Lyomyces guttulatus Xue W. Wang & L.W. Zhou, sp. nov.

Index Fungorum number: IF 900294; Mycobank number: MB 900294; Facesoffungi number: FoF 14057; Figs. 1, 2

Etymology – guttulatus (Lat.) referring to the numerous oil-like globules on basidia.

Holotype – LWZ 20200921-29a (HMAS).

Diagnosis – Characterized by annual, resupinate, adnate basidiomes, smooth to slightly grandinioid hymenophore, crystalline hyphae, tapering cystidia, subclavate to cylindrical basidia with numerous oil-like globules and broadly ellipsoid basidiospores.

Basidiomes annual, resupinate, adnate, cracked and brittle when dry, without odour. Hymenophore smooth to slightly grandinioid, lime to cream colored. Margin concolorous with subiculum, abrupt.

Hyphal system monomitic; generative hyphae with numerous clamp connections, hyaline, dichotomous branching, interwoven, thin-walled. Subhymenial hyphae frequently encrusted by crystals, 2.5–4.5 μm in diam. Tapering cystidia colourless, smooth, thin-walled, ca. 20×3 μm. Basidia subclavate to cylindrical, with numerous oil-like globules, ca. 20×4 μm, with four sterigmata and a basal clamp connection; basidioles abundant, similar in shape to basidia, but slightly smaller.

Basidiospores broadly ellipsoid, with a large oily drop, hyaline, smooth, thin-walled, IKI–, slightly CB+, 4–6×3–4 μm, L=4.98 μm, W=3.47 μm, Q=1.43–1.44 (60/2).

Material examined – China, Sichuan Province, Liangshan Yi Autonomous Prefecture, Leibo County, Mamize Nature Reserve, on fallen trunk of Picea, 21 September 2020, L.W. Zhou, LWZ 20200921-29a (HMAS, holotype). China, Sichuan Province, Yaan, Shimian County, Hongba Nature Reserve, on fallen branch of angiosperm, 10 August 2019, L.W. Zhou, LWZ 20190810-20b (HMAS).

GenBank numbers – LWZ 20190810-2b: ITS=OQ540898; LSU=OQ540858; LWZ 20200921-29a: ITS=OQ540899; LSU=OQ540859.

Notes – Lyomyces niveus and L. sambuci resembles L. guttulatus by having resupinate basidiomes, light colored hymenophore and crystalline hyphae. However, L. niveus differs from L. guttulatus in having capitate, fusiform cystidia and barreled basidia (Luo et al. 2021), while L. sambuci differs in its capitate cystidia (Langer 1994).

Figure 1 – Basidiomes of Lyomyces guttulatus (LWZ 20200921-29a, holotype)

Figure 2 – Microscopic structures of Lyomyces guttulatus (LWZ 20200921-29a, holotype). a Basidiospores. b Basidia. c Cystidia. d Basidioles. e Section in hymenium. Scale bars: a=5 μm, b–e=10 μm