Hypoxylon rubiginosum (Pers.: Fr.) Fr.

TELEOMORPH | CULTURES AND ANAMORPH | SPECIMENS EXAMINED | NOTES

NOTES

Cultures and anamorph have been described by Petrini and Müller (1986) on MA.

Two specimens of Sphaeria rubiginosa have been examined from the Persoon herbarium of L. Specimen 910, 263-1194 was cited by Miller (1961) as the type and fits the current concept of this species; it should be accepted as the lectotype. Specimen 910, 263-1191 is H. fuscum (Pers.: Fr.) Fr. In the protologue of H. florideum, two specimens were cited. Ravenel no. 1911 is cited as the type by Miller (1961).

Miller (1961) extended the definition of H. rubiginosum to cover those specimens with the ascospore size range 9-12.8 x 4-6 mm, with stromata less than 3 mm thick, and with dark brown granules. In this study, we restrict H. rubiginosum to those specimens with yellowish brown to brown granules containing orange-series KOH-extractable pigments, with a rusty to infrequently vinaceous stromatal surface, with ellipsoid-inequilateral ascospores (8-) 9-12 x 4-5.5 mm, with dehiscent perispore, and without massive basal tissue. White material on ostioles is sometimes present but is hardly as conspicuous as that in H. perforatum. Its geographical distribution is primarily in northern temperate areas. Also compare with H. cercidicolum, H. pelliculosum, and H. samuelsii.

There is a fungus that highly resembles H. rubiginosum but differs from it in having a Virgariella-like conidiogenous structure   and in having gray sporulating regions in culture. Greenhalgh and Chesters (1968) probably described cultures of this fungus as H. rubiginosum. We are not making a formal decision until more collections are studied. The cultural and anamorphic characteristics are described as follow.

Colonies on OA covering Petri dish in 3-4 wk, at first whitish, becoming ochreous (44), with fuscous (103) patches, felty, azonate, sectored, with diffuse margins; reverse umber (9).

Sporulating regions scattered over entire surface of colony, pale mouse gray (117) to grayish sepia (106).

Conidiogenous structure Virgariella-like, hyaline, smooth to finely roughened.

Conidiogenous cells hyaline, smooth, 20-45 x 2-2.5 mm.

Conidia hyaline, finely roughened, ellipsoid, 6-7.5 x 3-3.5 mm.

SPECIMENS EXAMINED:

MEXICO: Nuevo León state, Santiago municipality, El Cercado, 23.10.88, San Martín 1151 (CULTURED), wood (ITCV; JDR).

U.K.: North Wales, near Ruthin, 16.8.1990, Rogers, J.D., (CULTURED), wood of Fraxinus (JDR); North Wales, Gwynedd, near Harlech, 15.8.1990, Rogers, J.D., (CULTURED), decayed wood (JDR).

Two collections from Salix probably represent another distinct taxon:

SWEDEN: Medelpad, 3.9.1991, Laessøe, T 2447 (CULTURED), decorticated wood of Salix (JDR; K).

U.S.A.: Arizona, Apache Co., 10.11.1970, Goree 2898, decorticated wood of Salix (JDR).

Despite the fact that the anamorph is much like that of H. rubiginosum, they can be distinguished from typical H. rubiginosum by using perithecial sizes, ascospore morphology, and colony growth rate. Their perithecia are smaller, 0.1-0.2 mm diam; their ascospores are nearly equilateral and smaller, 7.5-9 (-10) x 3.5-4 mm; and they grow much slower, never reaching the edge of the Petri dish. We prefer not to make a formal decision on these two Salix collections until more collections are available. The cultural and anamorphic characteristics are as follow:

Colonies on OA never reaching the edge of Petri dish, at first whitish, becoming hazel (88), felty, azonate to faintly zonate, with entire margins; reverse blackish.

Sporulating regions near the center of colonies, sparse.

Conidiogenous structure Nodulisporium-like, hyaline, finely roughened.

Conidiogenous cells hyaline, smooth, 8-14 x 3-4.5 mm.

Conidia hyaline, smooth to slightly roughened, ellipsoid, 5-6 x 3-3.5 mm.