Helicosporium rubrum J. Ma & Y. Z. Lu, 2025

Peng, Tao, Lu, Yong-Zhong, Bai, Song, Zhang, Jing-Yi, Xiao, Xing-Juan, Wu, Na & Ma, Jian, 2025, Novel Helicosporium and Neohelicomyces (Tubeufiaceae, Tubeufiales) species from terrestrial habitats in China and Thailand, MycoKeys 112, pp. 81-101 : 81-101

Helicosporium rubrum J. Ma & Y. Z. Lu sp. nov.

Fig. 2

Holotype.

MFLU 24–0035 .

Etymology.

‘‘ rubrum ’’ refers to the red-brown colonies on the woody substrate.

Description.

Saprobic on decaying wood in a terrestrial habitat. Asexual morph Undetermined. Sexual morph: Ascomata 151–185.5 µm high, 138–157 µm diam., superficial, seated on a subiculum, solitary, scattered, globose to subglobose, bright reddish yellow to brown yellow, with central narrow ostiole; setae were not observed, comprising short projections of setae-like, 10–35 × 4.5–8 µm. Peridium 17.5–22 µm wide, composed of several layers of hyaline to bright yellow cells of textura angularis, outer layer yellow cells, and inner layer pale yellow to hyaline cells. Hamathecium comprising numerous, 1.5–2.5 µm wide, filiform, branched, septate, hyaline pseudoparaphyses. Asci 51–77 × 8–12.5 µm (x ̄ = 64 × 10 μm, n = 20), 8 - spored, bitunicate, fissitunicate, cylindrical to clavate or saccate, short-pedicellate, apically rounded, basally flexious. Ascospores 27–35 × 3–4.5 µm (x ̄ = 31.5 × 4 μm, n = 20), overlapping 2–3 - seriate, fusiform, tapering towards the ends, widest at the central part, straight to slightly curved, multi-septate, hyaline, smooth-walled.

Culture characteristics.

Conidia germinated on PDA, producing germ tubes within 10 hours. Colonies on PDA reached a diameter of 29 mm after 49 days of incubation at 25 ° C, exhibiting an irregular shape with radially furrowed at the centre and velvety surface, white to pale brown in PDA medium.

Material examined.

Thailand • Chiangmai, Mushroom Research Center (MRC), on rotting wood in a terrestrial habitat, 11 September 2020, Jing-Yi Zhang, Y 251 ( MFLU 24–0035 , holotype), ex-type living culture MFLUCC 24–0090 = GZCC 24–0149 .

Notes.

Our newly isolated strains ( MFLUCC 24–0090 and GZCC 24–0149 ) formed a sister relationship with H. flavum ( MFLUCC 16–1230 and GZCC 24–0487 ), supported by 100 % ML / 1.00 PP support (Fig. 1 ). A comparison of the ITS, LSU, and tef 1 - α sequence data between our strain ( MFLUCC 24–0090 ) and H. flavum ( MFLUCC 16–1230 ) revealed nucleotide base differences of 19 / 506 bp (3.8 %, including four gaps), 10 / 757 bp (1.3 %, without gap), and 26 / 904 bp (2.9 %, including four gaps), respectively. Morphologically, Helicosporium rubrum resembles H. flavum ( MFLU 17–0704 ) in having solitary, scattered, globose to subglobose, bright reddish-yellow to brown-yellow ascomata; bitunicate, fissitunicate, cylindrical to clavate asci; and fusiform, straight to slightly curved, multi-septate, hyaline ascospores ( Brahmanage et al. 2017). However, H. rubrum differs from H. flavum by having smaller asci (51–77 × 8–12.5 µm vs. 70–130 × 12–16 µm) and shorter ascospores (27–35 × 3–4.5 µm vs. 40–60 × 8–12 µm) ( Brahmanage et al. 2017). Additionally, H. flavum exhibits brown to black-brown setae, absent in H. rubrum ( Brahmanage et al. 2017). Therefore, based on morphological and molecular data, we propose Helicosporium rubrum as a new species ( Chethana et al. 2021).

Figures

Figure 1. Phylogram generated from the best scoring of the RAxML tree based on the combined LSU, ITS, tef 1 - α, and rpb 2 sequence dataset, indicating Helicosporium and Neohelicomyces species. Botryosphaeria agaves (MFLUCC 10–0051) and B. dothidea (CBS 115476) were selected as outgroup taxa. Bootstrap support values from maximum likelihood (ML) equal to or greater than 75 % and Bayesian posterior probabilities (PP) equal to or greater than 0.95 are shown near the nodes as ML / PP, respectively. “ T ” denotes ex-holotype strains. New species are in bold blue.

Figure 2. Helicosporium rubrum (MFLU 24–0035, holotype) a, b ascomata on the host surface c vertical sections of ascomata d peridium e hamathecium pseudoparaphyses f, g short projections of setae-like h – j asci l – o ascospores k germinating ascospore p, q surface and reverse colonies on PDA after 49 days of incubation at 25 ° C. Scale bars: 50 μm (c); 20 μm (g – j); 10 μm (d – f, k – o).