Genetic diversity in African yam bean accessions based on AFLP markers: towards a platform for germplasm improvement and utilization

Accurate knowledge of intra-specific diversity of underutilized crop species is a prerequisite for their genetic improvement and utilization. The diversity of 77 accessions of African yam bean (AYB, Sphenostylis stenocarpa) was assessed by amplified fragment length polymorphism (AFLP) markers. A total of EcoRI/MseI primer pairs were selected and 227 AFLP bands were generated, of which 59(26%) were found to be polymorphic in the 77 accessions of AYB. The most efficient primer combination for polymorphic detection was E-ACT/M-CAG with a polymorphic efficiency of 85.5%, while the least efficient was E-AGC/M-CAG with a polymorphic efficiency of 80.6%. The Jaccard genetic distance among the accessions of AYB ranged between 0.048 and 0.842 with a mean of 0.444. TSs98 and TSs104B were found to be the most similar accessions with a genetic similarity of 0.952. The neighbour-joining dendrogram grouped the 77 accessions of AYB into four distinct clusters comprising 8, 20, 21 and 28 accessions. The major clustering of the accessions was not related to their geographical origin. Cluster I was found to be the most diverse. The mean fixation index (0.203) and the mean expected heterozygosity (0.284) revealed a broad genetic base of the AYB accessions. The same germplasm set was previously evaluated for several agro-morphological traits. As the collection of additional AYB germplasm continues, the phenotypic profile, the clustering of the accessions and the AFLP primer combinations from this study can be used to augment breeding programmes.