Stilbochaeta guizhouensis W. M. Zhang & L. Lu, 2025

Zhang, Wangming, Feng, Qinying, Song, Xiaoyu, Zhou, Xinzhong, Xie, Wanqing, Lu, Juan & Lu, Li, 2025, Two new species of Stilbochaeta (Chaetosphaeriaceae, Chaetosphaeriales) from freshwater and terrestrial habitats in China, MycoKeys 121, pp. 67-78 : 67-78

Stilbochaeta guizhouensis W. M. Zhang & L. Lu sp. nov.

Fig. 2

Etymology.

The epithet “ guizhouensis ” refers to Guizhou Province, China, where the fungus was collected.

Holotype.

GZAAS 25–0001 .

Description.

Saprobic on decaying wood in a terrestrial habitat. Sexual morph Undetermined. Asexual morph Hyphomycetous. Colonies on the natural substrate effuse, hairy, brown, with white, glistening conidial mass. Mycelium mostly immersed, composed of branched, septate, smooth, brown hyphae. Setae 170–251 µm long, 5–7 µm wide at the base (x ̄ = 210 × 6 µm, n = 15), erect, slightly curved, dark brown at the base, pale brown towards the apex, apical cell with a round end, septate, unbranched, smooth. Conidiophores 63–251 µm long, 4–7 µm wide at the base (x ̄ = 122 × 5.5 µm, n = 15), macronematous, mononematous, brown at the base, fading to pale brown towards the apex, septate, unbranched, cylindrical, erect, straight or slightly curved, thin-walled, smooth, arising in groups from the bases of setae. Conidiogenous cells 19–30.5 µm long, 3.5–5 µm wide (x ̄ = 23.5 × 4.5 µm, n = 25), mono- or poly-phialidic integrated, terminal, determinate, clavate, ellipsoidal, collarette funnel-shaped. Conidia 10–16 µm long, 2–3.5 µm wide (x ̄ = 14.5 × 3 µm, n = 20), acrogenous, usually aggregated in slimy droplets, hyaline, 1 - septate, guttules, oblong to allantoid, slightly curved, rounded at ends, smooth, with 5–12.5 μm long hair – like appendages at both ends.

Culture characteristics.

Conidia germinating on PDA within 9 h and germ tubes arising from the terminal ends of the conidium. Colonies reached 32 mm diam. after 36 days of incubation at 25 ° C, irregular, with flat, pale brown to brown mycelia on the surface, in reverse, brown to black-brown with undulate margin.

Material examined.

China, Guizhou Province, Qianxinan Buyei and Miao Autonomous Prefecture, on decaying wood in a terrestrial habitat, 28 November 2024, Wang-Ming Zhang, GC 16 ( GZAAS 25–0001 , holotype), ex-type living culture GZCC 25–0001 ; Ibid., GC 18 ( GZAAS 25–0002 , paratype), living culture GZCC 25–0002 .

Notes.

In the phylogenetic tree (Fig. 1 ), our isolates GZCC 25–0001 and GZCC 25–0002 clustered together with 100 % ML and 1.00 BYPP support, indicating that they belong to the same species. This clade formed a distinct lineage with Stilbochaeta submersa ( MFLU 18–2321 and NN 047996 ), supported by 84 % ML and 0.98 BYPP, indicating that they represent two different species. A comparison of ITS and LSU sequences between GZCC 25–0001 and MFLU 18–2321 revealed nucleotide base differences of 11 / 533 bp (2.1 %, including one gap) and 5 / 797 bp (0.6 %, without a gap), respectively. Morphologically, Stilbochaeta guizhouensis ( GZAAS 25–0001 ) can be distinguished from Stilbochaeta submersa ( MFLU 18–2321 ) by longer conidiophores (up to 251 µm long vs. 62–122 (– 152) µm long) and larger conidiogenous cells (19–30.5 µm long, 3.5–5 µm wide vs. 13.5–16.5 µm long, 2.5–3.5 µm wide; Luo et al. (2019); Wu and Diao (2022)). Therefore, based on the findings from both molecular and morphological evidence ( Chethana et al. 2021), we introduce the two isolates, GZCC 25–0001 and GZCC 25–0002 , as a new species, namely Stilbochaeta guizhouensis .

Figures

Figure 1. Phylogenetic tree generated from the RAxML analysis, based on the combined dataset of LSU and ITS sequences. Bootstrap support values for ML (≥ 75 %) and BYPP (≥ 0.95) are indicated near their respective nodes. Codinaea assamica (CBS 139907) and C. dwaya (CBS 261.77) were selected as outgroup taxa. Ex-type and ex-epitype strains are denoted by “ T ” and “ E ”, respectively and newly-obtained isolates are indicated in bold red font. A dash (“ - ”) indicates bootstrap support values below 0.95 for BYPP.

Figure 2. Stilbochaeta guizhouensis (GZAAS 25–0001, holotype). a – c. Colonies on the natural substrate; d – h. Setae and conidiophores; i – l. Conidiophores and conidiogenous cells bearing funnel-shaped collarettes; m, n. Conidia; o. Germinated conidium; p, q Colonies on PDA from above and below. Scale bars: 50 μm (d – h); 20 μm (i – l); 10 μm (m – o).