Cortinarius subsalor and C. tibeticisalor spp. nov., two new species from the section Delibuti from China

Cortinarius subsalor and C. tibeticisalor, belonging to the section Delibuti, are described from China as new to science. Cortinarius subsalor has been found to be associated with Lithocarpus trees in subtropical China and resembling C. salor, but it differs from the later by having slender basidiomata and the narrower basidiospores. Cortinarius tibeticisalor was collected from eastern Tibetan Plateau, associated with Abies. It differs from other species within sect. Delibuti by having olive tinge of mature or dried basidiomata and bigger basidiospores. The molecular data also support C. subsalor and C. tibeticisalor as new species. The phylogenetic analyses and biogeography of sect. Delibuti are discussed and a key to the species of this section currently known in the world is provided.


INTRODUCTION
Cortinarius (Pers.) Gray is an ectomycorrhizal fungal genus, associated with a wide host range of plants, such as Betulaceae, Caesalpiniaceae, Cistaceae, Dipterocarpaceae, Fagaceae, Myrtaceae, Pinaceae, Rhamnaceae, Rosaceae, Salicaceae and some herbaceous plants (Frøslev, Brandrud & Jeppesen, 2006;Niskanen, 2008). The genus is distributed worldwide with nearly 3,000 species (Niskanen et al., 2018;Ammirati et al., 2021;Bidaud et al., 2021). Even though it is the largest genus among macrofungi, its species diversity is still unclear. Most of Cortinarius species were originally discovered from Europe and America but rarely in Asia and Africa (Horak, 1983;Garrido-Benavent et al., 2020;Xie et al., 2020). Several systems of subgenus and sections in Cortinarius are erected based on the macromorphology of geographically limited samplings, but these are not supported by phylogenetic studies (e.g. Fries, 1838;Trog, 1844;Orton, 1955; in Tibet are the plateau-alpine areas with coniferous forests dominated by Abies georgei var. smithii. Fresh basidiomata were photographed in the field. Dried specimens were deposited in the Herbarium of Mycology, Jilin Agricultural University (HMJAU), Changchun, China. Macroscopic characteristics were measured and recorded for every basidiomata and color codes followed Kornerup & Wanscher (1978). Microscopic features were examined and described in 5% KOH, Congo Red or Melzer's reagent and observed using a Zeiss AX10 light microscope. Thirty to forty mature basidiospores were measured (excluding apiculus and ornamentation) per collection. Q = variation in the L/W ratios between the specimens studied. X av. and Q av. = average value of basidiospores of per specimen.

Phylogenetic reconstruction
DNA extraction, PCR amplifications, and sequencing methods followed Xie et al. (2019) and Guan & Zhao (2020). The primers ITS1F and ITS4 were used amplification of nrDNA ITS region (White et al., 1990;Gardes & Bruns, 1993). The newly generated ITS sequences were submitted to GenBank. The ITS sequences for the phylogenetic analyses were selected based on results of BLASTn (>90% identity) in GenBank and UNITE and followed the publication by Garnica et al. (2016) and Soop et al. (2019). Two species in section Cyanites Nespiak were chosen as outgroup followed Xie et al. (2021).
Sequences (Table 1) for the phylogenetic analyses were aligned and edited with BioEdit 7.1.3.0 and Clustal X (Thompson et al., 1997;Hall, 1999). For phylogenetic analyses, Bayesian Inference (BI), Maximum Likelihood (ML) and Maximum Parsimony (MP) methods were implemented in this study. MrModeltest 2.3 was used to calculate the best model (HKY+I+G) for BI analysis (Nylander et al., 2008). The BI analysis was performed with MrBayes 3.2.6 (Ronquist & Huelsenbeck, 2003). Four Markov chains were run for 500,000 generations until the split deviation frequency value < 0.01, and sampled every 100th generation. The posterior probability values were estimated from the samples after discarding the first 25% (1,250) generations. A 50% majority rule consensus tree of all remaining trees were calculated. RAxML v. 1.5, implemented in raxmlGUI, were used to construct a ML tree, with a rapid bootstrapping algorithm involving 1,000 replicates (Silvestro & Michalak, 2012;Stamatakis, 2014). All parameters in the ML analysis were kept as defaults except for GTRGAMMA were chose as the model. The MP analysis was conducted in MEGA X (Kumar et al., 2018). The most parsimonious tree with length = 1,012 is shown. The consistency index is (0.442350), the retention index is (0.708912), and the composite index is 0.355860 (0.313587) for all sites and parsimony-informative sites (in parentheses). The bootstrap test was performed 1,000 replicates (Felsenstein, 1985). The MP tree was obtained using the Tree-Bisection-Regrafting (TBR) algorithm (Nei & Kumar, 2000) with search level 3 in which the initial trees were obtained by the random addition of sequences (10 replicates). The phylogenetic trees were visualized in

