Induced Systemic Resistance (ISR) by Beneficial Microbes

Induced Systemic Resistance (ISR) is a plant defense mechanism activated by beneficial microbes, particularly plant growth-promoting rhizobacteria (PGPR) and fungi (PGPF), following their colonization of plant roots. Unlike Systemic Acquired Resistance (SAR), which is triggered by pathogenic attack and relies on salicylic acid (SA), ISR is primarily mediated by jasmonic acid (JA) and ethylene (ET) signaling pathways. ISR enhances the plant’s defensive capacity systemically, without causing localized cell death or requiring continuous pathogen presence. Key regulatory components include microbial elicitors, root transcription factors like MYB72, and the central immune regulator NPR1. Beneficial microbes use strategies like biofilm formation, immune modulation.