Kirschsteiniothelia guizhouensis X. J. Xiao, Y. Z. Lu & K. D. Hyde 2025, sp. nov.

Kirschsteiniothelia guizhouensis X. J. Xiao, Y. Z. Lu & K. D. Hyde sp. nov. Fig. 3 Etymology. Referring to the collecting location at Guizhou Province in China. Holotype. HKAS 139503. Description. Saprobic on submerged decaying wood in a freshwater habitat. Sexual morph: Undetermined. Asexual morph: Colonies on natural substrate effuse, dark brown to black with white tip, hairy. Mycelium immersed, composed of brown to dark brown, branched, septate, smooth hyphae. Conidiophores 195–477 × 11–16 μm (x ̄ = 307 × 13.5 µm, n = 20), macronematous, mononematous, erect, straight to slightly curved, apically branched, cylindrical, tapering towards the apex, dark brown, multi-septate, thick-walled. Conidiogenous cells 5.5–16 × 4.5–8 μm (x ̄ = 11 × 6 µm, n = 30), monoblastic, integrated and discrete, terminal at the apex of the stem and branches, subcylindrical, light to dark brown. Conidia 36.5–65 × 8–16.5 μm (x ̄ = 50 × 12.5 µm, n = 20), acrogenous, solitary, dry, olivaceous brown to brown, pale brown to hyaline at the apex, obclavate, sometimes apical cell swollen to subglobose, rostrate, straight or curved, truncate at base, septate, slightly constricted at septa, with an apical, hyaline, mucilaginous sheath, 14–39 × 14–36 μm (x ̄ = 23 × 23 µm, n = 20). Cultural characteristics. Conidia germinating on PDA medium within 24 h and germ tube produced from apex. Colonies on PDA medium reaching to 19.5 mm diam in 13 days at 28 ° C in natural light, circular, dense, mycelium slightly aerial, with entire edge, dark green from above and below. Material examined. China • Guizhou Province, Xishui County, Guizhou Xishui National Nature Reserve, 28 ° 9 ' 17 " N, 105 ° 55 ' 50 " E, on decaying wood in freshwater, 2 October 2023, Xingjuan Xiao, NJS 11 (HKAS 139503, holotype), ex-type living strain GZCC 24-0034; • Ibid., NJS 36.1 (HKAS 139504, paratype), living strain GZCC 24-0041. Notes. In the phylogenetic tree, our strains (GZCC 24-0034 and GZCC 24-0041) cluster together, forming a sister clade to Kirschsteiniothelia acutisporum (MFLU 21-0127) (Fig. 1). A comparison of nucleotides between K. guizhouensis (GZCC 24-0034) and K. acutisporum showed similarity rates in the ITS 77 % (407 / 528 bp, 36 gaps), LSU 93 % (785 / 847 bp, 13 gaps), and SSU 96 % (818 / 849 bp, 2 gaps), indicating significant differences between the two species. Morphologically, our species exhibits distinct characteristics compared to K. acutisporum, including smaller conidia with a mucilaginous sheath (36.5–65 × 8–16.5 µm vs. 75–120 × 10.5–19.5 μm), and longer conidiophores which are branched at the apex (195–477 × 11–16 μm vs. 180–260 × 7–12.5 μm) (Jayawardena et al. 2022). Therefore, we propose K. guizhouensis as a new species.