Assessment of genetic diversity in cashew germplasm using RAPD and ISSR markers

Diversity and genetic relationship in 100 cashew germplasm accessions were analyzed by using RAPD and ISSR markers. Using 10 selected RAPD primers 60 bands were generated, of which 51 bands were polymorphic (85%), and with 10 selected ISSR primers 67 amplified bands were observed with 58 polymorphic bands (86.6%). Though both kinds of markers discriminated the accessions effectively, analysis of combined data of markers (RAPD + ISSR) resulted in better distinction of accessions. By combining markers, a total of 127 bands were detected, of which 109 bands (85.8%) were polymorphic and produced on an average of 5.45 polymorphic bands per primer. Primers with high polymorphic information content and marker index were identified for discriminating accessions. High percentage of polymorphism (>85%) observed with different markers indicated high level of genetic variation existing among the accessions. Genetic relationship estimated using similarity co-efficient (Jaccard’s) values between different pair of accessions varied from 0.43 to 0.94 in RAPD, 0.38 to 0.89 in ISSR and 0.43 to 0.87 with combined markers suggested a diversity (dissimilarity) ranging from 6 to 57%, 11 to 62% and 13 to 57% respectively and the diversity skewed around 50% indicated moderate diversity. The cluster analysis with UPGMA method separated the accessions broadly into 13 clusters and in that three into smaller clusters. Some correspondence between the molecular groupings and the morphological clusters were observed. Among the accessions, NRC-142 and NRC-12 were highly divergent and NRC-231 and NRC-232 were genetically similar.