Rosellinia thelena












Rosellinia thelena (Fr.: Fr.) Rabh.

Stromata usually densely gregarious, uniperitheciate, rarely fused together in a 2-3- peritheciate stroma, dark brown to black with a thin coating of pale subicular hyphae, subglobose with a broadly attached base, 0.8-1 mm diam, with conspicuous folds and ridges in the lower part when dry; ectostroma rather thin, brittle; subiculum densely felted, purplish brown, of finely interwoven hyphae, persistent, widely spreading.

Ostioles stout, broadly conical, darker than the stromatal wall.

Asci cylindrical, with apical apparatus urn-shaped with attenuated base, amyloid, 5.5-7.5 m high x 4.5-5.5 m broad.

Ascospores 19-26.5 x 6-8 m, ellipsoid-inequilateral to slightly oblong with broadly rounded ends, dark brown, with a straight germ slit nearly spore-length to 3/4 spore-length on the less convex side; both ends with a spiny cellular appendage 5-10 m long.

Anamorph in nature: not seen.

Specimens examined: FRANCE: Arige (09): Massat, Fort de Bellissens, 24 Aug. 1999, JF-99192, on bark of a trunk of Abies alba; Prades, Fort Domaniale, Bois de Font Frde, 1200 m, 28 Sept. 1997, JF-97169, on bark of Abies alba; Rimont, Las Muros, 08 Aug. 1997, JF-97128/1, on twigs and needles of Picea abies; Rimont, Las Muros, ruisseau de Peyrau, 30 Aug. 1999, JF-99195, on bark of Quercus robur; Rimont, Las Muros, ruisseau de Peyrau, 25 Nov. 2003, JF-03235, on bark of Alnus glutinosa; Salau, mine d'Anglade, 09 Jul. 2000, JF-00115, on bark of Fagus sylvatica. SWITZERLAND. Les Diablerets, 26 Aug. 1993, JFM-9354, on Picea.

Notes: Rosellinia thelena is representative of the subgenus Corrugata with its thin-walled stromata with stout ostioles and ridges in the lower part, seated on a felted widespreading subiculum. It is easily distinguished from R. desmazieresii and R. mycophila by its long, pointed cellular appendages at both ends of ascospores. Rosellinia thelena var. microspora is likewise very similar but merely differs from the typical variety in having smaller perithecia and shorter ascospores.

Ascospores of R. thelena exhibit variations in shape, dimensions and germ slit length, but the pointed cellular appendages up to 10 m long are conspicuous and distinctive, allowing an unambiguous identification.

Rosellinia thelena is typically associated with recently dead wood, twigs or needles ofconifers, but likewise occurs on wood of deciduous trees. This feature is most unusual within the Xylariaceae, where host-specificity for conifers is rare but apparently respected. Rosellinia thelena has been reported as endophyte (Petrini, 1993) from healthy looking conifers, that could explain why it develops so rapidly on recently fallen branches if environmental requirements, mostly a constant humidity, are satisfied.

Rosellinia thelena is known from Europe and North America (Petrini, 1993).