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Wood pellets can sustain the growth of Trichoderma spp. in soil; however, little is known about their side effects on the microbiota. The aims of this study were to evaluate the effect of wood pellets on the growth of Trichoderma spp. in bulk soil and on the soil microbial population’s composition and diversity. Trichoderma atroviride SC1 coated wood pellets and non-coated pellets were applied at the level of 10 g·kg−1 of soil and at the final concentration of 5 ×103 conidia·g−1 of soil and compared to a conidial suspension applied at the same concentration without the wood carrier. Untreated bulk soil served as a control. The non-coated wood pellets increased the total Trichoderma spp. population throughout the experiment (estimated as colony-forming unit g−1 of soil), while wood pellets coated with T. atroviride SC1 did not. The wood carrier increased the richness, and temporarily decreased the diversity, of the bacterial population, with Massilia being the most abundant bacterial genus, while it decreased both the richness and diversity of the fungal community. Wood pellets selectively increased fungal species having biocontrol potential, such as Mortierella, Cladorrhinum, and Stachybotrys, which confirms the suitability of such carriers of Trichoderma spp. for soil application. [ABSTRACT FROM AUTHOR]

The amount of nitrogen (N) deposition onto forests has globally increased and is expected to double by 2050, mostly because of fertilizer production and fossil fuel burning. Several studies have already investigated the effects of N depositions in forest soils, highlighting negative consequences on plant biodiversity and the associated biota. Nevertheless, the impact of N aerial inputs deposited directly on the tree canopy is still unexplored. This study aimed to investigate the influence of increased N deposition on the leaf-associated fungal and bacterial communities in a temperate forest dominated by Sessile oak [ Quercus petraea (Matt.) Liebl.]. The study area was located in the Monticolo forest (South Tyrol, Italy), where an ecosystem experiment simulating an increased N deposition has been established. The results highlighted that N deposition affected the fungal beta-diversity and bacterial alpha-diversity without affecting leaf total N and C contents. We found several indicator genera of both fertilized and natural conditions within bacteria and fungi, suggesting a highly specific response to altered N inputs. Moreover, we found an increase of symbiotrophic fungi in N-treated, samples which are commonly represented by lichen-forming mycobionts. Overall, our results indicated that N-deposition, by increasing the level of bioavailable nutrients in leaves, could directly influence the bacterial and fungal community diversity. [ABSTRACT FROM AUTHOR]

Aims: Plants host communities of fungal and bacterial endophytes, establishing a complex network of multipartite interactions, but the mechanisms whereby they interact are poorly understood. Some fungi, such as the beneficial mycorrhiza-like fungus Serendipita (=Piriformospora) indica, can be helped by bacteria for establishment, survival and colonization. Although this fungus harbors a Rhizobium as an endofungal bacterium, we hypothesized that other bacteria might also establish associations with the fungus and combining S. indica with bacteria might enhance plant growth and health. Methods: The interactions among S. indica and four endophytic Proteobacteria belonging to Methylobacterium, Tardiphaga, Rhodanobacter and Trinickia spp. were characterized in vitro and for their effect on tomato growth and biocontrol of Fusarium oxysporum and Rhizoctonia solani. Possible mechanisms behind these interactions were described based on genome and microscopic analyses, using fungal and bacterial strains tagged with fluorescent markers. Results: All bacteria stimulated S. indica growth in vitro. Moreover, several of the bacteria stimulated growth of tomato plants, but co-inoculations with S. indica and bacteria did not perform better than single inoculations. Contrarily, combinations of S. indica and bacteria significantly reduced disease progression of fungal pathogens. These microbes seem to cooperate in the process of root colonization for instance by increasing fungal sporulation and hyphae expansion, showing multipartite interaction between microbes and plants. Interestingly, the strain of Trinickia internally colonizes spores of S. indica as an endofungal bacterium during in vitro-co-culturing, suggesting further that the fungus might acquire formerly unrecognized genera of bacteria and genome analysis of the bacteria revealed many genes potentially involved in fungal and plant growth stimulation, biocontrol and root colonization, highlighting putative mechanisms of plant-fungal-bacterial interaction. Conclusions: Our study represents an important step towards unraveling the complex interactions among plants, S. indica, endophytic bacteria and fungal pathogens, and indicates that adding bacteria to fungal inoculum could have a remarkable impact on the plant-S. indica symbiosis. [ABSTRACT FROM AUTHOR]

