Differentiation of Medicinal Dendrobium Species (Orchidaceae) Using Molecular Markers and Scanning Electron Microscopyz
SZ-JIE WU1, YU-SHAN LIU1,2, TSENG-WEI CHEN1,3, CHANG-CHAI NG1,4, WEN-SHONG TZENG1 AND YUAN-TAY SHYU1*
1. Department of Horticulture, National Taiwan University, Taipei, Taiwan, R.O.C.
2. Industrial Technology Research Institute, Hsinchu, Taiwan, R.O.C.
3. Functional Assessment Department R&D Center, Sinphar Pharmaceutical CO., Ilan, Taiwan, R.O.C.
4. Chen Yung Memorial Foundationy, Taipei, Taiwan, R.O.C.
(Received: May 27, 2009 Accepted: September 22, 2009)
ABSTRACT
Dendrobium species have long been used as functional food supplements and herbal medicines in Asia. However, inappropriate usage of the Dendrobium species variants is rampant because of the considerable differences in the cost of the variants. Furthermore, the similar appearance of the dried plants of the Dendrobium species makes it difficult to discriminate among the individual members. In this study, simple and sensitive methods based on molecular and morphological studies were developed to verify authenticity of the Dendrobium species used in the preparation of medicines, particularly that of the most expensive variety, D. huoshanense. Molecular and anatomical differences among the 8 commonly used Dendrobium species (6 used for medicinal purposes and 2 for ornamental purposes) were studied. The ribosomal DNA internal transcribed spacer (ITS), chloroplast DNA trnL intron, and the trnL-trnF intergenic spacer (IGS) of the DNA of the 8 species were sequenced and compared. The comparison results highlighted considerable differences between the IGS region of D. huoshanense and that of other Dendrobium species to enable a clear distinction between them. A novel primer set was designed to specifically amplify the DNA of D. huoshanense. The leaf and stem morphologies of the 8 Dendrobium species were also studied by scanning electron microscopy (SEM). Granular mucilage and acicular grains in the vascular bundles were present only in the medicinal Dendrobium species but not in the ornamental ones.
Key words: Dendrobium species, ITS rDNA, cpDNA, scanning electron microscopy