基于核糖体ITS区和28S rRNA D2～D3区的短体线虫系统发育研究

PHYLOGENETIC ANALYSIS OF PRATYLENCHUS (NEMATODA, PRATYLENCHIDAE) BASED ON RIBOSOMAL INTERNAL TRANSCRIBED SPACERS (ITS) AND D2-D3 EXPANSION SEGMENTS OF 28S RRNA GENE

短体线虫又称根腐线虫,是世界分布最为广泛和最具破坏性的迁徙性植物内寄生线虫之一。本研究根据214条核糖体ITS序列,218条核糖体28S大亚基D2～D3序列,应用MEGA4.0软件,通过邻接法(NJ)构建了短体线虫的系统发育树。结果发现,2个系统树在整体上大致相似,仅在小的分支上存在差异。基于ITS序列的系统树将25种短体线虫至少分为8组,相应的基于D2～D3序列的系统树将23种短体线虫至少分为7组。其中,有3个大组内部的系统发育关系比较清晰。根据本研究的系统发育分析仍然无法从总体上确定短体线虫种间的系统发育关系。

The root lesion nematodes, Pratylenchus Flipjev, 1936, is one of the most widespread and destructive endoparasites that invade and migrate in roots of a variety of crops around the world. 214 nucleotide sequences of ribosomal ITS spacers, 218 sequences of D2- D3 segments of 28S ribosomal RNA were used for phylogenefic analysis of Pratylenchus nematodes. The phylogenetic trees were constructed using neighbor-joining method in MEGA 4.0 program. The results revealed that the two trees are broadly similar on the whole except that some divergences in minimal branches exist, and the 25 examined Pratylenchus species could be divided into at least 8 dades based on ITS phylogenetic tree corresponding to the 7 clades of 23 Pratylenchus species based on D2 -D3 phylogenetic tree. Of which, there are 3 large clades with relatively clear phylogenetic relationships within each clade. Accoding to the phylogenefic analysis of this study we are still unable to determine the general phylogenetic relationships of Pratylenchus speceies.