Tomentella exiguelata Y.H. Mu & H.S. Yuan, sp. nov.
Index Fungorum number: IF 900080; MycoBank number: MB 900080; Facesoffungi number: FoF 13398; Figs. 1, 2, 3
Etymology – Refers to the presence of slightly thick-walled basidia.
Holotype – IFP 019495
Basidiocarps annual, resupinate, adherent to the substrate, mucedinoid, without odour or taste when fresh, 0.5–1 mm thick, continuous. Hymenophoral surface granulose, grayish brown to light brown (6D3–6D4) and concolorous withsubiculum when dry. Sterilemargin often determinate, farinaceous, concolorous with hymenophore. Rhizomorphs absent. Subicular hyphae monomitic; generative hyphae clamped and rarely simple septate, thin- to slightly thick-walled, moderately branched, 3–5μmdiam, without encrustation, yellow in KOH, cyanophilous in sightly thick-walled hyphae, inamyloid. Subhymenial hyphae clamped and rarely simple septate, thin-to slightly thick-walled, frequently branched, 3–5 μm diam; hyphal cells more or less uniform, yellow in KOH, cyanophilousin sightly thick-walled hyphae, inamyloid. Cystidia absent. Basidia10–47 μm long and 4–8 μm diam at apex, 3–5μmat base, with a clamp connection or simple septate at base, utriform, thin-walled and rarely slightly thick-walled, not stalked, sinuous, yellow in KOH, yellow in distilled water, 4-sterigmate; sterigmata 2.5–4.5μmlong and 0.5–1 μm diam at base. Basidiospores thick-walled, (6.2–)7.1–8.1(–8.3)×(5.4–)5.8–6.9(–7.1) μm, L=7.33 μm, W=6.21 μm, Q=1.18–1.21 (n=60/2), subglobose, triangular or lobed in frontal view and subglobose to ellipsoid in lateral view, echinulate to aculeolate, yellow in KOH and in distilled water, cyanophilous, inamyloid; echinuli usually isolated, sometimes grouped in 2 or more, up to 2.5 μm long.
Material examined – China, Zhejiang Province, Kaihua County, Gutianshan National Nature Reserve, on fallen angiosperm debris, 24 July 2018, Yuan 12805 (IFP 019495, holotype); on fallen angiosperm branch, 25 July2018, Yuan 12900 (IFP 019496, paratype).
GenBank numbers – IFP 019495- MZ329771(ITS), MZ329775 (LSU). IFP 019496- MZ329772 (ITS), MZ329776 (LSU)
Notes – Tomentella exiguelata forms a close phylogenetic relationship with T. galzinii and T. subtestacea (Fig. 4). Tomentella galzinii and T. exiguelata share the following similar morphological and anatomical characteristics: mucedinoid basidiocarps adherent to the substrate, granulose hymenophoral surface, farinaceous sterile margin, similarwide subhymenial hyphae, and not stalked and sinuous basidia. However, T. galzinii has discontinuous and dull green to olive-brown basidiocarps, indeterminate sterile margin, and the presence of cystidia (Bourdot and Galzin 1924). Tomentella subtestacea resembles T. exiguelata in mucedinoid basidiocarps adherent to the substrate, clamped and rarely simple septate subicular hyphae, thin-to slightly thick-walled subhymenial hyphae, utriform and not stalked basidia and echinulate basidiospores of similar length. However, T. subtestacea can be distinguished by reddish-brown to grayish buff hymenophoral surface, arachnoid sterile margin, and the presence of cystidia (Svrček 1958).
Figure 1 – A basidiocarp of Tomentella exiguelata (IFP 019495, holotype). Scale bars=0.25 cm
Figure 2 – SEM of basidiospores of Tomentella exiguelata (IFP 019495, holotype)
Figure 3 – Microscopic structures of Tomentella exiguelata (IFP 019495, holotype). a Section through a basidiocarp. b Basidiospores in frontal view. c Basidiospores in lateral view
Figure 4 – Phylogram generated from maximum likelihood analysis-based on combined ITS and LSU sequence data. Related sequences were obtained from GenBank and Unite. One hundred and ten strains are included in the combined sequence analyses, which comprise 1451 characters withgaps. Single gene analyses were also performed and topology andclade stability compared from combinbed gene analyses. Odontia ferruginea (TU110988) is used as the outgroup taxon. Bootstrap support values for ML≥50% are given. The newly generated sequences are in bold