Introduction Plant-growth-promoting rhizobacteria (PGPR) colonize the rhizosphere of many plant species and confer beneficial effects, such as increased plant growth and reduced susceptibility to diseases caused by plant pathogenic fungi,bacteria, viruses and nematodes [1] . Some PGPR also elicit physical or chemical changes related to plant defense, a process referred to as ‘induced systemic resistance’ (ISR)[2] . ISR elicited by PGPR has suppressed plant diseases caused by a range of pathogens in both the greenhouse andfield [1,2] . However, fewer reports have been published onPGPR as elicitors of tolerance to abiotic stresses, such asdrought, salt and nutrient deficiency or excess. The subjectof PGPR-elicited tolerance to heavy metals has beenreviewed recently [3,4] , so it is excluded from this discussion. Here, we propose the term ‘induced systemic tolerance’ (IST) for PGPR-induced physical and chemicalchanges in plants that result in enhanced tolerance toabiotic stress, and we review recently published workrelated to this subject. Biotic stress is excluded from ISTbecause conceptually it is part of biological control and induced resistance.