Phytopathogenic Dothideomycetes - CBS - KNAW

Phylogenetic lineages in Pseudocercospora
Fig. 8. Microcyclospora quercina (CPC 10712). A, B. Colony on oatmeal and potato-dextrose agar, respectively. C–E. Conidiogenous cells giving rise to conidia (arrows). F.
Microcyclic conidiation. G, H. Conidia. Scale bars = 10 μm.
Clade 8: Microcyclosporella and zasmidium-like
Microcyclosporella Jana Frank, Schroers & Crous,
Persoonia 24: 101. 2010.
Epiphytic on leaves and fruit. Mycelium consisting of pale brown,
smooth to finely verruculose, branched, septate, 2–3.5 μm wide
hyphae, at times covered in a mucoid layer, with integrated, lateral,
truncate conidiogenous loci. Conidiophores mostly reduced to
conidiogenous cells. Conidiogenous cells integrated, intercalary
on hyphae, rarely terminal, cylindrical to doliiform, pale brown,
but hyaline if occurring in yeast-like sectors of colonies, smooth,
mono- or polyblastic, proliferating sympodially; loci inconspicuous,
truncate, unthickened, not darkened, pale brown to hyaline.
Conidia hyaline, smooth, subcylindrical to narrowly obclavate or
narrowly fusoid with acutely rounded apex and obconically truncate
base, guttulate, transversely 0–6-septate; microcyclic conidiation
common.
Type species: Microcyclosporella mali Jana Frank, Schroers &
Crous, Persoonia 24: 101. 2010.
Notes: Microcyclosporella was treated as part of the
Pseudocercosporella generic complex (Batzer et al. 2005), but has
since been shown to be polyphyletic within Mycosphaerellaceae
(Crous 2009, Crous et al. 2003, 2009b, c, Frank et al. 2010). The
clade accommodating Microcyclosporella contains many disjunct
elements that vary in morphology from Microcyclosporella s. str.
(hyaline structures) to pigmented structures, namely zasmidiumlike
(verrucuclose conidia) to pseudocercospora-like (smooth
conidia) (see Crous et al. 2009b). We suspect that these groups
may eventually be recognised as distinct genera, but more taxa
need to be examined to resolve this issue.
Clade 9: Paracercospora and pseudocercosporalike
Paracercospora Deighton, Mycol. Pap. 144: 47. 1979.
Foliicolous, phytopathogenic, causing leaf spots. Mycelium
internal, hyaline to pale olivaceous. Stromata absent to poorly
developed. Conidiophores fasciculate, smooth, subhyaline to pale
olivaceous. Conidiogenous cells integrated, terminal, mono- to
usually polyblastic, proliferating sympodially; conidiogenous loci
moderately conspicuous, with narrow thickening along the rim.
Conidia solitary, subcylindrical to obclavate-cylindrical, smooth,
subhyaline to pale olivaceous, with a narrow thickening along the
rim of the hilum.
Type species: Paracercospora egenula (Syd.) Deighton, Mycol.
Pap. 144: 48. 1979.
Specimens examined: Japan, Shimane, on leaves of Solanum melongena, 5 Aug.
1998, T. Mikami, CNS-415, cultures MUCC 883, MAFF 237766. South Korea,
Hongcheon, on leaves of S. melongena, 26 Oct. 2005, H.D. Shin, CBS H-20836,
culture CPC 12537.
Notes: Stewart et al. (1999) conducted the first phylogenetic
analysis of the Mycosphaerellaceae and concluded that the
marginal thickening that occurs along the rims of conidial
scars and hila, originally thought to be the main character to
distinguish Paracercospora from Pseudocercospora, was not
taxonomically significant and suggested that Paracercospora
be reduced to synonymy with Pseudocercospora. The current
study provides new evidence that Paracercospora is not a
synonym of Pseudocercospora, but no consistent morphological
characters that distinguish it from Pseudocercospora s. str.
have been identified. Conidia of Paracercospora egenula are
subhyaline to pale olivaceous with minimal marginal thickening
of the conidiogenous loci (Fig. 9). Conidial scars and hila of Ps.
fijiensis (Arzanlou et al. 2008) and Ps. basiramifera (Crous 1998)
are marginally thickened. Both of the latter species, which belong
to Pseudocercospora s. str., have pale to medium brown conidia.
At present Paracercospora may be defined by a combination of
the minimal marginal thickening of the conidiogenous loci and its
subhyaline conidia.
The taxonomic placement of Paracercospora is complicated
by two other taxa that resolve in the clade together with it. These
are Passalora brachycarpa (pale olivaceous, catenate conidia, and
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