Henningsomyces hengduanensis S.L. Liu & L.W. Zhou, sp. nov.

Index Fungorum number: IF 901053; Mycobank number: MB 901053; Facesoffungi number: FoF 14807; Figs. 1, 2

Etymology – hengduanensis (Lat.) referring to the type locality Hengduan Mountains.

Holotype – LWZ 20190807-11b (HMAS).

Diagnosis – Differing from Henningsomyces minimus in smaller tubes and smaller basidiospores (Wei and Qin 2009).

Basidiomes annual, soft when fresh, becoming a little chalky when drying, without odour or taste, white when fresh, turned cream when bruised or drying, consisting of tiny tubes. Tubes densely aggregated, each 0.2–0.3 mm long, 0.07–0.1 mm in diam. Subiculum absent.

Hyphal system monomitic; generative hyphae bearing both clamp connections and simple septa; tramal hyphae in tubes hyaline, smooth, thin-walled, often branched, winding, more or less tightly parallel along the tubes, 1.5–2 μm in diam; hyphae at tube margin finely branched. Cystidia absent. Basidia broadly clavate, with four sterigmata and a basal clamp connection, 15–20 × 6–8 μm. Basidiospores subglobose, hyaline, thin-walled, smooth, IKI–, CB–, 5–6×(4–)4.5–5 µm, L=5.5 µm, W=4.7 µm, Q=1.2 (n=60/2).

Material examined – China, Sichuan Province, Ganzi Tibetan Autonomous Prefecture, Jiulong County, Wahuishan Nature Reserve, on fallen trunk of Abies, 7 August 2019, L.W. Zhou, LWZ 20190807-11b (HMAS, Holotype); ibid., on fallen trunk of Abies, 7 August 2019, L.W. Zhou, LWZ 20190807-22b (HMAS).

GenBank numbers – LWZ 20190807-11b: ITS=OR557250, LSU=OR527276; LWZ 20190807-22b: ITS=OR557251, LSU=OR527277.

Notes – Henningsomyces hengduanensis has typical morphological characters of this genus, and falls within the clade of Henningsomyces as a distinct lineage (Fig. 3). Morphologically, H. hengduanensis resembles H. candidus, H. leptus and H. minimus by the absence of subiculum, but differs mainly in its smaller tubes (0.5–1 mm in length and about 0.2 mm in diam in H. candidus, 1.2–1.8 mm in length and 0.1–0.15 mm in diam in H. leptus, and up to 0.5 mm in length and 0.1 mm in diam in H. minimus; Wei and Qin 2009).

Figure 1 – Basidiomes of Henningsomyces hengduanensis (LWZ 20190807-11b, holotype). Scale bars: a=1 cm, b=1 mm

Figure 2 – Microscopic structures of Henningsomyces hengduanensis (LWZ 20190807–11, holotype). a A vertical section of basidiomes. b Basidia and basidioles. c Hyphae from tube margin. d Basidiospores. Scale bars: 10 μm

Figure 3 – Phylogeny generated by the maximum likelihood algorithm based on combined ITS and nLSU regions is presented along with the bootstrap values and the Bayesian posterior probabilities above 50% and 0.8, respectively, at the nodes. Holotypes are in bold and the newly generated sequences are in blue. Radulomyces copelandii Dai 15061 and Pterula echo AFTOL-ID 711 were selected as the outgroup taxa