Soluble and Volatile Metabolites of Plant Growth-Promoting Rhizobacteria (PGPRs): Role and Practical Applications in Inhibiting Pathogens and Activating Induced Systemic Resistance (ISR)

Plant growth-promoting rhizobacteria (PGPRs) release soluble and volatile compounds, which are implicated in antibiosis, cell signalling, induction of resistance and tolerance in plants against biotic and abiotic stresses. Due to public concerns about the potential environmental hazards of chemical use in agriculture, exploration of PGPRs for alternative antimicrobials is picking up momentum. Biochemical and metabolomics analyses of diverse PGPRs have identified several potential compounds for development and deployment in agriculture. Chemical profiling and functional analyses have provided fundamental insights into the nature of soluble and volatile chemicals produced by PGPRs. These studies are providing a solid launching point for further studies into unravelling the chemical basis of activities of PGPRs. In this chapter, some of these findings will be discussed, which will hopefully stimulate much needed additional investigations focused on exploring the full spectrum of the antimicrobial potential of PGPRs. Future challenges in the field, including biosafety concerns and potential ecological consequences of PGPR-derived antimicrobials will also be discussed.