Xenosporidesmium lignicola Y. Wang, H. W. Shen & Z. L. Luo 2026, sp. nov.

Xenosporidesmium lignicola Y. Wang, H. W. Shen & Z. L. Luo sp. nov. Fig. 2 Chinese name. 木生异葚孢 (Pinyin: mù shēng yì shèn bāo). Etymology. “ lignicola ” refers to the species inhabiting woody substrates. Holotype. HKAS 135961. Description. Saprobic on submerged decaying wood in freshwater habitat. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Colonies on superficial substratum, effuse, dark olivaceous, hairy. Mycelium mostly superficial, partly immersed, composed of branched, septate, hyaline to pale brown, smooth-walled hyphae. Conidiophores (26.5 –) 34–49 (– 60) × 3.2–4.5 μm (x ̄ = 41 × 3.9 μm, n = 40) mononematous, macronematous, erect, solitary or in small groups, cylindrical, straight or flexuous, brown to olivaceous brown, 2–4 - septate, mostly 3 - septate, truncate at the apex and tapering towards the rounded apex, slightly swollen at the base, smooth-walled. Conidiogenous cells 12.5–16.7 (– 19.7) × 3.5–4.5 μm (x ̄ = 14.7 × 3.9 μm, n = 40), monoblastic, integrated, terminal, cylindrical, narrowing at the tip, brown to olivaceous brown, smooth-walled. Conidia (27 –) 32–40 (– 43) × 8–10 (– 12) μm (x ̄ = 36 × 9.3 μm, n = 40) acrogenous, solitary, broadly fusiform to obclavate, pale brown to olivaceous brown, hyaline at apex, straight or slightly curved, 6–8 - distoseptate, rounded at the apex, truncate at the base, guttulate, smooth-walled, apical 1 (– 2) cells surrounded by a thin, subglobose mucilaginous sheath, 7–11 μm diam. Culture characteristics. Conidia germinating on PDA within 12 h producing germ tubes from the ends of conidium. Colonies growing on PDA for one month at room temperature in the dark. In surface view, colonies are pale yellowish-brown to beige, with a darker brown central zone, in reverse view, pale yellowish-brown to beige. Material examined. China, Yunnan Province, Dulongjiang River, 28.033444°N, 98.317358°E (elevation 1702 m), on submerged decaying wood, 1 May 2023, Ying Wang, S 4446 (HKAS 135961, holotype), ex-type culture, CGMCC 3.27664 = KUNCC 23-15808. Notes. In multigene phylogenetic analyses, Xenosporidesmium lignicola formed a well-supported clade together with X. aquaticivaginatum (MFLUCC 15-0624), X. bostenicum (KUNCC 22-10417), X. guttulatum (KUNCC 23-13374), X. nujiangense (DLUCC 983; KUNCC 23-14318), X. olivaceoconidium (MFLUCC 15-0380), and X. yangzonghaiense (KUNCC 23-14290), but was resolved as a genetically distinct lineage (Fig. 1). Morphologically, X. lignicola conforms to the diagnostic characters of Xenosporidesmium in possessing macronematous, mononematous, cylindrical, septate conidiophores; holoblastic, monoblastic, integrated, terminal, determinate, cylindrical, smooth conidiogenous cells, occasionally proliferating percurrently; acrogenous, obclavate, pale brown to olivaceous, straight or curved, distoseptate conidia that are paler toward the apex and bear an apical appendage or a mucilaginous sheath. Nevertheless, X. lignicola can be distinguished from its phylogenetically closely related species by a combination of morphological characteristics, as summarized in Table 1.