Application of SSR Markers in Determination of Putative Resistance to SPVD and Genetic Diversity among Orange Fleshed Sweet Potato

Abstract

Viruses are the second most important production constraint after the sweet potato weevil. Orange fleshed OFSPs) are characterized by medium to low resistance to sweet potato virus disease (SPVD). Therefore this studies were aimed at evaluating OFSPs for resistance to SPVD and their genetic diversity from six families. Thirteen OFSPs clones from five families and other four genotypes were selected by their moderate SPVD responses after challenge to viruses. They were screened using ten Simple sequence Repeats (SSR) markers, six of them being polymorphic. Neighbor joining tree was generated with DARwin Version 6.0.010 using unweighted pair group method with arithmetic means (UPGMA). Principal component analysis (PCA) and Pearson Correlation matrix were obtained with XLSTAT 2015 version. The test clones clustered in two groups separately from virus susceptible genotypes. This implied that SSR markers are useful in discriminating virus susceptible and resistant genotypes. A total of 18 alleles were detected with an average of 3.0 alleles per locus. The highest major or abundant alleles (0.94)  was observed in marker IBJ- 324 Major allele frequency mean of 0.69 for the six markers was obtained. Mean genetic diversity of the markers was 0.41. Average polymorphism information content was 0.36. Pearson’s correlation coefficient was used to determine relationship between genotypes screened with SSR markers. Virus susceptible genotypes Ejumula and Carrot C had the highest similarity matrix of 0.83. Lowest matrix was between F1C9 and F3C1 at -0.03. Pearson’s correlation coefficient revealed an average similarity of 0.54 among genotypes. This study therefore indicates that there is robust genetic diversity in SPVD resistant sweet potato genotypes. These genotypes can be used as parents in breeding programs aimed at improving the crop for the multiple traits.