PGPR-induced systemic resistance (ISR) in plant disease management

Abstract

Induced resistance is a physiological state of enhanced defensive capacity elicited by plant growth promoting rhizobacteria (PGPR) such as Pseudomonas putida, Serratia marcescens, Flavomonas oryzihabitans, Bacillus pumulus, etc. where the plant's innate defences potentiated against subsequent biotic challenges becomes a popular means of protection of the plant from pathogens through induced systemic resistance (ISR). A number of bacterial determinants act as resistance elicitor compound in the development of resistance in plants such as siderophore, pyoverdin, bacterial SA, fucose, rhamnose (lipopolysaccharide) and flagellins reported so far. The transcriptional activation of PR genes is differentially regulated by NPR1 which is not only required for the SA-dependent expression of PR genes that are activated during SAR, but also for the JA- and ET-dependent activation of defence responses resulting from rhizobacteria-mediated ISR. The enzymes that have been associated with ISR includes phenylalanine ammonia lyase (PAL), chitinase, β-1,3-glucanase, peroxidase (PO), polyphenol oxidase (PPO), superoxide dismutase (SOD), catalase (CAT), lipoxygenase (LOX), ascorbate peroxidase (APX) and proteinase inhibitors.