Molecular identification of ethnomedicinal Calotropis using DNA barcoding

The presence of high demand for the ethno-medicinally important plant Calotropis R.Br. (Apocynaceae Juss.) in the trade market makes substitution or adulteration likely. To address this problem of accurate species identification within this genus, DNA barcoding methods are employed. We investigated the species discriminating power of the recommended barcode loci (rbcL, matK, trnL-F and ITS) and their combinations using distance-based (inter- and intra-specific distances) and similarity-based (BM and BCM), phylogeny-based analyses of available Calotropis species. In the present study, the BLAST identity rate is high for the recommended barcode region rbcL (99.66–100 %), followed by matK (99.57–100 %), trnL-F (98.12–100 %) and ITS (97.50–100 %). A notable difference was found between inter- and intraspecific distances in all the selected genes except rbcL. The BM and BCM approaches revealed the highest rate of correct identification with ITS (60 %) as a single gene and the combination with ITS (50 %) as a double gene. It is further confirmed that only the ITS single gene successfully separated the Calotropis species in phylogenetic analysis, whereas the other single locus and double locus showed some ambiguity in discriminating the species properly. Therefore, we suggest that the nrITS gene is the most suitable barcode for differentiating Calotropis species.