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Truffles are ectomycorrhizal species forming edible ascocarps. The Italian white truffle (Tuber magnatum Pico) is the most famous and expensive species harvested to date; it comes exclusively from natural habitats in European countries. The annual production of T. magnatum is generally insufficient to respond to the high demands making its cultivation a research hotspot. The first attempt to cultivate T. magnatum started in the 1970s without success; only recently have mycorrhized plants been successfully produced. The aims of this study were (1) to assess the persistence of T. magnatum in the soil of plantations realized with mycorrhized plants and (2) to characterize the first T. magnatum orchard that produced ascocarps outside the known natural geographic range of this species. In 2018, five orchards were sampled in France, and T. magnatum was investigated in the soil. We confirmed that T. magnatum survived in the soil 3 to 8 years after planting. The key finding of this study was the harvest of T. magnatum ascocarps in 2019 and 2020 from one orchard. The production of ascocarps started 4.5 years after planting, and the ascocarps were harvested under different trees and during two consecutive seasons. A detailed analysis of the productive orchards (i.e., soil features, soil water availability, cultivation techniques) is presented. These results demonstrate the feasibility of T. magnatum cultivation worldwide by planting mycorrhized plants. The cultivation of T. magnatum could therefore become a real opportunity for farmers and could respond to the high demand of this high-priced food.

Harvest residue management is a key issue for the sustainability of Eucalyptus plantations established on poor soils. Soil microbial communities contribute to soil fertility by the decomposition of the organic matter (OM), but little is known about the effect of whole-tree harvesting (WTH) in comparison to stem only harvesting (SOH) on soil microbial functional diversity in Eucalyptus plantations. We studied the effects of harvest residue management (branches, leaves, bark) of Eucalyptus grandis trees on soil enzymatic activities and community-level physiological profiles in a Brazilian plantation. We measured soil microbial enzymatic activities involved in OM decomposition and we compared the community level physiological profiles (CLPP) of the soil microbes in WTH and SOH plots. WTH decreased enzyme activities and catabolic potential of the soil microbial community. Furthermore, these negative effects on soil functional diversity were mainly observed below the 0-5 cm layer (5-10 and 10-20 cm), suggesting that WTH can be harmful to the soil health in these plantations.

Chitin is one of the most abundant nitrogen-containing polymers in forest soil. Ability of ectomycorrhizal (EM) fungi to utilize chitin may play a key role in the EM symbiosis nutrition and soil carbon cycle. In forest, EM fungi exhibit high diversity, which could be based on function partitioning and trait complementarity. Although it has long been recognized that closely related species share functional characteristics, the phylogenetic conservatism of functional traits within microorganisms remains unclear. Because extracellular N-acetylglucosaminidase activity has been proposed as functional trait of chitin degradation, we screened this activity on 35 EM fungi species with or without chitin in the growth medium to (i) describe the functional diversity of EM fungi and (ii) identify potential links between this functional trait and EM fungal phylogeny. We observed large variations of the extracellular N-acetylglucosaminidase activities among the fungal strains. Furthermore, our results revealed two regulation patterns of extracellular N-acetylglucosaminidase activities. Indeed, these chitinolytic activities were stimulated or repressed in the presence of chitin, in comparison to the control treatment. These profiles of extracellular N-acetylglucosaminidase stimulation/repression might be conserved at a high phylogenetic level in the Basidiomycota phylum, as illustrated by the opposite patterns of regulation between Boletales and Agaricales. Finally, the downregulation of this activity by chitin, for some EM fungal groups, might suggest another chitin degradation pathway.

The patterns of the distribution of fungal species and their potential interactions with trees remain understudied in Neotropical rainforests, which harbor more than 16,000 tree species, mostly dominated by endomycorrhizal trees. Our hypothesis was that tree species shape the non-mycorrhizal fungal assemblages in soil and litter and that the diversity of fungal communities in these two compartments is partly dependent on the coverage of trees in the Neotropical rainforest. In French Guiana, a long-term plantation and a natural forest were selected to test this hypothesis. Fungal ITS1 regions were sequenced from soil and litter samples from within the vicinity of tree species. A broad range of fungal taxa was found, with 42 orders and 14 classes. Significant spatial heterogeneity in the fungal communities was found without strong variation in the species richness and evenness among the tree plots. However, tree species shaped the fungal assemblages in the soil and litter, explaining up to 18 % of the variation among the communities in the natural forest. These results demonstrate that vegetation cover has an important effect on the structure of fungal assemblages inhabiting the soil and litter in Amazonian forests, illustrating the relative impact of deterministic processes on fungal community structures in these highly diverse ecosystems.