Roussoella neoaquatica W.H. Tian & Maharachch., sp. nov.

Index Fungorum number: IF 901379; Mycobank number: MB 901379; Facesoffungi number: FoF 15112 Fig. 1

Etymology: Refers to the morphological similarity to Roussoella aquatica.

Holotype: HKAS 126513

Saprobic on dead culms of bamboo. Sexual morph Not observed. Asexual morph coelomycetous. Conidiomata 230–260×110–115 mm, black, scattered, forming under black, round-shape areas on the host surface, with a short neck, flattened at the base. Ostiolar neck black, short, with a large ostiole on the surface of conidiomata. Conidiophores reduced to conidiogenous cells. Conidiogenous cells 5–10×1.5–3 μm (x=7.1×2.2 μm, n=20) enteroblastic, annellidic, integrated, determinate, clavate or ampulliform to lageniform, hyaline, smooth-walled. Conidia 3.1–4.2×2.1–3 μm (x=3.7×2.6 μm, n=20), ellipsoidal, aseptate, straight, rounded at both ends, hyaline to yellow, smooth-walled.

Culture characteristics: On PDA, colony circular, covering the entire PDA tablet in 7 days at 25 °C, initially white, becoming yellowish brown after 20 days, surface rough, felt, with dense mycelium, dry, edge entire. Material examined: China: Sichuan Province, Chengdu, Guoxue Park, on dead culms of bamboo, 103° 55′ 23″ E, 30° 45′ 24″ N, 16 September 2021, W.H. Tian, W20-2 (HKAS 126513, holotype), ex-type UESTCC 22.0120.

GenBank numbers: ITS: OR762065; LSU: OR762066; tef1-α: OR763024.

Notes: The phylogenetic tree shows that the isolate UESTCC 22.0120 clusters with the ex-type strain of R. aquatica (MFLUCC 18–1040), which was introduced by Dong et al. (2020) from submerged wood in a stream in Yunnan Province, China. The BLASTn analysis of ITS of our isolate UESTCC 22.0120 showed 97% identity (534/548 bp, no gaps) with R. aquatica. Our collection shares similar morphological characteristics in the shape of conidiophores and conidia with R. aquatica (Dong et al. 2020). However, it differs from R. aquatica by having black short neck and large ostiole on the round-shape conidiomata, uniloculate, bigger conidiogenous cells (5.4–9.6×1.4–2.9 μm vs. 3–4×1.5–2 μm; (Dong et al. 2020), bigger hyaline to yellow conidia (3.1–4.2×2.1–3 μm vs. 2.7–3.5×2–2.5 μm (Dong et al. 2020). Therefore, Roussoella neoaquatica is introduced as a new species.

Figure 1 – Roussoella neoaquatica (HKAS 126513, holotype). a–c Conidiomata on bamboo host. d Section of conidiomata. e Peridium. f Conidiophores. g, h, p–s Conidiogenous cells. i–m, t–v Conidia. n–o Culture characteristics. Scale bars: d=50 μm, e, f, i=10 μm, g, h, j–m =2 μm, p–v =5 μm

Figure 2 – The phylogram of the best ML tree based on a combined dataset (LSU, ITS, rpb2 and tef1-α) of Roussoella. The scale bar indicates 0.04 changes. The tree is rooted with Torula hollandica (CBS 220.69). The best ML tree with a final likelihood value of −
17,448.644 is presented. The alignment dataset comprises 40 taxa with 3343 sites, including 1181 distinct patterns, 717 parsimony informative, 281 singleton sites and 2345 constant sites. Ultrafast bootstrap values for the maximum likelihood analysis equal to or greater than 75% and posterior probability for Bayesian analysis equal to or greater than 0.95 are indicated at the nodes. Type isolates are in bold, and the new taxa is in blue