Rosellinia corticium















Rosellinia corticium (Schw.: Fr.) Sacc.

Stromata uniperitheciate, usually densely gregarious, rarely fused into 2-3- peritheciate stroma, subglobose with a flattened to somewhat cupulate apex, often constricted at the base, brown to blackish, 0.8-1.3 mm high x 0.9-1.4 mm diam; ectostroma hard, carbonaceous; subiculum brown to purplish brown, abundant, woolly, persistent at least at the base of mature stromata, long adhering to side walls, usually conspicuous between the stromata.

Ostioles papillate, conical.

Asci cylindrical, with apical apparatus cylindrical to more or less urn-shaped, amyloid, 7-11 µm high x 4-6.5 µm broad.

Ascospores 19-27 x 7.5-10 (-12) µm, ellipsoid-inequilateral with broadly to narrowly rounded ends, dark brown, with a frequently sigmoid or oblique germ slit nearly spore-length on the more convex side; a cellular appendage usually present at one end, at times at both ends, with a slimy sheath around the whole spore visible on fresh and young material.

Anamorph in nature: Geniculosporium-like, grey to light brown, present on subiculum at young stages.

Specimens examined. FRANCE: Ariège (09): Lapenne, Parc des Bambous, banks of Hers river, 06 Apr. 2002, JF-02066, on rotten culms of Arundo donax; Rimont, Las Muros, 24 Sept. 2002, JF-02179, on Laurus nobilis; Rimont, Las Muros, 19 Dec. 2002, JF-02248, on Quercus robur; Rimont, Las Muros, ruisseau de Peyrau, 19 Dec. 2002, JF-02249, on Acer campestre, Rimont, Saurine, 12 Feb. 2002, JF-02030, on Salix caprea. Gironde (33), Mongauzy, 8 Feb. 1992, JFM-9201 on Quercus or Carpinus. Haute Garonne (31): Fourquevaux, 26 Mar. 1995, JFM-9527, on broad leaved tree; Saleich, Artihaguère, 10 Feb. 2000, JF-00010, on Populus tremula; Toulouse, CRS park, 11 Dec. 1994, JFM-94162, on broad leaved tree. Pyrénées Atlantiques (64): La Bastide-Villefranche, Lac de la Pounte, 06 Nov. 2003, JF-03233, on Platanus sp.; Sauveterre de Béarn, 22 Feb. 1992, JFM-9210, on broad leaved tree. Sarthe (72): La Ferté Bernard, 08 Aug. 1986, PL-860808-01, leg. Paul Leroy, on Quercus. Vendée(85): Avrillé, Bois de la Garde, 05 Jun. 2003, JF-03090, on Quercus.

Notes: Rosellinia corticium is macroscopically identical with R. aquila and both species are easily confused in the field. As stated by Petrini (1992), R. corticium is readily distinguished from R. aquila by larger ascospores, surrounded by a slimy sheath, and asci with a larger apical apparatus.

In fact the slimy sheath is often inconspicuous, except around immature ascospores, and a careful exmination of fresh material shows that a second cellular appendage is often present, although very inconspicuous.

Ju & Rogers (1999) also report variations in the presence and number of cellular appendages in both R. aquila and R. corticium in north American material, and consider the latter a large-spored species within the R. aquila complex. In our experience, in large-spored specimens we name R. corticium, the larger size of ascospores is correlated with larger apical apparati and germ slits frequently oblique to slightly sigmoid.

The collection JF-02248 is distinctive in that most stromata exhibit a pinkish grey ring around the flattened ostiolar area, a feature not previously reported. Other macrocospical and microscopical features are otherwise in full agreement with those of typical R. corticium.

Another collection (JF-02066) on Arundo donax deviates from typical features of R. corticium in having shorter ascospores 17-20 x 6.5-8 µm and smaller apical apparati 4.8-6 µm high x 3.4-4 µm broad. Although these characters rather recall R. aquila, this collection is tentatively kept in R. corticium owing to the complete slimy sheath surrounding its ascospores and presence of two cellular appendages. In this collection, ascospores exhibit a wide range of morphological variations, often beaked or misshapen, therefore their dimensions may be misleading. Additional collections are needed to clear up its connections with R. aquila or R. corticium.

Rosellinia corticium is not uncommon in our region, frequently colonizing branches of recntly fallen trees. It is plurivorous on deciduous trees wood, with an apparent host preference for Quercus. It has a worlwide distribution, known from Europe, North and South America (Brazil, Mexico) and Asia (India, Taiwan) (Petrini, 1992; San Martin Gonzalez & Rogers, 1995; Ju & Rogers, 1999). The absence of records of R. corticium from British Isles (Petrini, 1992; Rogers & Ju, 1998) where it seems "replaced" by R. aquila, is noteworthy but needs further confirmation.