Neodigitodesmium cheirosporum W.H. Tian & Maharachch., in Tian, Chen & Maharachchikumbura, Phytotaxa 559(2): 179 (2022)

Index Fungorum number: IF 844433; MycoBank number: MB 844433; Facesoffungi number: FoF 15895

Etymology – The name refers to the cheiroid conidia

Saprobic on submerged decayed wood in aquatic habitats. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Conidiomata sporodochial on natural substrate, superficial, compact, dark brown to black, with base attached on the surface of substrate. Conidiophores micronematous, reduced to conidiogenous cell. Conidiogenous cells 7–12 × 5–11 μm (x̅ = 9 × 7 μm, n = 15), holoblastic, at the base of the spore, hyaline. Conidia 35–70 × 9–24 μm (x̅ = 57 ×19 μm, n = 30), solitary, dictyosporous, conical shaped, cheiroid, not complanate, consisting of 1–4 rows with each row composed of 6–10 cells, with a hyaline basal connecting cell, not easy to separate, brown, subhyaline at the tip of peripheral rows.

Culture characteristics – Conidia germinating on PDA within 12 h at 25 °C in the dark. Colonies on PDA circular, woolly at the margin, raised at the center, reverse yellow to brown center with a white margin.

Material examined – CHINA, Sichuan Province, Chengdu, Baiyungou, on submerged decayed wood, 103°24′19″ E, 30°47′52″ N, 27 September 2021, W. H. Tian BY112_3 (HKAS 124014, holotype), ex-type culture CGMCC 3.23623 = UESTCC 22.0020.

Notes – Combined sequences of LSU, ITS, SSU and tef1 confirmed the isolate of Neodigitodesmium formed a distinct clade in Dictyosporiaceae. However, it could not assign to any known genera (FIG. 1). In the combined gene tree, Neodigitodesmium is phylogenetically related to the Vikalpa australiensis (HKUCC 8797), Aquadictyospora lignicola (MFLUCC 17-1318) and Aquadictyospora clematidis (MFLUCC 17-2080) (FIG. 1), but they are not clustered on one branch and have obvious morphological differences. Neodigitodesmium is morphologically similar to Digitodesmium, both having sporodochial conidiomata and acrogenous, cheiroid, digitate conidia (Kirk 1981; Nóbrega et al. 2021). However, Neodigitodesmium differs from Digitodesmium and other Dictyosporiaceae members in conical-shaped conidia, composed of 1–4 compactly arranged rows of dark brown cells, with a hyaline basal connecting conidiogenous cells (FIG. 1). Therefore, Neodigitodesmium is described as a new genus based on phylogeny and morphological evidence.

Figure 1 – Neodigitodesmium cheirosporum (HUEST 22.0020, holotype). a–c Colonies on the substrate d Squash mount of sporodochium e, f, k Conidiogenous cells g–j Conidia l–n Crushed conidium o Germinating conidium p, q Colonies on PDA after 30 days. Scale bars: d = 20 μm, e–o = 10 μm, Scale bars of e applies to e and f, Scale bars of g applies to g–o.