Study of genetic diversity in Indian and exotic sesame (Sesamum indicum L.) germplasm using random amplified polymorphic DNA (RAPD) markers

Fifty-eight accessions of sesame (Sesamum indicum L.), an important oil seed crop of the tropics and subtropics were analysed using random amplified polymorphic DNA (RAPD) technique. The material analysed comprised 36 collections from 18 different states of India and four adjoining countries of the Indian subcontinent, and 22 exotic accessions from 21 sesame growing countries around the world. The results from PCR amplifications with the selected 24 random 10-mer primers were statistically analysed. The value of Jaccard's similarity coefficients ranged from 0.19 to 0.89. The results indicated the presence of high level of genetic diversity. However, the extent of genetic diversity was greater in the collections from Indian subcontinent as compared to the exotics. Among the Indian accessions, the collections from Rajasthan and North-eastern states were highly diverse. The phenetic analysis grouped 48 out of 58 accessions in six clusters and the remaining highly diverse accessions were placed outside these close-knit clusters. The Bootstrap estimates obtained by Wagner parsimony analysis were significant for seven out of 49 nodes in the majority-rule consensus tree (>95% occurrence). The results of both the analyses were, however, broadly comparable when the constitution of the individual clusters were considered. The principal components analysis indicated that the first two components accounted for only 21% of the total variations and in order to explain >75% of variations 18 components were required. The high level of genetic diversity prevalent among the Indian collections is probably indicative of the nativity of this crop species. Similarly, the relatively lower level of polymorphism in exotic germplasm could be ascribed to the comparatively recent introductions of limited germplasm of this crop into some of the non-traditional sesame growing countries.