Comparison of the abilities of universal, super, and specific DNA barcodes to discriminate among the original species of Fritillariae cirrhosae bulbus and its adulterants

Fritillariae cirrhosae bulbus is a famous type of traditional Chinese medicine used for cough relief and eliminating phlegm. The medicine originates from dried bulbs of five species and one variety of Fritillaria. Recently, immature bulbs from other congeneric species, such as F. ussuriensis, have been sold as adulterants of Fritillariae cirrhosae bulbus in medicine markets owing to the high price and limited availability of the genuine medicine. However, it is difficult to accurately identify the bulbs from different original species of Fritillariae cirrhosae bulbus and its adulterants based on traditional methods, although such medicines have different prices and treatment efficacies. The present study adopted DNA barcoding to identify these different species and compared the discriminatory power of super, universal, and specific barcodes in Fritillaria. The results revealed that the super-barcode had strong discriminatory power (87.5%). Among universal barcodes, matK provided the best species resolution (87.5%), followed by ITS (62.5%), rbcL (62.5%), and trnH-psbA (25%). The combination of these four universal barcodes provided the highest discriminatory power (87.5%), which was equivalent to that of the super-barcode. Two plastid genes, ycf1 and psbM-psbD, had much better discriminatory power (both 87.5%) than did other plastid barcodes, and were suggested as potential specific barcodes for identifying Fritillaria species. Phylogenetic analyses indicated that F. cirrhosa was not a "good" species that was composed of multiple lineages, which might have affected the evaluation of the discriminatory ability. This study revealed that the complete plastid genome, as super barcode, was an efficient and reliable tool for identifying the original species of Fritillariae cirrhosae bulbus and its adulterants.