曲茎石斛及其近似种鉴别的形态和DNA分子证据

目的　探讨曲茎石斛 (南阳居群 )与同属近似种 :细茎石斛 (南阳居群 )、霍山石斛 (霍山居群 )、铁皮石斛(天台居群 )药材鉴别的形态及DNA分子证据。方法　对曲茎石斛 (南阳居群 )及其近似种的药材进行了外部形态和rDNAITS序列比较。结果　曲茎石斛及其近似种药材的外部形态虽无明显区别 ,但在rDNAITS序列上却存在着显著而稳定的差异。曲茎石斛 (南阳居群 )与铁皮石斛 (天台居群 )的rDNAITS序列的差异最小 ,绝对遗传距离为 7;但与细茎石斛 (南阳居群 )及霍山石斛 (霍山居群 )rDNAITS区的差异较大 ,绝对遗传距离分别为 4 0和 4 2。在rDNAITS区域中 ,作者共挑选了 7个碱基位点用作鉴别曲茎石斛 (南阳居群 )及其近似种的DNA证据。结论　根据药材的形态特征及rDNAITS区碱基序列差异 ,可准确鉴别曲茎石斛及其近似种药材。

MORPHOLOGICAL AND DNA MOLECULAR EVIDENCE FOR AUTHENTICATION OF DENDROBIUM FLEXICAULE FROM ITS ALLIED SPECIES OF DENDROBIUM

AIM To define morphological and molecular characters to distinguish Dendrobium flexicaule from its allied species D.flexicaule (Henan population), D.moniliforme (Henan population), D.huoshanense (Huoshan population) and D.officinale (Tiantai population). METHODS The morphological characteristics of D.flexicaule (population of Henan) and its allied species are compared. The sequences of rDNA ITS regions are exploited to explore the evidence for authenticating D.flexicaule (population of Henan) and its allied species. RESULTS The morphological characteristics of the herb of D.flexicaule (Henan population) and its allied species are summed up. Although the morphological difference is not much, the sequence difference of ITS regions among the four rDNAs is obvious and stable. The absolute genetic distance between the ITS region of D.flexicaule and D.officinale is 7 while that between the ITS region of D.flexicaule and D.moniliforme is 40 and that between the ITS region of D.flexicaule and D.huoshanense is 42. Seven sites of ITS region are defined as DNA character to identify D.flexicaule from the other three allied species. CONCLUSION The morphological characters and rDNA ITS sequences can be used to authenticate accurately D.flexicaule from three allied species of Dendrobium.