Helminthosporium juglandinum Voglmayr & Jaklitsch, Stud. Mycol. 87: 59 (2017)

Index Fungorum number: IF821199; MycoBank number: MB821199; Facesoffungi number: FoF 16295

Saprobic on dead twigs. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Colonies 730–1284 μm diam., effuse, dark brown to black, hairy. Mycelium immersed, forming stroma-like aggregations of dark brown pseudoparenchymatous cells. Conidiophores 420–970 × 7–11 (x̅ = 810 × 9 μm, n = 20), mononematous, macronematous, caespitose, erect, cylindrical, straight to slightly flexuous, wide at the base, unbranched, dark brown, with apical pore, multi-septate, with dark scars, smooth-walled. Conidiogenous cells mono- to polytretic, integrated, terminal and intercalary, cylindrical, cicatrized, with dark scars, with distinct pores. Conidia 54–120 × 12–18 (x̅ = 90 × 16 μm, n = 40), solitary, obclavate, straight to slightly curved, wider below than apex, truncate and with dark scar at base, upper cell tapering towards long apex, cylindrical, apically rostrate and pale brown, 6–12-distoseptate, smooth-walled. Conidial secession schizolytic.

Culture characteristics – Conidium germinating on PDA within 24 h and germ tubes produced from top ends. Colonies on PDA reaching 30 mm diam. in 13 days at room temperature, within a month, covering the Petri dish, effuse, hairy, mycelium radiating outwards, fimbriate edge, dense, white. Mycelium superficial and partly immersed, grayish brown, the edge of the reverse side is white, and the center is grayish brown.

Material examined – China, Yanting, Sichuan, (31°5′25′′N, 105°27′36′′E), dead twigs of Juglans regia (Juglandaceae), 18 May 2021, FeiHu Wang, WFH202205026 (SICAU 22-0140), living culture (SICAUCC 22-0142).

GenBank numbers – ITS: OP963841, LSU: OP964580, SSU: OP962303, rpb2: OQ281352 and tef1-ɑ: OQ281380.

Notes – Our isolate is in a well-clustered clade together with five other strains of Helminthosporium juglandinum. Phylogenetic analysis of the combined ITS, LSU, SSU rpb2, and tef1-ɑ ITS sequence data of Helminthosporium taxa shows that our strain (SICAUCC 22-0142) clusters with the ex-type strain H. juglandinum (MFLUCC 17-0241, CBS 136922, CBS 136911, CBS 136912, SICAUCC 22-0090) with moderate support (100 ML, 1 BYPP). H. juglandinum appears to be the most common of the three species known on Juglans in Europe and is apparently confined to that host.

Fig. 1 – Helminthosporium juglandinum (SICAU 22-0140) A. Colony in face view. B Punctiform conidiomata in face view. C Conidioma in side view. D Conidiomata in side view with column-like subcortical stromata representing transformed conidiomata of Diaporthe. E Conidiophores. F, G Conidiophore apices with apical conidia. H-J Conidia. K Germinated conidium. L, M Colonies on PDA. Scale bar: A=1000 μm, B, C= 500 μm, E =100 μm, G = 50 μm, H-K= 20 μm.