Pluteus umbrosoides 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 umbrosoides E. F. Malysheva , Mycol. Progr. 15: 880 (2016)

Figs 18 F – H , 21

Description.

Basidiomata medium-sized. Pileus 15–41 mm diam; plano-convex to convex; earthy yellow (2.5 Y 8 / 6), surface with black-brown (7.5 YR 3 / 2) recurved conical scales, denser in the middle forming a vein, becoming sparse toward the margin, margin straight and slightly crenulate. Context white (10 P 9 / 2), 3–6 mm thick. Lamellae free, 5–7 mm wide, crowded, white (10 P 9 / 2) to pink (7.5 RP 8 / 4), unequal, moderately thick, ventricose, edges even to flocculose and white. Stipe 21–76 × 5–9 mm, fibrous, solid, clavate, slightly expanded at the base, whitish overall (10 P 9 / 2), with brown (7.5 YR 4 / 4) glandular dots on the surface. Spore print unknown.

Basidiospores [40 / 2 / 1] 5.5–6.5 (– 7.0) × 5.0–6.0 µm, avL × avW = 6.1–6.5 × 5.5–5.9 µm, Q = 1.18–1.30 µm, avQ = 1.20–1.25 µm, broadly ellipsoid to ellipsoid, smooth, slightly pinkish, thick-walled. Basidia 24–28 × 7–9 μm, clavate, thin-walled, 4 - sterigmate, hyaline. Pleurocystidia 58–82 × 21–35 μm, rare, scattered, fusiform to broadly fusiform, with shorter necks, thin-walled, smooth, hyaline. Lamellar edge sterile. Cheilocystidia 37–63 × 16–21 μm, abundant, clustered, similar to Pleurocystidia, fusiform, commonly mucronate, thin-walled, smooth, generally with brown intracellular pigment. Pileipellis a trichohymeniderm composed of narrowed fusiform and clavate elements, with terminal elements 71–155 (– 174) × 17–25 μm, often grouped in clusters, pointed towards the apex, with brown intracellular pigment, thin- or slightly thick-walled. Stipitipellis a cutis, hyphae 4–7 μm diam, cylindrical, hyaline, thin-walled. Without caulocystidia. Clamp connections absent in all tissues.

Habitat.

Scattered on very rotten decaying wood in broad-leaved forests ( Q. mongolica ).

World distribution.

Russia ( Malysheva et al. 2016), China ( Hosen et al. 2018), Turkey ( Kaygusuz et al. 2019).

China distribution.

Jilin Province.

Additional specimens examined.

CHINA • Jilin Province, Cold Onion Ridge Forest Park . Scattered on very rotten decaying wood in broad-leaved forests ( Q. mongolica ); 25 August 2019, G. Rao, FJAU 66615 (Collection no.: Rao 614) (ITS: PQ 810780 , LSU: PQ 810741 ) .

Notes.

Malysheva et al. reported that P. umbrosoides is characterized by pink lamellae without brown margin, a densely squamose pileus which is veined around the center, a smooth stipe without brown squamules, ellipsoid basidiospores, pleurocystidia commonly capitate in shape, a trichohymeniderm pileipellis, and narrowly fusiform caulocystidia ( Malysheva et al. 2016).

Morphologically, the specimens from China are very similar to the type. Alternatively, we identified one major difference among specimens from China which is the absence of caulocystidia. Even though we observed the upper, middle, and basal parts of the stipe, exhibiting similarity with Hosen et al. (2018) specimens taken from Changbai Mountain, China, neither of which observed caulocystidia.

In the molecular phylogenetic tree, the Chinese specimens clustered in the same branch with P. umbrosoides from Russia, China, and Turkey and had high support (MLB = 100, BPP = 1, Fig. 3 ).

Figures

Figure 3. Phylogenetic tree of the / umbrosus clade and / pantherinus lineage 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 18. Basidiomata features. A – C. Pluteus costatus (A, B. FJAU 66589, C. FJAU 66618). D, E. P. umbrosus (FJAU 66590). F – H. P. umbrosoides (FJAU 66615). I, J. P. granularis (FJAU 66612). A – C. Photos by Di-Zhe Guo. D, E. Photos by Jia-Jun Hu. C, F – H. Photos by Gu Rao. I, J. Photos by Zheng-Xiang Qi. Scale bars: 1 cm.

Figure 21. A. Macroscopic characteristics of Pluteus umbrosoides. 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).