Helminthosporium guizhouense M. T. Zou & Yong Wang bis

Zou, Mengting, Al-Otibi, Fatimah, Hyde, Kevin David, Wang, Yong & Pan, Xue-Jun, 2024, New Helminthosporium (Massarinaceae, Dothideomycetes) and Nigrospora (Incertae sedis, Sordariomycetes) species associated with walnut (Juglans regia L.) in China, MycoKeys 109, pp. 265-284 : 265-284

Helminthosporium guizhouense M. T. Zou & Yong Wang bis sp. nov.

Fig. 3 a – r

Etymology.

The name refers to Guizhou, the province where the fungus was collected.

Diagnosis.

Helminthosporium guizhouense can easily be distinguished from H. caespitosum by its narrower conidia (13–16 µm vs. 27.3–35.5 µm).

Type.

China • Guizhou Province, QianXi City ; 26 ° 56 ' 11.58 ″ N, 105 ° 55 ' 15.46 ″ E; 1235 m; 24 January 2023; from rotten dead branch of Juglans regia , coll. M. T. Zou; HGUP 24-0007 (holotype); ex-type culture GUCC 23-0011 ( ITS: PP 915799 , LSU: PP 949847 , rpb 2: PP 947940; SSU: PP 949912 ) .

Description on the natural substrate.

Colonies hairy, brown, or blackish-brown, in groups. Mycelium partly immersed in the substratum, towards the surface forming stroma-like aggregations of light to brown pseudoparenchymatous cells.

Culture characteristics.

Colony on PDA 25 mm diam after 2 weeks in an incubator under dark conditions at 28 ° C, irregular circular, fat, raised, undulate, rough, with white and denser mycelium at the center, with white to deep-gray to creamy yellow, entire margin; reverse cream to yellow, with dark yellowish-brown spots. Teleomorph: Unknown. Anamorph: Conidiophores macronematous, erect, straight, or slightly curved, cylindrical, smooth, 171–718 μm long, 12–25 μm wide at the base, tapering to 7–13.5 μm near the apex, arising solitary or in fascicles from the stroma cells, erect, simple, straight or flexuous, thick-walled, brown to dark brown, with sympodial proliferation, 1–13 - septate. Conidia 61–114 × 13–16 µm (x ̄ = 85 × 18, n = 45), gradually tapering to 3–7 μm (x ̄ = 5, n = 45) at the distal end, with a 4–10 μm (x ̄ = 6, n = 42) wide, blackish-brown to black scars at the base, straight or flexuous, solitary, obclavate to rostrate, smooth-walled, hyaline, pale golden brown to brown, 8–12 - distoseptate, with angular lumina; wall up to 6 µm thick.

Habit.

Saprobic on decaying wood of Juglans regia .

Distribution.

China, Guizhou Province, Qianxi City

Other material examined.

China • Guizhou Province, Qianxi City ; 105 ° 92 ' E, 26 ° 93 ' N; 1235 m; 24 January 2023; from rotten dead branch of Juglans regia , coll. M. T. Zou, HGUP 24-0008 (holotype); living culture GUCC 24-0011, GUCC 24-0012, and GUCC 24-0013 .

Notes.

Based on the multi-gene phylogenetic tree (Fig. 1 ), our strains are clustered in a distinct branch adjacent to the strain of Helminthosporium caespitosum ( CBS 484.77). Topologically, there is a clear genetic distance between these taxa with ML-BS = 100 %, BYPP = 1 support. When comparing the ITS, LSU, rpb 2, and SSU nucleotides of H. guizhouense with H. caespitosum in the clade, there are 22 bp (0 gap) differences of 569 bp in ITS, 2 bp (0 gap) differences of 904 bp in LSU, and 38 bp (0 gap) differences of 401 bp in rpb 2, and 4 bp (0 gap) differences of 1098 bp in SSU. Our collection of H. guizhouense ( HGUP 24-0008) differs significantly from the holotype of H. caespitosum ( WU 38825 and WU 38826) ( Voglmayr and Jaklitsch 2017) in the length of conidiophores (171–718 × 9.5–23 µm vs. 27–37 × 12.2–14.5 µm), the size of conidia (61–114 × 13–16 µm vs. 82–109 × 27.3–35.5 µm), the number of septa (8–12 vs. 6–10) and the wall thickness of angular lumina (6 μm vs. 8 μm). In addition, the colonies on the natural substrate of H. guizhouense are hairy, brown, or blackish brown, in groups, whereas H. caespitosum is dark-red-brown, scattered, or crowded. Through our analysis and classification process, we have identified these three strains as a new species Helminthosporium guizhouense .

Figures

Figure 1. The maximum parsimony tree of 96 Helminthosporium taxa is based on ITS, LSU, rpb 2, and SSU genes. The tree was rooted with Periconia pseudodigitata (KT 1395). Bootstrap support values for ML greater than 75 % and Bayesian posterior probabilities greater than 0.95 are given near nodes, respectively. The new isolates were in red. Ex-type strains were marked by T. The scale bar indicates 0.05 expected changes per site.

Figure 3. Helminthosporium guizhouense sp. nov. (HGUP 24-0008, holotype) on rotten dead branch of Juglans regia a – c colonies on the natural substrat; d, e culture on PDA after 2 weeks (d above e reverse) f conidiophore bases, stroma cells, and conidia l conidiophore m colony, conidiophores, and stroma cells n conidiophore g – k, o – r conidia. Scale bars: 1000 µm (a); 500 µm (b, c); 50 µm (f – r).