Abstract

The genetic diversity and relationships of 70 accessions of yam belonging to Dioscorea cayenensis/Dioscorea rotundata complex (55), Dioscorea bulbifera (13) and Dioscorea alata (2, as a reference) were assessed using six inter simple sequence repeat (ISSR) primers. DNA was extracted from a bulk of two plants per accession using a modified cetyl trimethyl ammonium bromide (CTAB) method. Six ISSR primers amplified 77 fragments with 75 (97.40%) polymorphism at genus level. The genetic diversity, estimated by gene diversity and Shannon’s index were 0.36 and 0.53, respectively, revealing a high level of genetic variation at genus level. At species level, 75 bands were amplified for D. cayenensis/D. rotundata complex, out of which 71 were polymorphic accounting for 92.2% polymorphism. Gene diversity and Shannon's index for D. cayenensis/D. rotundata complex were 0.33 and 0.49, respectively. In the case of D. bulbifera, a total of 64 bands were scored, out of which 55 were found to be polymorphic which resulted in 71.4% polymorphism. Gene diversity and Shannon's index for this species were 0.24 and 0.47, respectively. Genetic diversity analysis of D. cayenensis/D. rotundata complex accessions showed that Gedeo was the most diverse among populations and South among groups. Analysis of molecular variance (AMOVA) indicated the presence of higher proportion of variation within species (63.9%) than among species (36.1%). AMOVA for D. cayenensis/D. rotundata complex also showed higher within population variation (53.6) than among populations (46.4). In addition, cluster analysis for relationship between D. cayenensis/D. rotundata complex accessions showed grouping of some of the accessions according to their population but it failed to produce clear species boundary between D. cayenensis/D. rotundata complex. The results suggest that there is a high level of genetic diversity in Ethiopia yams to be exploited for future improvement (breeding) of the crop.

Key words: Dioscorea bulbifera, Dioscorea cayenensis/Dioscorea rotundata complex, genetic diversity, yam.