Endophytic bacteria take the challenge to improve Cu phytoextraction by sunflower

Endophytic bacteria from roots and crude seed extracts of a Cu-tolerant population of Agrostis capillaris were inoculated to a sunflower metal-tolerant mutant line, and their influence on Cu tolerance and phytoextraction was assessed using a Cu-contaminated soil series. Ten endophytic bacterial strains isolated from surface-sterilized A. capillaris roots were mixed to prepare the root endophyte inoculant (RE). In parallel, surface-sterilized seeds of A. capillaris were crushed in MgSO4 to prepare a crude seed extract containing seed endophytes (SE). An aliquot of this seed extract was filtered at 0.2 μm to obtain a bacterial cell-free seed extract (SEF). After surface sterilization, germinated sunflower seeds were separately treated with one of five modalities: no treatment (C), immersion in MgSO4 (CMg) or SEF solutions and inoculation with RE or SE. All plants were cultivated on a Cu-contaminated soil series (13–1020 mg Cu kg−1). Cultivable RE strains were mostly members of the Pseudomonas genera, and one strain was closely related to Labrys sp. The cultivable SE strains belonged mainly to the Bacillus genera and some members of the Rhodococcus genera. The treatment effects depended on the soil Cu concentration. Both SE and SEF plants had a higher Cu tolerance in the 13–517 mg Cu kg−1 soil range as reflected by increased shoot and root DW yields compared to control plants. This was accompanied by a slight decrease in shoot Cu concentration and increase in root Cu concentration. Shoot and root DW yields were more promoted by SE than SEF in the 13–114 mg Cu kg−1 soil range, which could reflect the influence of seed-located bacterial endophytes. At intermediate soil Cu (416–818 mg Cu kg−1 soil), the RE and CMg plants had lower shoot Cu concentrations than the control, SE and SEF plants. At high total soil Cu (617–1020 mg Cu kg−1), root DW yield of RE plants slightly increased and their root Cu concentration rose by up to 1.9-fold. In terms of phytoextraction efficiency, shoot Cu removal was increased for sunflower plants inoculated with crude and bacterial cell-free seed extracts by 1.3- to 2.2-fold in the 13–416 mg Cu kg−1 soil range. Such increase was mainly driven by an enhanced shoot DW yield. The number and distribution of endophytic bacteria in the harvested sunflower tissues must be further examined

Diversity and P-solubilizing ability of mycorrhizosphere bacteria associated with Pinus pinaster in the Landes forest ecosystem

Ectomycorrhizal fungi (ECM) and their associated mycorrhizosphere bacteria (MB) play a major role in 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 MB associated to ECM, three collection campaigns of ECM root tips were performed from autumn 2005 to autumn 2006 throughout three forest stations. Five MB and nine ECM genera were identified overall through sequencing of 16S rDNA and mitochondrial large subunit rDNA fragment respectively. Dramatic seasonal changes were observed in the different MB-ECM associations especially in Burkholderia-Lactarius and Bacillus-Russula that were the most abundant ones. P-solubilizing ability of MB was shown to be taxon-dependent with a large majority of P-solubilizing isolates among Burkholderia, Pseudomonas and Paenibacillus contrary to Bacillus. Relationships between functional diversity of the MB-ECM associations and bioavailability of soil P remain to be investigated. (Résumé d'auteur)

Autecology of « cèpes ». Perspectives for the management of forest ecosystems

L’analyse des répartitions chorologiques et écologiques des Boletus de la section Edules montre qu’il s’agit d’espèces à large amplitude, depuis l’Afrique du nord jusqu’au Nord du Boréal. Pour chacune des espèces du groupe, cette large répartition s’accompagne d’une grande diversité à la fois des plantes-hôtes, des habitats et des conditions édaphiques. Certaines caractéristiques des écosystèmes forestiers sont plus favorables à la production de carpophores, en particulier les phases à forte dynamique et les perturbations pédologiques. Ces caractéristiques peuvent être liées à des phénomènes naturels ou anthropiques. Nous présentons des résultats issus d’observations dans différents écosystèmes forestiers du Sud-Ouest de la France,de l’Espagne et du Maroc. Ces observations nous amènent à proposer deux concepts de gestion : (i) la mycoforesterie qui est une gestion forestière orientée vers la production intensive de champignons comestibles ; (ii) la mycosylviculture qui correspond à une gestion forestière intégrée, prenant en compte, en plus de la production de bois, la préservation ou la restauration de communautés fongiques, la biodiversité et la possible valorisation économique de champignons comestibles

Le cyprès. Un arbre aux champignons fidèles et singuliers

National audienc

Quelques notions sur les grandes lignes de la classification des bolets.

National audienc

Definition et position taxonomique du genre Pleurotus dans la classification des champignons

National audienc

Definition et position taxonomique du genre Pleurotus dans la classification des champignons

National audienc

Les champignons sylvestres en France : une nouvelle donne pour la recherche et l'application

International audienc

Evolution du cortege fongique associe au pin maritime dans les conditions d'un peuplement experimental.

National audienc