title: Compatibility of rhizobial genotypes within natural populations of Rhizobium leguminosarum biovar viciae for nodulation of host legumes.
abstract: Populations of Rhizobium leguminosarum biovar viciae were sampled from two bulk soils, rhizosphere, and nodules of host legumes, fava bean (Vicia faba) and pea (Pisum sativum) grown in the same soils. Additional populations nodulating peas, fava beans, and vetches (Vicia sativa) grown in other soils and fava bean-nodulating strains from various geographic sites were also analyzed. The rhizobia were characterized by repetitive extragenomic palindromic-PCR fingerprinting and/or PCR-restriction fragment length polymorphism (RFLP) of 16S-23S ribosomal DNA intergenic spacers as markers of the genomic background and PCR-RFLP of a nodulation gene region, nodD, as a marker of the symbiotic component of the genome. Pairwise comparisons showed differences among the genetic structures of the bulk soil, rhizosphere, and nodule populations and in the degree of host specificity within the Vicieae cross-inoculation group. With fava bean, the symbiotic genotype appeared to be the preponderant determinant of the success in nodule occupancy of rhizobial genotypes independently of the associated genomic background, the plant genotype, and the soil sampled. The interaction between one particular rhizobial symbiotic genotype and fava bean seems to be highly specific for nodulation and linked to the efficiency of nitrogen fixation. By contrast with bulk soil and fava bean-nodulating populations, the analysis of pea-nodulating populations showed preferential associations between genomic backgrounds and symbiotic genotypes. Both components of the rhizobial genome may influence competitiveness for nodulation of pea, and rhizosphere colonization may be a decisive step in competition for nodule occupancy.
authors.affiliation: UMR Microbiologie des Sols-Géosol, Centre de Microbiologie du Sol et de L'Environnement, INRA, BP 86510, F-21065 Dijon Cedex, France. laguerre@dijon.inra.fr
authors.forename: Gisèle
authors.initials: G
authors.lastname: Laguerre
authors.forename: Philippe
authors.initials: P
authors.lastname: Louvrier
authors.forename: Marie-Reine
authors.initials: MR
authors.lastname: Allard
authors.forename: Noëlle
authors.initials: N
authors.lastname: Amarger
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D016172:DNA Fingerprinting / Q000379:methods; D005838:Genotype; D009586:Nitrogen Fixation / Q000235:genetics; D018532:Pisum sativum / Q000382:microbiology*; D018517:Plant Roots / Q000382:microbiology*; D010957:Plasmids / Q000235:genetics; D016133:Polymerase Chain Reaction; D016961:Rhizobium leguminosarum / Q000145:classification* / Q000235:genetics / Q000254:growth & development*; D012988:Soil Microbiology; D013559:Symbiosis; D031307:Vicia faba / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins