Hypoxylon perforatum










Hypoxylon perforatum (Schwein.: Fr.) Fr.

Stromata pulvinate or effused-pulvinate on bark, effused on wood, with inconspicuous to very conspicuous perithecial mounds, frequently wrinkled between perithecial mounds, 2-25 mm long x 2-8 mm broad x 0.5-1(-2.5) mm thick; surface dark brick (60), sepia (63), umber (9) to brown vinaceous (84) or dark vinaceous (82); dull yellow granules beneath surface, with KOH-extractable pigments amber (47) to ochreous (44) or greenish yellow (16); the tissue beneath the perithecial layer dark brown, inconspicuous or up to 2mm thick.

Perithecia spherical to obovoid, 250-300 (400) m diam x 300-400 m high.

Ostioles lower than the stromatal surface, conspicuously surrounded by a ring of white substance 60-120 m diam on mature stromata.

Asci 80-128 m total length x 6-8 m broad, the spore bearing-parts 51-80 m long, the stipes 24-51 m long, with apical ring discoid, amyloid, 0.8-1.5 high x 2-2.8 m broad.

Ascospores brown to dark brown, ellipsoid-inequilateral, often crescent-shaped, 9.7-11.5 x 4.7-5.3 m (M = 10.9 x 4.9 m), with straight germ slit spore-length; perispore dehiscent in 10% KOH, smooth.

Anamorph in nature: vinaceous buff (86) to greyish sepia (106), velvety, on young stromata or at margins. Conidiogenous structure Virgariella-like, pale brown, smooth. Conidiogenous cells hyaline, 11-17 x 2.5-3.5 m. Conidia broadly ellipsoid, 3.5-4.8 x 2.8-3.5 m.

Habitat: on bark or wood of various trees or shrubs, frequently found on branches that are not in contact with the soil. Very common on Fraxinus excelsior and Ulmus minor, also collected on Acer campestre, Coriaria myrtifolia, Cornus sanguinea, Corylus avellana, Cydonia oblonga, Eucalyptus sp., Fagus sylvatica, Frangula alnus, Juglans regia, Ligustrum vulgare, Mespilus germanica, Populus tremula, Prunus domesticus, Prunus padus, Prunus spinosa, Quercus ilex, Rhamnus catharticus, Robinia pseudoacacia, Rosa canina, Salix caprea, Sarothamnus scoparia, Sorbus torminalis.

Known distribution : worldwide.

Specimens examined: FRANCE, Arige (09): Rimont, Las Muros, 12 Sept. 1996, JF-96093, on Fraxinus excelsior; Rimont, Las Muros, 11 Nov. 1996, JF-96160, on Acer campestre; Rimont, Las Muros, 20 Dec. 1996, JF-96182, on Sorbus torminalis; Rimont, Las Muros, 19 Jul. 1997, JF-97101, on Populus tremula; Rimont, Las Muros, 26 Jul. 2000, JF-00128, on Populus tremula; Rimont, Las Muros, 02 Sept. 2000, JF-00181, on Fraxinus excelsior; Rimont, Las Muros, 17 Jun. 2001, JF-01113, on Cornus sanguinea; Saint Quirc, Fort communale, 03 Dec. 2000, JF-00257, on Eucalyptus sp.

Notes Hypoxylon perforatum has long been considered to be a synonym of H. rubiginosum (Miller, 1961), which, indeed, looks very similar. Later, Petrini and Mller (1986) proposed the varietal rank, as H. rubiginosum var. perforatum, on account of its short-stipitate asci. More recently Ju and Rogers (1996) considered it a distinct species, on account of its different KOH-extractable pigments and different anamorph.

In the field, H. perforatum is usually distinguished by its ostioles conspicuously encircled with a white substance but, unfortunately, young stromata lack this distinctive feature. Moreover this ostiolar feature may be encountered in several other taxa having similar stromatal colour, i. e., H. carneum, H. fuscum, H. intermedium, H. petriniae and H. rubiginosum. Hypoxylon carneum differs in having livid violet KOH-extractable pigments, H. petriniaeand H. rubiginosum in having orange KOH-extractable pigments. H. fuscum and H. intermedium both have similar yellow pigments in KOH to those of H. perforatum, but both have larger ascospores. The yellow pigments observed in H. perforatum are due to hypomiltin, a recently described new azaphilone, which is also present in H. intermedium (Hellwig et al., 2004), associated in both species to orsellinic acid. Although pigments of H. fuscum obtained in KOH are similar, they are due to very different compounds (Mhlbauer et al.,2002 and Quang et al., 2003).

In our area, H. perforatum is the more frequently encountered species of Hypoxylon and undoubtedly the more plurivorous one.