Cortinarius (Pers.) Gray is an important ectomycorrhizal genus with agaricoid to sequestrate basidiomata, rust brown basidiospore deposit and verrucose basidiospores (Peintner et al. 2001; Frøslev et al. 2006; Bhunjun et al. 2022). Many Cortinarius species have been used as indicator species for valuable natural environments in Europe due to their narrow ecological preferences and sensitivity to environmental change (Vesterholt 1991; Hallingbäck & Aronsson 1998). Many Cortinarius species are edible mushrooms, for example C. armillatus (Fr.) Fr., C. emodensis Berk. and C. sinensis L.H. Sun, T.Z. Wei & Y.J. Yao (Dai et al. 2010; Li et al. 2015; Xie 2018). Some species, for example C. collinitus (Pers.: Fr.) Fr. and C. violaceus (L.) Gray, with potential value of anti-tumor and antioxidant (Dai & Yang 2008; Dai et al. 2009; Li & Bao 2020). In addition, several species are notoriously poisonous, e.g. C. orellanus Fr. and C. speciosissimus Kühner & Romagn (Bau et al. 2014; Wu et al. 2019).

The latest phylogenomic study by Liimatainen et al. (2022) showed that the genus Cortinarius s.l. could be divided into ten genera. The recent research based on the ITS region in GenBank showed the species of Cortinarius s.s. maybe over 5 000 in the world, including more than one thousand undescribed species (Bhunjun et al. 2022). In China, 309 Cortinarius s.l. taxa have been reported, including nineteen taxa that originally described from China (Zang 1987; Yang 1992; Wei & Yao 2013; Xie 2018; Xie et al. 2019, 2020, 2021a, 2021b, 2022; Yuan et al. 2020; Luo & Bau 2021; Wang et al. 2022).

In this study, samples of one telamonioid species, C. liyui, were collected and described as a new species from Jilin Province, China. The morphological characters and phylogenetic analysis supported the recognition of this species within Cortinarius and confirmed this species belongs to a novel section Liyuorum.

Specimens were collected in Yanji, Jilin Province. Fresh fruit bodies were photographed in the field, and dried in an oven at 50 °C. Specimens have been deposited in the Herbarium of Mycology, Jilin Agricultural University (HMJAU), Changchun, China. The macroscopic characteristics were recorded from the fresh basidiomata. Microscopic characteristics were examined and described in 5% KOH, Congo Red or Melzer’s reagent under a Zeiss AX10 light microscope. The length/width ratios (Q) were calculated for individual basidiospores. X_av. and Q_av. refer to the average value of basidiospores of per specimen. The ornamentation of basidiospores was studied using a Hitachi, model SU8010, field emission scanning electron microscope (FESEM) in Jilin Agricultural University.

The DNA was extracted from dried specimens, using a NuClean PlantGen DNA Kit (CWBIO). Primers ITS1F and ITS4 were used to amplify internal transcribed spacer (ITS) region (White et al. 1990; Gardes & Bruns 1993). The nuclear large subunit rDNA (28S) region was amplified with primers LR0R and LR7 (Vilgalys & Hester 1990). The PCR amplification progress followed Xie et al. (2022) and amplicons were sequenced by Sangon Biotech (Shanghai) Co. Ltd.

The taxon sampling strategy for the selection of sequences for phylogenetic trees was to choose related taxa based on a BLASTn search in GenBank within Cortinarius (Table 1). Two partition datasets (ITS, 28S) were separately aligned and manually adjusted with BioEdit 7.1.3.0 (Hall 1999). Phyutility 2.2 was used to concatenate the aligned datasets (Smith & Dunn 2008). Section Orellani M.M. Moser was selected as an outgroup for phylogenetic analysis due to sect. Orellani separated from other lineages (Soop et al. 2019).

For phylogenetic analysis, Bayesian inference (BI) and maximum likelihood (ML) methods were used. For BI analysis, the best-fit models for ITS and 28S partitions were estimated using the Akaike information criterion (AIC), implemented in MrModeltest 2.3 (Nylander 2004). The BI analysis was performed with MrBayes 3.2.6 (Ronquist & Huelsenbeck 2003). Four Markov chains were run for 2 runs from random starting trees for 500 000 generations, sampling every 100th generation. The first 25% of trees were discarded to build the 50% majority rule consensus tree. RAxML 8.2.12, implemented in raxmlGUI, was used for ML analysis, with a rapid bootstrapping algorithm of 1 000 replicates (Silvestro & Michalak 2012; Stamatakis 2014). All default parameters with the GTRGAMMA model were used in the ML analysis.

The phylogenetic analysis includes 39 specimens, of which 13 are type specimens. In total, 21 sequences were newly generated. The best-fit models for BI analysis of both ITS and 28S were GTR+I+G. The ML tree is selected to represent the phylogeny (Fig. 1). The ML bootstrap values (ML) ≥60% and Bayesian posterior probabilities (BPP)≥0.90 are shown on the branches (ML/BPP).

