Helicosporium phellodendri S. P. Zou, Y. P. Xiao & Y. Z. Lu 2026, sp. nov.

Helicosporium phellodendri S. P. Zou, Y. P. Xiao & Y. Z. Lu sp. nov. Fig. 3 Etymology. the specific epithet “ phellodendri ” refers to the host genus name “ Phellodendron ” from which the fungus was isolated. Holotype. HKAS 145879. Description. Saprobic on dead wood of Phellodendron amurense. Sexual morph Undetermined. Asexual morph Hyphomycetous, helicosporous. Colonies on natural substrate superficial, effuse, gregarious, with masses of crowded, glistening conidia, yellowish-green. Mycelium partly immersed, partly superficial, composed of pale brown to brown, branched, septate, guttulate, smooth hyphae. Conidiophores 89–97 × 4–5 μm (x ̄ = 94 × 4.5 μm, n = 20), macronematous, mononematous, erect, cylindrical, straight or broadly curved, simple or occasionally branched, septate, brown at base, paler towards the apex, thick-walled. Conidiogenous cells 9.5–10.5 × 3.5–4.8 μm (x ̄ = 10 × 4.3 μm, n = 15), holoblastic, monoblastic, integrated, intercalary, cylindrical, pale brown to brown, smooth-walled. Conidia solitary, pleurogenous, helicoid, tapering towards the ends, 10.5–12.5 μm diam. and conidial filament 1.5–2 μm wide (x ̄ = 11.5 × 1.8 μm, n = 25), 60–65 μm long (x ̄ = 63 μm, n = 25), tightly coiled 2 ½ – 3 times, not becoming loose in water, multi-septate, hyaline, smooth-walled. Culture characteristics. Conidia produce germ tubes on PDA within 14 hours of incubation at 25 ° C. Colonies on PDA are circular, with a flat surface and entire edge, reaching a diameter of 26 mm after 36 days of incubation at 25 ° C. The colony appears dark brown to black at centre, brown at outer ring on the top view and brown on the reverse view. Material examined. China • Guizhou Province, Guiyang City, Qingzhen City, Maige Miao and Bouyei Ethnic Township, Xiaochong Village, 26°74′N, 106°37′E, on the rotting wood of Phellodendron amurense, 1 October 2024, Shi-Ping Zou, HB-Z 17-1 (HKAS 145879, holotype), ex-type culture GZCC 25-0005 • Ibid., HB-Z 17-2 (HKAS 145878), living culture GZCC 25-0006. Notes. Morphological examination indicated that Helicosporium phellodendri conforms to the generic concept of Helicosporium, characterised by pale yellow to yellow-green colonies on the natural woody substratum, erect setiferous cylindrical conidiophores with denticulate conidiogenous cells and hyaline to yellow-green helicoid conidia which are mainly becoming loosely coiled in water (Ma et al. 2024 b). Helicosporium phellodendri is morphologically similar to H. multidentatum, but differs in having longer conidia (105–130 μm vs. 60–65 μm), with more coils (3 ¼ – 3 ¾ vs. 2 ½ – 3). Furthermore, the conidia of H. multidentatum become loosely coiled in water, while those of H. phellodendri do not loosen (Xiao et al. 2023). Phylogenetic analysis (Fig. 1) also supports that H. phellodendri and H. multidentatum are distinct species. Strains GZCC 25-0005 and GZCC 25-0006 formed a well-supported, independent lineage within Helicosporium (Fig. 1). Helicosporium viridisporum and H. sexuale are closely related to H. phellodendri. However, H. viridisporum can be distinguished from H. phellodendri by its longer conidiophores (69–189 × 3–5 μm vs. 89–97 × 4–5 μm), denticulate conidiogenous cells and acropleurogenous, aseptate conidia (Lu et al. 2022). Helicosporium sexuale displays sexual morph (Boonmee et al. 2021), whereas, H. phellodendri exhibits asexual morph. Therefore, H. phellodendri is introduced here as a novel species.