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SAUDI JOURNAL OF BIOLOGICAL SCIENCES Volume 26, Issue 6, September 2019, Pages 1291-1297 https://doi.org/10.1016/j.sjbs.2019.05.004Get rights and content ABSTRACT Plants encounter many
biotic agents, such as viruses, bacteria, nematodes, weeds, and arachnids. These entities induce biotic stress in their hosts by disrupting normal metabolism, and as a result, limit plant
growth and/or are the cause of plant mortality. Some biotic agents, however, interact symbiotically or synergistically with their host plants. Some microbes can be beneficial to plants and
perform the same role as chemical fertilizers and pesticides, acting as a biofertilizer and/or biopesticide. Plant growth promoting rhizobacteria (PGPR) can significantly enhance plant
growth and represent a mutually helpful plant-microbe interaction. _Bacillus_ species are a major type of rhizobacteria that can form spores that can survive in the soil for long period of
time under harsh environmental conditions. Plant growth is enhanced by PGPR through the induction of systemic resistance, antibiosis, and competitive omission. Thus, the application of
microbes can be used to induce systemic resistance in plants against biotic agents and enhance environmental stress tolerance. _Bacillus subtilis_ exhibits both a direct and indirect
biocontrol mechanism to suppress disease caused by pathogens. The direct mechanism includes the synthesis of many secondary metabolites, hormones, cell-wall-degrading enzymes, and
antioxidants that assist the plant in its defense against pathogen attack. The indirect mechanism includes the stimulation of plant growth and the induction of acquired systemic resistance.
_Bacillus subtilis_ can also solubilize soil P, enhance nitrogen fixation, and produce siderophores that promote its growth and suppresses the growth of pathogens. _Bacillus subtilis_
enhances stress tolerance in their plant hosts by inducing the expression of stress-response genes, phytohormones, and stress-related metabolites. The present review discusses the activity
of _B. subtilis_ in the rhizosphere, its role as a root colonizer, its biocontrol potential, the associated mechanisms of biocontrol and the ability of _B. subtilis_ to increase crop
productivity under conditions of biotic and abiotic stress. KEYWORDS Rhizobacteria _Bacillus subtilis_ Biocontrol potential Biocontrol mechanism Biotic stress Abiotic stress ABBREVIATIONS
PGPR plant growth promoting rhizobacteria ACC 1-aminocyclopropane-1-carboxylate deaminase VOCs volatile organic compounds PGP plant growth promotion ISR induced systemic resistance LPs
lipopeptides JA jasmonic acid PAL phenylalanine ammonialyase POD peroxidase PPO polyphenol oxidase SOD superoxide dismutase GA3 gibberellic acid IAA indole acetic acid ABA abscisic acid
CITED BY (0) * Peer review under responsibility of King Saud University. © 2019 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University.