Roussoella guizhouensis S. Q. Guo, K. D. Hyde & Yong Wang bis 2025, sp. nov.

Roussoella guizhouensis S. Q. Guo, K. D. Hyde & Yong Wang bis sp. nov. Fig. 4 Etymology. The name refers to Guizhou Province, where the fungus was collected. Type. China • Guizhou Province, Guiyang City, 26°6'N, 106°7'E, 1071 m, 24 September 2023, from dead bamboo culms, coll. J. F. Mo, HGUP 24-0072 (holotype), ex-type culture GUCC 24-0199 (ITS: PQ 404882, LSU: PP 949847, rpb 2: PQ 399769, ef 1 - α: PQ 438563). Description. Saprobic on dead bamboo culms. Sexual morph: undetermined. Asexual morph: Pycnidia 998–3121 × 143–853 µm (x ̄ = 1749.6 × 430.9 µm, n = 10), stromatic on the substrate, develops above the epidermis and becomes raised when mature, ellipsoidal to irregular in shape, with a rough surface ranging in color from reddish-brown to black, composed of numerous dense, glossy black stromata globules stacked layer upon layer. Stroma ranges in color from light brown to black, being transparent and shaped like a hemisphere to a near-perfect sphere, with uniform size, smooth surface, glossy, with half embedded in the natural substrate and the other half exposed, a circular aperture is present at the top. On PDA medium: Pycnidia superficial, float above the stromata, shaped like hemispheres or spheres, appearing as viscous, mucoid masses with a flat base, colour ranging from dark brown to black, lacking a pycnidial wall, release brownish-yellow conidia mass. Conidiophores reduced to conidiogenous cells. Conidiogenous cell 5–8 × 1–2 µm (x ̄ = 6.2 × 1.7 µm, n = 10), enteroblastic, indeterminate, discrete, unbranched, clavate or ampulliform to lageniform, transparent to light brown, aseptate, smooth-walled. Conidia (1.7 –) 2.2–2.3 (– 2.6) × (1.3 –) 1.5–1.6 (– 1.9) µm (x ̄ = 2.3 × 1.6 µm, n = 50), oblong to ellipsoid, with rounded to obtuse ends, light brown to transparent, smooth-walled. Culture characteristics. Under dark conditions at 25 ° C, the colony reaches a diameter of 90 mm within seven days on PDA medium. Colony is dense, exhibiting a rough surface and a regular shape with a fluffy margin. Center is velvety, characterized by a grayish-white coloration surrounded by gray margins. Reverse side is grayish-black, featuring a small grayish-white circle in the middle, which produces a black pigment. Material examined. China • Guizhou Province, Guiyang City, 26°6'N, 106°7'E, 1071 m, 24 September 2023, from dead bamboo culms, coll. J. F. Mo, HGUP 24-0072 (holotype), living culture GUCC 24-0199, GUCC 24-0200 and GUCC 24-0201. Notes. Based on the multigene phylogenetic tree (Fig. 1), our strains grouped into a distinct clade, forming a sister clade to Roussoella aquatica (MFLUCC 18-1040, Dong et al. 2020), found in submerged wood from a stream in Yunnan, China, with 100 MLBS / BIPP 1.00 statistical support. A comparison of nucleotide data within ITS and LSU loci revealed discrepancies between R. guizhouensis and R. aquatica (ITS: 16 bp and LSU: 7 bp). Morphologically, R. guizhouensis is distinguishable from R. aquatica by having larger conidiogenous cells (5–8 × 1–2 µm vs. 3–4 × 1.5–2 µm) and smaller conidia (1.8–2.7 × 1.3–1.9 µm vs. 2.7–3.5 × 2–2.5 µm). Thus, we introduce Roussoella guizhouensis as a new taxon.