Genetic Diversity Of The Rhizobia And Screening Effective Rhizobia Strains Isolated From Arachis Hypogaea L. In Shandong Province

Shandong Province is the main area of cultivation and production of peanuts. It has better genetic diversity backgrounds and efficient rhizobium resources. To reveal the genetic diversity of rhizobia isolated from Shandong province and screen effective nitrogen-fixing bacteria strains, peanut rhizobia were collected and isolated from ten cities and counties in Shandong province,and all isolates were selected to determine their phylogenetic relationships through analyses of the 16 S rRNA gene, housekeeping genes(rec A, atpD and glnII) and symbiotic genes(nifH, nodC). The growth-promoting efficiency was tested by plant inoculation assay on peanut in greenhouse.A total of 345 peanut rhizobium strains were isolated from 10 counties samples and 22 representative strains were selected by sequence analysis of housekeeping genes recA. For the representative strains 16 S rRNA gene and housekeeping gene MLSA phylogenetic analysis showed that the isolated strains of Bradyrhizobium distributed B. liaoningense and B. yuanmingense, B. arachidis and an unknown species. NifH symbiotic genes and nodulation gene nodC phylogenetic analysis showed that nitrogen fixation and nodulation genes are highly conserved. The phylogenetic relationships are closer, but there is a big difference between the symbiotic genes and the housekeeping genes indicating the presence of peanut rhizobia population horizontal transfer symbiotic genes. Greenhouse and field experiments showed that the representative strains could form effective nodules with peanut and effective on symbiotic nitrogen fixation. The representative strains YIC61059 possessed prominent growth-promoting effect on peanut growth.Correlation analysis between rhizobial species and soil factors suggested that available nitrogen, total nitrogen and organic matter are the main factors in peanut rhizobium population distribution in Shandong. Low level of soil nitrogen and high phosphorus properties were benefical to the distribution B. liaoningense, and a high level of total nitrogen and organic matter in soil played the most important role in the distribution of B. yuanmingense. The distributions of new stocks were impacted by local high phosphorus and low alkali greater.In summary, it was found that severe genetic diversity and germplasm resources existed in peanut rhizobia from Shandong. Peanut rhizobia in this region showed well nodulation and symbiotic nitrogen fixation ability. PH, available phosphorus and potassium are the main factors influencing the distribution of peanut rhizobia in Shandong province. The representative strain YIC61059 has a significant positive effect on yield growth and it has good prospects of application.