Hypoxylon salicicola

              

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Hypoxylon salicicola Granmo.

Stromata effused, with inconspicuous to conspicuous perithecial mounds, 35-65 mm long x 5-20 mm broad x 0.4-0.5 mm thick; surface dark rust (39) to sepia (63), brown vinaceous (84), finely cracked between perithecial mounds when mature, with dark brick (60) effused margins when immature; dark orange granules beneath surface and between perithecia, with KOH-extractable pigments fulvous (43) to rust (39); the tissue below the perithecial layer usually inconspicuous, dark brown.

Perithecia spherical to obovoid, 250-350 m diam.

Ostioles black, lower than the stromatal surface, frequently at the centre of slight circular depression.

Asci 110-125 m total length x 6-6.5 m broad, the spore bearing-parts 42-70 m long, the stipes 55-65 m long, with apical ring weakly amyloid, obsolete, discoid, 0.6 m high x 2-2.4 m broad.

Ascospores brown, ellipsoid nearly equilateral, 7.2-9.6 x 3-4.2 m ( M = 8.4 x 3.8m), with straight germ slit spore-length; perispore dehiscent in 10% KOH, smooth.

Anamorph in nature: reported as Nodulisporium-like by Ju & Rogers (1996) from cultures..

Habitat: According to Granmo (1999), H. salicicola is found on dry branches and trunks of Salix sp., once on Prunus padus, either on wood or on bark.

Known distribution: northern Europe (North Norway, Sweden, Granmo 1999) and USA (Arizona, Ju & Rogers 1996).

Specimens examined: NORWAY. Troms: Bardu: Srdalen, 0.5 km S of Srmo, 11 Jun. 1999, AG 50/99, leg. det. A. Granmo, on decaying branch of Salix sp (wood and cortex).Troms: Bardu: Setermoen, Moegga, 29 Jul. 2000, AG 46/2000, leg. det. A. Granmo,on Salix sp.

Notes.

Hypoxylon salicicola is still unknown in France, and we are very grateful to Dr. Granmo for the two specimens we received from him. Its is likely to have a distribution restricted to arctic alpine regions in Europe, therefore it should be searched for in Alps and Pyrnes. For a more complete description, the reader is referred to Granmo (1999).

This species is clearly morphologically related to H. rubiginosum, from which it differs in smaller perithecia, asci and ascospores. Moreover the nearly equilateral ascospores of H. salicicola differ from those of H. rubiginosum which are inequilateral. Ju & Rogers (1996) reported two collections from Sweden and USA (Arizona) on Salix with similar morphological features, which have a Nodulisporium-like anamorph in culture with a slow growth rate compared with that of H. ruboginosum.

HPLC data are not yet available for H. salicicola and the Arizona specimen. Hypoxylon rubiginosum (Pers.: Fr.) Fr. var. microsporum Whalley (Whalley, 1981) is another taxon known from Australia and Sierra Leone, similar to H. rubiginosum but with smaller ascospores 7.5-8.5 x 4-4.5 m, for which further studies are needed to assess its relationships with H. rubiginosum and H. salicicola.