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- The response of Betula pubescens to inoculation with an ectomycorrhizal fungus and a plant growth promoting bacterium is substrate-dependentPublication . Sousa, Nadine R.; Franco, Albina R.; Ramos, Miguel A.; Oliveira, Rui S.; Castro, Paula M. L.The combination of ectomycorrhizal (ECM) fungi and plant growth promoting bacteria (PGPB) has considerable potential in forestry. Here we report on the combined effects of PGPB Mesorhizobium sp. and the ECM fungus Paxillus involutus on the growth of Betula pubescens in two different substrates, a forest soil and an alkaline anthropogenic sediment. Growth, nutrient concentration and mycorrhizal formation of B. pubescens were determined at the end of the experiment and the fungal and bacterial communities were assessed by denaturing gradient gel electrophoresis. The combined effects of ECM and PGPB enhanced root and shoot growth most in the forest soil with Mesorhizobium appearing to stimulate mycorrhizal formation. However, in the alkaline sediment, an antagonistic interaction was detected between P. involutus and Mesorhizobium sp., with Mesorhizobium sp. alone stimulating growth. The significant interaction between the ECM and the PGBP across the two substrates is discussed.
- Degradation of 3-fluorophenol and Sodium Trifluoroacetate by Ectomycorrhizal fungiPublication . Franco, Albina R.; Ramos, Miguel; Sousa, Nadine R.; Silva, Débora S.; Oliveira, Rui S.; Castro, Paula M. L.
- Effect of diflubenzuron on the development of Pinus pinaster seedlings inoculated with the ectomycorrhizal fungus Pisolithus tinctoriusPublication . Ramos, Miguel A.; Sousa, Nadine R.; Franco, Albina R.; Costa, Vítor; Oliveira, Rui S.; Castro, Paula M. L.Diflubenzuron (DFB) is an insecticide commonly used to control forest pests. The objectives of this study were to assess the effect of diflubenzuron on the development of Pinus pinaster seedlings and Pisolithus tinctorius under laboratory conditions and to study the possible protective role of this ectomycorrhizal fungus against the effects of diflubenzuron. In vitro experiments revealed that diflubenzuron inhibited fungal growth at all tested concentrations (0.01, 0.1, 1, 10 and 100 mg L−1). Root growth was inhibited at the two highest diflubenzuron concentrations. The activity of the antioxidant defence system of non-inoculated P. pinaster increased at 1 and 10 mg DFB kg−1 substrate, and inoculation increased the threshold to the highest concentration. The protective role of the ectomycorrhizal fungus was seen in the increase of CAT activity. This study revealed that despite causing no mortality, diflubenzuron has the ability to cause sub-lethal damage to P. pinaster. The disproportionate use of this insecticide may lead to higher amounts of its residues in soil and the biosphere, endangering trees, fungi and their symbiosis.
- Mycorrhizal symbiosis affected by different genotypes of Pinus pinasterPublication . Sousa, Nadine R.; Ramos, Miguel A.; Franco, Albina R.; Oliveira, Rui S.; Castro, Paula M. L.Background and aims Higher growth rate and morphological traits have been the major criteria for selecting trees in breeding programs. The symbiotic associations between P. pinaster and ectomycorrhizal fungi can be an effective approach to enhance plant development. The aimof thisworkwas to assess whether the establishment of mycorrhizal symbiosis at nursery stage was affected by tree breeding. Methods Seeds of P. pinaster from a clonal population, designed to select for various traits, and from neighboring wild plants were inoculated with compatible ectomycorrhizal fungi: Suillus bovinus, Pisolithus tinctorius or Rhizopogon roseolus, and grown in individual cells containing forest soil, in a commercial forest nursery. Growth and nutritional traits, colonisation parameters and the fungal community established were assessed. Results R. roseolus and P. tinctorius were the most efficient isolates in promoting plant development. Inoculated selected saplings had an overall superior development than their wild counterparts, with up to a 4.9-fold in root dry weight and a 13.6-fold increase in the total number of ectomycorrhizal root tips. Differences in fungal community were revealed through the denaturing gradient gel electrophoresis profile of each treatment. Conclusions The results from our study suggest that the selected genotype benefits more from the mycorrhizal association and therefore this could be a valuable biotechnological tool for the nursery production of P. pinaster.
- Potential of persistent ectomycorrhizal fungi in fire impacted soil to degrade fluorinated pollutantsPublication . Franco, Albina; Sousa, Nadine R.; Ramos, Miguel; Oliveira, Rui S.; Castro, P. M. L.