Pluteus ussuriensis E. F. Malysheva

Qi, Zheng-Xiang, Wang, Li-Bo, Qian, Ke-Qing, Shi, Li-Li, Hu, Jia-Jun, Tuo, Yong-Lan, Rao, Gu, Samwel Jacob, Muharagi, Liu, Rui-Peng, Liu, Ming-Hao, Guo, Di-Zhe, Liu, Ya-Jie, Zhang, Bo, Li, Xiao & Li, Yu, 2025, Integrating morphology, phylogeny, substrate, and distribution: clarifying the major phylogenetic framework of Pluteus sect. Hispidoderma (Agaricales, Pluteaceae) and describing 18 species, IMA Fungus 16, pp. e 154329-e 154329 : e154329-

Pluteus ussuriensis E. F. Malysheva , in Justo, Malysheva, Bulyonkova, Muñoz, Ferisin, Dovana, Kaygusuz, Saar, Antonín, Vellinga, Lebeuf, Minnis, Grootmyers, Kalichman, Parker, Miller, Russell, Berbee, Pacholek, Ceska & Pradeep, Mycologia: 20 (2025)

Figs 25 A – E , 28

Description.

Basidiomata medium-sized. Pileus 28–35 mm diam; campanulate when young, surface orange-red (7.5 YR 8 / 16); plano-convex or convex when mature, bright yellow (2.5 Y 8 / 12), slightly brownish (10.0 YR 7 / 16); smooth, margin slightly translucently striate, with straight margin. Context dirty white (10.0 YR 9 / 4), odorless, 3–5 mm thick. Lamellae initially dirty white (10.0 YR 9 / 4), turning pink at maturity (10.0 YR 8 / 8), free, crowded, thick, unequal, slightly ventricose, 6–7 mm wide. Stipe 68–72 × 8–10 mm, cylindrical, hollow, partly spirally curled, slightly thicker at the base, fibrous, white to brown at the base (10.0 YR 9 / 10). Odorless. Spore prints pink.

Basidiospores [210, 7, 4] 6.0–6.5 (– 7.0) × 5.0–5.5 (– 6.0) μm, avL × avW = 6.3–6.5 × 5.2–5.4 µm, Q = 1.09–1.40 μm, avQ = 1.18–1.24 μm, broadly ellipsoid to ovoid, slightly pinkish, smooth, thin-walled. Basidia 25–32 × 7–11 μm, clavate, thin-walled, 4 - sterigmate, and hyaline in KOH. Pleurocystidia 55–102 × 22–36 μm, numerous, scattered, fusiform to subfusiform, obtusely rounded apically, tapering basally, commonly provided with 1–2 digitiform excrescences at apex, thin-walled, smooth, hyaline. Lamellar edge sterile. Cheilocystidia 41–79 × 18–29 μm, abundant, clustered, subfusiform to fusiform, mostly apically mucronate to rostrate, 8–20 μm long, thin-walled, hyaline. Lamellar trama divergent. Pileipellis a trichoderm with radial hyphae, with terminal elements 62–143 × 14–29 μm, hyphae at the center extending outwards, with cylindrical or fusiform elements, thick-walled, with slightly tan intracellular pigment. Stipitipellis a cutis, hyphae 6–11 µm diam, cylindrical, hyaline, thin-walled. Caulocystidia absent. Clamp connections absent in all tissues.

Habitat.

Solitary on rotting wood in broad-leaved or mixed forests.

World distribution.

Russian Far East ( Justo et al. 2025), China.

China distribution.

Jilin Province.

Additional specimens examined.

