目的：本研究应用ITS2序列作为DNA条形码对9种广东耳草属药材进行鉴定研究。方法：收集广东耳草属药材样本，通过植物基因组DNA提取、PCR扩增以及产物的双向测序获得ITS2序列，所得序列采用CodonCode Aligner进行拼接。用MEGA 6.06进行比对，分析种内和种间遗传距离，并构建系统进化树。结果：9种耳草属植物65条序列长度范围为208-224bp，共有92个碱基变异位点，种内遗传距离（0.002）明显小于种间遗传距离（0.202）。NJ和ML聚类树结果基本一致，除耳草与金毛耳草关系较近难以区分外，其余7个物种种内样本分别聚在一支，表现出单系性。结论：ITS2序列基本能够准确的鉴定广东耳草属药材，可作为耳草属药材基原植物鉴定的候选条形码序列。

ITS2 sequence was taken as a DNA barcode to identify Hedyotis medicinal plants in Guangdong Province.Samples from Hedyotis were collected and the ITS2 regions were amplified and sequenced.The sequences were assembled by CodonCode Aligner and analyzed by MEGA 6.06.The Kimura 2-Parameter(K2P)distances were computed,while the phylogenetic tree was built using the neighbor-joining(NJ)and test maximum likelihood(ML)models.It was found that the length of ITS2 region varied from 208-224 bp with 92 variable sites.The intraspecific distance(0.002)was much shorter than the interspecific distance(0.202).The outputs of NJ tree chimed with that of ML tree.Apart from the indistinguishability between Hedyotis and H.chrysotricha in the NJ and ML trees,the other samples of the seven species were clustered to one branch respectively,featuring monophyly.In conclusion,the ITS2 sequence provided the molecular evidence behind the identification of the nine species of Hedyotis medicinal plants in Guangdong Province and could be treated as an ideal DNA barcode for identifying species of Hedyotis medicinal materials.

广东省中医院院内专项（2015KT1817）：岭南中草药DNA条形码分子鉴定和生态适宜性研究，负责人：黄志海。