title: Ectomycorrhizal symbiosis affects functional diversity of rhizosphere fluorescent pseudomonads.
abstract: Here we characterized the effect of the ectomycorrhizal symbiosis on the genotypic and functional diversity of soil Pseudomonas fluorescens populations and analysed its possible consequences in terms of plant nutrition, development and health. Sixty strains of P. fluorescens were isolated from the bulk soil of a forest nursery, the ectomycorrhizosphere and the ectomycorrhizas of the Douglas fir (Pseudostuga menziesii) seedlings-Laccaria bicolor S238N. They were characterized in vitro with the following criteria: ARDRA, phosphate solubilization, siderophore, HCN and AIA production, genes of N2-fixation and antibiotic synthesis, in vitro confrontation with a range of phytopathogenic and ectomycorrhizal fungi, effect on the Douglas fir-L. bicolor symbiosis. For most of these criteria, we demonstrated that the ectomycorrhizosphere significantly structures the P. fluorescens populations and selects strains potentially beneficial to the symbiosis and to the plant. This prompts us to propose the ectomycorrhizal symbiosis as a true microbial complex where multitrophic interactions take place. Moreover it underlines the fact that this symbiosis has an indirect positive effect on plant growth, via its selective pressure on bacterial communities, in addition to its known direct positive effect.
authors.affiliation: UMR INRA-UHP Interactions Arbres/Micro-organismes, 54280 Champenoux, France. klett@nancy.inra.fr
authors.forename: Pascale
authors.initials: P
authors.lastname: Frey-Klett
authors.forename: Michaël
authors.initials: M
authors.lastname: Chavatte
authors.forename: Marie-Lise
authors.initials: ML
authors.lastname: Clausse
authors.forename: Sébastien
authors.initials: S
authors.lastname: Courrier
authors.forename: Christine
authors.initials: C
authors.lastname: Le Roux
authors.forename: Jos
authors.initials: J
authors.lastname: Raaijmakers
authors.forename: Maria Giovanna
authors.initials: MG
authors.lastname: Martinotti
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Pierrat
authors.forename: Jean
authors.initials: J
authors.lastname: Garbaye
mesh_terms: D001487:Basidiomycota / Q000254:growth & development / Q000502:physiology*; D005838:Genotype; D006856:Hydrogen Cyanide / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism; D038821:Mycorrhizae / Q000254:growth & development / Q000502:physiology*; D018517:Plant Roots / Q000382:microbiology; D011157:Population Dynamics; D011551:Pseudomonas fluorescens / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D028224:Pseudotsuga / Q000382:microbiology*; D017262:Siderophores / Q000378:metabolism; D012988:Soil Microbiology; D013559:Symbiosis / Q000502:physiology
chemical_list: D007210:Indoleacetic Acids; D017262:Siderophores; D006856:Hydrogen Cyanide; C030737:indoleacetic acid