CHINA • Jilin Province, Cold Jungle National Nature Reserve ; 5 August 2021, G. Rao, FJAU 66576 (Collection no.: Rao 1287) (ITS: PP 516606 , LSU: PP 516656 , tef 1: PP 551592 ) . CHINA • Jilin Province, Cold Jungle National Nature Reserve . Solitary on decaying wood in broad-leaved forests; 7 August 2021, G. Rao, FJAU 66577 (Collection no.: Rao 1297) (ITS: PP 516608 , LSU: PP 516657 , tef 1: PP 551593 ) . CHINA • Jilin Province, Hà N ội Vi ệt Nam Conservation Station Front Hill ; Scattered on rotting wood in mixed Q. mongolica and U. pumila forests; 42°15'27.75"N, 126°15'28.78"E, alt. 756 m, 18 July 2021, M. H. Liu, FJAU 66578 (Collection no.: Lmh 045) (ITS: PP 516607 , LSU: PP 516658 , tef 1: PP 551594 ) . CHINA • Jilin Province, Hà N ội Vi ệt Nam Conservation Station Front Hill ; Scattered on rotting wood in mixed Q. mongolica and U. pumila forests; 42°15'20.77"N, 126°10'78.88"E, alt. 825 m, 8 August 2021, M. H. Liu, FJAU 66579 (Collection no.: Lmh 102) (ITS: PP 516609 , LSU: PP 516659 , tef 1: PP 551595 ) .

Notes.

Pluteus ussuriensis is characterized by its bright yellow and smooth pileus, white stipe that expanded at the base, and cheilocystidia that are rostrate at the top and measure 8–20 μm long.

Justo described P. ussuriensis in 2025, and we compared all the characters and found that morphologically (pileus, stipe, lamellae, basidiospores, pleurocystidia, pileipellis) are very similar, its sequence bases are the same, and the substrate ecology is on decaying wood in broad-leaved forests, and the distribution is in the Changbaishan Mountains. Meanwhile, we also observed some differences, such as the apical projection being longer in our collections of cheilocystidia, and the projection described by Justo et al. (2025) being shorter or more pointed; no caulocystidia were observed in our collections, and a few caulocystidia were observed by Justo et al. (2025); and there are 4 tef 1 base differences. We consider the similarities and differences together, and here identify the Chinese specimen as P. ussuriensis , a newly recorded species from China. However, the differences all belong to be part of the intraspecific variation, as Justo et al. (2025) describe the species in the / leoninus clade, and cheilocystidia vary considerably from specimen to specimen of the same species.

Phylogenetic analyses indicate that the four Chinese specimens cluster in the same branch as Justo et al. (2025) P. ussuriensis and are strongly supported. (MLB = 100, BPP = 1, Fig. 4 ). P. ussuriensis and P. roseipes are considered sister groups, and their distinction can be based on genetic distance differences and geographic distribution. Their ITS genetic distance is 0.012 (SE = 0.005), tef 1 genetic distance is 0.075 (SE = 0.014); P. ussuriensis is distributed in East Asia, and P. roseipes is distributed in the Czech Republic, Denmark, Estonia, France, Italy, Slovenia, Spain, and Turkey ( Justo et al. 2011 a, b; Pradeep et al. 2012; Lezzi et al. 2014; Menolli et al. 2015 a; Ferisin and Dovana 2018; Kaygusuz et al. 2019; Justo et al. 2025).

Figures

Figure 4. Phylogenetic tree of the / leoninus clade of the sect. Hispidoderma. The best tree from the ML and BI analysis of the ITS + tef 1 dataset. The two values of internal nodes respectively represent the Maximum Likelihood bootstrap (MLBP) / Bayesian posterior probability (BIPP). Nodes with a bootstrap probability (BP) ≥ 80 and a Bayesian posterior probability (PP) ≥ 0.80 are indicated in the phylogram. This study species is in bold and red font.

Figure 25. Basidiomata features. A – E. Pluteus ussuriensis (A, B. FJAU 66576, C, D. FJAU 66577, E. FJAU 66578). F – H. P. leoninus (F. FJAU 66581, G, H. FJAU 66580). A – D. Photos by Gu Rao. E. Photos by Ming-Hao Liu. F. Photos by Di-Zhe Guo. G, H. Photos by Zheng-Xiang Qi. Scale bars: 1 cm.

Figure 28. A. Macroscopic characteristics of Pluteus ussuriensis. B. Basidiospores. C. Basidia and Pleurocystidia. D. Pleurocystidia. E. Cheilocystidia. F. Pileipellis elements. Scale bars: 1 cm (A); 10 µm (B – E); 20 µm (F).