Validation of DNA barcoding markers in common Mucuna species of India for taxonomy and pharmacognosy applications

Members of genus Mucuna are economically important due to their pharmaceutical and nutritional properties. The genus in India is represented by 10 species including perennial and annual life form. The genus represents considerable taxonomical ambiguities which is a major challenge in breeding and authentication purposes for taxonomy and pharmacognosy applications. Here we report efficacy of the DNA barcodes viz. a nuclear (nrITS2) and three chloroplast (matK, rbcl and trnH-psbA) regions in understanding the phylogenetic relationships among the four common species of Mucuna in India. Comparative analysis on the species discriminatory ability of these four genes was done on a group of 46 accessions of Mucuna representing 4 species. We found nrITS2 was effective in resolving all species with a mean intraspecific distance of 0.006 and mean interspecific distance of 0.104. Molecular investigations of the all the four regions revealed M. bracteata as the immediate perennial ancestor of annual M. pruriens. It is also observed in the present study none of the four barcode markers were unable to distinctly resolve two botanical varieties of M. pruriens viz., var. pruriens and var. utilis. Based on these outcomes we propose nrITS2 could be a suitable DNA barcode to resolve taxonomic boundaries of closely related Mucuna species, which share close phenotypic features and could also be used to authenticate the ingredients in the raw Mucuna products used in herbal preparations.