Inocybe is the largest genus in the family Inocybaceae, with approximately 1000 species worldwide. Basic data on the species diversity, geographic distribution, and the infrageneric framework of Inocybe are still incomplete because of the intricate nature of this genus, which includes numerous unrecognized taxa that exist around the world. A multigene phylogeny of the I. umbratica–paludinella group, initially designated as the “I. angustifolia subgroup”, was conducted using the ITS-28S-rpb2 nucleotide datasets. The seven species, I. alabamensis, I. angustifolia, I. argenteolutea, I. olivaceonigra, I. paludinella, I. subangustifolia, and I. umbratica, were confirmed as members of this species group. At the genus level, the I. umbratica–paludinella group is a sister to the lineage of the unifying I. castanea and an undescribed species. Inocybe sect. Umbraticae sect. nov. was proposed to accommodate species in the I. umbratica–paludinella group and the I. castanea lineage. This section now comprises eight documented species and nine new species from China, as described in this paper. Additionally, new geographical distributions of I. angustifolia and I. castanea in China are reported. The nine new species and I. angustifolia, I. castanea, I. olivaceonigra, and I. umbratica are described in detail and illustrated herein with color plates based on Chinese materials. A global key to 17 species in the section Umbraticae is provided. The results of the current study provide a more detailed basis for the accurate identification of species in the I. umbratica-paludinella group and a better understanding of their phylogenetic placement.

Oyster mushroom spherical virus (OMSV) is a positive-sense single-stranded RNA mycovirus which is associated with a devastating oyster mushroom die-back disease. However, little is known about its diversity, and the effects of OMSV infection on its fungal host are not well understood. In this study, we determined the nearly complete nucleotide sequence of OMSV isolated from cultivated oyster mushrooms in China. Sequence analysis suggested that the virus represents a new strain of OMSV (referred to here as OMSV-Ch). A GenBank BLAST search of the genomic sequences demonstrated that the OMSV-Ch had the highest identity (74.9%) with the OMSV from Korea (OMSV-Kr). At the amino acid–sequence level, these two strains shared 84.1% identity in putative replication protein (RP) and 94.1% identity in coat protein (CP). Phylogenetic analysis based on RP showed that OMSV-Ch clustered with OMSV-Kr, closely related to Tymoviridae. Phylogenetic analysis based on both the RP and CP showed that OMSV had a distant clade relationship with tymoviruses, marafiviruses, and maculaviruses. We obtained the OMSV-Ch-free Pleurotus ostreatus strain via single hyphal tip cultures combined with high-temperature treatment. Preliminary studies indicate that OMSV-Ch can significantly inhibit mycelial growth, cause malformations of the fruiting bodies, and reduce the yield of P. ostreatus. Co-cultivation resulted in horizontal transmission of the OMSV-Ch to a virus-cured strain. The findings of our study contribute to the prevention and control of mycoviral diseases in the future.

Mycoviruses are viruses that specifically infect and replicate in fungi. Several mycoviruses have been previously reported in Pleurotus ostreatus, including the oyster mushroom spherical virus (OMSV), oyster mushroom isometric virus (OMIV), Pleurotus ostreatus spherical virus (POSV), and Pleurotus ostreatus virus 1 (PoV1). This study was designed to develop a multiplex RT-PCR for simultaneous detection and differentiation of the four P. ostreatus mycoviruses. Four pairs of primers were designed from conserved regions based on the reported sequences and the multiplex RT-PCR products were 672 bp for OMSV, 540 bp for OMIV, 310 bp for POSV, and 200 bp for PoV1. The optimal annealing temperature of the multiplex RT-PCR was 62 °C and the detection limits of the plasmids were 100 fg for OMSV and OMIV and 1 pg for POSV and PoV1. This technique was successfully applied for the detection of OMSV, OMIV, and POSV from different P. ostreatus strains and the plasmid containing the PoV1 sequence. This methodology can serve as a powerful diagnostic tool for the survey of the incidence and epidemiology of the four P. ostreatus mycoviruses, further contributing to the prevention and treatment of mycoviral diseases in P. ostreatus.

