Soil origin, mycorrhizal plant partners and environmental factors affect the growth and development of SongRong (Tricholoma matsutake). In order to clarify the relationships of fungi–bacteria networks and various influence factors in the habitat of SongRong, we chose three collection sites with a Quercus mongolica pure forest (plot A without SongRong was used as the control sample site), Q. mongolica mixed Rhododendron dauricum (plot B) and Q. mongolica mixed with R. dauricum and Pinus densiflora (plot C). By using high-throughput sequencing, we obtained a total of 4930 fungal and 55501 bacterial amplicon sequence variants (ASVs) based on internally transcribed spacer ribosomal RNA (ITS rRNA) and 16S ribosomal RNA (16S rRNA) sequencing via the Illumina NovaSeq platform. In the habitat soil of SongRong (plot B and plot C), alpha or beta diversity and species compositions of fungi and bacteria were different from plot A. The fungal–bacterial networks follow the selection rule that few dominant genera account for the greater relative abundance. Forest types, but not the host itself, drove the fungal–bacterial networks of the forest soil, and soil physicochemical characteristics and texture affected their abundance. The abundance of Tricholoma was affected by the fungal and bacterial abundance in the habitat.

Three new phlegmaciod species of Thaxterogaster, T. borealicremeolinus, T. rufopurpureus, and T. sinopurpurascens spp. nov., from subtropical China were described based on their morphological characteristics and molecular data. Thaxterogaster borealicremeolinus belongs to the sect. Cremeolinae and differs from the other species in this section in its larger basidiospores and its habitat in the Northern Hemisphere associated with Quercus sp. trees. Thaxterogaster rufopurpureus and T. sinopurpurascens belong to sect. Purpurascentes, in which T. rufopurpureus is characterized by a pileus with a reddish-brown coloration when mature and a clavate stipe, while T. sinopurpurascens is characterized by a violet basidiomata, except for a greyish orange to brown pileus, the distinctly marginate bulb of its stipe, and its distribution in subtropical China. The phylogenetic analyses were performed based on nrITS, and detailed descriptions of the new species are provided herein.