Entoloma acutiflavum Z. W. Liu, Y. Y. Cui & Zhu L. Yang, 2025

Liu, Ze-Wei, Li, Jing, Yang, Zhu L. & Cui, Yang-Yang, 2025, Four new species of Entoloma subgen. Cubospora (Entolomataceae, Agaricales) from Yunnan Province, China, MycoKeys 124, pp. 331-356 : 331-356

Entoloma acutiflavum Z. W. Liu, Y. Y. Cui & Zhu L. Yang sp. nov.

Figs 2 , 3 , 4

Diagnosis.

Pileus greyish yellow, with acuminate papilla at center. Basidiospores cuboid. Lamellar edge heterogeneous. Cheilocystidia elongated clavate, subcylindrical elongated clavate, or subcylindrical. Pileipellis with intracellular and incrusted pigment. Clamp connections present.

Holotype.

China • Yunnan Province: Baoshan, Longyang District , 25.2996°N, 98.7855°E, elev. 2200 m, in the litter layer of mixed broadleaf-conifer forest, 7 August 2022, Jin Li 085 ( HKAS 150128 ).

Etymology.

Refers to the yellowish pileus with acuminate papilla at center.

Description.

Basidioma small to medium-sized. Pileus 28–42 mm in diam., conical, with acuminate papilla at center; greyish beige (4 C 2), light yellow (3 A 4) to greyish yellow (3 C 3, 4 C 5), margin concolorous or paler to yellowish white (2 A 2); striate sometimes shallowly sulcate, beige (4 C 3) or concolorous with pileus, towards the center up to 1/3 to 4/5 diam.; surface dry, smooth, occasionally hygrophanous, margin undulate; context thin. Lamellae sinuate, slightly crowded, 2–3 mm wide, with 1–3 tiers of lamellulae, narrowly ventricose, blond (4 C 4) or brownish orange (5 C 4), edge concolorous. Stipe 46–115 × 4–6 mm, central, cylindrical, usually tapering upwards, hollow; apex yellowish white (1 A 2) or greyish yellow (2 C 4, 3 C 3), sometimes downwards darker to beige (4 C 3); slightly with longitudinal or oblique striae, with white fibrils or smooth, base slightly swollen and with white mycelium. Odor and taste not observed.

Basidiospores [69/2/2] (9.3) 9.6– 10.9 – 12.3 (12.9) × (8.9) 9.2– 10.4 – 12.1 (12.7) μm [Q = 1.00–1.12 (1.20), Q = 1.05 ± 0.04], cuboid, most with 4 angles in side-view, rarely with 5 angles, lacking elongated angles. Basidia 45–79 × 11–22 μm, clavate, 4 - spored, colorless. Lamellar edge heterogeneous. Cheilocystidia 28–89 × 7–18 μm, elongated clavate or subcylindrical, occasionally ventricose, hyaline or with pale yellowish green droplet-like content, thin-walled. Pleurocystidia absent. Lamellar trama regular, made up of cylindrical hyphae 3–12 μm diam., smooth, colorless. Pileipellis a cutis composed of cylindrical and fusiform hyphae, 2–16 μm wide, thin-walled, with yellowish brown intracellular pigment, also sometimes incrusting. Stipitipellis composed of longitudinally arranged, cylindrical hyphae 3–16 μm wide; terminal cells clavate to elongated clavate, 37–76 × 7–12 μm; both hyphae and terminal cells in stipitipellis with colorless intracellular content. Clamp connections present in all tissue. Refractive hyphae sometimes occur in lamellar trama.

Habitat.

Solitary or scattered in the litter layer of mixed broadleaf-conifer forests.

Known distribution.

Yunnan Province, China.

Additional material examined.

China • Yunnan Province: Baoshan, Longyang District , 25.2996°N, 98.7855°E, elev. 2200 m, in the litter layer of mixed broadleaf-conifer forest, 7 August 2022, Xue-Ping Fan 502 ( HKAS 150127 ) .

Notes.

Entoloma acutiflavum is similar to E. submurrayi and E. murrayi morphologically; meanwhile, E. acutiflavum and E. submurrayi form a close and stable clade in the phylogenetic tree. Compared to E. submurrayi reported from subtropical regions of China, E. acutiflavum differs in its dry pileus with brownish and orangish tinges, white fibrils on the stipe, heterogeneous lamellar edge, and encrusted pigment on the pileipellis ( Chen et al. 2024). Entoloma murrayi , a widespread species, can be distinguished by its absence of clamp connections and sterile lamellar edge ( Selby et al. 1859; Horak 1976; He 2012). In addition, E. neotropicale and E. flavescens have yellow basidiomata that are similar to those of E. acutiflavum . However, E. neotropicale has an appressed-fibrillose pileus with a more obtuse papilla and indistinct striations on the pileus margin ( Karstedt et al. 2024). Entoloma flavescens possesses a shiny pileus partially covered with whitish silky scales, shorter cheilocystidia, and an almost hyaline pileipellis ( Sato et al. 2025).

Figures

Figure 2. Basidiospores of four new species of Entoloma subg. Cubospora under SEM. a, b. E. acutiflavum HKAS 150128, holotype; c, d. E. bichromum HKAS 150132, holotype; e, f. E. guttuliferum HKAS 150129, holotype; g, h. E. rufosquamulosum HKAS 130186, holotype. Scale bars: 2 μm.

Figure 3. Basidiomata of four new species of Entoloma subg. Cubospora. a, b. E. acutiflavum HKAS 150128, holotype; c, d. E. bichromum (c) HKAS 150131, (d) HKAS 150132, holotype; e, f. E. guttuliferum HKAS 150129, holotype; g, h. E. rufosquamulosum HKAS 130186, holotype. Scale bars: 10 mm.

Figure 4. Microscopic features of Entoloma acutiflavum (HKAS 150128, holotype). a. Basidiospores; b. Basidia; c. Cheilocystidia; d. Pileipellis; e. Stipitipellis. Scale bars: 10 μm (a – c); 20 μm (d, e).