Plants exert strong selective forces on rhizosphere microbes, largely through root exudates. Because root exudation is a dynamic process and influences important microbial functions, there is a possibility that plants may vary the selection they impose on soil microbial communities in ways that improve plant performance or alleviate plant stress. We highlight examples of rhizobacteria that aid in several biological and ecological processes when plants are experiencing biotic and abiotic stresses. We suggest that plant-driven selection is altered under stress conditions, and may be used by plants to recruit microbes with stress-alleviating functions. We also highlight current techniques that have been used to study root exudation processes in detail. Our understanding in this area is limited because current research focuses on simple plant-microbe interactions, but achieving a fuller understanding of these mechanisms at the microbiome level is critical to expanding agriculture into marginal lands to enhance global food security. © 2013 John Wiley & Sons, Ltd.