Abstract:
Sweet potato an ideal tuber crop due to its hardy nature and consistent performance even in stressful growing conditions. Viral diseases such as sweet potato virus disease (SPVD)
complex caused by synergistic interaction of Sweet Potato Feathery Mottle Virus and Sweet Potato Chlorotic Stunt Virus are a major cause of yield losses due to lack of resistant varieties. Breeding, promotion and adoption of orange fleshed sweet potato (OFSPs) varieties can be enhanced by identification of virus tolerant clones. However, prerequisite information on changes in quantitative contents such as beta carotene, dry matter, iron and zinc due to virus infection is not well documented. This study aimed at screening ninety sweet potato clones for responses to sweet potato viruses, dry matter, micronutrients levels. Nitrocellulose membrane ELISA and Reverse transcriptase-PCR were used to detect sweet potato viruses and validate results obtained NCM-ELISA respectively. The virus free clones were selected and planted in a field with high SPVD pressure in Randomized Complete Block Design (RCBD) with three replications. Disease progression scores was scored on a scale of 1-9 after two months interval. Root dry matter, beta carotene zinc and iron were quantified. One-way ANOVA was used to compare the mean data in Genstat Version 2014.1. Thirteen clones from five families and four other genotypes were screened using conventional PCR for presence of Simple Sequence Repeats linked to SPVD resistance. Neighbor joining tree was generated
using DARwin version 6.0.010 using Unweighted Pair Group Method with Arithmetic Means (UPGMA). XLSTAT 2015 version was used to generate Principal Component Analysis (PCA) while Genetic distance was computed using GenAIEx version 6.5. The test clones clustered in two groups separate from virus susceptible genotypes. Significant differences in beta-carotene, dry matter and iron among families (P< 0.05). There was negative correlation (r=-.296*). A total of 18 alleles were detected with an average of 3.0 alleles per locus. Mean genetic diversity of the markers was 0.41. Pearson‟s correlation coefficient revealed an average similarity of 0.54 among sweet potato genotypes. Further evaluation of SSR markers is proposed in order to identify markers that can be suitably used to analyze germplasm for various traits such as dry matter, micronutrients and weevil resistance. The study has identified two clones (F1C7 and F4C15) with dry matter, carotene, iron and zinc traits ideal for sweet potato improvement.
