ITS sequences of 15 representative species of five sections in the genus Populus L. were determined. By using direct sequencing of PCR product, it was found that the fragments of internal transcribed spacers (ITS) are about 594 bp in length. The length of ITS-1 and ITS-2 is about 220 bp and 210 bp, respectively, while that of 5.8s is 164 bp. Its G+C content is about 69.0%. The number of phylogenetically informative loci is higher in ITS-2 than in ITS-1. Transversion and transition are two main factors that drive the ITS evolution, and more insertions and deletions occurred in ITS-2. Taking Salix matsudana Koidz. and Salix suchowensis Cheng as outgroups, phylogenetic analysis of ITS sequences using PAUP 4.0 software indicated that Populus is monophyletic group and can be divided into two main clades. One is the section Leuce , and the other is the remaining sections.
用ITS序列研究杨属各组之间的系统发育关系
史全良 诸葛强 黄敏仁*王明庥
（南京林业大学林木遗传和基因工程国家林业局重点实验室，南京210037）
关键词： 杨树；内转录间隔区（ITS）序列；系统发育
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