关键词: 木瓜属, 近缘属, ITS2, DNA条形码, 鉴定

Abstract: Conduct molecular identification of Chaenomeles from its closely related genera by ITS2（nuclear internal transcribed spacer 2）sequence fragments，aiming at investigating the feasibility of application of methodology of ITS2. The DNA samples were extracted and purified，the PCR amplification and bidirectional sequencing of the materials were carried out to get 22 ITS2 sequences. Then the 22 ITS2 sequences obtained together with 8 ITS2 sequences from GenBank database were aligned by Clustal X（version 1.81），with manual adjustments assisted by BioEdit. MEGA program（version 5.05）was employed to estimate the intraspecific and interspecific genetic distances. NJ（Neighbor-Joining）and ML（Maximum Likelihood） trees were constructed based an K2P（Kimura-2-parameter）distance of the ITS2 sequences in order to evaluate the former results identified. The range of intraspecific differences of Chaenomeles and its closely related genera was 0 to 0.0274，with a mean value of 0.0029；While the interspecific differencevalue was from 0.011 to 0.112，with a mean value of 0.075. These indicates a significant difference between interspecific and intraspecific values. Further on，NJ and ML phylogenetic tree of different species of Chaenomeles and its closely related genera were constructed. These two methods gave rise to a similar result. Various species were clustered together，formed a monophyletic group. The supporting rates of the above results were all above 50%. The results showed that the ITS2 barcoding was a fast and accurate method for the identification of Chaenomeles and its closely related genera.

Key words: Chaenomeles, related genera, ITS2, DNA barcoding, identification