna unguiculata) because it prevalent in all major cowpea growing areas worldwide, and the use of host resistance is the primary method to control this disease. Genetic diversity and association analysis were conducted for CoBB resistance in 249 USDA germplasm accessions, originally collected from 42 countries. Genotyping by sequencing (GBS) was used for single nucleotide polymorphism (SNP) discovery. A total of 1031 SNPs were used for genetic diversity and association analysis in this study. Three well-differentiated genetic populations and admixtures were postulated in the cowpea panel by STRUCTURE 2.3.4 and MEGA 6. Association analysis for CoBB resistance was done using single marker regression, general linear mode, and mixed linear mode using Tassel 5, GAPIT and QGene 4. Four SNP markers (C35046071_1260, C35084634_455, scaffold96328_3387, and scaffold96765_4430) were identified to be strongly associated with CoBB resistance with >70 % selection accuracy. These markers can be utilized in cowpea breeding for CoBB resistance through marker-assisted selection. [ABSTRACT FROM AUTHOR]