Stereum tropicum S.H. He, Y.F. Cao & Y.L. Xu, sp. nov.

MycoBank number: MB; Index Fungorum number: IF; Facesoffungi number: FoF 12563;


Sexual state:Fruiting body – Basidiomata annual, effused or with narrowly reflexed pilei, separable from substrate, densely coriaceous, up to 12.5 cm long, 5 cm wide, 1.4 mm thick at base. Pileal surface concentrically zonate, brownish orange when juvenile, becoming buff to light brown when dry, more or less glabrous to slightly rough, not cracked with age; margin thin out, distinct. Context brown, corky, up to 1.1 mm thick.

Microscopic structures – Hyphal system dimitic, generative hyphae simple separation, colorless, smooth, slightly thick-walled, often septate, rarely branched, more or less parallel to the substrate, 2.1–5.5 μm in diam. Skeletal hyphae hyaline, thick-walled, unbranched, not septate, 3.9–6 µm in diam. Subicular generative hyphae hyaline, thin to thick-walled, unbranched, interwoven, 1.9–3.4 µm in diam. Crystal masses scattered throughout section. Subhymenium thickening; acanthophyses numerous, thin-walled, with a few protuberances near the apex and slightly projecting. Gloeocystida colorless, thick-walled, unbranched, cylindrical, with a simple separation at the base, up to 88 × 6 μm, immersed or projecting. Basidia clavate, colorless, thick-walled, with 4 sterigmata and a basal simple septum, 19–29 × 3.9–5.9 µm; basidioles dominant; basidioles in shape similar to basidia, but slightly smaller. Basidiospores ovoid, colorless, thin-walled, smooth, amyloid, acyanophilous, (5–)5.2–7 × (2.9–)3–3.8(–4) µm, L = 6.08  µm, W = 3.18  µm, Q = 1.91 (n = 30/1).

Asexual state: not observed.

Material examined: CHINA, Hainan Province, Lingshui County, Diaoluoshan Nature Reserve, On fallen angiosperm trunk, 2 July 2019, He 5968 (BJFC 030843, holotype); Hainan Province, Lingshui County, Diaoluoshan Nature Reserve, on dead angiosperm branch, 5 July 2019, He 6050 (BJFC030925, paratypes).

Distribution: Vietnam

Sequence data: He 5968  ITS: MW263990 (ITS5/ITS4); LSU: MW263974 (LR0R/LR7) He 6050  ITS: MW263991 (ITS5/ITS4); LSU: MW263975 (LR0R/LR7)

Notes: Stereum tropicum is characterized by effused Pilei Pileal surface concentrically zonate generative hyphae simple separation, often septate, rarely branched, acanthophyses numerous, Gloeocystida cylindrical.

Fig. 2. Microscopic structures of Stereum tropicum (BJFC 030843, holotype). a. Basidiospores. b. Basidia. c. Basidioles. d. Acanthophyses. e. Skeletocystidia. f. Acutocystidia. g. Hyphae from subiculum. – Scale bars = 10 µm.