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- A genotype dependent-response to cadmium contamination in soil is displayed by Pinus pinaster in symbiosis with different mycorrhizal fungiPublication . Sousa, Nadine R.; Ramos, Miguel A.; Marques, Ana P. G. C.; Castro, Paula M. L.Soil contamination with Cd is of primary concern and beneficial soil restoration strategies urge. The aim of this work is to evaluate the response of two different genotypes of Pinus pinaster (wild and selected) to Cd contamination and to assess how inoculation with ectomycorrhizal fungi, Suillus bovinus and Rhizopogon roseolus, influenced each genotype. Seedlings were exposed to soil contaminated at 15 and 30 mg Cd kg−1. Plant growth, mycorrhizal traits and Cd accumulation in different tissues of the plant were determined at harvest. The fungal community was assessed by denaturing gradient gel electrophoresis. At 15 mg Cd kg−1 S. bovinus increased aboveground development in both genotypes. At 30 mg Cd kg−1 non-inoculated wild genotype accumulated more Cd in the shoots (1.7-fold) than the selected genotype; inoculation with R. roseolus decreased Cd concentration in the roots of the selected genotype whereas the opposite occurred in the wild genotype. Cd concentration in the root system was the parameter most influenced by the interaction between the three studied variables. The fungal community established was affected by the Cd concentration in the soil. Results show that different genotypes of P. pinaster react differently to Cd exposure depending on the mycorrhizal association. The importance of considering the combination between plant genotype and its symbiotic partners when aiming at the forestation of degraded land is highlighted.
- 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.
- Selection of high performance strains of edible mycorrhizal fungi for improved abiotic stress resistancePublication . Ramos, Miguel A.; Serafim, Cindy; Sousa, Nadine R.; Castro, Paula M. L.
- The effect of ectomycorrhizal fungi forming symbiosis with Pinus pinaster seedlings exposed to cadmiumPublication . Sousa, Nadine R.; Ramos, Miguel A.; Marques, Ana P. G. C.; Castro, Paula M. L.Cadmium is one of the most toxic heavy metals and its accumulation in the upper layers of forest soils affects plants, microorganisms and their interactions. Adequate strategies for the reforestation of metal contaminated sites are of vital importance. The aim of this work was to evaluate the response of Pinus pinaster seedlings to Cd exposure and to assess the effect of inoculation with two selected ectomycorrhizal fungi, Suillus bovinus and Rhizopogon roseolus on that response. Seedlings were exposed to soil contaminated at 15 and 30 mg Cd kg−1. Shoot biomass of P. pinaster decreased ca. 36% when exposed to 15 mg Cd kg−1. Overall, colonization by S. bovinus significantly enhanced shoot development up to 30% in contaminated soil while colonization by R. roseolus produced no significant effect at both Cd concentrations tested and significantly increased the level of Cd in the shoots at both Cd concentrations. Metal accumulation in the shoots and roots of non-inoculated and S. bovinus-inoculated seedlings increased at the higher Cd levels whereas R. roseolus-inoculated seedlings were not sensitive to Cd variation in the soil. The results from our research show that inoculation with ECM fungi has a significant impact on metal uptake and development of P. pinaster seedlings; the differential response induced by the two tested species highlights the importance of selecting the appropriate strains for nursery inoculation, and, as such, this biological tool ought to be considered in reforestation processes of heavy metal contaminated areas by woody species.
- 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.