Kretzschmaria deusta

              

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Kretzschmaria deusta (Hoffm.: Fr.) P. Martin.

For synonyms, see Rogers and Ju, 1998.

Stromata superficial, effused-pulvinate, orbicular to irregularly lobed, frequently fused together and spreading over the substrate surface, 10-50 mm diam x 2-3 mm thick, loosely attached to the substrate through narrow connections and thus easily separated from the substrate, with sloping to less frequently abrupt margins; surface lead grey, then brown to black, with reticulate cracks, outer stromatal layer black, carbonaceous, 0.20-0.25 mm thick; internal stromatal tissue soft, at first white, becoming grey to grey brown with age and finally disintegrating; the tissue below the perithecial layer blackish, woody, up to 1.5 mm thick. Perithecia spherical to ovoid, 0.6-1.3 mm diam x 0.9-1.5 mm high, arranged in one layer. Ostioles conical, shiny black, coarsely papillate. Asci long stipitate, with apical apparatus amyloid, urn-shaped, 4-7 (-9) m high x 3.5-4 m broad in the broadest part. Ascospores dark brown, 25-31 x 7-10 m, fusoid-inequilateral, frequently with pinched ends, with straight germ slit half spore-length on the flattened side.

Anamorph in nature entirely covering young stromata, white to dark grey, consisiting of palisadic conidiophores, assigned to Hadrotrichum Fuckel by Petrini and Mller (1986).

Specimens examined: FRANCE, Arige (09): Rimont, La Maille, 14 Aug. 1998, JF-98104, on bark of Tilia platyphyllos; Rimont, Las Muros, ruisseau de Peyrau, 20 Jul. 2002, JF-02131,on bark of Quercus robur.

Notes: Kretzschmaria deusta is a conspicuous and well known fungus, characterized by its widely effused black and carbonaceous stromata that become hollow with age and are easily separated from the substrate. Its identification is readily confirmed by microscope observation of its large fusoid ascospores with a short germ slit. Some tropical species resemble K. deusta in having ustulinoid stromata, they can be distinguished relying on size and morphology of ascospores, germ slit and apical apparatus. A recent illustrated account of K. deusta was given by Laesse et al., (2000).

Kretzschmaria deusta is often said to grow mainly on Fagus, but it has been reported on most of Angiospermous trees in Europe and North America. It may be found growing either on dead wood or at the base or the roots of living trees and is highly suspected to have a pathogen activity in addition to its saprophytic activity.