Molecular authentication and differentiation of Dendrobium species by rDNA ITS region sequence analysis

Owing to their significant medicinal and edible values, the natural Dendrobium species have underdone over-collection and habitat destruction, and cultivated species emerged for candidates. However, these Dendrobium plants are similar in shape to be easily confused, leading to extreme difficulties for identification based on their morphological and chemical features. In this study, the rDNA ITS region sequence analysis was developed for rapid and accurate identification of thirteen wild and cultivated Dendrobium species belonging to two sections Formosae and Chrysotoxae. By cloning and sequencing the rDNA ITS region genes from 13 Dendrobium species, the phylogenetic relationships among them were analyzed. Results showed that the variation of the ITS region, together with the lengths and Guanine and Cytosine contents of ITS, 5.8s rDNA, ITS1 and ITS2 sequences occurred in the tested Dendrobium species, and which from section Chrysotoxae was higher than that from section Formsae. Phylogenetic analysis based on neighbor-joining and maximum p-arsimony trees indicated that the Dendrobium species of sections Formosae and Chrysotoxae could be well divided into two groups. A majority of Dendrobium species exhibited distinctive ITS2 secondary structures, while for those with close genetic relationships were similar. Therefore, the ITS2 region sequence analysis is simple, quick, and highly reliable that can be used as an effective tool for molecular identification and classification, as well as the reconstruction of the phylogeny of wild and cultivated Dendrobium species belonging to different sections.