Genetic diversity and relationships among Dioscorea alata L., and related Dioscorea species revealed by AFLP analysis

AFLP markers were successfully employed to detect genetic diversity and assess their genetic relationships among Dioscorea alata and related Dioscorea species accessions collected from several sites in Asia. Analysis of 51 accessions of D. alata and related Dioscorea spp., with 5 AFLP primer combinations detected a total of 265 fragments, of which 143 (56.3%) were polymorphic at the species level. Shannon's index of diversity Hs of AFLP variations for D. opposita, D. alata and D. bulbifera were 2.46, 2.98 and 2.22, respectively. The accessions of D. alata exhibited highest intra-group variation. The accessions of Polynesia exhibited highest intra-group variation in D. alata. Thus, Polynesia may he considered to the center of variation of D. alata accessions. Most of the AFLP variation (79%) resided within intra-species. In the phylogenetic tree, two major clusters were reoganized; Group 1, including 6 accessions of D. opposita, 1 accession of D. japonica, 2 accessions of D. alata, 2 accessions of D. bulbifera and 1 accession of D. nipponica, Group II, including 1 accession of D. opposita and 38 accessions of D. alata. Although most accessions of D. opposita and D. alata were clearly separated, some samples of these species and other Dioscorea spp., could not be discriminated by the AFLP analyses. Thus, the taxonomic classifications of Dioscorea spp., by the morphological characters do not correspond to the cluster by AFLP markers. Therefore, particular attention should be given to the sampling of Dioscorea spp., accessions in order to obtain a more accurate assessment of taxonomic classification of these gene pools. This study provided an insight of genetic diversity of intra-species of Dioscorea spp., and their geographic variations.