The phylogenetic analysis recovered 12 sections of Cortinarius, including the outgroup. Every section formed a separately monophyletic lineage with strong statistical support. The specimens of Cortinarius liyui clustered in sect. Liyuorum (100%/1). Section Liyuorum was separated into single lineage and formed a sister relationship (65%/0.96) with sect. Spilomei (Moënne-Locc. & Reumaux) Consiglio, D. Antonini & M. Antonini (93%/1).

Cortinarius sect. Liyuorum M.L. Xie, R.Q. Ji & T.Z. Wei sect. nov.

Fungal Name: FN571217

Diagnosis. Basidiomata small. Pileus brown with violet tinge, hygrophanous. Lamellae grayish violet to rusty brown. Stipe slender, cylindrical or slightly clavate, with violet tinge, then brown. Universal veil white and spares. Basidiospores rather small, subglobose to broadly ellipsoid, rarely ellipsoid. Pileipellis with an epicutis and a developed hypodermium.

Type species. Cortinarius liyui M.L. Xie, R.Q. Ji & T.Z. Wei

Etymology. Named after the type species of the section.

Cortinarius liyui M.L. Xie, R.Q. Ji & T.Z. Wei sp. nov.Fig. 2

Fungal Name: FN571211

Diagnosis. Similar to Cortinarius subg. Telamonia species, but differs in its small and slender basidiomata, violet-tinged pileus and stipe when young, together with the small and subglobose to broadly ellipsoid basidiospores.

Holotype. Sandaowan, Yanji, Jilin Province, CHINA, on ground in Quercus mongolica forests, alt. 620 m, 23 Sept. 2020, M.L. Xie, 20XML13068 (HMJAU58939).

Etymology. liyui, in honor of Chinese mycologist Prof. Yu Li, and celebrating his 80th birthday.

Pileus 18-40 mm in diam., plano-convex, somewhat depressed at the center, strongly hygrophanous; violet brown at first, then reddish brown to grayish brown, paler at the margin, translucently striate, especially at the margin, somewhat wrinkled when mature. Lamellae up to 5 mm wide, emarginated, medium-spaced, grayish violet when young, then yellowish brown to rusty brown, edge even. Stipe 30-63×3-4 mm, cylindrical or somewhat thickened at the base, surface fibrillose, lightly purple at first, later grayish brown to dark brown, basal mycelium white, hollow when mature. Context violet tinge at first, then reddish brown. Odor radish. Universal veil white, sparse. Basidiospore deposit rust brown.

Basidiospores (150/5/5) 6.4-7.7(8.5)×5.5-6.9 (7.5) μm, Q=1.04-1.25(1.33), X_av.=6.9-7.3×6.0- 6.2 μm, Q_av.=1.16-1.2, subglobose to broadly ellipsoid, moderately verrucose, moderately to strongly dextrinoid. Basidia clavate, 4-spored, colorless or lightly olivaceous brown to olivaceous brown. Lamellar trama hyphae smooth, up to 25 μm wide, lightly olivaceous brown. Lamellar edge fertile, with small clavate sterile cells. Pileipellis duplex: epicuits hyphae 2.5-8 μm wide, lightly olivaceous brown to olivaceous brown, smooth; hypodermium developed, hyphae lightly olivaceous brown, 7-23 μm wide, smooth. Clamp connections present.

Ecology and distribution. Solitary or gregarious on ground in Quercus mongolica forests. Known from Jilin Province, also from Zhejiang Province based on the ectomycorrhizal sequence (JQ991711).

Additional specimens examined. Sandaowan, Yanji, Jilin Province, on ground in Quercus mongolica forests, alt. 620 m, 23 Sept. 2020, M.L. Xie, 20XML13047 (HMJAU58935), 20XML13055 (HMJAU58936), 20XML13056 (HMJAU58937), 20XML13062 (HMJAU58938).

Cortinarius sect. Liyuorum forms a monophyletic clade in the phylogenetic tree, and is a sister to sect. Spilomei, but without robust support. The pileus of sect. Spilomei species is usually weakly hygrophanous and non-striate, and its universal veil is yellowish to reddish and usually forming characteristic rusty red squamules on the stipe (Dima et al. 2016). Our new section might belong to the subgenus Camphorati Liimat., Niskanen & Ammirati (Liimatainen et al. 2022), but the morphological features of the new species differ from those of the subgenus. At present, we are not sure which subgenus the new section belongs to. Further research is needed in the future.

Cortinarius liyui is characterized by its small and slender basidiomata with violet tinge when juvenile, additionally by its strongly hygrophanous pileus, medium-spaced lamellae, white and sparse universal veil, and small and subglobose to broadly ellipsoid basidiospores. This is a typical telamonioid species for its strongly hygrophanous basidiomata and can be easily distinguished from other telamonioid species by the violet tinge basidiomata and subglobose basidiospores. The ITS sequences of Jilin specimens are identical. In phylogenesis, a sequence (JQ991711) from the ectomycorrhizal sample from Zhejiang Province, subtropical China, clustered with the Jilin specimens, but had one bp substitution, here we treated it as C. liyui and considered this species had a distribution in subtropical China as well.

The authors are grateful to Mr. CAO Zhenyuan for his kind help in the fieldwork.