Plant tissues host complex fungal and bacterial communities, and their composition is determined by host traits such as tissue age, plant genotype and environmental conditions. Despite the importance of bark as a possible reservoir of plant pathogenic microorganisms, little is known about the associated microbial communities. In this work, we evaluated the composition of fungal and bacterial communities in the pear (Abate and Williams cultivars) and apple (Golden Delicious and Gala cultivars) bark of three/four-year-old shoots (old bark) or one-year-old shoots (young bark), using a meta-barcoding approach. The results showed that both fungal and bacterial communities are dominated by genera with ubiquitous attitudes, such as Aureobasidium , Cryptococcus , Deinococcus and Hymenobacter , indicating intense microbial migration to surrounding environments. The shoot age, plant species and plant cultivar influenced the composition of bark fungal and bacterial communities. In particular, bark communities included potential biocontrol agents that could maintain an equilibrium with potential plant pathogens. The abundance of fungal (e.g. Alternaria , Penicillium , Rosellinia , Stemphylium and Taphrina ) and bacterial (e.g. Curtobacterium and Pseudomonas ) plant pathogens was affected by bark age and host genotype, as well as those of fungal genera (e.g. Arthrinium , Aureobasidium , Rhodotorula , Sporobolomyces ) and bacterial genera (e.g. Bacillus, Brevibacillus , Methylobacterium , Sphingomonas and Stenotrophomonas ) with possible biocontrol and plant growth promotion properties. [ABSTRACT FROM AUTHOR]

Plant-associated microbial communities interact with their host and are important components of the biodiversity of natural and agro-ecosystems. Scarce knowledge is available on the establishment of plant microbiota in perennial woody plants. In this work the variability in bacterial and fungal communities in aboveground organs was analysed in leaves, bark, flowers and fruits on three apple cultivars (Gala, Fuji and Golden), in order to understand changes of the microbiota community structure from orchard planting to the first year of fruit production. Our results indicate that Proteobacteria, Bacterioidetes, Actinobacteria and Firmiculites were the dominant bacterial phyla across all samples. The majority of fungal sequences were assigned to Ascomycota and Basidiomycota. The bacterial genera Pseudomonas and Sphingomonas , and the fungal genera Aureobasidium and Filobasidium , represented a major component of the aboveground microbiota. Different parts of the apple plant harboured a specific microbiota and the effect of plant organ on the bacterial and fungal taxonomic structure exceeded the influence of sampling time and plant genotype. This work highlights the specificity of the microbiota associated with aboveground apple organs, changes of the microbiota composition during the plant development from orchard planting to the first year of fruit production, and the negligible effects of apple cultivar. [ABSTRACT FROM AUTHOR]

Soil fungi, as a major decomposer of organic matter, govern carbon (C) cycle and act as crucial regulators of the soil C and nutrient balance in terrestrial ecosystems. Climate change and parent material alter important environmental conditions that may affect fungal community. However, very little is known about the diversity and community structure of soil fungi along elevation gradients with distinct parent material properties. We investigated the effects of climate and vegetation changes on soil fungal diversity and community structure at two Austrian alpine sites with different bedrock properties (limestone at the Hochschwab site and silicate at the Rauris site), but with similar climatic conditions. At these sites we sampled soils from 0 to 25 cm depth along three elevation gradients ranging from 900 to 2100 m above sea level and examined how the fungal communities vary by using Illumina MiSeq sequencing. Our results show that the fungal community structures at the Hochschwab and the Rauris site were defined by elevation-induced changes in vegetation and associated differences in soil pH. In forest soils, symbiotrophic fungi (mainly belonging to the class Agaricomycetes , phylum Basidiomycota) were dominant at the Hoschwab site, while at the Rauris site the Ascomycota were the most dominant phyla. The change to grass dominated vegetation generally increased the contribution of saprotrophic fungi (mainly belonging to various classes of the phylum Mucoromycota) at both elevational sites. Prevalence of ectomycorrhizal fungi and associated lignolytic enzymes induced soil C loss might explain lower soil organic C stocks at the Rauris site compared to the Hochschwab site. Our results suggest that parent material can modulate fungal communities indirectly via vegetation (e.g., litter quality) adapted to particular soil conditions. Therefore, changes in fungal structural composition might exert important consequences on ecosystem C balances. • Fungal richness and diversity indices were higher at Hochschwab than at Rauris site. • Basidiomycota phylum dominated Hochschwab site, while Ascomycota at Rauris. • Forest to grassland shift increased saprotrophic fungal contribution at both sites. [ABSTRACT FROM AUTHOR]