Bacterial biogeography in two functionally contrasting rhizospheres - nitrogen-fixing [i]Medicago truncatul[/i]a and ectomycorrhizal[i] Pinus pinaster[/i] - Archive ouverte HAL Accéder directement au contenu
Communication Dans Un Congrès Année : 2012

Bacterial biogeography in two functionally contrasting rhizospheres - nitrogen-fixing [i]Medicago truncatul[/i]a and ectomycorrhizal[i] Pinus pinaster[/i]

Résumé

Even though rhizospheric pH displays high variability, possible links between pH and bacterial biogeography at the rhizosphere scale remain largely unknown. The aim of this study was to document the spatial distribution of bacterial communities in relation to soil pH around roots of two functionally contrasting plants, a coniferous tree and an annual legume. Pinus pinaster, with and without ectomycorrhizal inoculation (Rhizopogon roseolus), and two Medicago truncatula genotypes (Jemalong 6 and DZA 315-16), inoculated with Sinorhizobium medicae, were cultivated in thin mini-rhizoboxes. After two months, millimetre-scale mapping of the following parameters were performed on 18 cm2 zones: presence of roots, mycorrhizae and nodules; soil pH, using noninvasive planar optodes; and different taxonomic and functional (nitrifiers and denitrifiers) groups of bacteria, using Q-PCR. Rhizosphere acidity was highly heterogeneous, with lowest pH close to mycorrhizal roots of Pinus pinaster and nodules and dense roots of Medicago truncatula. Both soil pH and quantities of bacterial phyla showed highest variability in the rhizosphere of Pinus pinaster with mycorrhiza, followed, in order of decreasing variability, by Medicago truncatula DZA 315-16, Medicago truncatula Jemalong J6, and Pinus pinaster without mycorrhiza. The spatial patterns of bacterial phyla were consistently related to soil pH, with the strongest relationship in the rhizosphere of Pinus pinaster with mycorrhizal inoculation. This pioneering documentation of bacterial biogeography at the rhizosphere scale provides completely new insights in how mycorrhizal and nitrogen-fixing symbioses generate spatial heterogeneity in soil pH and bacterial community composition.
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Dates et versions

hal-01268644 , version 1 (04-02-2016)

Identifiants

  • HAL Id : hal-01268644 , version 1
  • PRODINRA : 268185

Citer

Georg Carlsson, Benoît Cloutier-Hurteau, Stephan Blossfeld, Anne-Laure Pablo, Claude Plassard, et al.. Bacterial biogeography in two functionally contrasting rhizospheres - nitrogen-fixing [i]Medicago truncatul[/i]a and ectomycorrhizal[i] Pinus pinaster[/i]. 4. International Congress of the European Soil Science Societies. Eurosoil 2012: soil science for the benefit of mankind and environment, Jul 2012, Bari, Italy. ⟨hal-01268644⟩
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