基于DNA条形码技术对喉红石斛的植物学分类研究

目的 利用DNA条形码技术探索喉红石斛Dendrobium christyanum的分类归属问题，并建立一种新的ITS2二级结构的信息挖掘方法。方法 提取分属5个组14种石斛的DNA，对ITS序列（ITS1-5.8 S-ITS2）进行PCR扩增，测序，获得ITS序列；基于序列信息，计算遗传距离、构建系统发育树，对ITS2的二级结构进行预测，并对其进行量化、聚类分析。结果 喉红石斛与黑毛组的矮石斛D.bellatulum、长距石斛D.longicornu的遗传距离最小，NJ系统发育树与ITS2二级结构的系统聚类图均显示喉红石斛与黑毛组石斛聚为一支，且喉红石斛与黑毛组石斛的二级结构图基本一致。结论 喉红石斛与黑毛组石斛的亲缘关系最近，应归属于黑毛组；新建立的ITS2二级结构量化分析方法可提供更多的分类信息，具有更高水平的分类潜能。这是首次运用DNA条形码进行石斛组间的分类研究，为石斛属植物系统提供了重要依据。

Botanical Classification of Dendrobium christyanum based on DNA barcode technology

Objective To explore the classification of Dendrobium christyanum by using DNA barcode technology, and establish a new information mining method for ITS2 secondary structure. Methods Extraction of DNA from 14 Dendrobium species belonging to 5 groups. The ITS sequence (ITS1-5.8 S-ITS2) was amplified by PCR and sequenced to obtain ITS sequence. Based on the sequence information, the genetic distance was calculated and the phylogenetic tree was constructed. The secondary structure is predicted, quantified and clustered. Results The genetic distance of D.christyanum are closest to Dendrobium longicornu and D. bellatulum belong to Section Formosae. NJ phylogenetic tree and ITS2 secondary structure cluster diagram also showed that D. christyanum and Dendrobium species which belong to Section Formosae were divided into one branch. The secondary structure of D. christyanum is consistent with that of Section Formosae. Conclusion The relationship among the D. christyanum and Dendrobium species of Section Formosae are the closest, and D. christyanum should be categorized as the Section Formosae. The newly established quantitative analysis method of ITS2 secondary structure can provide more classification information and have higher classification potential. This is the first time that DNA barcode has been used to classify and identify among Dendrobium groups, which provides an important basis for the identification and classification of Dendrobium resources.