用ITS序列研究杨属各组之间的系统发育关系

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 ITS1 and ITS2 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 ITS2 than in ITS1. Transversion and transition are two main factors that drive the ITS evolution, and more insertions and deletions occurred in ITS2. 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.