Assessment and characterization of genetic diversity in Withania somnifera (L.) Dunal using RAPD and AFLP markers
Genetic diversity of 23 accessions of Withania somnifera collected from different geographical regions of India was estimated by employing Random Amplification of Polymorphic DNA (RAPD) and Amplified Fragment Length Polymorphism (AFLP) markers. Eighteen RAPD primers and six AFLP primer combinations revealed 37.82 and 43.94% polymorphism, respectively, among 163 and 286 genetic loci amplified. The AFLP assay revealed higher levels of polymorphism among the tested W. somnifera accessions compared to the RAPD. Mean genetic diversity based on Shannon index ranged from 1.33 (RAPD) to 5.13 (AFLP). Unweighted pair group method based on arithmetic average (UPGMA) analysis was performed on Jaccard’s similarity coefficient matrix. The matrix reveals, two main clusters, wild accessions formed one cluster and the cultivated accessions formed the other. The cultivated accessions are well separated from the wild ones at a low similarity value of 0.3, indicating that cultivated and wild accessions are highly distinct. Morphologically cultivated accessions were also quite distinct from the wild ones and the cluster analysis of RAPD and AFLP fingerprints clearly discriminated the five cultivated accessions of W. somnifera. A strong correlation was observed between morphology and molecular marker systems. Identification of specific markers to wild as well as cultivated accessions is yet another important finding in the present study. Such genetic diversity is useful in facilitating the development of large number of new varieties through hybridization, transfer of useful genes, thus maximizing the use of such available germplasms as genetic resource materials for breeders. The present input, first of its kind in Ashwagandha, will thus assist the marker assisted crop improvement programme.
Key words: Withania somnifera, genetic diversity, RAPD, AFLP, polymorphism, Shannon index.