Pleosporales - CBS - KNAW

Fungal Diversity
1988; Scheinpflug 1958). Over 400 epithets of Didymosphaeria
were included until the monograph of Aptroot (1995).
Aptroot (1995) examined more than 3000 specimens under
the name Didymosphaeria. The type specimen of Didymosphaeria
(Fungi Rhenani 1770) represents the widespread and
common D. futilis (Aptroot 1995). In this study, we did not
get the lectotype specimen, but described the type of D. futilis
(Sphaeria futilis). Using a narrow concept (ignoring differences
of host or country of origin), Aptroot (1995) accepted
only seven species, which were closely related with the
generic type of Didymosphaeria with over 100 synonyms
distributed among them. Many taxa were found to belong to
other groups, i.e. Aaosphaeria, Amphisphaeria, Astrosphaeriella,
Dothidotthia, Flagellosphaeria, Kirschsteiniothelia, Megalotremis,
Montagnula, Munkovalsaria, Mycomicrothelia,
Parapyrenis or Phaeodothis. Didymosphaeria is mainly characterized
by a peridium consisting of flattened or irregular cells
or completely hyphae; a hamathecium consisting of narrow,
trabeculate paraphysoids or paraphyses, richly anastomosing
above the asci; and brown thinly distoseptate ascospores.
Didymosphaeriaceae was maintained as a separated family
within Pleosporales by Aptroot (1995) because of the
distoseptate ascospores and trabeculate pseudoparaphyses
mainly anastomosing above the asci. This proposal, however,
has not received much support (Lumbsch and Huhndorf 2007).
Phylogenetic study
There have been few molecular investigations of
Didymosphaeria when compared to the morphological
studies. Didymosphaeria futilis resided in the clade of
Cucurbitariaceae (or Didymosphaeriaceae) (Plate 1). The
correct identification of the Didymosphaeria strain used for
sequencing, however, has not been verified.
Concluding remarks
Didymosphaeria is a well established genus represented
by D. futilis. Of particular significance are the narrow
pseudoparaphyses which anastomose above the asci and
brown 1-septate ascospores with indistinct distosepta. Familial
placement of Didymosphaeria is unclear yet because
of insufficient molecular data.
Dothidotthia Höhn., Ber. Deutsch. Bot. Ges. 36: 312
(1918). (Didymellaceae)
Generic description
Habitat terrestrial, saprobic. Ascomata medium-sized, solitary,
clustered or somewhat gregarious, erumpent, subglobose,
apex somewhat papillate to depressed, coriaceous. Peridium
composed of a few layers of dark brown cells of textura
angularis, and giving rise dark brown, thick-walled hyphae in
the basal region, 2-layered. Hamathecium septate pseudoparaphyses
branched in upper part above asci. Asci 8-spored,
bitunicate, clavate, straight to curved. Ascospores biseriate to
obliquely uniseriate, ellipsoid, pale brown, 1-septate.
Anamorphs reported for genus: Dothiorella and Thyrostroma
(Hyde et al. 2011; Phillips et al. 2008).
Literature: Barr1989b; Phillips et al. 2008.
Type species
Dothidotthia symphoricarpi (Rehm) Höhn., Ber. Deutsch.
Bot. Ges. 36: 312 (1918). (Fig. 28)
≡ Pseudotthia symphoricarpi Rehm, Ann. Mycol. 11:
169 (1913).
Ascomata up to 500 μm high×550 μm diam., gregarious
clustered, rarely solitary, erumpent, subglobose, apex somewhat
papillate to depressed, coriaceous (Fig. 28a). Peridium 20–
80 μm thick, composed of 3–6 layers of dark brown cells of
textura angularis, giving rise dark brown, thick-walled hyphae
in the basal region, 2-layered, outer layer wall thicker and inner
layer wall thinner (Fig. 28b). Hamathecium hyaline, septate
pseudoparaphyses, 2–3 μm wide, branched in upper part above
asci. Asci 70–120×15–22 μm, 8-spored, bitunicate, clavate,
straight to curved (Fig. 28c, d and e). Ascospores (20-)22–23
(−26)×(8-)9–10(−11) μm, biseriate to obliquely uniseriate and
partially overlapping, ellipsoid tapering towards subacutely
rounded ends, pale brown, 1-septate, constricted at the septum,
smooth (Fig. 28f) (description referred to Phillips et al. 2008).
Anamorph: Thyrostroma negundinis (Phillips et al. 2008).
Material examined: USA, North Dakota, on branches
of Symphoricarpos occidentalis Hook. (NY, holotype);
Colorado, San Juan Co, c. 0.5 mile up Engineer Mountain
Trail from turnoff at mile 52.5, Hwy 550, dead twigs of
Symphoricarpos rotundifolius A. Gray, 24 Jun. 2004, A.W.
Ramaley 0410 (BPI 871823, epitype).
Notes
Morphology
Dothidotthia was formally established to accommodate
Pseudotthia symphoricarpi (Montagnellaceae, Dothideales)
(von Höhnel 1918a). Many mycologists considered Dothidotthia
closely related to a genus of Venturiaceae such as
Dibotryon by Petrak (1927), or Gibbera by von Arx and
Müller (1954) and Müller and von Arx (1962). Dothidotthia
had been treated as a synonym of Gibbera (von Arx 1954;
Müller and von Arx 1962), which was followed by
Shoemaker (1963) and Eriksson and Hawksworth (1987).
Based on the coelomycetous anamorphic stage and peridium
structure, shape of asci, as well as morphology of
pseudoparaphyses, Barr (1987b, 1989b) retrieved Dothidotthia,
and considered it closely related to Botryosphaeria
(Botryosphaeriaceae). Currently, 11 species are included
within Dothidotthia (http://www.mycobank.org, 01–2011).