Hypoxylon ticinense L. Petrini.
Stromata discoid 10-28 mm diam,or effused-pulvinate 22-50 mm
long x 10-19 mm broad x 1-1.5 mm thick, with inconspicuous perithecial
mounds; surface irregular, undulating, surface sienna (8), rust (39), powdery when young with a villose,
ochreous (44) to sienna (8) margin, becoming dark brick (60) to
sepia (63) when mature;
orange granules beneath surface and between perithecia,
with KOH-extractable pigments orange (7) to sienna (8); the tissue below the
perithecial layer blackish brown to black, 0.5-1 mm thick.
Perithecia obovoid to tubular, 200-250 µm diam x 250-500 µm
Ostioles lower than the stromatal surface, infrequently
surrounded by a ring of white material (25-) 40-60 µm diam.
Asci 80-95 µm total length x 4-5.5 µm broad, the spore
bearing-parts 34-53 µm long, the stipes 40-72 µm long, with apical ring
weakly amyloid to amyloid, discoid, 0.3-0.5 µm high x 1-1.5 µm broad.
Ascospores light brown to brown, ellipsoid-inequilateral,
4.8-6.8 x 2.7-3.4 µm (M = 5.9 x 2.9 µm), with faint straight germ slit
spore-length; perispore dehiscent in 10% KOH, smooth.
Anamorph in nature: ochreous (44), velvety, on young stromata.
Conidiogenous cells yellowish, slightly roughened, 15-20 x 3-3.5 µm;
conidia broadly ellipsoid, 3.5-4 x 2.5-3µm. The conidiogenous structure is
Virgariella-like. The rusty powdery coating on immature stromata
consists of coarsely incrusted orange hyphae 3.5-5 µm wide, producing
globose chlamydospores 4-5.5 µm diam, yellow to orange.
Habitat: on wood or bark of various hosts, usually at the lower
side of branches lying on the ground in damp places. Mostly found on
Crataegus oxyacantha and Fraxinus excelsior, but
occasionally recorded on Acer negundo, Corylus avellana, Malus sylvestris,
Prunus spinosa , Salix caprea (present study), and on Sambucus nigra
(Leroy & Surault 1999), likewise
on "Negundo aceroides", Populus alba, "Padus avium"and
(Ripková & Hagara, 2003).
Known distribution: Europe: Croatia, Czech Republic (Ripková
& Hagara, 2003), France and Switzerland, probably more widespread in Europe.
Specimens examined: FRANCE, Ariège(09): Rimont,
Las Muros, 22 Sept. 1996, JF-96095, on bark of Crataegus
oxyacanthae; Rimont, Las Muros, ruisseau de Peyrau, 25 Aug.
1999, JF-99205, on bark of Crataegus oxyacanthae; Rimont, Las
Muros, 26 Jul. 2000, JF-00129, on a stump of Fraxinus excelsior;
Rimont, Las Muros, ruisseau de Peyrau, 02 Sept. 2001, JF-01181, on bark of
Fraxinus excelsior. Pyrénées Atlantiques (64):
Mauléon, les Barthes de l'Hôpital Saint Blaise, 06 Jun. 1999, JF-99254, on
Prunus spinosa; Mauléon, les Barthes de l'Hôpital Saint Blaise, 06
Jun. 1999, JF- 99255, on Corylus avellana.
Notes: Hypoxylon ticinense is a striking fungus, with distinctive
stromata that are usually discoid, pulvinate, thick and undulating,
surrounded when immature by a bright yellow to orange fimbriate margin.
Perithecia are small-sized, often tubular and lie on a thick blackish
basal tissue. These features are usually distinctive enough for its field
identification but confusion is possible with
which has a very similar stromatal morphology. The
latter differs from H. ticinense in having larger ascospores
which are ellipsoid-equilateral, with perispore indehiscent in KOH.
Another diagnostic feature could be the colour of the discoid area
surrounding the ostioles, black in H.
subticinense, absent or white in H. ticinense, but this
should be checked on more material before being considered constant.
While they both contain mitorubrin and orsellinic acid as prevailing
metabolites, the two latter species are readily distinguished by HPLC analyses:
H. ticinense lacks the azaphilones rubiginosins A and C, and therefore
belongs to the fragiforme chemotype, but contains mitorubrinol acetate
which is lacking in H. subticinense
(Hellwig et al., 2004;
Stadler et al., 2004b).