Bacteria-Mediated Elicitation of Induced Resistance in Plants upon Fungal Phytopathogen

Abstract

Plants are sessile organism and primary producer of the ecosystem and communicate with above- and belowground communities that consist of benign/pathogenic microbes. Among these interactions, phytopathogenic fungi and oomycetes are the major causative agents of infectious crop plant diseases. To control these pathogens is extremely difficult, and a very small percentage of applied fungicides used for crop protection reach the target pathogen. To combat with such pathogen, higher level of resistance in addition to indigenous immune system is required which is elicited by plant growth-promoting bacteria (PGPB) in the form of induced systemic resistance in plants. Induced systemic resistance is prior activation of resistance in plants through PGPB via root priming that leads to defense-related protein activation which is independent of salicylic acid and dependent on jasmonic acid and ethylene. In case of it, nonexpressor of pathogenesis-related protein 1 (NPR1) plays the most important role by regulating hormonal defense signaling pathway leading to activation of pathogenesis-related and defense-related protein depending on the preceding signals. PGPB-elicited induced resistance showed that some of the bacterial determinants are responsible for the elicitation of induced systemic resistance (ISR). Although PGPB seem to actively suppress local host defense responses in the roots, it also produces elicitors that are responsible for the onset of systemic immunity. This chapter focuses on recent research study concerning the interaction between PGPB and plants under biotic stress condition.