A preliminary analysis of diversity among East African sweet potato landraces using morphological and simple sequence repeats (SSR) markers

Abstract

East Africa is known to have a wide range of sweet potato landraces and, therefore, is considered to be a secondary center of diversity. In this study, we assessed the diversity among sweet potato landraces from Kenya, Uganda and Tanzania using morphological and simple sequence repeats (SSR) markers. Two hundred and sixty-six landraces collected from agro-ecologically-distinct locations were screened for morphological characters using the CIP Research Guide. Morphological characters were recorded and phylogenetic analysis using UPGMA showed a close relatedness amongst the East African sweet potato landraces with the majority having a 0.1-0.5 range of Nei’s genetic distance from each other. The landraces, however, formed two major sub-clusters, irrespective of geographical origin. Based on the morphological analysis, 57 landraces that were fairly distant were further analysed using four SSR primers specific for sweet potato. Each primer pair was able to generate between two and five polymorphic and clearly scorable fragments. Phylogenetic analysis using UPGMA revealed similar results for the morphological characters. However, in each analysis, landraces from Tanzania tended to cluster together, suggesting that they are morphologically and genetically distinct from the Kenyan and Ugandan accessions. AMOVA, performed to further examine the relationships, indicated greater diversity than revealed by phylogenetic analysis suggesting that SSR markers are more reliable in assessing genetic diversity.