Low levels of genetic diversity detected by RAPD analysis in geographically distinct accessions of Bacopa monnieri

Abstract

Brahmi (Bacopa monnieri) is a traditional Indian medicinal plant known for its natural nootropic action of saponins present in large amount in its shoots. A collection of 24 B. monnieri accessions from different agro-climatic zones of India and an introduction from Malaysia maintained in the field genebank at CIMAP was analysed for RAPD variation. Among the 40 random primers tested, 29 primers generated one or more polymorphic bands. The number of polymorphic bands generated was primer dependent, ranging from 2 to maximum of 8. Similarity matrices were generated from the RAPD data on the basis of Nei's estimates of similarity indices and dendrograms were constructed based on UPGMA clustering. All the accessions were found to be in the range of 0.8-1.0 of similarity, which is indicative of a narrow genetic base among the various accessions with a medium level of polymorphism. It was possible to differentiate individual accessions, showing differences in morphological and growth properties at DNA level. The observed low levels of genetic variation were attributed to interplay of sexual and vegetative modes of reproduction and similarity of local environments in habitats of B. monnieri.