Basidiodendron dehongense Q. Yuan & C. L. Zhao 2026, sp. nov.

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Basidiodendron dehongense Q. Yuan & C. L. Zhao sp. nov. Figs 9, 10, 11 Diagnosis. Basidiodendron dehongense differs from other species by its slightly olivaceous to buff hymenial surface, subclavate cystidia, and broadly ellipsoid to subglobose basidiospores. Etymology. Dehongense (Lat.). Referring to the type locality, Dehong, Yunnan Province, China. Type. CHINA • Yunnan Province, Dehong, Ruili City, Tongbiguan Provincial Nature Reserve, 24°11'N, 97°31'E, elevation 1,945 m asl., on fallen angiosperm branch, leg. C. L. Zhao, 3 Nov. 2024, CLZhao 42161 (SWFC 00042161, holotype). Description. Basidiomata annual, resupinate, closely adnate, membranaceous, without odor or taste when fresh, up to 10 cm long, 5 cm wide, and up to 100 µm thick. Hymenial surface smooth, slightly olivaceous to buff when fresh, turning to buff to cream upon drying. Sterile margin narrow, buff, up to 1 mm. Hyphal system monomitic; generative hyphae with clamp connections, colorless, thin-walled, smooth, interwoven, 2–4 µm in diameter, IKI –, CB –; tissues unchanged in KOH. Leptocystidia subclavate, colorless, thin-walled, smooth, 18.5–28 × 3.5–6.5 µm. Hyphidia arising from generative hyphae, nodulose, rarely branched, colorless, thin-walled, 1–2.5 µm in diameter. Basidia ellipsoid to ovoid, longitudinally septate, two- to four-celled, 10.5–13.5 × 7–10 µm, involucres well developed, often totally covering basidial cells. Basidioles dominant, similar to basidia in shape, but slightly smaller. Basidiospores broadly ellipsoid to subglobose, colorless, thin-walled, smooth, usually with one or more oil drops, IKI –, CB –, 5.5–7.5 × 4.5–6.5 µm, L = 6.46 µm, W = 5.33 µm, Q = 1.17–1.21 (n = 60 / 2). Additional specimen examined (Paratype). CHINA • Yunnan Province, Dehong, Ruili City, Tongbiguan Provincial Nature Reserve, 25°21'N, 98°06'E, elevation 1,600 m asl., on fallen angiosperm branch, leg. C. L. Zhao, 3 Nov. 2024, CLZhao 50617 (SWFC 00050617). Notes. Basidiodendron dehongense was shown to group within Basidiodendron in a sister relationship to B. luteogriseum in the combined ITS + nrLSU + TEF 1 phylogenetic inference (Fig. 2). However, B. luteogriseum differs from B. dehongense by its pruinose hymenial surface and shorter basidiospores (4.1–5.1 × 4–5.1 µm vs. 5.5–7.5 × 4.5–6.5 µm; Spirin et al. 2020). Morphologically, B. dehongense resembles B. cinerellum, B. groningae Schoutt. & Spirin, and B. inconspicuum Spirin & Malysheva by having a smooth hymenial surface. However, B. cinerellum can be separated from B. dehongense by its pruinose basidiomata and warted basidiospores (Spirin et al. 2021). Basidiodendron groningae is distinct from B. dehongense by its pruinose-reticulate basidiomata and spiny, narrower basidiospores (6–7.9 × 6.2–8.2 µm vs. 5.5–7.5 × 4.5–6.5 µm; Spirin et al. 2021). Basidiodendron inconspicuum is separated from B. dehongense by its pruinose-reticulate basidiomata and minutely warted basidiospores (Spirin et al. 2021).