Cosmospora elegans Czachura & Janik 2025, sp. nov.

Cosmospora elegans Czachura & Janik sp. nov. Figs 3, 4 Etymology. The name refers to the visually attractive appearance of cultures of this species. Typus. Poland, Małopolskie Province, Tatra County, the Tatra National Park, Dolina Białego, isolated from the resin of Picea abies, 16. Jul. 2021, leg. P. Czachura (holotype: KRAM F-60000; culture ex-type: CBS 152410). Description. Mycelium consisting of branched, septate, hyaline to subhyaline or yellowish orange in mass, smooth hyphae, 1.7–4.2 µm diam., with occasional anastomoses. Chlamydospores rarely formed, subglobose to broadly ellipsoidal, hyaline to subhyaline, smooth, aseptate, 8.1–13.1 × 6.1–9.5 µm, intercalary or terminal, single. Conidiophores arising laterally or terminally from somatic hyphae, 20.2–74.7 μm long, unbranched or branched, hyaline, smooth- and thin-walled, bearing terminal and lateral conidiogenous cells, or reduced to single conidiogenous cells borne laterally or terminally on aerial hyphae. Conidiogenous cells monophialidic, subulate or subcylindrical, hyaline, smooth- and thin-walled, 20.2–55.4 μm long, at the base 2.0–3.3 μm wide and at the apex 1.2–1.9 μm wide, without noticeable periclinal thickening, collarettes absent or sometimes a minute apical collarette can be present. Microconidia ellipsoidal, cylindrical, slightly allantoid or obovoid to clavate, hyaline, smooth- and thin-walled, aseptate, 3.5–14.7 × 2.3–3.8 μm. Culture characteristics. Colony on MEA umbonate with fimbriate margin, slightly radially folded from the colony centre toward margin, yellow with white margin, reaching 21 mm diam. after 2 weeks at 15 ° C and 35 mm diam. after 2 weeks at 25 ° C, reverse luteous. Colony on OA flat with slightly fimbriate margin, whitish to creamy with yellowish margin, reaching 21 mm diam. after 2 weeks at 15 ° C and 39 mm diam. after 2 weeks at 25 ° C, reverse fuscous black to pale brown at margin. Colony on PDA umbonate with fimbriate margin, radially folded from the colony centre toward margin, creamy at centre becoming yellow toward the outer part of colony with white margin, reaching 20 mm diam. after 2 weeks at 15 ° C and 34 mm diam. after 2 weeks at 25 ° C, reverse bright luteous with whitish margin. Colony on SNA flat with slightly undulate and slightly fimbriate margin, whitish, reaching 22 mm diam. after 2 weeks at 15 ° C and 40 mm diam. after 2 weeks at 25 ° C, reverse whitish. Notes. Cosmospora elegans clusters as a fully-supported lineage (MLB = 100 %, BPP = 1) to the closest phylogenetic relative – Cosmospora viridescens (Fig. 2), from which it can be differentiated mainly by the size and the shape of conidia. C. elegans has more elongated conidia in shape (mostly ellipsoidal and cylindrical) and larger in size (3.5–14.7 μm) in contrast to C. viridescens whose conidia are globose or reniform and reaching 4–8 μm long (Booth 1959). Additionally, C. elegans has smaller conidiophores which reach 74.7 μm in length in the type specimen whereas conidiophores of C. viridescens reach 500 μm (Booth 1959). Moreover, C. elegans rarely forms single chlamydospores in contrast to C. viridescens in which chlamydospores are absent (Booth 1959).