Genetic Divesity And Phylogeny Of Rhizobia Isolated From Oxytropis In Ruoergai Plateau, Sichuan, China

Nitrogen is one of the most important essential elements for plant growth,and the main source of soil nitrogen includes chemical nitrogen fertilizer and the biological nitrogen fixation of soil microorganisms.Symbiotic nitrogen fixation of Rhizobium and leguminous plants is the most efficient system in biological nitrogen fixation, leguminous plants and Rhizobium symbiotic system is strong and efficient,and is beneficial to the agricultural,environmental and ecological sustainable development.In this paper,26 rhizobia isolated from Oxytropis DC in Ruoergai plateau, Sichuan province,were studied by SDS-PAGE of whole cell protein,BOXAIR-PCR fingerprinting,16S rDNA and IGS PCR-RFLP,and 16S rDNA full length sequence.SDS-PAGE of whole cell protein analysis showed that all the strains clustered into 7 different groups at the similarity of 71%,and these strains belonged to genus of Mesorhizobium and Rhizobium,repectively.Abundant bands were amplified in analysis of BOXAIR-PCR,which revealed that the genetic diversity among these rhizobial isoltes was existed,and all the strains clustered into 8 genetic groups at the similarity of 71%,and also grouped within the genus of Mesorhizobium and Rhizobium,.The results of 16S rDNA and IGS PCR-RFLP analysis indicated that the results of two methods were in good agreement with each other.The 16S rDNA PCR-RFLP analysis resulted in 19 different genotypes and 2 phylogenetic branches formed at the boundary of 68%similar level,and 6 genetic groups were formed at the level of 94% similarity;while,IGS PCR-RFLP analysis formed 9 genetic groups at the level of 90%similarity.The 16S rRNA genes sequences of eight representative strains,i.e.REG320, REG309,REG316,REG305,REG314,REG325,REG321 and REG301 was analyzed, and the phylogenic tree was constructed.The results showed that,strains REG320, REG309,REG316 and REG305 belong to genus of Rhizobium,and REG314,REG325,REG321 and REG301 distributed in genus of Mesorhizobium,however, all the strains belonged to 6 difernent rhizobial species.