Phaeoisaria yadongensis Y. Li, S.C. He, & Q. Zhao, sp. nov. (Fig.2)

Index Fungorum number: IF 902648; Facesoffungi number: FoF 17340

Etymology: The specific epithet refers to the locality where the fungus was collected: Yadong County, Xizang Autonomous Region, China.

Holotype: HKAS 134928.

Saprobic on the damping decayed wood in moist grass. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Colonies effuse, scattered, solitary, brown to dark brown, often obscured by a white conidial mass. Synnemata 107 – 136 μm (x = 124 μm, n = 20), synnemata base 8 – 16 μm (x = 13 μm, n = 20), synnemata middle 6 – 10 μm (x = 8 μm, n = 20), synnemata apex 3 – 7 μm (x = 5 μm, n = 20) with apical cells white, erect, brown to dark brown, composed of compactly parallel appressed conidiophores, cylindrical. Conidiophores 98 – 133 μm (x = 115 μm, n = 20), septate at the base, brown to dark brown with smooth surface. Conidiogenous cells 12 – 27 μm × 2 – 3 μm (x = 18 × 2.5 μm, n = 20), polyblastic, concentrated, smooth, every conidiogenous cells have many denticulate conidiogenous loci, hyaline to light brown, and aseptate. Conidia 5 – 6 μm × 2 μm (x = 5.5 × 2 μm, n = 30), fusiform to ellipsoid, smooth, hyaline, aseptate, and contain 1 – 2 guttulae.

Culture characteristics — Colonies on PDA reach 5 cm in diameter at 25˚C after 3 weeks of incubation. Initially smooth and buff to brown, later often with numerous synnemata. The reverse side is greyish brown at the center and olivaceous near the margin, exudate, or noticeable odour.

Material examined — CHINA, Xizang Autonomous Region, Yadong County (27° 47′ N 88° 80′ E, 4184m), on damp, decaying wood, collected on 27 July 2023, Shu-Cheng He, LY13 (HKAS 134928, holotype); ex-type culture, KUNCC 24 - 17782. ibid. LY20, (HKAS 134929, paratype), living culture, KUNCC 24 - 17883.

Notes —The multi-locus phylogenetic analysis indicated that P. yadongensis forms a sister clade with P. clematidis. Phaeoisaria yadongensis can be distinguished from P. clematidis by 1 – 2 guttules in its conidia (Luo et al. 2018). Additionally, the synnemata aspect ratio of P. yadongensis is significantly smaller than that of P. clematidis (15.5 vs. 55 μm) (Luo et al. 2018, Xu et al. 2024a). Phaeoisaria clematidis has been reported on submerged wood in freshwater habitats, including the Lancang River and Ranwu Lake, whereas P. yadongensis was collected from decaying wood (Luo et al. 2018, Xu et al. 2024a). Both species were collected from high-altitude regions, with P. yadongensis found at 4,184 m and P. clematidis at 3,850 m (Luo et al. 2018, Xu et al. 2024a). Nucleotide comparisons revealed differences between P. yadongensis and P. clematidis were detected in the ITS region (13/525, 2.09%), while no variations were observed in the LSU and SSU regions. Based on morphological and phylogenetic analyses, P. yadongensis is proposed as a novel species.