Plant Growth Promotion and Biocontrol Mediated by Plant-Associated Bacteria

Abstract

The rhizosphere, defined as the volume of soil under the physical, chemical and biological influences of plant roots, is a region of enormous microbial diversity and activity. This microbial activity is essential for plant nutrition and health since it favours the uptake of nutrients by the plant and offers resistance against a wide range of plant pathogens. Bacteria are the main microbial representatives in the rhizosphere, and plant growth-promoting rhizobacteria (PGPR) stimulate plant growth by multiple mechanisms. In this chapter, we present an overview of the strategies employed by PGPR to exert their beneficial effects on the colonized plants. The direct effects of PGPR on plant growth are mainly derived from their capacity to improve the nutritional status of plants and the production of phytohormones. Alternatively, beneficial rhizospheric bacteria can also promote plant health by protecting plants against pathogens mainly through the induction of systemic resistance and the production of exoenzymes and multiple antagonistic metabolites. Here, special attention has been given to the biosynthesis and biological activities of bioactive volatiles, non-ribosomal peptides and polyketides by PGPR. Finally, the promising use of PGPR-based products as sustainable agricultural practices is discussed.