Genetic Diversity Assessment Of Yams (dioscorea Spp.) From Ethiopia Using Inter Simple Sequence Repeat (issr) Markers

The genetic diversity and relationships of 70 accessions of yam belonging to Dioscorearncayenensis/Dioscorea rotundata complex (55), Dioscorea bulbifera (13) and Dioscorearnalata (2 as a reference) were assessed using six ISSR primers. DNA was extracted from arnbulk of two plants per accession using a modified CTAB method. Six ISSR primersrnamplified 77 fragments with 75 (97.40%) polymorphism at genus level. The geneticrndiversity, estimated by Gene diversity and Shannon’s index were 0.36 and 0.53,rnrespectively, revealing a high level of genetic variation at genus level. At species level 75rnbands were amplified for D. cayenensis/D. rotundata complex, out of which 71 werernpolymorphic accounting for 92.2% polymorphism. Gene diversity and Shannon's index forrnD. cayenensis/D. rotundata complex were 0.33 and 0.49, respectively. In case of D.rnbulbifera a total of 64 bands were scored, out of which 55 were found to be polymorphicrnwhich resulted in 71.4% polymorphism. Gene diversity and Shannon's index for thisrnspecies were 0.24 and 0.47, respectively. Genetic diversity analysis of D. cayenensis/D.rnrotundata complex accessions showed that Gedeo were the most diverse amongrnpopulations and South among groups. Analysis of molecular variance (AMOVA) indicatedrnthe presence of higher proportion of variation within species (63.9%) than among speciesrn(36.1%) which could be due to presence of several shared bands. AMOVA for D.rncayenensis/D. rotundata complex also showed higher within population variation (53.6)rnthan among populations (46.4). This could be due to gene flow through seed materialsrnexchange among local farmers. Cluster analysis showed grouping of most of the accessionsrnaccording to their species. In addition, cluster analysis for relationship between D.rncayenensis/D. rotundata complex accessions showed grouping of some of the accessionsrnaccording to their population but it failed to produce clear species boundary between D.rncayenensis/D. rotundata complex. The results suggested that there exists a high level ofrngenetic diversity in yams of Ethiopia to be exploited for future improvement (breeding) ofrnthe crop.

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