title: Biodiversity and biogeography of rhizobia associated with soybean plants grown in the North China Plain.
abstract: As the putative center of origin for soybean and the second largest region of soybean production in China, the North China Plain covers temperate and subtropical regions with diverse soil characteristics. However, the soybean rhizobia in this plain have not been sufficiently studied. To investigate the biodiversity and biogeography of soybean rhizobia in this plain, a total of 309 isolates of symbiotic bacteria from the soybean nodules collected from 16 sampling sites were studied by molecular characterization. These isolates were classified into 10 genospecies belonging to the genera Sinorhizobium and Bradyrhizobium, including four novel groups, with S. fredii (68.28%) as the dominant group. The phylogeny of symbiotic genes nodC and nifH defined four lineages among the isolates associated with Sinorhizobium fredii, Bradyrhizobium elkanii, B. japonicum, and B. yuanmingense, demonstrating the different origins of symbiotic genes and their coevolution with the chromosome. The possible lateral transfer of symbiotic genes was detected in several cases. The association between soil factors (available N, P, and K and pH) and the distribution of genospecies suggest clear biogeographic patterns: Sinorhizobium spp. were superdominant in sampling sites with alkaline-saline soils, while Bradyrhizobium spp. were more abundant in neutral soils. This study clarified the biodiversity and biogeography of soybean rhizobia in the North China Plain.
authors.affiliation: State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China.
authors.forename: Yan Ming
authors.initials: YM
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Wen Feng
authors.initials: WF
authors.lastname: Chen
authors.forename: En Tao
authors.initials: ET
authors.lastname: Wang
authors.forename: Chang Fu
authors.initials: CF
authors.lastname: Tian
authors.forename: Qin Qin
authors.initials: QQ
authors.lastname: Li
authors.forename: Yun Zeng
authors.initials: YZ
authors.lastname: Zhang
authors.forename: Xin Hua
authors.initials: XH
authors.lastname: Sui
authors.forename: Wen Xin
authors.initials: WX
authors.lastname: Chen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D044822:Biodiversity; D002681:China; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics; D058974:Phylogeography; D012230:Rhizobiaceae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D017422:Sequence Analysis, DNA; D013025:Glycine max / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D010088:Oxidoreductases; C029130:nitrogenase reductase; D017351:N-Acetylglucosaminyltransferases; C060771:NodC protein, Rhizobiales