title: Diversity and biogeography of rhizobia isolated from root nodules of Glycine max grown in Hebei Province, China.
abstract: A total of 215 rhizobial strains were isolated and analyzed with 16S rRNA gene, 16S-23S intergenic spacer, housekeeping genes atpD, recA, and glnII, and symbiotic genes nifH and nodC to understand the genetic diversity of soybean rhizobia in Hebei province, China. All the strains except one were symbiotic bacteria classified into nine genospecies in the genera of Bradyrhizobium and Sinorhizobium. Surveys on the distribution of these rhizobia in different regions showed that Bradyrhizobium japonicum and Bradyrhizobium elkanii strains were found only in neutral to slightly alkaline soils whereas Bradyrhizobium yuanmingense, Bradyrhizobium liaoningense-related strains and strains of five Sinorhizobium genospecies were found in alkaline-saline soils. Correspondence and canonical correspondence analyses on the relationship of rhizobial distribution and their soil characteristics reveal that high soil pH, electrical conductivity, and potassium content favor distribution of the B. yuanmingense and the five Sinorhizobium species but inhibit B. japonicum and B. elkanii. High contents of available phosphorus and organic matters benefit Sinorhizobium fredii and B. liaoningense-related strains and inhibit the others groups mentioned above. The symbiotic gene (nifH and nodC) lineages among B. elkanii, B. japonicum, B. yuanmingense, and Sinorhizobium spp. were observed in the strains, signifying that vertical gene transfer was the main mechanism to maintain these genes in the soybean rhizobia. However, lateral transfer of symbiotic genes commonly in Sinorhizobium spp. and rarely in Bradyrhizobium spp. was also detected. These results showed the genetic diversity, the biogeography, and the soil determinant factors of soybean rhizobia in Hebei province of China.
authors.affiliation: State Key Laboratory of Agrobiotechnology/College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Qin Qin
authors.initials: QQ
authors.lastname: Li
authors.forename: En Tao
authors.initials: ET
authors.lastname: Wang
authors.forename: Yun Zeng
authors.initials: YZ
authors.lastname: Zhang
authors.forename: Yan Ming
authors.initials: YM
authors.lastname: Zhang
authors.forename: Chang Fu
authors.initials: CF
authors.lastname: Tian
authors.forename: Xin Hua
authors.initials: XH
authors.lastname: Sui
authors.forename: Wen Feng
authors.initials: WF
authors.lastname: Chen
authors.forename: Wen Xin
authors.initials: WX
authors.lastname: Chen
mesh_terms: D020369:Bradyrhizobium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D002681:China; D014644:Genetic Variation; D008969:Molecular Sequence Data; D010802:Phylogeny; D012230:Rhizobiaceae / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D053204:Root Nodules, Plant / Q000382:microbiology*; D013025:Glycine max / Q000254:growth & development / Q000382:microbiology* / Q000502:physiology; D013559:Symbiosis