Pseudocosmospora chlamydospora Xiao Qian Wu, Z. Q. Zeng & W. Y. Zhuang 2026, sp. nov.

Pseudocosmospora chlamydospora Xiao Qian Wu, Z. Q. Zeng & W. Y. Zhuang sp. nov. Figs 2, 3 Etymology. The specific epithet refers to the chlamydospores produced in culture. Typification. China • Beijing City, Miyun District, roadside near Miyun Reservoir, on fruitbodies of Paraeutypella karsti growing on rotten bark, 8 September 2022, W. Y. Zhuang, Z. Q. Zeng & H. D. Zheng, 13067 (holotype HMAS 255842, ex-type culture CGMCC 3.29438). Description. Mycelium not visible on natural substratum. Perithecia superficial, solitary to gregarious, non-stromatic or with a basal stroma, subglobose to globose with a truncate apex, laterally collapsed upon drying, orange-red to bright red, turning dark red in 3 % KOH, becoming light yellow in 100 % LA, 144–217 × 101–185 μm. Perithecial walls of two layers, 17–28 μm thick; the outer layer of textura angularis, 10–21 μm thick, cells 2.5–8 × 1.6–4.1 μm, walls 0.9–1.4 μm thick; the inner layer of textura prismatica, 5–10 μm thick, cells 4.7–13.2 × 1.6–3.3 μm, walls 0.8–1.3 μm thick. Asci clavate, with a simple apex, eight-spored, 42.7–56.7 × 3.4–5.7 μm. Ascospores ellipsoidal, 1 - septate, hyaline to light yellow-brown, smooth-walled, uniseriate, overlapping obliquely, 5.9–8.8 × 3–4.7 μm. Colony characteristics. Colony on PDA 43 mm diam. after 28 d at 25 ° C, crustose, beige, light yellow to salmon-pink, on SNA 44 mm in diam. after 28 d at 25 ° C, with sparse whitish aerial mycelium. Conidiophores acremonium- to verticillium-like, septate, of indefinite length, hyaline, with 1–2 whorls and a terminal whorl of 2–4 phialides. Phialides subulate, tapering toward the apex, 5–24 μm long, 1.1–1.9 μm wide at the base, 0.6–1.2 μm wide at the tip. Conidia rod-shaped, fusiform, ellipsoidal, lemon-shaped or subglobose, rare clavate, unicellular, smooth, hyaline, non-guttulate, 2.5–5.7 × 1.3–2.7 μm. Chlamydospores globose to subglobose, rarely oblong, smooth-walled, hyaline, 3.4–8.4 μm in diam. Notes. Amongst the known species of Pseudocosmospora, P. chlamydospora most resembles P. rogersonii in similar host fungus, subglobose perithecia with a truncate apex, ellipsoidal and smooth ascospores, and pink colony on PDA (Herrera et al. 2013). However, the new species differs in having smaller asci (42.7–56.7 × 3.4–5.7 μm vs. 54–69 × 5.7–8.4 μm), shorter ascospores (5.9–8.8 μm vs. 7.9–12.2 μm), and producing globose to subglobose chlamydospores. Sequence comparisons revealed that there were 8 bp, 12 bp, 81 bp, 102 bp and 103 bp divergences detected for the ITS, LSU, tub 2, rpb 1 and tef 1 - α regions between P. chlamydospora and P. rogersonii (Table 3). The multi-gene phylogenetic analyses showed that P. chlamydospora is closely related to P. curvispora and two unnamed species (MLBS / MPBP / BIPP = 100 % / 100 % / 1.0). However, P. chlamydospora can be easily distinguished by its shorter asci (42.7–56.7 µm vs. 53–68 µm) and ascospores (5.9–8.8 µm vs. 8–10 µm), wider conidia (1.3–2.7 µm vs. 0.8–1.2 µm), and forming globose to subglobose chlamydospores (Zeng and Zhuang 2021) (Table 4). Thus, both the morphological feature and sequence data indicated that they represent different taxa.