Exploring DNA barcode for accurate identification of threatened Aconitum L. species from Western Himalaya

Aconitum species, belonging to Ranunculaceae, have high medicinal importance but due to their overexploitation come under IUCN (International Union for Conservation of Nature) red list. The precise identification of the Aconitum species is equally important because they are used in herbal formulations. The present study aimed to develop an efficient DNA barcode system for the authentic identification of Aconitum species.

A set of 92 barcode gene sequences (including 12 developed during the present study and 80 retrieved from NCBI) of 5 Aconitum species (A. heterophyllum, A. vialoceum, A. japonicum, A. napellus, and A. stapfianum) were analyzed using three methods (tree-based, distance-based, and similarity-based) for species discrimination. The PWG-distance method was found most effective for species discrimination. The discrimination rate of PWG- distance ranged from 33.3% (rbcL + trnH-psbA) to 100% (ITS, rbcL + ITS, ITS + trnH-psbA and rbcL + ITS + trnH-psbA). Among DNA barcodes and their combinations, the ITS marker had the highest degree of species discrimination (NJ-40%, PWG-100% and BLAST-40%), followed by trnH-psbA (NJ-20%, PWG-60% and BLAST-20%). ITS also had higher barcoding gap as compared to other individual barcodes and their combinations. Further, we also analyzed six Aconitum species (A. balfourii, A. ferox, A. heterophyllum, A. rotundifolium, A. soongaricum and A. violaceum) existing in Western Himalaya. These species were distinguished clearly through tree-based method using the ITS barcode gene with 100% species resolution.

ITS showed the best species discrimination power and was used to develop species-specific barcodes for Aconitum species. DNA barcodes developed during the present study can be used to identify Aconitum species.