Highlights of the Didymellaceae - Studies in Mycology

www.studiesinmycology.org
Phoma And relAted pleoSporAleAn generA
Fig. 11. Phoma minor (CBS 325.82). A–C. Fourteen-day-old colonies on OA (A), MEA (B) and CHA (C). D–E. Pycnidia. F. Section of the pycnidial wall. G. Conidia. Scale bars:
D = 200 μm; E = 100 μm; F–G = 10 μm.
Three species, Ph. clematidina, Ph. glaucii and Ph. aquilegiicola
form a separate clade (Group C) within the Didymellaceae, and
are treated above. Also Ph. nigripycnidia and Ph. narcissi are not
accommodated here.
In contrast to the Heterospora species that are absent in
this clade, several current Phoma taxa recovered here have
been associated with the section Phyllostictoides, such as Ph.
artemisiicola, Ph. caricae-papayae, Ph. cucurbitacearum, Ph.
heliopsidis, Ph. rudbeckiae, and the quarantine-organisms Ph.
ligulicola var. ligulicola and var. inoxydabilis (De Gruyter 2002).
These are all included in subclade S1 (BPP = 0.93, RBS = 73 %).
These species do produce a percentage of multicellular conidia in
culture that are often considerably larger than the regular aseptate
ones. However, Boerema et al. (1997) decided to exclude the
Ph. ligulicola varieties and Ph. cucurbitacearum from section
Heterospora, as the sizes of the Stagonosporopsis-like conidia do
not always exceed that of the aseptate conidia in these species. A
sister clade to subclade S1 is S2, which hosts the potato pathogens
Ph. andigena and Ph. crystalliniformis – formerly known as Ph.
andina var. crystalliniformis. Both species originate from the Andes
region, and are regarded as serious quarantine pathogens in large
parts of the world (Smith et al. 1992).
In addition, three other subclades can be recognised in this
clade. One (S3) comprises the species Ph. schneiderae and Ph.
subboltshauserii (both of the section Heterospora) as well as Ph.
astragali. This species is known as a pathogen of Astragalus spp.,
and is characterised by a high percentage of “distorted” conidia,
but thus far, no records have been made of a Stagonosporopsislike
synanamorph. Whereas records of Ph. astragali and Ph.
schneiderae are mainly limited to the American continent, Ph.
43