Potential use of Bacillus spp. as an effective biostimulant against abiotic stresses in crops-A review

Environmental (abiotic) stresses significantly threaten the worldwide crop production and food security. Rapid, drastic changes in the global climate have exacerbated such stresses for crops. Plant-associated bacteria have been shown to enhance stress resistance and cope with the negative impacts of various abiotic stresses through the induction of various mechanisms. In soil, the rhizosphere and endosphere of plants, the Bacillus genus is a predominant bacterial genus. Members of this genus, which are tremendously diverse both metabolically and genetically, survive for a long time under unfavorable environmental conditions due to their ability to form longlived, stress-tolerant spores. Bacillus spp. secrete several metabolites that trigger plant growth and enhance plants' tolerance to biotic and abiotic stresses. Some of the Bacillus species are available commercially as phytostimulants, biopesticides, and biofertilizers. Due to this functional versatility, the Bacillus genus is one of the most widely used in the agro-biotech industry. However, the potential of the Bacillus genus has not yet been sufficiently realized, and transferring technology related to the genus from the lab environment to real world applications in the field needs to be emphasized. A better understanding of mechanisms of action of beneficial Bacillus spp. is needed for the development of products to support green biotechnology in agriculture and industries. This report comprehensively reviews the applications of Bacillus spp. in abiotic (e.g., salinity, drought, inorganic and organic pollutant toxicity, nutritional imbalance, low-high temperatures, and waterlogging) -stressed agriculture and discusses their potentials for the development of new products of biotechnological implications, highlighting gaps that remain to be explored to improve and expand on Bacillus-based biostimulants.