Potential of RAPD and ISSR markers for assessing genetic diversity among Stevia rebaudiana Bertoni accessions

In the present study, genetic diversity among 16 collections of Stevia rebaudiana Bertoni was assessed to compare the efficiency of two-marker systems over one marker using RAPD and ISSR markers. How well these two marker systems discriminated the Stevia collections was compared. In fact, all the Stevia accessions included in the present study have been growing under different altitudes, ranging 250 to 2250 m at different geographical conditions. The 22 selected RAPD primers yielded 66 scorable bands, 54 of which were polymorphic (81.8%). While the 23 selected ISSR primers amplified 49 bands, 44 of which were polymorphic (89.8%). The genetic similarity among the accessions varied from 0.365 to 0.887 when pooled data from ISSR and RAPD were analyzed through UPGMA. The analysis of combined data set of both the techniques clustered the genotypes, based on their geographic locations. Both genotypes A & B collected from Solan (Himachal Pradesh) were known to be contrasting for different levels of rebaudioside-A and stevioside and have been singled out by all the dendrograms generated by the techniques separately. High polymorphism obtained indicates that both techniques are efficient for evaluating genetic diversity in S. rebaudiana, though ISSR yielded more polymorphism. Usually, a combination of diverse marker types is recommended to provide an accurate assessment by comparison of results.