山蚂蝗慢生根瘤菌的遗传多样性及系统发育

Genetic diversity and phylogeny of bradyrhizobia associated with Desmodium spp.

【目的】研究我国亚热带和温带地区与山蚂蝗共生的慢生根瘤菌遗传多样性和系统发育。【方法】采用BOX-PCR和多位点基因序列分析(nifH,nodC和recA基因)方法对分离自我国不同地区的29株山蚂蝗慢生根瘤菌进行遗传多样性和系统发育分析。【结果】BOX-PCR分析表明供试的山蚂蝗慢生根瘤菌形成25个基因遗传型,具有丰富的基因组多样性。多位点基因序列分析发现代表菌株位于慢生根瘤菌的3个分支上,分别与埃氏慢生根瘤菌(Bradyrhizobium elkanii),大豆慢生根瘤菌(Bradyrhizobium japonicum)和圆明慢生根瘤菌(Bradyrhizobium yuanmingense)亲缘关系近。【结论】我国山蚂蝗慢生根瘤菌具有丰富的遗传多样性,共生基因系统发育分析表明它们多与持家基因共同进化,并以垂直进化为主。

[Objective]Genetic diversity and phylogeny of bradyrhizobial strains associated with Desmodium spp.in subtropic and temperate regions of China were analyzed.[Methods] We studied 29 desmodia isolates from different regions with BOX-PCR fingerprinting and multilocus sequence analysis(nifH,nodC and recA gene) to describe the genotypic characteristics and phylogenetic relationships.[Results] We achieved 25 genotypes with BOX-PCR genomic fingerprinting analysis,indicating that the tested strains had a great diversity at genomic level.The representative bradyrhizobial strains were located in three phylogenic branches with multilocus sequence analysis(nifH,nodC and recA gene),that was closely related to Bradyrhizobium elkanii,Bradyrhizobium japonicum and Bradyrhizobium yuanmingense,respectively.[Conclusion] The desmodia bradyrhizobia had abundantly diversity.Diverse symbiotic genes including nifH and nodC genes were also found in these strains that indicated that the symbiotic genes were mainly maintained by vertical transfer in these bradyrhizobial populations and coevolved with housekeeping genes.