Cassava is ideal for biofortification due to its popularity as a root staple among populations with high vitamin A malnutrition. The crop is vegetatively propagated and retains the enhanced trait across generations. The combining ability for beta-carotene content and important yield trait was evaluated in a cassava F1 generation. Ten high beta-carotene clones from International Institute of Tropical Agriculture (IITA) were hybridized with ten local clones in a North Carolina Design II mating design. The F1 population was evaluated at the Kenya Agricultural Research Institute (KARI). A total of 125 families were evaluated, including 35 reciprocal crosses. The IITA parents had highly significant (P ≤ 0.001) General Combining Ability (GCA) for pulp colour and plant height. The GCA of the local parents was significant (P≤ 0.05) for harvest index, number of lobes (P≤ 0.05) and for plant height (P≤ 0.001). The Specific Combining Ability (SCA) was significant for harvest index and plant height at P≤ 0.05 and P≤ 0.001 respectively. Root pulp colour was influenced by both additive and non-additive genetic effects. There were also maternal effects associated with the trait. Results indicated that local cassava varieties can be improved for beta-carotene content without a decline in agronomic performance.

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This study was conducted to characterize Dioscorea spp. in Kenya using morphological and molecular characteristics. Data on 22 morphological traits were subjected to cluster analysis and multivariate analysis using principal component (PCA). The dendrogram of cluster analysis revealed three main groups: Species distribution based on PC-1 and PC-2 showed the distantly related species in each quarter; D. alata L. (1 st quarter), D. bulbifera L. (2 nd quarter), D. cayenensis Lam. (3 rd quarter) and D. minutiflora Engl. (4 th quarter). In molecular characterization, one sub-cluster grouped D. minutiflora Engl. and D. burkilliana J. Miege as one genetic group. However not all D. minutiflora Engl. species were in one specific cluster showing that there may be variation within the species. D. alata L. and D. bulbifera were seen to be potentially related because they shared a common origin. D. bulbifera L. and D. cayenensis Lam. genotypes clustered together, indicating that the species might be closely related. Generally, the rbcL marker demonstrated the phylogeny of Kenyan Dioscorea spp L. Comparison of morphological and molecular data analysis gave almost similar results. From the study, the phylogenetic relationships of Kenyan Dioscorea spp. were established and morphological and molecular characterization was efficient in establishing species relatedness among Dioscorea spp.