Nomenclature
The electronic version of this article in Portable Document Format (PDF) will represent a published work according to the International Code of Nomenclature for algae, fungi, and plants, and hence the new names contained in the electronic version are effectively published under that Code from the electronic edition alone. In addition, new names contained in this work have been submitted to MycoBank from where they will be made available to the Global Names Index. The unique MycoBank number can be resolved and the associated information viewed through any standard web browser by appending the MycoBank number contained in this publication to the prefix "http://www.mycobank. org/MycoTaxo.aspx?Link=T&Rec=". The online version of this work is archived and available from the following digital repositories: PeerJ, PubMed Central, and CLOCKSS.
Diagnosis. Pileus hemispherical to applanate, violet, glutinous, margin wavy, somewhat olive when mature; lamellae for a long time violet, then pale grayish violet to violet gray; stipe robust, bluish gray to brown with olive tinge; veil glutinous, violet. Basidiospores on average 10.3-10.8 × 8.7-8.9 µm, subglobose to broadly ellipsoid, rarely ellipsoid. Differing from other species in sect. Delituti by the olive tinge of basidiomata and the large basidiospores.

DISCUSSION
Cortinarius subsalor is similar to C. betulinus, C. salor and C. transiens (Melot) Soop due to the bluish tinge of the basiodiomata. However, C. betulinus is usually grayish blue at the margin of the pileus and soon fading, the stipe is often pale and the veil usually is yellow (Kibby, 2005;Niskanen et al., 2008;Soop, 2014). The pileus of C. transiens has a violet tone towards the margin, while the centre is more olive gray to yellowish brown even in young specimens, the stipe is pale, and the gelatinous veil is olive brown (Soop, 1990(Soop, , 2014. In China, sometimes some bluish myxacioid species have been misidentified as C. salor (MHHNU30409, GenBank: MK250915), collected from Hunan Province. Our phylogenetic analyses showed that this sequence belong to the new species C. subsalor. Cortinarius salor has persistently lilaceous lamellae, the stipe is more robust (>10 mm thick) and the base is more grayish brown, the basidiospores are rounder (7-9 × 6-8 µm), and it occurs in European woodlands (Orton, 1955;Consiglio, Antonini & Antonini, 2003;Soop, 2014). Based on these features, C. salor can be distinguished from the Asian C. subsalor. Cortinarius tibeticisalor is characterized by the basidiomata usually violet when young, then grayish orange to brown with an olive tinge, larger basidiospores and a restricted distribution in the Tibetan Plateau. Cortinarius tibeticisalor is similar to C. salor in young stage, however, the basidiospores (7-9 × 6-8 µm) of C. salor are significantly smaller and rounder, and the basidiomata never have olive tinge (Orton, 1955;Consiglio, Antonini & Antonini, 2003;Soop, 2014).
According to our phylogenetic analyses, sect. Delibuti demonstrates a widely distributed lineage of Cortinarius, in both the Northern and Southern Hemispheres. This bihemispherical distribution is also seen in several other lineages in Cortinarius, such as Anomali, Bolares, Camphorati, Defibulati, Illumini, and Vibratiles, this is concordant with other studies (e.g. Harrower et al., 2015;Garnica et al., 2016;Soop et al., 2019). The nrDNA ITS region is not suitable to draw conclusions for comprehensive phylogenetic evaluation, however, there are some interesting patterns indicated in sect. Delibuti to be further discussed. The basal lineages (clade A and B) of Delibuti are solely distributed in the Australasia showing a presumable origin of this section in Australasia. Interestingly, clade D contains species from multiple continents in the Northern and Southern Hemispheres. Some species are distributed in Asia (Cortinarius sp., LC175538), in Europe (Cortinarius sp., JF907917), and South America, like Cortinarius sp. (MF599228) from Colombia and C. illitus Moser & Horak (1975) originally described from Argentina, but also found in North America (according to the sequences in GenBank).These patterns could explain that the evolution of sect. Delibuti is limited to the ectomycorrhizal host specificity, as well as geographic barriers (Wang & Qiu, 2006;Brandrud, 1996;Wilson, Hosaka & Mueller, 2017;Feng et al., 2016). The evolution and origin of sect. Delibuti, including the genus Cortinarius will be a subject for future research.
IKA-05) financed by the National Research, Development and Innovation Office. There was no additional external funding received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Grant Disclosures
The following grant information was disclosed by the authors:

DNA Deposition
The following information was supplied regarding the deposition of DNA sequences: The ITS sequences are available at GenBank: MW911726, MW911727, and MW911729 to MW911735.

Data Availability
The following information was supplied regarding data availability: The matrix of newly generated ITS sequences is available in the Supplemental Files. The ITS matrix for phylogenetic analyses is available in the Supplemental Files and at TreeBASE: S28399. It is also available at Figshare: Xie, Meng-Le; Chen, Jun-Liang; Phukhamsakda, Chayanard; Dima, Bálint; Fu, Yong-Ping; Ji, Rui-Qing; et al. (2021)

New Species Registration
The following information was supplied regarding the registration of a newly described species:

Supplemental Information
Supplemental information for this article can be found online at http://dx.doi.org/10.7717/ peerj.11982#supplemental-information.