Odontia huanrenensis Y.H. Mu, H.S. Yuan & Y.C. Dai, sp. nov.
Index Fungorum number: IF 840455; MycoBank number: MB 840455; Facesoffungi number: FoF 09972; Figs. 1, 2, 3
Etymology – The specific epithet “huanrenensis” refers to the Huanren County, where the specimen is found.
Holotype – Yuan 10663
Basidiomata annual, resupinate, easily separable from the substrate, arachnoid, continuous, without odour or taste when fresh, becoming cottony upon drying, up to 0.25 mm thick. Hymenophoral surface light brown to brown (6D7–6E8) when dry, hydnoid; spines conical, up to 0.4 mm long, 0.1–0.2 mm wide at the base, evenly distributed, 2–4 per mm, turning darker or concolorous with subiculum. Subiculum mostly brown. Sterile margin determinate, byssoid, concolorous with hymenophore. Rhizomorphs present in subiculum and margins, 10–50 μm diam.; rhizomorph surface rather smooth; hyphal structure in rhizomorphs dimitic, differentiated, of type C (according to Agerer 1987–2008), compactly arranged; generative hyphae in center of rhizomorph simple-septate, thick-walled, 3–5 μm diam., colorless in KOH; skeletal hyphae at outer part of rhizomorph thick-walled, 1–2 μm diam., grayish yellow in KOH, cyanophilous, inamyloid. Hyphal structure subicular hyphae monomitic, generative hyphae with clamp connections, thin- to slightly thick-walled, 2.5–4 μm diam., occasionally collapsed, without encrustation, grayish yellow in KOH, acyanophilous, inamyloid. Subhymenial hyphae with clamp connections, thin-walled, 3–4 μm diam.; hyphal cells more or less uniform, colorless in KOH, acyanophilous, inamyloid. Spine tramal hyphae monomitic, generative hyphae with clamp connections, slightly thick-walled, 2.5–4(–5) μm diam., grayish yellow in KOH, cyanophilous, inamyloid.
Hymenium cystidia and cystidioles absent. Basidia 18–33 μm long and 5–9 μm diam. at apex, 3–4 μm at base, with a clamp connection at base, clavate, stalked, sinuous, without transverse septa, grayish yellow in KOH and in distilled water, bearing 4 sterigmata; sterigmata up to 3 μm long, 1–2 μm diam. at base. Basidiospores (7–) 7.1–9.4(–9.9)×(6–)6.1–8.3(–9) μm in lateral and frontal face, L=8.48 μm, W=7.6 μm, Q =1.12–1.13 (n=60/2), irregular globose frontal and ellipsoid lateral face, oildrops absent, verruculose, light brown in KOH and in distilled water, acyanophilous, inamyloid; warts usually grouped in 2 or more, bi- to trifurcate alike, 1–1.6 μm long. Chlamydospores absent.
Material examined – CHINA, Liaoning Province, Huanren County, Laotudingzi Nature Reserve, on fallen angiosperm trunk, 20 October 2015, H.S. Yuan (Yuan 10663, holotype); Qingyuan County, ecological observatory station, on fallen angiosperm trunk, 23 October 2015, H.S. Yuan (Yuan 10741).
GenBank numbers – Yuan 10663: ITS=MW033326; Yuan 10741: ITS=MW033327.
Notes – Odontia huanrenensis is closely related to O. aculeata and O. ferruginea in phylogeny (Fig. 4). Odontia huanrenensis is similar to O. aculeata in having resupinate, arachnoid, continuous basidiomata separable from the substrate, hydnoid hymenophoral surface, determinate and byssoid sterile margin, a dimitic hyphal system in the rhizomorphs, monomitic and clamped subicular hyphae, the absence of cystidia and irregular globose to ellipsoid and verruculose basidiospores (Figs. 1, 2 and 3). However, O. aculeata differs from O. huanrenensis in having thinner basidiomata (up to 0.15 mm vs. up to 0.25 mm in O. huanrenensis), longer spines (up to 1 mm vs. up to 0.4 mm in O. huanrenensis), clamped and thin-walled generative hyphae in the center of rhizomorph, thin-walled spinal tramal hyphae and shorter basidia (12–15 μm vs. 18–33 μm in O. huanrenensis) (Yuan et al. 2018). Odontia huanrenensis shares features with O. ferruginea including hydnoid basidiomata, a dimitic hyphal system in the rhizomorphs, clamped subicular hyphae and verruculose basidiospores of similar shape. However, O. ferruginea differs from O. huanrenensis in having longer spines (up to 1.75 mm vs. up to 0.4 mm in O. huanrenensis), the presence of simple-septate and pseudoskeletal hyphae in spine trama and clamped generative hyphae in rhizomorphs (Larsen 1967; Kõljalg 1996).
Figure 1 – Odontia huanrenensis (Yuan 10663, holotype): Basidiomata
Figure 2 – Odontia huanrenensis (Yuan 10663, holotype): SEM of basidiospores
Figure 3 – Odontia huanrenensis (drawn from the holotype), microscopic structures. a Section through basidiomata. b Section through rhizomorph. c Basidiospores in frontal and lateral view
Figure 4 – Maximum likelihood tree illustrating the phylogeny of Odontia huanrenensis, O. parvispina and related taxa based on ITS sequence dataset. Fifty sequences are included in the analyses. Polyzellus multiplex SMI299 was selected as the outgroup taxa. Branches are labeled with maximum likelihood bootstrap support greater than 50% (MLBS), parsimony bootstrap proportions greater than 50% (MPBS) and Bayesian posterior probabilities greater than 0.95 (BYPP). The new species and new record are in bold