Dimorphiseta formosana K. W. Cheng & H. A. Ariyaw., 2025

Cheng, Kai-Wen, Yang, Jiue-in, Srimongkol, Piroonporn, Stadler, Marc, Karnchanatat, Aphichart & Ariyawansa, Hiran A., 2025, Fungal frontiers in toxic terrain: Revealing culturable fungal communities in Serpentine paddy fields of Taiwan, IMA Fungus 16, pp. e 155308-e 155308 : e155308-

Dimorphiseta formosana K. W. Cheng & H. A. Ariyaw. sp. nov.

Fig. 29

Typification.

TAIWAN • Wanrung Township , Hualien County, 23°42'40.3"N, 121°24'48.2"E, serpentine soil in rice field, 2 nd November 2022, K. W Cheng, holotype, NTUPPMH 22-224 (Permanently preserved in a metabolically inactive state), ex-holotype NTUPPMCC 22-291 .

Etymology.

Named after Formosa, the former name of Taiwan, where the type specimen was collected.

Description.

Sexual morph undetermined. Asexual morph No sporulation on PDA and MEA, conidiomata produced very few on carnation leaves and surface of WA. Conidiomata 260–460 µm diam, randomly scattered, superficial, sporodochial, stromatic, subglobose to irregular in outline, dark green to black, agglutinated slimy mass of conidia. Setae thick-walled, hyaline, smooth, septate, straight to slightly curved, tapering to sharp apices, 170–240 µm long, 4–6 µm wide at broadest part. Conidiophores unbranched, hyaline to green, smooth to lightly verrucose, arising from basal stroma. Conidiogenous cells phialidic, hyaline, cylindrical, smooth, with collarette at tip, 17.2–22.7 µm × 1.7–2.3 µm (x ̄ = 20 × 1.9 µm, n = 25). Conidia aseptate, hyaline, fusiform, smooth, few with funnel-shaped apical appendage, 7.8–9.0 µm × 2.1–3 µm (x ̄ = 8.4 × 2.6 µm, L / W ratio = 3.32, n = 50).

Culture characteristics.

Colony reaching 60 mm diam with white, fluffy, cotton-like mycelium in center that gradually thinned toward the edges with a slightly irregular margin. A slight yellowish-green pigment diffused in PDA and the reverse side of the medium appeared canary yellow.

Notes.

This study introduces Dimorphiseta formosana as a new species, described from a single strain obtained from serpentine soil. D. formosana forms a distinct clade with moderately high statistical support (68 % / 0.98) based on multi-locus phylogenetic analysis (Fig. 30 ). Furthermore, D. formosana exhibits significant genetic divergence from its closest relative, the ex-type strain of D. obtusa ( CGMCC 3.19206 ), across four loci: ITS (491 / 516 bp, identities 95.2 %, including 1 gap), cmd A (501 / 572 bp, identities 87.6 %, including 12 gaps), rpb 2 (608 / 721 bp, identities 84.3 %), and tub 2 (254 / 307 identities, 82.7 %, including 1 gap). Furthermore, our new species can be differentiated from D. obtusa ( CGMCC 3.19206 ) by its smaller conidia, measuring 8–9 µm × 2–3 µm compared to 9–11 µm × 2–4 µm as reported by Liang et al. (2019) (Fig. 29 ). Even though its conidiogenous cells and conidia closely resemble those of the ex-type strain of D. terrestris ( CBS 127345 ), our species lacks any Type I setae ( Lombard et al. 2016). Additionally, while both D. formosana and D. serpentinicola were isolated from serpentine environments, D. formosana demonstrated a faster growth rate on PDA and produced a more vibrant yellow on the reverse side of the culture.

Figures

Figure 29. Morphology of Dimorphiseta formosana NTUPPMCC 22-291. A, B 14 - days-old colony on PDA; C Conidiomata; D Setae; E Conidiophores and conidiogenous cells; F Conidia (red arrow: funnel-shaped appendage). Scale bars: 0.2 mm (C); 50 µm (D); 10 µm (E, F).

Figure 30. Maximum likelihood (ML) phylogenetic tree based on a concatenated dataset of ITS, cmd A, rpb 2, and tub 2. In total, 22 strains representing 19 taxa were included in the concatenated dataset, with 2424 characters (ITS 569 bp, cmd A 709 bp, rpb 2 721 bp, and tub 2 425 bp) including alignment gaps. The tree was rooted with Inaequalispora prestonii CBS 175.73. MLB ≥ 70 % and BPPs ≥ 0.95 were shown at each node; values lower than these thresholds are indicated by a hyphen (–). The scale bar indicates the number of estimated substitutions per site. The strains introduced in this study are in red and novel species are in bold. The ex-type strains are marked with T.