Fungal Interactions Matter: Tricholoma matsutake Domination Affect Fungal Diversity and Function in Mountain Forest Soils

SIMPLE SUMMARY: Tricholoma matsutake forms a symbiotic association with hosts, developing mycelial aggregations, called ‘shiro’. The fungal diversity living in shiro soil play key roles in nutrient cycles for this economically important mushroom, but have not been profiled across large spatial and environmental gradients. Here, we mainly aimed to study the fungal characteristics in the bulk soil (non-shiro) and shiro, using phospholipid fatty acids and illuninan sequencing in five habitats across landscapes in southwestern China. T. matsutake causes a lower fungal diversity and simplifies the fungal community composition in shiro soil compared with non-shiro soil across five forest types. We also found that geo-graphical proximity was accompanied by a similar fungal community structure but different contributions from specific species under five forest types. Among the co-existed fungi, Oidiodendron were found to collaborate with T. matsutake, whereas Helotiales and Mortierella showed a negative correlation with it. The selection of these taxa may be related to their ability to compete with resources and different nutrient strategists in the soil. Overall, we conclude that T. matsutake generate a dominance effect to shape the fungal community and diversity in shiro soil across distinctive forest types. ABSTRACT: Tricholoma matsutake forms a symbiotic association with coniferous trees, developing mycelial aggregations, called ‘shiro’, which are characterized by distinct chemical and physical properties from nearby forest bulk soil. The fungal diversity living in shiro soil play key roles in nutrient cycles for this economically important mushroom, but have not been profiled across large spatial and environmental gradients. Samples of shiro and non-shiro (nearby bulk soil) were taken from five field sites where sporocarps naturally formed. Phospholipid fatty acids (PLFA) and Illumina MiSeq sequencing were combined to identify fungal biomass and community structure. Matsutake dominated in the shiro, which had a significantly reduced saprotrophic fungi biomass compared to non-shiro soil. Fungal diversity was negatively correlated with the relative abundance of T. matsutake in the shiro soil. The fungal community in the shiro was characterized by similar fungal species composition in most samples regardless of forest types. Matsutake coexisted with a specific fungal community due to competition or nutrient interactions. Oidiodendron was positively correlated with the abundance of T. matsutake, commonly cohabitant in the shiro. In contrast, Helotiales and Mortierella were negatively correlated with T. matsutake, both of which commonly inhabit the non-shiro soil but do not occur in shiro soils. We conclude that T. matsutake generate a dominance effect to shape the fungal community and diversity in shiro soil across distinctive forest types.