[DNA molecular identification of Herba Dendrobii and its adulterant species based on ITS sequence analysis].

To identify Herba Dendrobii and its adulterant species on molecular level, the rDNA ITS sequences of 17 species of Herba Dendrobii were studied. Genomic DNA of Dendrobium was extracted using the modified cetyltrimethyl ammonium bromide (CTAB) method. The PCR products of the rDNA ITS sequences of Dendrobium (32 materials) were purified and then sequenced. The characteristic of the sequences and the genetic distance were compared between Bulbophyllum odoratissimum and Dendrobium, Dendrobium interspecies and different populations. Phylogenetic trees were constructed using the UPGMA method by the biology softwares including BioEdit, MEGA4.0 etc. The PCR products were purified and then sequenced. It was built up that the database of rDNA ITS sequences of 17 species of Herba Dendrobii (32 materials). The ITS1 was 228-234 bp, the GC content accounting for 45.7%-53.0%. Its variable sites were 167, accounting for 67.34%. The Parsim-Informative positions were 106, accounting for 42.74%. The ITS2 was 241-247 bp, the GC accounting for 44.8% - 55.7%. The variable sites were 165, accounting for 66.27%. The Parsim-Informative positions were 115, accounting for 46.18%. The genetic distance between B. odoratissimum and Dendrobium was 0.295. The average genetic distance was 0.142 between Dendrobium species, and there were 2-156 variable nucleotides. The average genetic distance between different populations was 0.002, and there were 2-156 variable nucleotides. The genetic distance between B. odoratissimum and Dendrobium was greater than that of Denrobium interspecies. Meanwhile, the genetic distance between Denrobium species was also greater than that of different populations (varieties). The molecular phylogeny tree was constructed on the database of rDNA ITS the sequences of 17 species of Herba Dendrobii using the biology softwares. Then 10 materials on molecular level were authenticated. It is concluded that using of the whole sequences database of 17 species of Herba Dendrobii and heredity analysis softwares, and measuring the sequences of rDNA ITS of the inspected species, can authenticate the Dendrobium on molecular level, and provide basis for molecular authentication.