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

Pseudocosmospora chloroxantha Xiao Qian Wu, Z. Q. Zeng & W. Y. Zhuang sp. nov. Figs 4, 5 Etymology. The specific epithet refers to the greenish yellow pigments on surface of colony. Typification. China • Beijing City, Yanqing District, Baili Landscape Gallery, on Paraeutypella karsti growing on rotten bark, 31 August 2022, W. Y. Zhuang, Z. Q. Zeng & H. D. Zheng, 13057 (holotype HMAS 255843, ex-type culture CGMCC 3.29437). Description. Mycelium not visible on the natural substratum. Perithecia superficial and gregarious, non-stromatic or with a basal stroma, subglobose to globose with a truncate apex, laterally collapsed upon drying, bright red to brownish red, turning dark red in 3 % KOH, becoming light yellow in 100 % LA, 132–230 × 127–210 μm. Perithecial walls of two-layers, 19–37 μm thick; the outer layer of textura globulosa to t. angularis, 11–24 μm thick, cells 2.8–11.7 × 2–5.5 μm, walls 0.8–1.4 μm thick; the inner layer of textura prismatica, 9–15 μm thick, cells 5.9–14.5 × 1.6–3.1 μm, walls 0.8–1.7 μm thick. Asci cylindrical to clavate, with a simple apex or with an apical ring, eight-spored, 53–76.8 × 4.7–9.2 μm. Ascospores ellipsoidal to broad ellipsoidal, 1 - septate, hyaline to light yellow-brown, smooth-walled, uniseriate, overlapping obliquely, 7.1–11.5 × 3.7–6.3 μm. Colony characteristics. Colony on PDA 46 mm in diam. after 28 d at 25 ° C, crustose, surface greenish yellow and reverse yellowish-brown, on SNA 42 mm in diam. after 28 d at 25 ° C, with sparse whitish aerial mycelium. Conidiophores acremonium- to verticillium-like, septate, of indefinite length, and hyaline, with 1–2 whorls and a terminal whorl of 2–4 phialides. Phialides subulate, tapering toward the apex, 9.6–31.1 μm long, 0.9–2 μm wide at the base, 0.8–1.4 μm wide at the tip. Conidia rod-shaped to cylindrical, rarely ellipsoidal, unicellular, smooth-walled, hyaline, non-guttulate, 2.6–8.5 × 1.2–2.4 μm. Notes. Among the existing species of the genus, P. chloroxantha is morphologically similar to P. rogersonii and P. chlamydospora in having similar hosts, subglobose and laterally collapsed perithecia with a truncate apex, ellipsoidal and smooth ascospores, and conidia without guttules (Herrera et al. 2013). However, P. chloroxantha differs from P. rogersonii in longer conidia (2.6–8.5 μm vs. 2.9–5.5 μm) and rod-shaped to cylindrical conidia, and differs from P. chlamydospora in larger asci (53–76.8 × 4.7–9.2 μm vs. 42.7–56.7 × 3.4–5.7 μm), longer ascospores (7.1–11.5 μm vs. 5.9–8.8 μm), rod-shaped to cylindrical conidia, and the absence of chlamydospores. Additionally, there were 15 bp, 4 bp, 81 bp, 98 bp and 101 bp nucleotide divergences between the type of P. chloroxantha and P. rogersonii, and 10 bp, 8 bp, 70 bp, 82 bp and 84 bp unmatched loci were found between the type of P. chloroxantha and P. chlamydospora in the ITS, LSU, tub 2, rpb 1 and tef 1 - α regions (Table 3). Phylogenetic analyses showed that P. chloroxantha is closely associated with P. beijingensis with strong support (MLBS / MPBP / BIPP = 98 % / 80 % / 1.0). However, the P. chloroxantha differs morphologically from the latter in having larger asci (53–76.8 × 4.7–9.2 µm vs. 38–58 × 2.5–5 μm), wider ascospores (3.7–6.3 µm vs. 2.5–4 µm), production of greenish yellow pigments in culture, and longer conidia (2.6–8.5 µm vs. 2.6–4.5 µm) (Table 4). Therefore, both morphological and molecular data support the establishment of P. chloroxantha.