ABSTRACT
ABSTRACT Interactions between plant and bacteria result in the activation of various plant mechanisms during the resistance phase. These responses to bacteria can be associated with cell signaling of bacteria in pathogenesis. Evidence shows that bacteria can be inhibited by two types of resistance: one that is constitutive and another that occurs for a limited period by chemical and biological stimulants. Constitutive systems involve the inhibition of bacteria in the pre-form phase of resisitance (i.e., during the invasion period) by producing toxic compounds when cells are injured, or by a combination of physiological factors. Known interactions, particularly between plants and pathogens, result in either successful infection (compatible response) or resistance (incompatible response). Advances in studies on bacterial pathogens have revealed the possibilities of using these systems to gain new insight into the nature of plant resistance to pathogens. Induced resistance systems include hypersensitive reaction (HR) as well as other protection responses which depend upon stimulants that mimick pathogen effectors. HR is elicited by most phytopathogenic bacteria (in particular, Pseudomonads, Xanthomonads, and especially Erwinia amylovora) when introduced into non-host plants, but not by most saprophytic bacteria. The second type of induced resistance is a protective reaction that can be induced by prior inltration of living cells with avirulent or incompatible strains. Resistance is also induced by heat-killed cells of the bacteria. Responses to strains and chemical stimulants are generally local in plant organs, at the original site(s) of
10.1 Introductıon ..........................................................................................................................206 10.2 What Is Host Resistance to Bacteria? ...................................................................................206 10.3 An Overview of Induced Resistance and Bacterial Pathogens ............................................207
