Xylodon muchuanensis Xue W. Wang & L.W. Zhou, sp. nov.

Index Fungorum number: IF 900297;  Mycobank number: MB 900297; Facesoffungi number: FoF 14060; Figs. 1, 2

Etymology – muchuanensis (Lat.) referring to the type locality Muchuan County, Sichuan Province, China.

Holotype – LWZ 20200819-2b (HMAS).

Diagnosis – Characterized by annual, resupinate, adnate basidiomes, poroid, cream to buff hymenophore, a monomitic hyphal system, the presence of capitate cystidia, clavate to subcylindrical basidia, and broadly ellipsoid basidiospores.

Basidiomes annual, resupinate, adnate, cracked and brittle when dry. Hymenophore poroid, cream to buff at young prat and cinnamon-buff at old part. Margin concolorous or slightly paler than subiculum, abrupt.

Hyphal system monomitic; generative hyphae with clamp connections, hyaline, dichotomous branching, interwoven, slightly thick-walled, 3.5–4.5 μm in diam, occasionally with encrustation. Capitate cystidia embedded in hymenium, ca. 30×3.5 μm, with a round swollen top, about 7.5–8.5 μm in diam. Basidia clavate to subcylindrical, 15–20×4–5 μm, with four sterigmata and a clamp connection at the base; basidioles similar in shape to basidia but smaller. Basidiospores broadly ellipsoid, with an oily drop, hyaline, smooth, thin-walled, IKI–, slightly CB+, (4.1–)4.2–5.2(–5.3)×3.1–3.6 μm, L=4.46 μm, W=3.32 μm, Q=1.33–1.36 (60/2).

Material examined – China, Sichuan Province, Leshan, Muchuan County, on fallen branch of angiosperm, 19 August 2020, L.W. Zhou, LWZ 20200819-2b (HMAS, holotype); ibid., on fallen trunk of angiosperm, 19 August 2020, L.W. Zhou, LWZ 20200819-3a (HMAS).

GenBank numbers – LWZ 20200819-2b: ITS=OQ540902; LSU = OQ540861; LWZ 20200819-3a: ITS= OQ540903; LSU=OQ540862.

Notes – Phylogenetically, Xylodon muchuanensis groups with several other poroid species of Xylodon (Fig. 3). Of these species, X. muchuanensis is most similar to X. taiwanianus by sharing poroid hymenophore and ellipsoid basidiospores; however, Xylodon taiwanianus differs from X. muchuanensis by its suburniform basidia and the presence of resinous matter on the top of capitate cystidia (Wu 2001).

Figure 1 – Basidiomes of Xylodon muchuanensis (LWZ 20200819-2b, holotype)

Figure 2 – Microscopic structures of Xylodon muchuanensis (LWZ 20200819-2b, holotype). a Basidiospores b Basidia c Cystidia d Basidioles e Section through a basidiomes. Scale bars: a=5 μm, b–e=10 μm

Figure 3 – Phylogram generated by the maximum likelihood algorithm based on combined nLSU and ITS sequence data is presented along with the bootstrap values and the Bayesian posterior probabilities above 50% and 0.8, respectively, at the nodes. Type specimens are in bold and the isolates of new species characterized are in blue