Ganoderma obscuratum
Ganoderma obscuratum J. He and S.H. Li
MycoBank number: MB845721
Basidiomata annual, sessile to substipitate, coriaceous to woody hard, light in weight. Pileus: single, flabelliform to reniform or shell-shaped, applanate, projecting up to 6 cm, 4.5 cm wide and 1 cm thick at the base. Pileus surface dark brown (8E8) when fresh becoming greyish brown (7E8) when dry, and covered by a thin hard crust, laccate, glabrous and shiny, with dense concentric furrows. Margin: buff (8B2) to generally concolorous, entire, subacute to obtuse, slightly wavy, cracked when dry. Context: up to 0.7 cm thick, homogeneous, yellowish brown (5D5) to chestnut brown (6E8), with black melanoid lines, hard corky. Tubes: 0.2–0.4 cm long, concolorous with the base of the context, corky, unstratified. Pores: 6–9 per mm, circular, dissepiments slightly thick, entire; pores surface white to greyish white (2B1) when fresh, pale brown (6D6) to dark brown (7E7) when bruising and drying. Stipe: up to 6.5 cm long and 2.2 cm diam, flattened to cylindrical, fibrous to spongy, concolorous with pileus surface. Hyphal system trimitic: generative hyphae 2.0–4.0 μm in diameter, colorless, thin-walled, with clamps connections; skeletal hyphae 2.0–8.0 μm in diameter, thick-walled with a wide to narrow lumen or sub-solid, arboriform with few branches, yellowish brown to golden yellow; binding hyphae 1.0–3.0 μm in diameter, thick-walled, branched and flexuous, colorless to pale yellow, scarce; all the hyphae IKI–, CB+; tissues darkening in KOH.
Basidiospores almond-shaped to narrow ellipsoid, apex subacute, with apical germ pore, yellowish to yellowish brown, IKI–, CB+, inamyloid; double-walled with moderately thick walls, exospore wall smooth, endospore wall with inconspicuous spinules; (40/2/2; 8.0) 8.5–9.0–9.0 (9.5) × 4.5–5.2–5.0 (5.5) μm, L = 9.09 μm, W = 5.22 μm, Q = (1.58) 1.61–1.75–1.87 (2.08), Qm = 1.75 ± 0.11 (including myxosporium). Basidia: broadly clavate, colorless, with a clamp connection and four sterigmata, thin-walled, 15–25 × 5–9 μm; basidioles in shape like the basidia, colorless, thin-walled, 10–21 × 4–8 μm.
Specimens examined: China, Yunnan Province, Zhaotong City, Yiliang County, Xiaocaoba Town (104°14′18″E, 27°47′59″N), on a dead tree of Acer sp., alt. 1,905 m, Shu-Hong Li, 12 August 2019, Lsh89 (HKAS 123772).
Notes: Phylogenetic analyses showed that Ganoderma obscuratum clusters as a sister taxon to G. yunlingense with good statistical support (100% ML/1.00 PP, Figure 3). Morphologically, G. obscuratum differs from G. yunlingense by having thin basidiomata, dark brown and laccate pileus surface when fresh, homogeneous context and non-stratified tubes, smaller pores (6–9 per mm), and narrow ellipsoid basidiospores with spinules on the endospore wall (Sun et al., 2022). Ganoderma alpinum described from Yunnan Province is morphologically similar to G. obscuratum by having the hard basidiomata with greyish brown pileus surface, homogeneous context and non-stratified tubes. However, G. alpinum differs by the larger pores (5–7per mm), and smaller basidiospores (6.2–7.8 × 4–5.5 μm, Sun et al., 2022). Ganoderma applanatum also has sessile basidiomata and homogeneous context, but it differs from G. obscuratum by having a perennial basidiomata with pale pileus surface and smaller basidiospores (5–8 × 4–6 μm, Moncalvo and Ryvarden, 1997; Hapuarachchi et al., 2019; Sun et al., 2022). Besides, G. applanatum and G. obscuratum were well separated in the phylogenetic analyses.
