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

Kirschsteiniothelia xishuiensis X. J. Xiao, Y. Z. Lu & K. D. Hyde sp. nov. Fig. 4 Etymology. Referring to the collecting location at Xishui District in China. Holotype. HKAS 132145. Description. Saprobic on decaying wood in a terrestrial habitat. Sexual morph: Undetermined. Asexual morph: Colonies on natural substrate effuse, dark brown to black, hairy. Mycelium immersed, composed of brown to dark brown, branched, septate, smooth hyphae. Conidiophores 170–280 × 8–13 µm (x ̄ = 207 × 10.5 µm, n = 20), macronematous, mononematous, erect, straight to slightly curved, unbranched, cylindrical, dark brown, multi-septate, thick-walled. Conidiogenous cells 13–17.5 × 5.5–9 µm (x ̄ = 15.5 × 7 μm, n = 20), monoblastic, integrated, terminal, cylindrical, mid to dark brown. Conidia 35.5–67.5 × 11–20 µm (x ̄ = 48.5 × 15.5 μm, n = 20), acrogenous, solitary, dry, olivaceous brown to soot brown, paler at apex, obclavate, rostrate, straight or curved, truncate at base, septate, constricted at septa, with an apical, hyaline, mucilaginous sheath, 13–39 × 14–35 µm (x ̄ = 24 × 23 μm, n = 20). Cultural characteristics. Conidia germinating on PDA medium within 12 h and germ tube produced from truncate end. Colonies on PDA medium reaching to 35 mm diam in 35 days at 28 ° C in natural light, circular, dense, mycelium slightly aerial, with irregular margin, grayish brown at center, yellowish brown at outer ring from above and below. Material examined. China • Guizhou Province, Xishui County, Guizhou Xishui National Nature Reserve, 28 ° 33 ' 50 " N, 106 ° 24 ' 9 " E, on decaying wood in a forest, 3 October 2023, Xingjuan Xiao, S 12 (HKAS 132145, holotype), ex-type living strain GZCC 24-0052. Notes. Phylogenetically, Kirschsteiniothelia xishuiensis (GZCC 24-0052) formed a distinct clade basal to K. submersa (S- 481, S- 601, and MFLUCC 15-0427), K. sichuanensis (UESTCC 24.0127) and K. extensum (MFLU 21-0130) (Fig. 1). BLASTN analysis of K. xishuiensis (GZCC 24-0052) reveals 93 % identity (452 / 483, 7 gaps) to K. submersa (S- 601) in the ITS gene region. Similarly, K. xishuiensis shows 93 % identity (410 / 443, 4 gaps) to K. sichuanensis (UESTCC 24.0127) and 93 % identity (463 / 497, 5 gaps) to K. extensum (MFLU 21-0130) when analyzed using ITS. Morphologically, K. xishuiensis is similar to K. extensum in having straight to slightly curved, unbranched, cylindrical, dark brown, multi-septate conidiophores, but differs from K. extensum in having shorter and wider conidia with a gelatinous rounded sheath at the apex (35.5–67.5 × 11–20 µm vs. 45–120 × 5–12 μm), and larger conidiophores (170–280 × 8–13 μm vs. 80–230 × 6.5–9.5 μm) (Jayawardena et al. 2022). Therefore, we propose K. guizhouensis as a new species based on both morphology and molecular data.