Belbahri 2011 ) andcox2-based trees (Hudspeth
et al. 2000 ),Sapromycesis basal to the Peronos-
poromycetes, whereas in LSU rRNA trees it is
basal to the Saprolegniomycetes but without
strong support (Fig.3.5b) (Petersen and Rosen-
dahl 2000 ; Riethmu ̈ller et al. 1999 ). In combined
cox2 and nrLSU analyses it was placed basal to
the remaining Peronosporomycetes with maxi-
mum support (Thines et al.2009c).Sapromyces,
however, has a number of anomalous features
not normally associated with this order. The
zoospores are released directly from the sporan-
gium and, in S. androgynous, contain large
structured K-bodies (Gotelli and Hanson
1987 ), both of which are features normally asso-
ciated with Saprolegniomycetes (Beakes 1987 ,
1989 ). There is clearly an urgent need for other
genera in this order to be sequenced.
TheCOII amino acidsequences derived fromcox2 gene
analyses revealed thatSapromyceshas the same signa-
ture amino acid insertion-deletion (indel) sequence
LEF/Tas that found in other members of the Peronos-
porales rather than theYTDindel found in the Lepto-
mitaceae (Cook et al. 2001 ; Hudspeth et al. 2000 , 2003 ).
- Albuginales
Dick (2001a) placed the white blister rusts
(Fig.3.13) in their own family, the Albuginaceae,
in the Peronosporales (Tables3.3 and 3.4).
However, numerous phylogenetic studies
using LSU rDNA and cox2 sequences have
shown that the white blister rusts form a statis-
tically well-supported clade that is alwaysearly
diverging in the peronosporomycete clade
(Hudspeth et al. 2003 ; Riethmu ̈ller et al. 2002 ;
Thines and Spring 2005 ; Thines et al. 2008 ,
2009a) and always quite separate from other
members of the Peronosporales. This led Thines
and Spring ( 2005 ) to introduce the orderAlbu-
ginalesfor white blister rusts containing a single
familyAlbuginaceae(Table3.5). Current multi-
locus phylogenies continue to support the deep
branching of the Albuginales (Thines and Vogl-
mayr 2009 ; Thines et al.2009b), although their
relationship to some lagenidiaceous groups
remains to be explored, especially, as in single-
locus SSU rRNA phylogenies,Albugoseems to
cluster amongst the Pythiales (Lara and Bel-
bahri 2011 ; Sekimoto et al. 2009 ), although with-
out significant support.
The Albuginales are obligate biotrophic
pathogensof angiosperms forming blister-like
lesions on the leaves. They produce intercellu-
lar hyphae with small stalkedglobose haustoria
(Fig.3.13b) (Coffey 1975 ; Mims and Richard-
son, 2002 ; Soylu et al. 2003 ). Another feature of
white blister rusts is theirsubepidermalmode
of sporulation (Fig. 3.13a), with the fungus
enzymatically separating the epidermis from
the mesophyll to create a cavity in which spor-
ulation takes place in rust-like fashion (Heller
and Thines 2009 ). Dispersive sporangia are
produced in abasipetal fashionfrom the apex
of unbranched sporogenous hyphae (Fig.3.13a)
(Beakes 1987 ; Heller and Thines 2009 ; Mims
and Richardson 2002 ). Zoospore formation
from the deciduous conidiosporangia is fre-
quently suppressed, although it can occur,
releasing a cluster of zoospores into a transient
vesicle (Fig.3.13c–e), which quickly ruptures,
releasing free-swimming zoospores (Fig.3.13f).
White blister rust species have thick, multilay-
ered verrucose oospore walls (Fig. 3.13g)
(Thines et al.2009a) whose outer layers seem
to be derived from the periplasm (Beakes
1981b; Tewari and Skoropad 1977 ). Upon ger-
mination, oospores convert into sporangia and
release zoospores directly into a transient vesi-
cle (Fig.3.13h).
White blister rusts parasitize a broad range
of mostly herbaceous flowering plants, and
recent molecular studies have shown consider-
able genetic diversity within this order (Choi
et al. 2006 , 2007 , 2008 ,2011a,b; Mirzaee et al.
2013 , Ploch et al. 2010 , 2011 ;Thinesetal. 2008 ,
2009c;VoglmayrandRiethmu ̈ller 2006 ). Cur-
rently three genera,Albugo,Pustula,andWilsoni-
ana, are parasitic to rosids, asterids, and the
Caryophyllales respectively (Thines and Spring
2005 ; Thines and Voglmayr 2009 ). White blister
rusts, in contrast to many oomycete plant
pathogens, cause little or no visible damage to
the tissues they infect (Kemen and Jones 2012 ;
Thines and Kamoun 2010 ). There is increasing
evidence supporting the endophytic habit ofA.
candidawhereasymptomaticinfectionsarewide-70 G.W. Beakes et al.