title: DNA barcoding the Dioscorea in China, a vital group in the evolution of monocotyledon: use of matK gene for species discrimination.
abstract: BACKGROUND
  Dioscorea is an important plant genus in terms of food supply and pharmaceutical applications. However, its classification and identification are controversial. DNA barcoding is a recent aid to taxonomic identification and uses a short standardized DNA region to discriminate plant species. In this study, the applicability of three candidate DNA barcodes (rbcL, matK, and psbA-trnH) to identify species within Dioscorea was tested.
  
  
  RESULTS
  One-hundred and forty-eight individual plant samples of Dioscorea, encompassing 38 species, seven varieties and one subspecies, representing majority species distributed in China of this genus, were collected from its main distributing areas. Samples were assessed by PCR amplification, sequence quality, extent of specific genetic divergence, DNA barcoding gap, and the ability to discriminate between species. matK successfully identified 23.26% of all species, compared with 9.30% for rbcL and 11.63% for psbA-trnH. Therefore, matK is recommended as the best DNA barcoding candidate. We found that the combination of two or three loci achieved a higher success rate of species discrimination than one locus alone. However, experimental cost would be much higher if two or three loci, rather than a single locus, were assessed.
  
  
  CONCLUSIONS
  We conclude that matK is a strong, although not perfect, candidate as a DNA barcode for Dioscorea identification. This assessment takes into account both its ability for species discrimination and the cost of experiments.
authors.affiliation: Jiangsu Province Key Laboratory for Plant Ex Situ Conservation, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, People's Republic of China.
authors.forename: Xiao-Qin
authors.initials: XQ
authors.lastname: Sun
authors.forename: Ying-Jie
authors.initials: YJ
authors.lastname: Zhu
authors.forename: Jian-Lin
authors.initials: JL
authors.lastname: Guo
authors.forename: Bin
authors.initials: B
authors.lastname: Peng
authors.forename: Ming-Ming
authors.initials: MM
authors.lastname: Bai
authors.forename: Yue-Yu
authors.initials: YY
authors.lastname: Hang
mesh_terms: D002681:China; D058893:DNA Barcoding, Taxonomic / Q000379:methods*; D027742:Dioscorea / Q000145:classification* / Q000235:genetics*; D019143:Evolution, Molecular; D017343:Genes, Plant / Q000235:genetics*; D056426:Genetic Loci / Q000235:genetics; D014644:Genetic Variation; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D018709:Statistics, Nonparametric