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

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Basidiodendron tenissimum Q. Yuan & C. L. Zhao sp. nov. Figs 24, 25, 26 Diagnosis. Basidiodendron tenissimum differs from other species by its buff to cinnamon-buff, smooth hymenial surface, subcylindrical to subclavate with an obtuse apex, occasionally sinuous in the basal position cystidia, and ellipsoid to globose basidiospores. Etymology. Tenissimum (Lat.). Referring to the type specimens having tenuous basidiocarps. Type. CHINA • Yunnan Province, Dehong, Yingjiang County, Tongbiguan Provincial Nature Reserve, 25°50'N, 97°36'E, elevation 1,000 m asl., on fallen angiosperm branch, leg. C. L. Zhao, 21 Jul. 2023, CLZhao 30794 (SWFC 00030794, holotype). Description. Basidiomata annual, resupinate, closely adnate, coriaceous, without odor or taste when fresh, up to 8 cm long, 4 cm wide, and 50–100 µm thick. Hymenial surface smooth, cream to buff when fresh, buff to cinnamon-buff upon drying, cracking. Sterile margin narrow, white to cream, up to 1 mm. Hyphal system monomitic; generative hyphae with clamp connections, colorless, thin-walled, smooth, rarely branched, interwoven, 1.5–2 µm in diameter, IKI –, CB –; tissues unchanged in KOH. Gloeocystidia numerous, thin-walled, subcylindrical to subclavate with an obtuse apex, occasionally sinuous in the basal position, 17–34 × 3.5–6 µm. Hyphidia absent. Basidia narrowly ovoid to ellipsoid, longitudinally septate, four-celled, 8–10 × 5.5–9 µm, involucres absent. Basidioles dominant, similar to basidia in shape, but slightly smaller. Basidiospores ellipsoid to globose, colourless, thin-walled, smooth, usually with one oil drop, IKI –, CB –, 4–5 (– 5.5) × 4–5 µm, L = 4.79 µm, W = 4.64 µm, Q = 1.02–1.04 (n = 60 / 2). Additional specimen examined (Paratype). CHINA • Yunnan Province, Dehong, Yingjiang County, Tongbiguan Provincial Nature Reserve, 24°45'N, 97°35'E, elevation 1,760 m asl., on fallen angiosperm branch, leg. C. L. Zhao, 21 Jul. 2023, CLZhao 30844 (SWFC 00030844). Notes. The combined ITS + nrLSU + TEF 1 phylogenetic analysis revealed that Basidiodendron tenissimum formed a single lineage (100 % ML, 1.00 BPP) and grouped with two taxa, B. dehongense and B. luteogriseum (Fig. 2). However, B. dehongense can be delimited from B. tenissimum by its membranaceous basidiomata with a slightly olivaceous to buff hymenial surface and longer basidiospores (5.5–7.5 × 4.5–6.5 µm vs. 4–5 × 4–5 µm). Basidiodendron luteogriseum differs from B. tenissimum by its pruinose hymenial surface (Spirin et al. 2020). Morphologically, B. tenissimum resembles B. inconspicuum and B. iniquum in having a smooth hymenial surface. However, B. inconspicuum is distinct from B. tenissimum by its pruinose-reticulate hymenial surface and larger basidiospores (5–6.2 × 5.2–6.5 µm vs. 4–5 × 4–5 µm; Spirin et al. 2021). Basidiodendron iniquum can be separated from B. tenissimum by its pale cream-colored or greyish hymenial surface and longer basidiospores (4.9–6.2 × 4.1–5.2 µm vs. 4–5 × 4–5 µm; Spirin et al. 2020).

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.