Stereum vietnamensis S.H. He & Y.F. Cao, sp. nov.
MycoBank number: MB; Index Fungorum number: IF; Facesoffungi number: FoF 10789;
Description
Sexual state:Fruiting body – Basidiomata annual, effused-reflexed to distinctly pileate, dimidiate, imbricate, easily detached from substrate, soft corky to woody hard, projecting up to 4 cm long, 2 cm wide, 2 mm thick at base, incurved after dry. Pileal surface tomentose to hirsute when juvenile, becoming glabrous with age, light brown to dark brown, distinctly concentrically zonate and sulcate; margin distinct, sharp. Hymenophore smooth to tuberculate, light orange [5A(4–5)], greyish orange [5B(3–4)] to brownish orange [5C(3–4)], slightly darkening in KOH, uncracked; margin indistinct, concolorous with hymenophore. Context cream to light brown, up to 0.8 mm thick.
Microscopic structures – Hyphal system monomitic; all hyphae without clamps. Cortex (a dark line between tomentum and subiculum) present, dark brown, composed of densely interwoven and agglutinated hyphae. Subiculum well-developed, thick, with a compact texture, with hyphae agglutinated and parallel to substrate; generative hyphae colorless to pale yellow, thick-walled, smooth, rarely branched, frequently septate, 2.5–4 µm in diam. Skeletal hyphae pale yellow, distinctly thick-walled, smooth, unbranched, without septa, 3–5 µm in diam. Subhymenium thickening; generative hyphae colorless, slightly thick-walled, smooth, slightly agglutinated, vertically arranged, 2–3.5 µm in diam. Skeletocystidia colorless to pale yellow, thick-walled, tubular to subulate, with a thin-walled and tapered apex, arising from subhymenium, embedded, up to 250 µm long, 16 µm wide. Acutocystidia numerous, colorless, thin-walled, smooth. Basidia clavate, colorless, thin-walled, smooth, with four sterigmata and a basal simple septum, 18–28 ´ 4–5 µm; basidioles numerous, in shape similar to basidia, but slightly smaller. Basidiospores ellipsoid to ovoid, colorless, thin-walled, smooth, amyloid, acyanophilous, 4.5–5 ´ 2.5–3.2 µm, L = 4.8 µm, W = 3 µm,Q = 1.6 (n = 30/1).
Asexual state: not observed.
Material examined: VIETNAM, Lam Dong Province, Bi Doup Nui Ba National Park, on fallen angiosperm trunk, 15 October 2017, He 5248 (BJFC 024766, holotype, isotype in BJM).
Distribution: Vietnam
Sequence data: LSU: MW528939 (LROR/LR7)
Notes: Stereum vietnamensis is characterized by the hard basidiomata with a brown pileal surface, large skeletocystidia and small basidiospores. Stereum gausapatum (Fr.) Fr. is similar to S. vietnamensis by sharing the hard basidiomata with a brown pileal surface but differs in having larger cylindrical basidiospores (6–10 ´3.5–4.5 µm, Bernicchia and Gorjón 2010). Macroscopically, S. vietnamensis resembles Xylobolus princeps (Jungh.) Boidin, which however, differs in having larger basidiomata and numerous acanthocystidia (Ryvarden 2012).
![Picture10](https://www.facesoffungi.org/wp-content/uploads/2022/05/Picture10-1-709x1024.jpg)
Fig. 10. Stereum vietnamensis (BJFC 024766, holotype). a Basidiomata. b Basidiospores. c Basidia and a basidiole. d Acutocystidia. e Gloeocystidia. f. Generative hyphae from subiculum. Scale bars: a = 1 cm, b–f = 10 µm.