Assessing the genetic diversity of cowpea [Vigna unguiculata (L.) Walp.] accessions from Sudan using simple sequence repeat (SSR) markers

Abstract

Genetic diversity and phylogenetic relationships among 252 cowpea (Vigna unguiculata (L.)Walp) accessions collected throughout the six geographical regions of Sudan were evaluated using simple sequence repeat (SSR) molecular markers. Eighteen (18) published primer pairs were selected based on their informativeness, out of which 16 primer pairs gave reproducible results among all of the cowpea accessions tested. A total of 129 alleles were detected from the 16 loci with an average of 8.1 alleles per locus. Heterozygosity values ranged from 0.01 to 0.13 with an average occurrence of 0.05 while the gene diversity ranged from 0.34 to 0.85 with an average of 0.60. The polymorphism information content (PIC) varied from 0.33 to 0.83 with an average of 0.56. Sudanese Cowpea germplasm clustered into three main groups with control germplasm obtained from the International Institute for Tropical Agriculture (IITA) showing distribution along two groups. This study confirms earlier suggestions that cowpea was first introduced into Sudan from West African countries into western Sudan (Kordofan and Darfur) regions. Accession TVU 8812-IITA Benin was found to be the most divergent cowpea accession within the individuals followed by accession HSD 5738 Sudan-Blue Nile and HSD 6782 Sudan-South Kordofan.   Key words: Simple sequence repeat, microsatellites, genetic diversity, cowpea.