Abstract: To identify the six medicinal materials in Swertia. by ITS2 sequences.Total genomic DNA from all the samples were extracted using the Plant Genomic DNA kit.The ITS2 regions were amplified,bidirectional sequenced and aligned.The average GC content was analyzed through MEGA 6.0 software.The intra-versus inter-specific genetic distances of the ITS2 regions were computed in accordance with the kimura 2-parameter (K2P) model and Neighbor-joining (NJ) phylogenetic trees were constructed using MEGA6.0.Secondary structure has been analyzed through online ITS2 database.The length of ITS2 from six medicinal materials in Swertia varied in 230-232bp and average GC content was 61.2%-64.0%.The intraspecific variation of six medicinal materialswas small respectively.The intraspecific variation of S.delavayi was largest,and the average intraspecific genetic distance was 0.02.However,the average interspecific genetic distance of the six medicinal materials in Swertia was 0.03-0.09.The results of secondary structure of ITS2 showed that the stem-and-loop structure and four arms of ITS2 from these samples have significant difference.NJ trees can identify the six medicinal materials,which present the obvious monophyly.ITS2 regions can identify the six medicinal materials in Swertia effectively and accurately.Which lay a foundation for the relevant in-depth study of these six medicinal materials,and provide an important reference as the identification of others Swertia.

Key words: Swertia, medicinal materials, ITS2, molecular identification