title: Validation of the ITS2 region as a novel DNA barcode for identifying medicinal plant species.
abstract: BACKGROUND
  The plant working group of the Consortium for the Barcode of Life recommended the two-locus combination of rbcL+matK as the plant barcode, yet the combination was shown to successfully discriminate among 907 samples from 550 species at the species level with a probability of 72%. The group admits that the two-locus barcode is far from perfect due to the low identification rate, and the search is not over.
  
  
  RESULTS
  Here, we compared seven candidate DNA barcodes (psbA-trnH, matK, rbcL, rpoC1, ycf5, ITS2, and ITS) from medicinal plant species. Our ranking criteria included PCR amplification efficiency, differential intra- and inter-specific divergences, and the DNA barcoding gap. Our data suggest that the second internal transcribed spacer (ITS2) of nuclear ribosomal DNA represents the most suitable region for DNA barcoding applications. Furthermore, we tested the discrimination ability of ITS2 in more than 6600 plant samples belonging to 4800 species from 753 distinct genera and found that the rate of successful identification with the ITS2 was 92.7% at the species level.
  
  
  CONCLUSIONS
  The ITS2 region can be potentially used as a standard DNA barcode to identify medicinal plants and their closely related species. We also propose that ITS2 can serve as a novel universal barcode for the identification of a broader range of plant taxa.
authors.affiliation: Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, People's Republic of China. slchen@implad.ac.cn
authors.forename: Shilin
authors.initials: S
authors.lastname: Chen
authors.forename: Hui
authors.initials: H
authors.lastname: Yao
authors.forename: Jianping
authors.initials: J
authors.lastname: Han
authors.forename: Chang
authors.initials: C
authors.lastname: Liu
authors.forename: Jingyuan
authors.initials: J
authors.lastname: Song
authors.forename: Linchun
authors.initials: L
authors.lastname: Shi
authors.forename: Yingjie
authors.initials: Y
authors.lastname: Zhu
authors.forename: Xinye
authors.initials: X
authors.lastname: Ma
authors.forename: Ting
authors.initials: T
authors.lastname: Gao
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Pang
authors.forename: Kun
authors.initials: K
authors.lastname: Luo
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Xiwen
authors.initials: X
authors.lastname: Li
authors.forename: Xiaocheng
authors.initials: X
authors.lastname: Jia
authors.forename: Yulin
authors.initials: Y
authors.lastname: Lin
authors.forename: Christine
authors.initials: C
authors.lastname: Leon
mesh_terms: D018744:DNA, Plant / Q000235:genetics*; D001330:Electronic Data Processing; D010946:Plants, Medicinal / Q000235:genetics*; D016133:Polymerase Chain Reaction
chemical_list: D018744:DNA, Plant