Cylindrotrichum formosanum K. W. Cheng & H. A. Ariyaw. 2025, sp. nov.

Cylindrotrichum formosanum K. W. Cheng & H. A. Ariyaw. sp. nov. Fig. 22 Typification. TAIWAN • Guanshan Township, Taitung County, 23°02'12.8"N, 121°11'22.0"E, serpentine soil in rice field, 2 nd November 2022, K. W Cheng, holotype, NTUPPMH 22-220 (Permanently preserved in a metabolically inactive state), ex-holotype NTUPPMCC 22-287, ex-isotype NTUPPMCC 22-286. Etymology. Named after Formosa, the former name of Taiwan, where the type specimen was collected. Description. Sexual morph undetermined. Asexual morph Conidia produced on carnation leaves and WA. Conidiophores solitary, subcylindrical, light brown, unbranched, straight to slightly flexuous, and thick-walled. Conidiogenous cells subcylindrical, light brown to light gray, terminal or intercalary, with flared collarettes. Conidia solitary or aggregated in clusters, subcylindrical to slightly curved, with an obtuse apex, guttules, hyaline, smooth-walled, and 0 to 3 - septate, 13.4–19.9 µm × 3.8–6.1 µm (x ̄ = 16.3 × 4.6 µm, L / W ratio = 3.6, n = 50). Chlamydospores rusty copper-brown, circular to slightly ellipsoidal, clustered 1–3 on PDA and WA. Single chlamydospores 6.1–8.9 µm × 5.9–8.4 µm (x ̄ = 7.3 × 7.2 µm, L / W ratio = 1.0, n = 50). Culture characteristics. Colony reaching 60 mm diam with flat, spreading, gray margin and dark gray blue in the center, reverse similar. Notes. Cylindrotrichum formosanum NTUPPMCC 22-287 is typical of Cylindrotrichum in having straight to flexuous, brown, subcylindrical conidiophores, terminal or intercalary conidiogenous cells with flared collarettes, and subcylindrical, smooth, hyaline conidia (Fig. 22; Réblová et al. 2011; Crous et al. 2022). However, our strains (NTUPPMCC 22-286 and NTUPPMCC 22-287) can be easily differentiated from its closely related species based on both phylogeny and morphology (Fig. 23). C. formosanum present a distinct clade with a strongly support (96 % / 1.00) as a sister group to C. parahennebertii in our multi-locus phylogenetic analysis. Moreover, the ex-type strain of C. formosanum (NTUPPMCC 22-287) exhibits significant genetic divergence from the ex-type strain of C. parahennebertii (CBS 148282), with 84.2 % identity in the ITS region (378 / 449 bp, including 41 gaps) and 97.3 % identity in the LSU region (783 / 805 bp, including 2 gaps). Morphologically, C. formosanum produces larger conidia than C. parahennebertii (x ̄ = 16.3 × 4.6 µm versus 13.5 × 3.8 µm). Additionally, conidia of C. formosanum are 0 - to 3 - septate, whereas C. parahennebertii consistently produces distinctly 3 - septate conidia (Fig. 22; Crous et al. 2022). Beyond commonly observed morphological features, this study also reports a novel characteristic for Cylindrotrichum species: the presence of rusty copper-brown, circular to slightly ellipsoidal chlamydospores observed in culture (Fig. 22 L). Based on these molecular and morphological differences, we propose our two strains (NTUPPMCC 22-286 and NTUPPMCC 22-287) as a novel species, Cylindrotrichum formosanum.