idiales,andLeptomitales. In his final synopsis,
Sparrow added a further two orders, theRhipi-
diales, which he split from theLeptomitales,
and theEurychasmales, which he split from
theSaprolegniales(Table3.3) (Sparrow 1976 ).
The most recent taxonomic revision of the
group (summarized in Table3.4) was made by
Dick (2001a) based on a critical and scholarly
re-evaluation of primarily morphological data
(Table3.4).
As part of this revision Dick (2001a) introduced the
subphylum and class namesPeronosporomycotinaand
Peronosporomycetesrespectively (Table3.4), in place
of the traditional informal group/class namesoomy-
cete/Oomycotafirst introduced by Winter in 1879
(Dick2001a). He argued that higher-level nomenclature
should also reflect the type genus (Peronospora) rather
than a morphological character (the oospore) after
which the group had traditionally been named. As
recommended by Le ́vesque ( 2011 ), the common name
oomycete is retained in this account, and we use
Oomycotaas the formal phylum name.
However, since the revision of Dick (2001a)
was published, many molecular taxonomic
studies of oomycetes have been conducted
(examples shown in Fig.3.5), and it is now
apparent that many of his changes are not sup-
ported by sequence data (cf. Tables3.4and3.5).
The oomycetes nevertheless form a statistically
well-supportedmonophyletic clade(Figs.3.1b
and3.5). Two single-locus [SSU rRNA and large
subunit (LSU) rRNA] phylogenetic trees are
given in Fig.3.5, which include unpublished
sequence data for a number of recent isolates
of less-studied taxa (Fig.3.5b). Recent molecu-
lar studies have shown that many of the tradi-
tional taxonomic paradigms used to classify
these organisms require re-evaluation (Runge
et al.2011a; Thines 2009 ; Voglmayr 2008 ), and
many order- and family-level circumscriptions
need to be redefined. Resolving the taxonomic
position of many of the smaller, less-studied
orders is also problematic due to either a com-
plete lack of sequence data or under-
represented taxon sampling (Table3.5).
In the following section on the preliminary
taxonomic framework for the oomycetes, any
newly introduced taxonomic names that have
not been formally described are indicated by
quotation marks (“ ”) at first mention. Orders
and families that molecular data suggest are not
monophyletic but that cannot at present be
properly resolved are designated by a ~ symbol
before their name, indicating that they will
require taxonomic revision in the future. Two
monophyletic class-level clades, the “Saproleg-
niomycetes” and Peronosporomycetes [but
note that this name is used in a revised way
from that of Dick (2001)], are recognized in this
account (Fig.3.6, Table3.5); they correspond
approximately to the two galaxies proposed by
Sparrow ( 1976 ) (Table3.3). In addition, a num-
ber of less-resolvedearly-diverging cladeswill
almost certainly merit class-level designation
(Fig.3.6). However, until more robust data are
available, they are grouped into four orders but
are not assigned to classes at present and are
listed asincertae sedis(Table3.5). A revisedTable 3.5(continued)
Part 3: Graminicolus downy mildews (GDM) Eraphthora,Graminivora,Peronosclerospora,
Poakatesthia
Sclerospora,Scleropthora,Viennotia
Part 3: Brassicolous downy mildews (BDM) Hyaloperonospora,Perofascia
Part 3: Downy mildews with coloured conidia (DMCC) Peronospora,Pseudoperonospora
Part 3: Downy mildews with pyriform haustoria (DMPH) Basidiophora,Benua,Bremia,Novotelnova
Paraperonospora,Plasmopara,Plasmoverna,
Protobremia
aGenera inboldhave been sequenced
bGenus placement requires confirmation
cGenera introduced by Uzuhashi et al. ( 2010 )
Tildedenotes genus which is not monophyletic and will need revision
52 G.W. Beakes et al.