Background: Bolete cultivation is economically and ecologically valuable. Ectomycorrhizae are advantageous for plant development and productivity. This study investigated how boletes affect the formation of Pinus thunbergii and Quercus acutissima ectomycorrhizae using greenhouse-based mycorrhizal experiments, inoculating P. thunbergii and Q. acutissima with four species of boletes (Suillus bovinus, Suillus luteus, Suillus grevillei, and Retiboletus sinensis). Results: Three months after inoculation, morphological and molecular analyses identified S. bovinus, S. luteus, S. grevillei and R. sinensis ectomycorrhizae formation on the roots of both tree species. The mycorrhizal infection rate ranged from 40 to 55%. The host plant species determined the mycorrhiza morphology, which was independent of the bolete species. Differences in plant growth, photosynthesis, and endogenous hormone secretion primarily correlated with the host plant species. Infection with all four bolete species significantly promoted the host plants’ growth and photosynthesis rates; indole-3-acetic acid, zeatin, and gibberellic acid secretion increased, and the abscisic acid level significantly decreased. Indole-3-acetic acid was also detected in the fermentation broths of all bolete species. Conclusions: Inoculation with bolete and subsequent mycorrhizae formation significantly altered the morphology and hormone content in the host seedlings, indicating growth promotion. These findings have practical implications for culturing pine and oak tree species.

The cultivation of Bolete has very high economic value and ecological value. In order to select suitable symbionts for cultivation, we conducted greenhouse-based mycorrhizal experiments on four boletes(Suillus bovinus, Suillus luteus, Suillus grevillei and Retiboletus sinensis) and two plants(Pinus thunbergii and Quercus acutissima). All plant seedlings were either inoculated or not inoculated with the four Bolete liquid strains. Three months after inoculation, Suillus bovinus, Suillus luteus, Suillus grevillei and Retiboletus sinensis ectomycorrhizae were successfully formed on these two tree species, as evidenced by both morphological and molecular analyses. The mycorrhizal infection rate of all plants reached 40–55%, and the morphology of mycorrhiza is determined by the type of host plant and has nothing to do with the species of Bolete. Subsequently, plant growth, photosynthesis and endogenous hormone secretion were evaluated, mainly affected by host species. The infection of four boletes significantly promoted the growth and photosynthesis rate of host plants, the secretion of IAA, ZT and GA increased, and ABA decreased significantly. In addition, we found IAA in the fermentation broth of four kinds of Bolete. And Retiboletus sinensis can differentiate fruiting bodies by artificial pure culture.

Entoloma clypeatum, a kind of edible ectomycorrhizal fungus, can be usually symbiotic with Rosaceae fruit trees. Fruit trees have become an important part of China’s agriculture. The present work focused on exploring how E. clypeatum affected symbiotic Rosaceae plants and establishing a symbiotic culture with Malus robusta, Pyrus betulifolia and Prunus armeniaca rootstocks. The results showed that E. clypeatum and three Rosaceae plants can generate cylindrical or clavate mycorrhizae. The inoculation treatment had different degrees of positive effects on the three plants. Relative to the non-inoculated group, biomass in symbiotic plants increased (32.8%–191.1%), and photosynthesis enhanced. In the level of plant endogenous hormones, the concentration of zeatin, auxin and gibberellin increased (45.45%–228.95%), and the concentration of abscisic acid decreased (35.99%–76.21%). In roots and leaves of plants, the activities of antioxidant enzymes increased (19.0%–249.8%), soluble sugar, soluble protein and free proline concentrations increased (24.9%–373.3%), and the concentration of malondialdehyde decreased (43.6%–79.1%). According to these findings, E. clypeatum stimulated the growth of M. robusta, P. betulifolia and P. armeniaca and improved stress tolerance and adaptability. Our study provides a basis for developing and applying E. clypeatum, facilitates fruit tree industry development and serves as a resource for studying ectomycorrhizal fungi.