ABSTRACT
Interplay of signaling systems in plant-pathogen interactions is the key component in the
development of diseases in plants (Vidhyasekaran, 1997, 2002, 2004, 2007; Yang et al., 2005).
Signaling between fungal pathogens and plants begins when they meet on the plant surface
(Fujita et al., 2004a). The evidence is strong that plant-fungal interactions begin, and perhaps
their outcomes (susceptibility or resistance) are determined, during the very first few minutes of
association and perhaps even earlier (Heath, 2000). If the signals at the plant surface are
perceived as favorable by the fungi, the fungal spores germinate and either directly penetrate
the cuticle or penetrate the cuticle by producing appressorium and infection peg (Nielsen et al.,
2000; Wright et al., 2000; Apoga et al., 2001; Lev and Horwitz, 2003; Fujita et al., 2004b; Li
et al., 2004). Both the physical and chemical plant signals may be involved in the penetration
process. The plant signals may be used by the fungus to trigger the expression of the genes
necessary to penetrate into the host (Dickman et al., 2003; Tsuji et al., 2003; Yang et al., 2005).
