The production of Tuber magnatum has drastically decreased due to rising temperatures and ecosystem degradation, prompting growing interest in biological and sustainable approaches to support its conservation in natural habitats. We hypothesized that inoculation with nitrogen-fixing bacteria could influence T. magnatum mycelial development and the composition of the associated soil microbiota. This study tested this hypothesis by evaluating Bradyrhizobium japonicum as a bio-inoculant in a productive white truffle ground in Sant’Angelo in Vado (Marche, Italy). Soil samples were collected from four areas treated with the bacterial inoculum and four untreated ones. Sampling was carried out before inoculation and one year later. T. magnatum biomass was quantified using species-specific quantitative PCR. An increase in mycelium biomass was observed in three of the four treated plots. In parallel, the soil bacterial communities were characterized using 16S rDNA-based Next-Generation-Sequencing (NGS). Multivariate analysis of the metabarcoding data showed a significant effect of sampling time on the soil bacterial community, with no significant Area × Time interaction, while Acidobacteriota remained consistently dominant across all conditions. These findings suggest that Bradyrhizobium inoculation did not produce a significant effect on T. magnatum mycelial abundance across plots, nor a detectable treatment-specific shift in the composition of the surrounding soil bacterial community. Further investigation is needed on its potential role in truffle-associated microbial dynamics.
Forest soil profiles exhibit sharp vertical contrasts, but how arbuscular mycorrhizal fungal (AMF) diversity and composition vary across organic and mineral layers remains incompletely understood. We sampled eight independent plots spanning two forest types within a subtropical mountain reserve. AMF communities were profiled in morphologically defined fermentation (F) and humus (H) layers and mineral topsoil (B; 0–10 cm below the local organic–mineral boundary). Soil chemistry, labile carbon and nitrogen pools, and potential extracellular enzyme activities were also measured. Alpha diversity did not differ detectably among layers, whereas community composition shifted primarily through lineage replacement and abundance re-ranking. Leave-one-plot-out cross-validation recovered strict F–H–B ordering in seven of eight plots at the 151-lineage resolution. Associations between continuous projection scores and ordinal layer position persisted across sequence resolutions. At the 151-lineage resolution, H occupied an intermediate, noncollinear position on average, although its categorical assignment was unstable. Soil biochemical properties also varied among layers. The chemical and enzyme principal component axes showed no detectable additional association with AMF composition after adjustment for layer and plot. These findings characterize a recurring pattern of vertical turnover without a detectable decline in diversity among layers within the sampled plots. The underlying mechanisms and the geographic and temporal generality of this pattern remain untested.
The French black truffle is the prized fruiting body of the ectomycorrhizal fungus Tuber melanosporum Vittad. Optimizing the growth of T. melanosporum while mitigating ectomycorrhizal fungal competitors are important goals for producers, particularly in novel growing regions. We investigated the influence irrigation on (1) the abundance of T. melanosporum extramatrical mycelium and (2) the communities of ectomycorrhizal fungi in soil and roots in an 8 year old T. melanosporum-Quercus robur L. orchard located in Vancouver, British Columbia, Canada that had yet to produce truffles. Irrigation treatments were characterized by high (− 30 kPa mean soil water potential), moderate (− 80 kPa), or low (non-irrigated) soil moisture. Soil samples were collected monthly from July to September 2021, at 50 cm and 100 cm from the base of trees. Droplet digital PCR was used to estimate the abundance and distribution of T. melanosporum extramatrical mycelia in the soil. The ectomycorrhizal fungal community in soil and on mycorrhizal root tips were examined using PacBio Sequel II. Moderate irrigation had 17
Arbuscular mycorrhizal fungi (AMF) play a crucial role in crop productivity and agroecosystem processes. However, the composition of soil AMF communities and the factors associated with their diversity and distribution in Ohio remain poorly understood. We profiled both soil AMF and physico-chemical characteristics in 18 soybean fields across agricultural regions in Ohio. AMF sequences were recovered through amplicon sequencing of the 18S ribosomal gene coupled with PacBio technology. We detected 14 genera belonging to six families of the Glomeromycota. The family Glomeraceae accounted for 39
Many photosynthetic orchids combine photosynthesis with fungal carbon acquisition, yet the isotopic relationships between orchids and their fungal partners remain poorly resolved. Direct stable isotope analysis of pelotons and extraradical fungal tissues can refine fungal baselines and clarify nutritional dynamics in orchid mycorrhizas. We investigated Cremastra appendiculata, a photosynthetic orchid with contrasting mycorrhizal states, by comparing fungal communities between individuals with and without coralloid rhizomes and analyzing the δ13C and δ15N values of leaves, protocorms, coralloid rhizomes, pelotons, Psathyrellaceae rhizomorphs, dead wood, and autotrophic reference plants. Psathyrellaceae-associated individuals were strongly enriched in 13C relative to autotrophic reference plants, indicating substantial acquisition of fungal carbon, whereas rhizoctonia-associated individuals exhibited little 13C enrichment and appeared predominantly autotrophic. Leaf δ15N values exceeded those of the associated fungal tissues in both states, suggesting plant-mediated 15N enrichment during nitrogen assimilation and allocation to leaves. Coralloid rhizome pelotons did not differ detectably in δ13C or δ15N between digestion stages. Pelotons resembled extraradical Psathyrellaceae rhizomorphs in δ15N but had higher δ13C values, indicating tissue-specific carbon isotope baselines. Psathyrellaceae tissues were less 13C enriched than fungal tissues reported from fully mycoheterotrophic orchids associated with wood-decaying fungi. These results support contrasting nutritional states in C. appendiculata: a predominantly autotrophic, rhizoctonia-associated state and a more fungus-dependent, Psathyrellaceae-associated state. The fungal isotope pattern raises the possibility that bidirectional carbon transfer persists even in the latter state. Determining whether the orchid transfers carbon to its fungal partners requires controlled culture or tracer experiments.
