山东省是我国花生种植和生产的主要地区，其花生根瘤菌遗传多样性和高效共生菌株种质资源较为丰富。为揭示山东省花生根瘤菌种群结构和遗传多样性，本研究从山东省10个县市采集新鲜的花生根瘤分离出根瘤菌，对菌株的16S rRNA基因、持家基因（recA、atpD、glnII）序列进行系统发育分析以确定根瘤菌的系统发育地位，同时对共生基因nifH、nodC序列进行系统发育分析，并通过温室盆栽接种实验筛选高效共生固氮根瘤菌菌株。

从10个县市采样点共分离到345株花生根瘤菌菌株，通过持家基因recA序列分析选定22株代表菌株。对代表菌株的16S rRNA基因与持家基因MLSA系统发育分析表明，所分离到的菌株分布于Bradyrhizobium的B. liaoningense和B. yuanmingense、B. arachidis和一个潜在新种群。共生基因nifH和结瘤基因nodC系统发育分析表明固氮基因和结瘤基因高度保守，系统发育关系较近，但与16S rRNA、持家基因系统发育存在较大差异，表明花生根瘤菌种群之间存在共生基因的横向转移。温室盆栽实验表明代表菌株均能与花生有效结瘤固氮，高效固氮菌株YIC61059在大田小区实验中能够对花生起到显著的促生增产作用。

根瘤菌与土壤因子相关性分析表明：有效氮、全氮和有机质是影响山东省花生根瘤菌种群分布的主要因素。低磷、高氮的土壤有利于B. liaoningense的分布，高水平的全氮和有机质有利于B. yuanmingense的分布，高磷和低碱的土壤对潜在新种群影响较大。

综上所述，山东省花生根瘤菌具有丰富的遗传多样性和种质资源。该地区的花生根瘤菌具有较好的结瘤和共生固氮能力，pH、速效磷和速效钾是影响山东省花生根瘤菌分布的主要因素，本研究筛选出的高效共生固氮花生根瘤菌YIC61059促生增产效果明显，具有良好的应用前景。

 

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 16S rRNA gene, housekeeping genes (recA, 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 16S 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.