Bacillus subtilis-Mediated Abiotic Stress Tolerance in Plants

Abstract

Abiotic stresses have a significant negative impact on global agricultural productivity. The application of the beneficial plant growth-promoting bacterium (PGPB) Bacillus subtilis is a sustainable and environmentally friendly strategy to cope with the adverse effects of abiotic stresses on plants. A review of the literature indicates that B. subtilis exerts growth-stimulating and protective effects on different plant species under various environmental stresses, including drought, salinity, heavy metals, etc. Despite numerous studies, the pathways by which B. subtilis induces plant tolerance to stress, and the mechanisms of interaction in the systems “B. subtilis – host plants – stress” leading to the increase of plant growth and tolerance, are not completely understood. These mechanisms are driven by wide range of biologically active substances, not yet fully characterized, which improve the bioavailability of macro-/micronutrients and induce systemic resistance and tolerance to the stressors. The most effective bacterium in growth promotion and plant protection against stress might be the endophytic B. subtilis which is living inside the plant tissues. They are less dependent on external environmental factors than epiphytic strains and provide long-term protection to the host plant which, along with the promotion of growth, is economically beneficial. Therefore, the precise understanding the mechanisms used by B. subtilis is extremely important to fully utilize the potential of this microbe as a component of organic agriculture, and as an agent to increase plant productivity and maintain long-term sustainability in a clean environment. A solid understanding of how these biological systems work will contribute to our future food security. This chapter presents numerous examples where the application of B. subtilis has successfully improved plant abiotic stress tolerance. The recent progress made in understanding the role of B. subtilis in plant growth, development and defense responses to different abiotic stresses is discussed. The current state of knowledge of the fundamental physiological and biochemical mechanisms of B. subtilis-induced abiotic stress tolerance in host plants and the potential of B. subtilis in reducing postharvest food losses are also reviewed.