Differentiation of the Chinese minority medicinal plant genus Berchemia spp. by evaluating three candidate barcodes

The genus Berchemia comprises important Chinese plants with considerable medicinal value; however, these plants are often misidentified in the herbal medicinal market. To differentiate the various morphotypes of Berchemia species, a proficient method employing the screening of universal DNA barcodes was used in this work. Three candidate barcoding loci, namely, psbA-trnH, rbcL, and the second internal transcribed spacer (ITS2), were used to identify an effective DNA barcode that can differentiate the various Berchemia species. Additionally, PCR amplification, efficient sequencing, intra- and inter-specific divergences, and DNA barcoding gaps were employed to assess the ability of each barcode to identify these diverse Berchemia plants authentically; the species were differentiated using the Kimura two-parameter and maximum composite likelihood methods. Sequence data analysis showed that the ITS2 region was the most suitable candidate barcode and exhibited the highest interspecific divergence among the three DNA-barcoding sequences. A clear differentiation was observed at the species level, in which a maximum distance of 0.264 was exhibited between dissimilar species. Clustal analysis also demonstrated that ITS2 clearly differentiated the test species in a more effective manner than that with the two other barcodes at both the hybrid and variety levels. Results indicate that DNA barcoding is ideal for species-level identification of Berchemia and provides a foundation for further identification at the molecular level of other Rhamnaceae medicinal plants.