Poaceascoma serpentinum 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-

Poaceascoma serpentinum K. W. Cheng & H. A. Ariyaw. sp. nov.

Fig. 3

Typification.

TAIWAN • Guanshan Township , Taitung County, 23°02'17.6"N, 121°11'26.3"E, serpentine soil in rice field, 3 rd November 2022, K. W. Cheng, holotype, NTUPPMH 22-216 (Permanently preserved in a metabolically inactive state), ex-holotype NTUPPMCC 22-222 .

Etymology.

Named after the serpentine soil from which the species was isolated.

Description.

Sexual morph undetermined. Asexual morph Conidiophores submerged in WA, hyaline, flexuous, rarely straight, septate, sometimes branched, 10–25 µm. Conidiogenous cells hyaline to pale brown, holoblastic, monoblastic, terminal, occasionally intercalary, subcylindrical to swollen. Conidia hyaline to pale brown when immature, brown to dark brown when mature, ellipsoidal to broadly ellipsoidal or ovoid, finely verrucose, 3–5 septate, 31.3–48.6 µm × 12–15.7 µm (x ̄ = 37.8 × 14 µm, L / W ratio = 2.72, n = 30). Chlamydospores brown to dark brown, dumb-bell-shaped, terminal, straight or sometimes curved, occasionally branched, 108–163 µm in length, 8–15 µm in width.

Culture characteristics.

Colony exhibits slow growth, reaching 35 mm diam with pale gray, fluffy to floccose surface and smooth margins. Reverse side of the colony showed a central brownish color that gradually fades into a lighter beige ring toward the edges.

Notes.

This study describes Poaceascoma serpentinum as a novel fungal species based on a single strain ( NTUPPMCC 22-222 ) isolated from serpentine soil. In our phylogenetic tree, Poaceascoma serpentinum forms a distinct clade within the genus Poaceascoma (Fig. 4 ). Moreover, Po. serpentinum exhibits significant genetic divergence from its closest relatives, the ex-type strain of Po. koreanum ( CMML 20-44 ) and Po. magnum ( CMML 20-47 ) with 83.6 % and 87.4 % identity in the ITS region (414 / 495 bp, including 24 gaps; 414 / 492, including 10 gaps). For tef- 1, the identities are 840 / 890 (94.4 %) and 849 / 890 (95.4 %), respectively. Previously, species in this genus have been described solely based on their sexual stage or chlamydospore-like structures with no documented asexual stage ( Zang et al. 2023; Liu et al. 2025). However, in the present study, we observed only the asexual stage of NTUPPMCC 22-222 but did not observe any sexual stage of the fungus even when carnation leaves were used as the substrate (Fig. 3 ). As a result, morphological comparisons between NTUPPMCC 22-222 and its closely related species are not possible. While this study establishes Po. serpentinum as a distinct species, future studies should aim to recover additional isolates from similar environments to further validate its phenotypic variation and ecological distribution. Notably, this study is also the first to document the asexual morphology of a Poaceascoma species.

Figures

Figure 3. Morphology of Poaceascoma serpentinum NTUPPMCC 22-222. A, B 14 - days-old colony on PDA; C, G – M Immature and mature conidia; D – F Chlamydospores. Scale bars: 0.2 mm (C); 20 µm (D – G); 10 µm (H – M).

Figure 4. Maximum likelihood (ML) phylogenetic tree based on a concatenated dataset of ITS, LSU, SSU, and tef- 1. In total, 32 strains representing 26 taxa were included in the concatenated dataset, with 3357 characters (ITS 606 bp, LSU 840 bp, SSU 1021 bp, and tef- 1 890 bp) including alignment gaps. The tree was rooted with Multiseptospora thailandica MFLUCC 11-0183. 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.