Use of expressed sequence tags-derived simple sequence repeat (SSR) markers for population studies of released and elite sweet potato

Development of improved varieties of sweet potato to meet specific end users in the sub-Saharan African region has the potential of transforming the crop’s market, consumption and health benefits. Molecular biology techniques such as fingerprinting are key to crop improvement, and critical for numerous genetic studies. This study, carried out in Ghana, seeks to determine genetic relatedness among two populations of sweet potato (released and elite), as well as to identify polymorphic and informative markers for diversity studies. Twenty expressed sequence tags-simple sequence repeat (EST-SSR) markers were used for analysis of DNA assembled. A total of 169 alleles were obtained, with an average of 8.5 alleles per locus. Pairwise genetic distance among genotypes ranged from 12 – 89. GenAlex v6.4 analysis showed that a higher genetic diversity existed within elite genotypes than the released lines. Results analyzed using Popgene version 1.31 software indicated that on the basis of both populations studied, EST-SSR markers utilized were very polymorphic (95%) and showed genetic diversity (I =0.888, He= 0.548) suggesting high heterozygosity in the collected varieties. The overall Fit (0.372%) and Fis (0.088%) suggest high genetic diversity within populations, and gene flow (1.95) indicate an exchange of genes between released sweet potatoes and elite ones. Ewens-Watterson test was conducted to test the neutrality. From the results obtained, markers CB329940, CB330477 and CB330936 showed high allelic polymorphism among varieties used and were recommended to be included in diversity studies.    Key words: Genetic diversity, genetic relatedness, expressed sequence tags-simple sequence repeat (EST-SSR), populations, released sweet potato, elite sweet potato.