Morphological and molecular diversity of progenies derived from reverting and non-reverting sweet potato genotypes

Abstract

Sweet potato production is mainly constrained by sweet potato viruses. Some East African sweet potato cultivars are known to revert from the virus infections while the American cultivars seldom revert. Full diallel crosses between reverting and non-reverting sweet potato genotypes in previous research has yielded progenies with varying reversion potential. However, information is lacking on the morphological and molecular diversity of these progenies. The objective of this study was to characterize the morphological and molecular diversity of progenies derived from reverting and non-reverting sweet potato genotypes. Morphological evaluation was done using 16 standardized descriptors; and involved four parents (NASPOT 11, NASPOT 1, New Kawogo [all East African] and Resisto [American]), 121 progenies and two outliers (Ejumula and Tanzania). Molecular evaluation involved the four parents, 10 progenies from each cross (NASPOT 11 X Resisto, NASPOT 1 X Resisto and New Kawogo X Resisto) and three outliers (Ejumula, Tanzania and Ipomoea setosa) using six simple sequence repeat primers. Morphological and molecular analysis were carried out using XLSTAT and GenAlEx software packages. There was significant (P<0.001) morphological and molecular variation among the progenies. The number of leaf lobes strongly correlated with leaf lobe type (r = 0.940). Cluster analysis grouped the 121 progenies into six clusters, cluster II being the largest with 62 progenies. The first seven principal components contributed to 80.98% of total variation with Eigen values greater than 0.8. Stepwise discriminant analysis showed that seven morphological traits were sufficient in differentiating the progenies (P≤0.0001). Analysis of molecular variance showed significant variation (P<0.001) within and among populations. The number of alleles per locus ranged from 2 to 4. Shannon’s information index (I) ranged from 0.325 to 1.061 with a mean of 0.634. The diversity index (H) ranged from 0.180 to 0.642 with a mean of 0.380. Nei’s pairwise genetic distance ranged from 0.2 to 0.8 with a mean of 0.39. Cluster analysis grouped the 30 progenies into four clusters, cluster II being largest with 16 progenies. The first four principal components contributed to 90.16% of total variation with Eigen values greater than 0.6. Markers IBU5, IBU4, and IBS166 had significant power (P≤0.0001) in discriminating the progenies; and revealed moderate to high variability within the progenies. Characters (number of leaf lobes and leaf lobe type), and primer IBS166 were very important in determining diversity within the progenies derived from reverting and non-reverting parents. These morphological characters and molecular marker can be used for future identification and breeding of reverting sweet potato genotypes