Pleurothecium aquisubtropicum J. Ma, Y.Z. Lu & K.D. Hyde, sp. nov.

Index Fungorum number: IF 559508; MycoBank number: MB 559508; Facesoffungi number: FoF 08709; Fig. 1

Etymology – Referring to the aquatic habitat and collecting site in subtropical country, China.

Holotype – GZAAS 21–0384

Saprobic on decaying wood in a freshwater stream. Asexual morph: Colonies on natural substrate superficial, effuse, brown or dark brown, smooth. Mycelium immersed or superficial, smooth. Conidiophores 82–177×3.5–5.5 μm (x̄ =121.3×4.3 μm, n=20), macronematous, mononematous, sucylindrical, straight, unbranched, smooth, septate, brown, paler towards the apex. Conidiogenous cells 25–38×2.7–3.8 μm (x̄ =29.6×3.2 μm, n=15), holoblastic, polyblastic, integrated, terminal, subhyaline to pale brown, subcylindrical. Conidia 13.4–15.5 × 3.4–5.5 μm ( x̄ = 14.4 × 4.4 μm, n = 21), acrogenous, solitary, aseptate, pale brown, straight, guttulate, hyaline or pale green, smooth. Sexual morph: Not observed.

Culture Characters – Colonies growing slowly on PDA, reaching 37 mm in 35 days at 25 °C, flat, filiform, round, gray or white, smooth; In reverse, milky at the center, brown or dark brown at the margin.

Material examined – China, Guizhou Province, Xishui County, on decaying wood submerged in a freshwater stream, 13 February 2021, Jian Ma, TL2(GZAAS 21–0384, holotype); ex–type living culture, GZCC 21–0670.

GenBank numbers – OM339436 (ITS), OM339433 (LSU)

Notes – Our new collection fits well with the generic concept of Pleurothecium in having macronematous, mononematous, brown conidiophores, polyblastic, integrated conidiogenous cells and septate, smooth allantoid  or fusiformis conidia. In our phylogenetic analyses, our new collection of Pleurothecium aquisubtropicum was placed within Pleurothecium and is basal to other Pleurothecium species (Fig. 2). Pleurothecium aquisubtropicum resembles P. aquaticum in the shape of the conidiophores, and conidia (Luo et al. 2018a, b). However, Pleurothecium aquisubtropicum differs from P. aquaticum by its darker and longer conidiophores (82–177 μm vs 53–65 μm) and smaller conidia (13.5–15.5 × 3–5.5 μm vs 19–21 × 4.5–5.5 μm). Hence, based on both morphology and phylogeny, we introduce our collection as a new species of Pleurothecium aquisubtropicum.

Figure 1 – Pleurothecium aquisubtropicum (GZAAS 21–0384, holotype) a Colony on decaying wood b–c Conidiophores with attached conidia d–g Conidiogenous cells and conidia h–j Conidia k Germinating condium l–m Colony on PDA from above and below. Scale bars: b, c=20 μm, d–k=10 μm

Figure 2 – Phylogram generated from maximum likelihood analysis based on combined LSU and ITS sequence data. Twenty–six taxa were included in the combined analyses, which comprised 1420 characters (LSU: 910, ITS: 510) after alignment. The best scoring RA×ML tree with a final likelihood value of is presented. Bootstrap support values for ML≥50% and BYPP≥0.95 are given above the nodes. The tree is rooted with Conioscypha lignicola CBS 335.93 and C. japonica CBS 387.84