Abstract
The over-collection and habitat destruction of natural Dendrobium populations for their commercial medicinal value has led to these plants being under severe threat of extinction. In addition, many Dendrobium plants are similarly shaped and easily confused during the absence of flowering stages. In the present study, we examined the application of the ITS2 region in barcoding and phylogenetic analyses of Dendrobium species (Orchidaceae). For barcoding, ITS2 regions of 43 samples in Dendrobium were amplified. In combination with sequences from GenBank, the sequences were aligned using Clustal W and genetic distances were computed using MEGA V5.1. The success rate of PCR amplification and sequencing was 100%. There was a significant divergence between the inter- and intra-specific genetic distances of ITS2 regions, while the presence of a barcoding gap was obvious. Based on the BLAST1, nearest distance and TaxonGAP methods, our results showed that the ITS2 regions could successfully identify the species of most Dendrobium samples examined; Second, we used ITS2 as a DNA marker to infer phylogenetic relationships of 64 Dendrobium species. The results showed that cluster analysis using the ITS2 region mainly supported the relationship between the species of Dendrobium established by traditional morphological methods and many previous molecular analyses. To sum up, the ITS2 region can not only be used as an efficient barcode to identify Dendrobium species, but also has the potential to contribute to the phylogenetic analysis of the genus Dendrobium.
Highlights
Dendrobium Sw., one of the most important genera in the family Orchidaceae, comprising more than 1000 species [1,2,3,4], is mainly distributed in tropical and subtropical Asia, and Northern and Eastern Australia [5]
The lengths of the internal transcribed spacer 2 (ITS2) sequences used for the analyses were in the range of 243–258 bp, with an average of 248 bp
As in many previous studies [13,14,22,29], we found that ITS2 was a sufficiently variable DNA region among Dendrobium species for determination of genetic divergence, and demonstrated a higher capability of successful discrimination
Summary
Dendrobium Sw., one of the most important genera in the family Orchidaceae, comprising more than 1000 species [1,2,3,4], is mainly distributed in tropical and subtropical Asia, and Northern and Eastern Australia [5]. All these species are contained in the Conventions on International Trade in Endangered Species of Fauna and Flora (CITES). For the commercial production of medicinal plants, Dendrobium plants are subjected to massive collection for trading in the medicine market in China.
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