Hypoxylon sp. aff. rubiginosum GUM 1587

Pourmoghaddam, Mohammad Javad, Lambert, Christopher, Surup, Frank, Khodaparast, Seyed Akbar, Krisai-Greilhuber, Irmgard, Voglmayr, Hermann & Stadler, Marc, 2020, Discovery of a new species of the Hypoxylon rubiginosum complex from Iran and antagonistic activities of Hypoxylon spp. against the Ash Dieback pathogen, Hymenoscyphus fraxineus, in dual culture, MycoKeys 66, pp. 105-133 : 105

Hypoxylon sp. aff. rubiginosum GUM 1587 Figs 4 , 5

Teleomorph.

Stromata superficial, pulvinate to effused-pulvinate, up to 5 cm long × 0.6-2 cm wide, with inconspicuous to conspicuous perithecial mounds; surface Luteous (12), Orange (7) to Ochreous (44); Orange (7) granules beneath the surface, Orange (7) and Leaden Black (126) granules between the perithecia, with KOH-extractable pigments Orange (7). Perithecia obovoid, compressed-obovoid to spherical, 0.27-0.50 high × 0.23-0.35 mm wide. Ostioles umbilicate, inconspicuous, usually overlain with conspicuous white substance. Asci 8-spored, cylindrical, with amyloid, discoid apical apparatus, 0.5-1 µm high × 2-2.5 µm wide, stipe up to 180 µm long; spore-bearing portion 80-100 × 5.5-7 µm. Ascospores smooth, unicellular, brown to dark brown, ellipsoid, inequilateral with narrowly rounded ends, 8-10 (-11) × (3-) 4-4.5 (-5) µm, with straight to slightly sigmoid germ slit spore-length on convex side; perispore dehiscent in 10% KOH, conspicuous coil-like ornamentation in SEM; epispore smooth.

Cultures and anamorph.

Colonies on OA covering a 9 cm Petri dish in 3 wk, at first white, becoming Luteous (12) from outwards, cottony, slightly zonate with diffuse margins; finally, attaining a variety of different colours. Conidiogenous structure branching virgariella-like as defined by Ju and Rogers (1996), (Fig. 5C-G ). Conidiophores hyaline, smooth to finely roughened. Conidiogenous cells hyaline, smooth to finely roughened, 15-30 × 2-3 μm. Conidia hyaline, smooth to ellipsoid, 4-6 × 2-3 μm.

Specimen examined.

Iran, Guilan Province, Astaneh-Ashrafieh County, Safra-Basteh forest, 37°20'19"N, 49°58'26"E, 14 m elev., on fallen branch of Quercus castaneifolia , 4 Oct 2016, M.J. Pourmoghaddam (GUM 1587; culture MUCL 57724).

Notes.

This specimen resembles H. rubiginosum in many respects. However, it has slightly smaller ascospores [8-10 (-11) × (3-) 4-4.5 (-5) vs. 9-13 × 4-5.5 µm] and the germ slit of the ascospores is often slightly sigmoid. The most significant differences were noted in the anamorphic structures with virgariella-like branching patterns. This anamorph actually resembles that of H. petriniae . However, this species is normally associated with Fraxinus and differs from Hypoxylon aff. rubiginosum GUM 1587 in having Lilac (54), Vinaceous (57) to Brown Vinaceous (84) stromatal surface colours (owing to the presence of BNT, which was not found in the Iranian specimen). It also differs in having more elongate to irregularly effused stromata with black margins and its ascospores are larger (8-11.5 (-13) × 4.8-6 μm) and have a straight germ slit.

Figures

Figure 4. Hypoxylon aff. rubiginosum (GUM 1587) A, B stromatal habit C close-up view of stromatal surface, with stromatal pigments in 10 % KOH D stroma in section showing perithecia and ostioles E mature and immature asci in water F ascus in water G ascus in Melzer's reagent H ascus tip in Melzer's reagent I ascospores in 10 % KOH with dehiscent perispore J ascospore in water, with germ-slit K ascospore under SEM. Scale bars: 5 mm (A, B); 1 mm (C); 0.5 mm (D); 20 µm (E-G); 10 µm (H-J); 2 µm (K).

Figure 5. Culture and anamorphic structures of Hypoxylon aff. rubiginosum (GUM 1587) on OA A, B surface of colony after 1 and 8 wk of incubation (respectively, left to right) C-G general view of anamorph structure with virgariella-like branching patterns H, I conidiogenous cells and immature conidia J mature conidia. Scale bars: 20 µm (C-G); 10 µm (H-J).