Four new species of Russula subsect. Cyanoxanthinae, viz. Russula atrochermesina Y.L. Chen & J.F. Liang, R. lavandula Y.L. Chen, B. Chen & J.F. Liang, R. lilaceofusca Y.L. Chen & J.F. Liang and R. perviridis Y.L. Chen, B. Chen & J.F. Liang, from China are proposed, based on morphological and molecular evidence. Russula atrochermesina can be distinguished by its violet pileus with tuberculate-striate margin, distant lamellae that stain greyish-yellow when bruised, basidiospores ornamented by isolated warts, wide hymenial cystidia on lamellae edges, cystidia content negative reaction in sulphovanillin and branched subterminal cells in pileipellis. Russula lavandula has a purplish-white to violet red pileus with a yellow centre, frequently present lamellulae and furcations, stipe often with pale yellow near the base, isolated basidiospores ornamentation and unbranched cuticular hyphal terminations, while R. lilaceofusca is characterised by its lilac brown to dark brown pileus, crowded lamellae with lamellulae and furcations, stipe often turning reddish-yellow when bruised, subreticulate basidiospores ornamentation and clavate hymenial cystidia often with capitate appendage whose contents that change to reddish-black in sulphovanillin. Russula perviridis is characterised by its large basidiomata, smooth pileus surface, frequently present lamellulae and furcations, stipe with yellow-brown tinge, globose to broadly ellipsoid basidiospores with subreticulate ornamentation, long hymenial cystidia that turn greyish-black in sulphovanillin and symbiotic with Quercus semecarpifolia. Phylogenetic analyses, based on multi-gene ITS+LSU+mtSSU+rpb2, indicate that R. atrochermesina, R. lavandula, R. lilaceofusca and R. perviridis are closely related to R. pallidirosea and R. purpureorosea, R. banwatchanensis, R. lakhanpalii and R. nigrovirens, respectively.

Suillus luteus is an edible ectomycorrhizal fungus (EMF). The S. luteus strain LS88 secretes many phytohormones, including salicylic acid (SA) and indole-3-carboxylic acid (ICA). LS88 was inoculated to the tree Pinus massoniana and treated with the amino acid fertilizer GGR6. Plant growth parameters, plant enzyme activities, chlorophyll contents, and element contents were analyzed. Our results show that GGR6 may help the development of S. luteus-P. massoniana ectomycorrhiza. Moreover, LS88 and GGR6 synergistically affect P. massoniana growth and element uptake. Phytohormone detection on the roots of LS88-inoculated P. massoniana seedlings showed that LS88 could significantly increase the ICA content within a week. The SA content in the roots in the inoculated group seedlings increased slightly, but the salicylic acid 2-O-β-glucoside (SAG) content decreased. Therefore, we speculate GGR6 may enhance the growth-promoting effect of EMF on plants, and LS88 affects P. massoniana growth through secreting phytohormones.

Two new species of Russula are described and illustrated in this paper. Russula clavulus is recognised by a pale yellow pileus centre, white margin with tuberculate striation, white to pale lamellae with small pale yellow spots, white to light yellow spore print, subglobose to broadly ellipsoid spores with short or long ridges and hymenial cystidia on lamellae sides that are mainly subclavate or fusiform. Russula multilamellula is morphologically characterised by the brownish orange to hazel pileus centre and satin white to yellowish-white margin with brownish tinge, lamellulae that are usually irregular in length and often anastomosing with lamellae, subglobose to broadly ellipsoid spores with short or long ridges and clavate hymenial cystidia. The combination of morphological features and multigene phylogenetic analyses of ITS-nrLSU-RPB2-mtSSU data indicated that these two new taxa belong to Russula subg. Heterophyllidia sect. Ingratae.

Suillus bovinus is a wild edible ectomycorrhizal fungus with important economic and ecological value, which often forms an ectomycorrhiza with pine trees. We know little about the mechanisms associated with the metabolism and symbiosis of S. bovinus and its effects on the nutritional value. In this study, the whole-genome sequencing of S. bovinus was performed using Illumina, HiFi, and Hi-C technologies, and the sequencing data were subjected to genome assembly, gene prediction, and functional annotation to obtain a high-quality chromosome-level genome of S. bovinus. The final assembly of the S. bovinus genome includes 12 chromosomes, with a total length of 43.03 Mb, a GC content of 46.58%, and a contig N50 size of 3.78 Mb. A total of 11,199 coding protein sequences were predicted from genome annotation. The S. bovinus genome contains a large number of small secreted proteins (SSPs) and genes that encode enzymes related to carbohydrates, as well as genes related to terpenoids, auxin, and lipochitooligosaccharides. These genes may contribute to symbiotic processes. The whole-genome sequencing and genetic information provide a theoretical basis for a deeper understanding of the mechanism of the mycorrhizal symbiosis of S. bovinus and can serve as a reference for comparative genomics of ectomycorrhizal fungi.

Ectomycorrhizal fungi employ different strategies for mycelial growth and host colonization under varying nutrient conditions. However, key genes associated with mycorrhizal interaction should be influenced solely by the inoculation treatment and not by nutrient variations. To utilize subtle nutrient differences and rapidly screen for key genes related to the interaction between Suillus luteus and Pinus massoniana, we performed an inoculation experiment using culture bottles containing high- and low-nutrient media. Interestingly, S. luteus LS88 promoted the growth of P. massoniana seedlings without mature ectomycorrhiza, and the impact of LS88 inoculation on P. massoniana roots was greater than that of nutrient changes. In this study, the resequenced genome of the LS88 strain was utilized for transcriptome analysis of the strain. The analysis indicated that a unique gene encoding glutathione S-transferase (GST) in LS88 is likely involved in colonizing P. massoniana roots. In this study, the GST gene expression was independent of nutrient levels. It was probably induced by P. massoniana and could be used as a marker for S. luteus colonization degree.