288 M. BABADOOST
Orsomando et al. 2001; Fellbrich et al. 2002; Gaulin et al. 2002; Qutob
et al. 2002). Some of these effectors induce defense responses in both
susceptible and resistant plants and are referred to as general elicitors.
Based on similarity to self and non-self-recognition models of the ani-
mal innate immune system, these general elicitors have been likened
to pathogen-associated molecular patterns (PAMPs), which are surface-
derived molecules that induce the expression of defense response genes
and the production of antimicrobial compounds in host cells (Gomez-
Gomez and Boller 2002; Nurnberger and Brunner 2002).
III. OOMYCETE DISEASES OF CUCURBITS AND THEIR
MANAGEMENT
Traditionally, the fight against plant diseases was intended to elim-
inate pathogens and was referred to as “plant disease control.” But
over time, approaches to reducing plant diseases have evolved and the
term “plant disease management” has become more germane (Fry 1982;
Jacobsen 2001; Maloy and Baudoin 2001; Maloy 2005). Unlike disease
control, which implies complete control, disease management attempts
to reduce disease levels below economic thresholds, since complete
elimination of diseases is typically not practical. The choice of dis-
ease management techniques varies with the pathogen, the host, and
the environment in which they interact. With oomycete diseases, effec-
tive disease management strategies are mostly determined by disease
forecasting rather than traditional calendar spray procedures and the
use of integrated approaches.
Major oomycete diseases of cucurbits are caused byPhytophthora
capsici,Pseudoperonospora cubensis,andPythiumspp. (Leonian 1922;
Gottlieb and Butler 1939; Waterhouse and Brothers 1981; Erwin and
Ribeiro 1996; Gubler and Davis 1996b; Thomas 1996; Zitter et al. 1996;
Babadoost et al. 2004; Colucci and Holmes 2010).Phytophthora drech-
slerialso has been reported as a causal agent of root rot in some areas
(Zitter et al. 1996).
A. Phytophthora Blight
Phytophthora capsiciwas first described by Leon H. Leonian as caus-
ing a disease in pepper in New Mexico in 1922 (Leonian 1922). The
first report ofP. capsicicausing disease in cucurbits was in 1937 in
California and Colorado (Tomkin and Tucker 1937; Kreutzer et al.
1940). Since then,P. capsicihas been observed in cucurbits in most