title: Evaluation of seven DNA barcodes for differentiating closely related medicinal Gentiana species and their adulterants.
abstract: BACKGROUND
  Species identification of living organisms by standard DNA sequences has been well-accepted. Consortium for the Barcode of Life (CBOL) recommends chloroplast regions rbcL and matK as the DNA barcodes for the land plants. This study aims to evaluate the feasibility and limitations of rbcL, matK, and 5 other commonly used regions as the DNA barcodes for the medicinal Gentiana and their adulterants, Gentiana. rhodantha and Podophyllum hexandrum.
  
  
  METHODS
  The species differentiation power of rbcL, matK, nuclear internal transcribed spacer (ITS) and 5S rRNA intergenic spacer, and chloroplast trnH-psbA, trnL-F and rpl36-rps8 intergenic spacers were tested in different medicinal Gentiana, including Gentiana scabra, Gentiana triflora, Gentiana manshurica and Gentiana rigescens, from common adulterants such as Gentiana rhodantha and Podophyllum hexandrum (a toxic herb producing podophyllotoxin).
  
  
  RESULTS
  All seven tested loci could be used to differentiate medicinal Gentiana species from their adulterants, and to distinguish Guanlongdan from Jianlongdan. In terms of general differentiation powers, rbcL and matK had no significant advantages over the other five loci. Only the 5S rRNA and trnL-F intergenic spacers were able to discriminate the closely related species G. triflora, G. scabra and G. manshurica.
  
  
  CONCLUSIONS
  The DNA barcodes rbcL and matK are useful in differentiation of closely related medicinal species of Gentiana, but had no significant advantages over the other five tested loci.
authors: State Key Laboratory of Phytochemistry and Plant Resources in West China (CUHK), Institute of Chinese Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong, China. pcshaw@cuhk.edu.hk.
authors: Ka-Lok
authors: KL
authors: Wong
authors: Paul Pui-Hay
authors: PP
authors: But
authors: Pang-Chui
authors: PC
authors: Shaw
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