Induction of systemic acquired disease resistance in plants by chemicals

Plants defend themselves from pathogen infection through a wide variety of mechanisms that can be either local or systemic, constitutive or inducible (32, 70, 108, 109). In most cases, the extent to which these various systems affect disease progression is poorly understood, and is an area of extensive biochem­ ical and genetic research. One particular inducible systemic response, known as systemic acquired resistance (SAR), has become a subject of increasing inquiry. SAR is a b road, physiological immunity that results from infection with a necrogenic pathogen. In addition, certain natural and synthetic chemical compounds can trigger similar plant responses. This chapter reviews the liter­ ature on chemicals that apparently act by stimulating the natural defense response in the plant. To put this information in context, we first describe what is known at present about the occurrence of SAR in various species, and our current concept of pathogen-induced SAR. Other recent reviews related to biologically induced SAR and signal transduction complement our discussion (40, 73, 84, 99, 108)