Acanthostereum brunneum S.H. He & Y.F. Cao, sp. nov.

MycoBank number: MB; Index Fungorum number: IF; Facesoffungi number: FoF 10782;

Description

Sexual state: Fruiting body – Basidiomata annual, resupinate, effused, adnate, easily separated from substrate, coriaceous, brittle when dry, first as small round patches, later confluent. Hymenophore smooth, greyish brown [6B(3–6)], brownish-orange [6C(3–8)] to light brown [6D(3–8)], turning reddish-black in KOH, uncracked; margin abrupt, slightly elevated, indistinct and concolorous with hymenophore. Context light brown, up to 1.5 mm thick. Microscopic structuresHyphal system monomitic; all hyphae without clamps. Subiculum well-developed; hyphae colorless to pale yellow, thick-walled, smooth, rarely branched, moderately septate, tightly interwoven, more or less parallel to substrate, 2–3 µm in diam. Subhymenium indistinct; hyphae colorless, thin- to thick-walled, smooth, tightly interwoven, 2–2.5 µm in diam. Gloeocystidia vesicular to racket-shaped, colorless, slightly thick-walled, smooth, embedded, 25–40 × 15–25 μm. Acanthophyses numerous, variable in shape and size, mostly subclavate to subcylindrical, with few to many spines at apex, colorless, thin- to slightly thick-walled, 20–40 × 2–6 μm. Hyphidia present, colorless, thin-walled, smooth, slightly branched. Basidia not seen; basidioles numerous, clavate, colorless, thin-walled, smooth, with a basal septum. Basidiospores subcylindrical to subfusiform, colorless, thin-walled, smooth, amyloid, acyanophilous, (9–) 10–12 (–12.7) × 4–5 µm, L = 11.3 µm, W = 4.7 µm, Q = 2.4 (n = 12/1). Asexual state: not observed.

Material examined: CHINA, Yunnan Province, Baoshan County, Gaoligongshan Nature Reserve, on fallen angiosperm branch, 30 November 2015, He3407 (BJFC 021803) & He 3447 (BJFC 021843, holotype, isotype in BJM); Yongde County, Daxueshan Nature Reserve, on fallen angiosperm branch, 28 August 2015, He 2735 (BJFC 021173).

Distribution: China

Sequence data: ITS: MW533078 (ITS5/ITS4); LSU: MW528913 (LROR/LR7)

Notes: Acanthostereum brunneum is characterized by the brown basidiomata, vesicular to racket-shaped gloeocystidia, numerous acanthophyses and large cylindrical basidiospores. Acanthostereum chinensis is similar to A. brunneum by sharing the brown basidiomata and large cylindrical basidiospores but differs in having brown and thick-walled skeletocystidia and hyphidia (Boidin et al. 1979). Acanthostereum wakullum differs from A. brunneum by having subcylindrical pseudocystidia and smaller basidiospores (8–10 × 3–3.5 µm, Burdsall et al. 1981). In the phylogenetic tree, A. brunneum formed a strongly supported distinct lineage.

Fig. 1. Acanthostereum brunneum (BJFC 021843, holotype). a Basidiomata. b Basidiospores. c–e Acanthophyses. f Gloeocystidia. g Hyphidia. h Hyphae from subiculum. Scale bars: a = 1 cm, b–h = 10 µm.