Plant–Rhizobacteria Interactions to Induce Biotic and Abiotic Stress Tolerance in Plants

Abstract

Climate change and extreme environmental conditions are recognized as the most challenging threats to agricultural systems, leading to significant limitations in crop production and yield worldwide. It is a big concern to increase or maintain crop productivity under changing climate conditions to cater for increasing food demand. Among abiotic stresses, salinity, drought and extreme heat are the most common stresses. Abiotic stresses contribute to reducing crop plant production by 50% or more. Like the effects of abiotic stress, constant exposure to biotic stresses—which include pathogen infections and pest and insect attacks—contribute to a major drop in crop productivity and wastage of crops. There is also constant pressure from extreme weather conditions due to climate change and the incidence of biotic stresses. There is a great need to develop biotic and abiotic stress resilience in crops to mitigate the adverse effects of stresses. Such resilience can be achieved through development and adoption of eco-friendly approaches in agricultural systems for crop sustainability and food security. The focus on plant–microbe interactions has attracted more attention in recent years for inducing plant resistance and defence against abiotic and biotic stresses. Plant growth–promoting rhizobacteria facilitate abiotic stress resilience in plants by several strategies through activation of plant growth regulators (which include ethylene, auxin (indole-3-acetic acid)), activity of enzymes such as 1-aminocyclopropane-1-carboxylate (ACC)–deaminase and production of bacterial products such as exopolysaccharide. Diverse plant–microbe interactions in the rhizosphere also help to regulate plant defence pathways under adverse conditions through induction of systematic resistance or systemic acquired resistance. Moreover, other strategies such as microbial antagonism through production of several compounds such as antibiotics, siderophores, bacteriocins and secondary metabolites further boost disease resistance in plants.