Helminthosporium velutinum Link [as ‘Helmisporium’], Mag. Gesell. naturf. Freunde, Berlin 3(1-2): 10 (1809)

Index Fungorum number: IF250075; MycoBank number: MB250075; Facesoffungi number: FOF01053

Saprobic on dead twigs. Sexual morph: Undetermined. Asexual morph: Colony on walnut substrate effuse, black, hairy. Mycelia immersed and composed of unbranched, septate, thick-walled hyphae. Colonies discrete, punctiform, sometimes confluent, usually in large groups, black, and effuse. Conidiophores 310–890 × 9–16 (x̅ = 760 × 14 μm, n = 20), tapering to 7–13 μm near the apex, arising solitarily or in ascicles from the stroma cells, simple, straight or flexuous, cylindrical, thick-walled, smooth, brown to dark brown. Conidia 40–108 × 9–17 μm (x̅ = 86 × 13 μm, n = 40), gradually tapering to 4–8 μm at the distal end, with a 2–4 μm wide, blackish-brown to black scar at the base, straight or flexuous, obclavate to rostrate, smooth-walled, pale golden brown to brown, 6–14-distoseptate, with angular lumina; wall up to 3 μm thick.

Culture characteristics – Conidia germinated on PDA within 12 h, shoot tube is produced at the top first ends, bud tubes can be produced at both ends. Cultures grew slow on PDA, and Colonies reached 50 mm in diameter after 18 days at 25°C. Colony was originally white, then olive, the center is slightly protruding, and the surface is covered with white hyphae, the center of the reverse side is black, and the edge is light olive.

Material examined – China, Junlian, Sichuan, (28°11′36′′N, 104°34′5′′E), dead twigs of Juglans regia (Juglandaceae), 26 April 2022, FeiHu Wang, WFH202204041 (SICAU 22-0141), living culture (SICAUCC 22-0143).

GenBank numbers – ITS: OP963842, LSU: OP964581, SSU: OP962304, rpb2: OQ281353 and tef1-ɑ: OQ281381.

Notes – The multigene phylogenetic analysis based on combined LSU, SSU, ITS, rpb2, and tef1-α sequence data confirm the identity of Helminthosporium velutinum. The type species of the Helminthosporium genus, H. velutinum is characterized by solitary, cylindrical, unbranched, brown conidiophores that produce obclavate, distoseptate conidia (Luttrell 1957, 1963, 1964, Hughes 1980). H. velutinum is by far the most commonly recorded and best-known species of the genus. Remarkably, it has been recorded worldwide from a wide range of woody and herbaceous substrates; more than 100 hosts are listed in Farr & Rossman (2019).

Fig. 1 – Helminthosporium velutinum (SICAU 21-0141) A Symptoms on a dead twig observed on host. B, D Conidiophores lateral in side view. C Colonies in face view. E-I Conidiophores with apical and lateral conidia and pores. J-L. Conidia. M Germinating conidium. N, O Colonies on PDA. Scale bar: C, D =500 μm, B = 200 μm, E-I = 50 μm, J-M = 20 μm.