Tricholomopsis cortinata G. S. Wang, T. Guo & J. P. Liao sp. nov.

Etymology.

The epithet “ cortinata, ” referring to the cortinate annulus on the stipe.

Diagnosis.

Tricholomopsis cortinata differs from the other species of the genus Tricholomopsis by its distinctly smaller basidiomata, small scales on the pileus, cortinate annulus on the stipe, and globose basidiospores.

Holotype.

China • Fujian Province: Yongan City, Tianbaoyan National Nature Reserve, altitude 890 m, 18 Jun 2024, Jinpeng Liao 163420 (KUN- HKAS 151682); GenBank ITS: AA 136285, 28 S: AA 136290.

Description.

Basidiomata small. Pileus 1–2 cm, plano-convex to applanate, dry, light yellow, yellow to dark yellow (2 A 6–2 A 7, 4 A 5–4 A 8), ornamented with minute, concolorous scales. Lamellae narrowly adnate to sinuate, up to 1 mm broad, close to crowded, light yellow, yellow to dark yellow (2 A 6–2 A 7, 4 A 5–4 A 8), with abundant lamellulae. Stipe 1–4 cm long, 0.1–0.3 cm thick, cylindrical, light yellow to yellow (2 A 6–2 A 7, 4 A 5) with minute, pale yellow (1 A 2–1 A 3) granules. Partial veil cortinate, white (1 A 1), membranous-floccose, leaving remnants on the stipe surface as thin, fibrillose-flocculent patches.

Basidiospores [60 / 3 / 2] 5.0–5.9 (– 6.2) × 4.9–5.7 (– 5.8) μm, Q = (0.91 –) 1.00–1.06 (– 1.07), Q _av. = 1.02 ± 0.03, globose, thin-walled, colorless and hyaline, smooth, non-amyloid; apiculus small. Basidia 15–40 × 5–6 μm, 4 - spored or 2 - spored, narrowly clavate to flexuose, thin-walled; sterigmata 3–5 μm long. Cheilocystidia 35–40 × 15–32 μm, broadly clavate to spheropedunculate, colorless hyaline, abundant, forming a sterile belt along the lamellar edge. Pleurocystidia absent. Pileipellis a cutis with the transition to a trichoderm at regular intervals, 20–40 μm thick, and composed of radially arranged, thin-walled hyphae 5–12 μm wide and encrusted with brown pigments. Clamp connections present in all parts of basidioma.

Habitat and distribution.

Solitary to gregarious on soil among bamboo- Lauraceae mixed forests.

Additional specimens examined.

China, • Shanghai City, Sheshan National Forest Park, altitude 54 m, 20 Sep 2020, Ting Guo 2115 (KUN- HKAS 151683); • same location, altitude 56 m, 20 Sep 2024, Ting Guo 2120 (KUN- HKAS 151684); • same location, 4 Aug 2021, Ting Guo 2343 (KUN- HKAS 151685).

Notes.

Tricholomopsis cortinata is morphologically most similar to T. bambusina and T. sasae within sect. Bambusinae. It resembles these species in having yellow-toned basidiomata and a general association with bamboo-related substrates but differs in possessing a well-developed cortinate annulus on the stipe and distinctly smaller basidiomata. Microscopically, T. cortinata is distinguished by globose to subglobose basidiospores, whereas those of T. bambusina and T. sasae are typically ellipsoid. Cheilocystidia in T. cortinata are broadly clavate to spheropedunculate and form a well-defined sterile lamellar edge, while those of related species are generally narrower and differ in shape. The presence of a cortinate annulus represents an unusual feature within Tricholomopsis and further distinguishes T. cortinata from previously described species.