title: Genetic diversity and symbiotic evolution of rhizobia from root nodules of Coronilla varia.
abstract: Ninety symbiotic rhizobial isolates from root nodules of Coronilla varia growing in the Shaanxi province of China were characterized. Combined with the results of RFLP patterns, six genotypes were defined among the rhizobial strains and they were divided into three genomic genera. These included Mesorhizobium sp., M. alhagi, M. amorphae, M. metallidurans/M. gobiense as the dominant group (86.7%), and Rhizobium yanglingense and Agrobacterium tumefaciens as the minor groups, according to analysis of the corresponding 16S rRNA, nodC and nifH genes. Five nodC types, which mainly grouped into the Mesorhizobium genus, were obtained from all the isolates examined, implying that nodC genes probably occurred from the native habitat through lateral transfer and long-term adaptation, finally evolving toward M. alhagi. Four different nifH types, displaying obvious differences compared to those of 16S rRNA and nodC, implied that possible lateral transfer of the symbiotic genes occurred between different genera. The association between soil components and the genetic diversity of the rhizobial population demonstrated that combined genotypes were positively correlated with the pH of soil samples.
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Life Sciences, Northwest A & F University, Yangling Shaanxi 712100, China.
authors.forename: Wenquan
authors.initials: W
authors.lastname: Yang
authors.forename: Zhaoyu
authors.initials: Z
authors.lastname: Kong
authors.forename: Weimin
authors.initials: W
authors.lastname: Chen
authors.forename: Gehong
authors.initials: G
authors.lastname: Wei
mesh_terms: D016960:Agrobacterium tumefaciens / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D001426:Bacterial Proteins / Q000235:genetics; D002681:China; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D007887:Fabaceae / Q000382:microbiology* / Q000502:physiology; D014644:Genetic Variation; D059128:Mesorhizobium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012231:Rhizobium / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D053204:Root Nodules, Plant / Q000382:microbiology*; D017422:Sequence Analysis, DNA; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S