Induced disease resistance

Abstract

During the co-evolutionary arms race between plants and pathogens, plants evolved a sophisticated defense system to ward off their enemies. In this plant immune system, plant receptor proteins recognize non-self molecules of microbial origin, which leads to the activation of a basal level of disease resistance. The onset of these local plant immune reactions often triggers a systemic acquired resistance (SAR) in tissues distal from the site of infection. Beneficial microbes in the rhizosphere microbiome stimulate a phenotypically similar induced systemic resistance (ISR) that, like SAR, is effective against a broad spectrum of pathogens. There are differences and similarities in the SAR and ISR signaling pathways. The plant defense hormone salicylic acid is a major regulator of SAR, whereas jasmonic acid and ethylene play important roles in ISR. Priming of systemic tissue to express an accelerated defense response upon attack by a pathogen is a common phenomenon in both SAR and ISR. This chapter will outline the current concept of the plant immune system, with special emphasis on mechanisms of systemically induced disease resistance and priming for enhanced defense.