Hypoxylon sp. aff. rubiginosum GUM 1588

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 1588 Fig. 6

Teleomorph.

Stromata superficial, pulvinate, up to 1 cm long × 0.2-0.5 cm wide, with inconspicuous to conspicuous perithecial mounds; surface Orange (7) to Apricot (42); Orange (7) granules beneath the surface and Laeden Black (126) granules between the perithecia, with Orange (7) KOH-extractable pigments. Perithecia obovoid to compressed-obovoid, 0.35-0.65 high × 0.3-0.45 mm wide. Ostioles umbilicate, inconspicuous. Asci with amyloid, discoid apical apparatus, 1-1.5 µm high × 2-3 µm wide, stipe up to 160 µm and spore-bearing portion 70-100 × 6-8 µm long. Ascospores smooth, unicellular, brown to dark brown, ellipsoid, inequilateral with narrowly-rounded ends, 10-15 × 5-6.5 µm, with straight to slightly sigmoid germ slit spore-length on convex side; perispore dehiscent in 10% KOH; epispore smooth.

Cultures and anamorph.

Colonies on OA covering a 9 cm Petri dish in 3 wk, at first white, becoming whitish, cottony, azonate with entire margins; remaining mainly uncoloured with Pale Luteous tinges. Anamorph not produced in culture.

Specimen examined.

Iran, Mazandaran Province, Tonekabon County, Do-hezar forest, 36°42'30"N, 50°49'43"E, 456 m elev., on dead branches (host unknown), 28 Oct 2016, M.J. Pourmoghaddam (GUM 1588; culture MUCL 57725).

Notes.

This specimen is morphologically similar to Hypoxylon aff. rubiginosum GUM 1587, but it can be distinguished by its larger ascospores [10-15 × 5-6.5 vs. 8-10 (-11) × (3-) 4-4.5 (-5) μm]. H. rubiginosum sensu stricto differs from this specimen in having smaller ascospores [(8-) 9-12 × 4-5.5 vs. 10-15 × 5-6.5 μm]. In addition, the stromatal secondary metabolite profile is similar to that of H. rubiginosum with two unknown azaphilone compounds of the mitorubrin / rubiginosin family (UC 2, retention time = 8.7 min, 442 Dalton and UC 3, RT = 10.6 min, 884 Da) and rubiginosin A. H. guilanense differs from Hypoxylon aff. rubiginosum GUM 1588 in having stromata with hemispherical to pulvinate shape and difference in average ascospores sizes (12-15 × 5-6 vs. 10-15 × 5-6.5 μm) with straight germ slit. H. texense differs from Hypoxylon aff. rubiginosum GUM 1588 in having Rust (39) to Dark Brick (86) KOH-extractable pigments and much smaller ascospores [9.1-10.8 (-11.5) × (4.0-) 4.5-5.4 (-5.7) vs. 10-15 × 5-6.5 μm].

Figures

Figure 6. Hypoxylon aff. rubiginosum (GUM 1588) A stromatal habit B close-up view of stromatal surface, with stromatal pigments in 10 % KOH C section of stroma showing perithecia and ostioles D ascus in Melzer's reagent E ascospores in 10 % KOH with dehiscent perispore. Scale bars: 2.5 mm (A); 0.5 mm (B, C); 20 µm (D); 10 µm (E).