Induced Systemic Resistance in Biocontrol of Plant Diseases

Induction of resistance to pathogens by some strains of plant growth-promoting rhizobacteria (PGPR) and other microorganisms is termed induced systemic resistance (ISR). In contrast to systemic acquired resistance, ISR develops as a result of the colonization of plant roots by PGPR and other plant-beneficial microorganisms. ISR is mediated predominantly by a jasmonate- or ethylene-sensitive pathway. Some strains of Pseudomonas, Bacillus, Serratia, Trichoderma, etc., elicit ISR in plants against different pathogens. PGPR may activate inducible defense mechanisms in the plant in a way similar to pathogenic microorganisms. The modes of action in ISR may involve, inter alia, a variety of determinants. Though ISR offers a broad-spectrum disease management strategy, much remains to be discovered about how the determinants are perceived and ultimately give rise to ISR. In addition to unraveling the molecular regulation in ISR, deciphering microbial signals that are most effective in eliciting resistance is equally challenging for future research endeavors.