Diversity of mycorrhiza and mycorrhizosphere bacteria associated with Pinus pinaster in the Landes forest according to vasrious soil phosphorus regimes

Waseem Muhammad, Domergue Odile, Prin Yves, Plassard Claude, Duponnois Robin, Guinberteau Jacques, Bakker Mark, Augusto Laurent, Trichet Pierre, Saur Etienne, Hinsinger Philippe, Jaillard Benoît, Galiana Antoine. 2010. Diversity of mycorrhiza and mycorrhizosphere bacteria associated with Pinus pinaster in the Landes forest according to vasrious soil phosphorus regimes. In : 1er Congrès International sur les Symbioses Mycorhiziennes Ecosystèmes et Environnement en Milieu Méditerranéen, 11-13/10/2010, Marrakech, Maroc : [Abstracts] = 1er Congrès International Mycorrhizal Symbiosis Ecosystems and Environment of Mediterranean Area. Hafidi Mohamed (ed.), Duponnois Robin (ed.). Université Cadi Ayyad-Faculté des sciences Semlalia. Marrakech : Faculté des Sciences Semlalia, Résumé, pp. 34-35. Congrès International MYCOMED (Symbioses Mycorhiziennes Ecosystèmes et Environnement en Milieu Méditerranéen). 1, Marrakech, Maroc, 11 October 2010/13 October 2010.

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Abstract : The maritime pine (Pinus pinaster), distributed from Morrocan Atlantic coast to South of Europe, is the most planted forest species in France with about 1 million hectares located in the Landes region. Ectomycorrhizal fungi (ECM) and their associated mycorrhizosphere bacteria (MB) could play a major role in plant phosphorous (P) nutrition of maritime pine, particularly in the Landes forest ecosystem considering the low bioavailability of P in its sandy-acidic soils. In order to characterize the diversity and P-solubilizing ability of ECM-MB associations in different soil P conditions, three collection campaigns of ECM root tips were conducted from autumn 2005 to autumn 2006 across three forest stations. The ECM roots tips were systematically sampled from soil cores and separated into distinct morphotypes. Extracts of crushed ECM root tips were then transferred onto Trypcase medium for MB isolation. About 200 ECM-MB associations were successfully characterized based on sequencing of a fragment of mitochondrial large subunit rRNA gene and 16S rDNA respectively. From nine ECM genera identified overall (i.e.Lactarius, Russula, Suillus, Scleroderma, Thelephora, Tomentella, Xerocomus, Hygrophorus and Amanita from the most to the less abundant ones), five MB genera were isolated: Burkholderia (38%), Bacillus (28%), Pseudomonas (18%), Paenibacillus (11%) and Sphingobium (5%).Dramatic seasonal and annual changes were observed in the different MB-ECM associations especially in Burkholderia-Lactarius and BacillusRussula that were the most abundant ones. A factorial correspondence analysis showed significant and high affinities between two MB-ECM taxa associations in particular: Burkholderia-Lactarius and Bacillus-Russula. The less represented ECM taxa such as Thelephora, Suillus/Gomphidius and Scleroderma are also mainly associated to Burkholderia and Bacillus but in about equal proportions without any particular affinity. On the other hand, Pseudomonas, Paenibacillus and Sphingobium did not seem to have particular affinity for a given ECM fungal taxon. The P-solubilizing ability of MB was assessed on Tri-Calcium Phosphate (TCP) agar medium. Regardless of the season, P-solubilizing ability of the most abundant MB was taxon-dependent with a large majority of P-solubilizing isolates in both Pseudomonas and Paenibacillus (95 and 87% respectively) contrary to Bacillus which contained almost equal proportions of P-solubilizing and non-P-solubilizing isolates. In Pierroton forest station where contrasted P-fertilization regimes were applied for successive years, we found that the proportion of P-solubilizing MB isolates was significantly higher ([kappa]2 test) in non-P-fertilized plots than in P-fertilized ones, reaching 66% vs 33% respectively. These results show that the ectomycorrhizal symbiosis could determine the structure of the different bacterial populations in the mycorrhizosphere and thus select bacteria potentially beneficial to the symbiosis and to the plant. Deeper investigations are needed to highlight closer relationships between functional diversity of the MB-ECM associations and bio-availability of soil P. (Résumé d'auteur)

Mots-clés Agrovoc : Pinus pinaster, Mycorhizé

Mots-clés géographiques Agrovoc : Aquitaine

Classification Agris : P34 - Soil biology
K10 - Forestry production

Auteurs et affiliations

  • Waseem Muhammad, INRA (FRA)
  • Domergue Odile, INRA (FRA)
  • Prin Yves, CIRAD-BIOS-UMR LSTM (FRA) ORCID: 0000-0002-3706-0045
  • Plassard Claude, INRA (FRA)
  • Duponnois Robin, IRD (SEN)
  • Guinberteau Jacques, INRA (FRA)
  • Bakker Mark, CIRAD-BIOS-UMR AMAP (FRA)
  • Augusto Laurent, INRA (FRA)
  • Trichet Pierre, INRA (FRA)
  • Saur Etienne, ENITAB (FRA)
  • Hinsinger Philippe, INRA (FRA)
  • Jaillard Benoît, INRA (FRA)
  • Galiana Antoine, CIRAD-BIOS-UMR LSTM (FRA) ORCID: 0000-0002-5293-5049

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