Volvopluteus yunnanensis D. G. Zheng. & Karun. 2025, sp. nov.

Volvopluteus yunnanensis D.G. Zheng. & Karun., sp. nov. FIGURE 2 Index Fungorum number: IF903946 Etymology: “ yunnanensis ” refers to the type locality, Yunnan Province, China. Holotype: China, Yunnan Province, Qujing City, Shizong County, on soil, 24°39′08′′ N 104°10′19′′ E, elev. 2,128 m, 21 June 2024, D.G. Zheng, (SH41 = GMB-W1183). Basidiomata medium to large. Pileus 59–85 mm diameter, surface dry, initially hemispherical to conic, umbonate center, orange white (5A2) with grey (5B2) when young, after maturity, with dark blonde (5D4) center and birch grey (5C2) sides, from center to the periphery are greying brown like nutria (5F3) to yellowish brown (5E4) when dried, shiny and minutely radially appressed silky fibrillose in dry conditions. Margin striate, radially fibrillose, slightly cracked at edge. Lamella numerous, free, ventricose, white (A1) with uneven, serrated edges. Stipe 120–137 × 11–13 mm, cylindrical, white, glabrous, not viscid, when youth visibly broadening towards the base and in maturity with bulbous base enclosed in sac-like volva. Volva white, membranous, tightly packed with stipe base, not woolly at the outer surface. Smell and taste not tested. Basidiospores (10.8–)11.3–12.9(–13.4) × (5.7–)6.0–6.9(–7.0) µm, Q = 1.70–1.99, Q m = 1.87, ellipsoid to oblong, occasionally subglobose, smooth, greyish green, internal finely verrucose, thick-walled, apiculus prominent. Basidia 43–54 × 10–15 µm, 4-spored, a few 2-spored, rarely unisterigmate, clavate, granular, obtuse apex, slightly attenuated in the middle, hyaline or with pale intracellular brown pigment, finely verrucose. Pleurocystidia 60–82 × 16–25 µm, narrowly to broadly fusiform, narrowly utriform, commonly rostrate, with one apical excrescence up to 5.5–8 μm long, hyaline, thin-walled, frequent all over lamellar faces. Cheilocystidia (55–)60–86 × 14–27 μm, mostly cylindrical, clavate, obovoid, absent an apical papilla or excrescence, hyaline, thin-walled, forming a sterile layer at the lamellae edge. Pileipellis ixocutis, composed of hyphae 3–7 μm wide; hyphae cylindrical or irregular in outline, hyaline, smooth, thin-walled, embedded in thick gelatinous matrix. Stipitipellis hyphae 5–12 μm in width, cylindrical, colorless, with thin, smooth walls, hyphae cross-linked together to form a pore network shape. Clamp connection is absent in all tissues. Habitat: Scattered on the soil around with rich humus in broad-leaved forest. Distribution: Only reported from Yunnan, China. Additional specimens examined: China, Yunnan Province, Qujing City, Shizong County, 24°39′22′′ N 104°10′18′′ E, elev. 2,120 m, 21 June 2024, S.C. Karunarathna, (QJ342 = GMB-W1187, isotype). GenBank numbers: GMB-W1183: nrLSU = PQ836323, nrITS = PQ764862. GMB-W1187: nrLSU = PQ836324, nrITS = PQ809775. Notes: In our phylogenetic analyses, our collections (GMB-W1183 and GMB-W1187) were closely related to Vp. asiaticus (TNSF15191) and were separated with statistical support of 100% BS/1.00 PP (Figure 1). Based on nucleotide comparisons, Vp. yunnanensis (GMB-W1183) is different from Vp. asiaticus (TNSF15191) by 19/649 bp (2.9%, without gap) of the ITS. In morphology, Vp. yunnanensis is different from Vp. asiaticus by pileus with dark blonde (5D4) center and birch grey (5C2) sides at maturity, slight crack at the edge, bigger basidiospores (11.3– 12.9 × 6.0–6.9 μm vs. 10.2–12.3 × 6.3–7.2 μm), bigger basidia (43–54 × 10–15 μm vs. 29–37 × 11–13 μm) and bigger pleurocystidia (60–82 × 16–25 μm vs. 48–66 × 15–27 μm) (Justo et al. 2011 b, Kalinina & Malysheva 2023). Volvopluteus yunnanensis has dry, lackluster pileus, but the pileus of Vp. asiaticus, glutinous when wet, shiny on drying. Moreover, Vp. yunnanensis has a membranous volva with a smooth outer surface, lacking any woolly texture. Thus, we identify our new collection as Vp. yunnanensis sp. nov. based on both morphological and molecular phylogenetic analyses.