Molecular identification of Cistanches Herba and its adulterants based on nrITS2 sequence

Abstract

Cistanches Herba is a commonly used Chinese medicine for its tonification properties. However, it is often confused and substituted with the dried succulent stems of Orobanche pycnostachya, Orobanche coerulescens, Boschniakia rossica, Cistanche salsa, Cistanche sinensis and Cynomorium songaricum. Identifying Cistanches Herba based only on its morphological and chemical appearance is generally difficult. To develop a convenient and efficient identification method for discriminating Cistanches Herba and its adulterants, the second internal transcribed spacer (ITS2) of the ribosomal DNA of 39 individuals from Cistanches Herba and its adulterants were examined in this study. A phylogenetic tree was constructed using the neighbor-joining (NJ) and Kimura 2-parameter (K2P) methods. The results showed that the length of ITS2 sequence of Cistanche deserticola and Cistanche tubulosa were 229 and 233 bp, respectively. The intraspecific genetic distance of the two botanical origins of Cistanche Herba were both lower than their respective interspecific genetic distance with their adulterants. In the cluster dendrogram, C. deserticola and C. tubulosa were both monophyletic, and were distinguished from their adulterants. In conclusion, ITS2 can be used as a DNA barcode to efficiently identify Cistanches Herba and its adulterants, and can provide important information for quality evaluation, resource protection, exploitation, and sustainable utilization of this medicinal material. Key words: Cistanches Herba, Orobanchaceae, internal transcribed spacer (ITS2), DNA barcode, molecular Identification.