DArTseq-based genome-wide SNP markers reveal limited genetic diversity and highly structured population in assembled West African cowpea germplasm

The potential of cowpea (Vigna unguiculata [L] Walp) to contribute to food security and livelihood sustenance of sub-Sahara Africans is constantly threatened by many biotic and abiotic stresses that are aggravated by climate change. To address these threats, cowpea breeding programs in the subregion prioritize climate-resilience traits and resistance to biotic stresses. However, before successful trait discovery and implementation, it is essential to characterize diversity and population structure of cowpea germplasm. To test the hypothesis that assembled cowpea germplasm exhibits limited and narrow genetic diversity with a well-defined population structure, we assessed the level of genetic variability and characterized the population structure of 188 cowpea genotypes using 5147 Single Nucleotide Polymorphism (SNP) markers. The structure results revealed five major genetic groups with moderate levels of genetic diversity and an admixture level of 17 %. Discriminant analysis and phylogenetic analysis supported this finding, indicating the presence of distinct groups within the cowpea population. The analysis of molecular variance (AMOVA) showed 27 % among population variance, 64 % within-population variance, and 9 % within individual variance. While considering the origin, the AMOVA showed 16 % among population variance, 75 % among individual variance, and 9 % within individual variance. This study provides valuable insights for future cowpea improvement programs by facilitating the selection of suitable progenitors for population development, and contributing in the conservation of cowpea genetic resources. Addressing these challenges and enhancing cowpea's diversity and resilience are crucial steps towards ensuring food security and sustainable livelihoods in sub-Saharan Africa