Mitigation of Heat Stress in Solanum lycopersicum L. by ACC-deaminase and Exopolysaccharide Producing Bacillus cereus: Effects on Biochemical Profiling

Abstract

Soil microorganisms might be assessed for their capabilities of plant growth promotion in order to identify heat tolerant strategies for crop production. The planned study was conducted to determine the potential of heat tolerant plant growth promoting rhizobacteria (PGPR) in mitigating heat stress effects in tomato. Bacillus cereus was evaluated for plant growth promoting activities and assessed for 1-aminocyclopropane-1-carboxylate (ACC-deaminase) (0.76–C0.9 μM/mg protein/h), and exopolysaccharide (0.66–C0.91 mg/mL) under normal and heat stressed conditions. Plant growth regulators were evaluated through High Performance Liquid Chromatography. Bacterial inoculation effects on important physiological and biochemical parameters were evaluated under normal and heat stressed conditions in growth chamber. The morphological-physiological traits significantly revealed drastic effects on both of un-inoculated tomato varieties under heat stress conditions. Bacterial augmentation significantly promoted shoot, root length, leaf surface area, fresh and dry weight. Heat stress enhanced extracellular polymeric substances (EPS) production and cleavage of ACC into a-ketobutyrate and ammonia due to ACC-deaminase producing bacteria that significantly reduced the adverse effects of heat on tomato growth. In conclusion, the applied plant growth promoting rhizobacteria (PGPR) bacterial strain proved as potential candidate for improving tomato crop growing under heat stressed conditions. However, it is highly suggested to validate the current results by conducting field trials.

Successful Plant Growth-Promoting Microbes: Inoculation Methods and Abiotic Factors

“…High and low temperatures potentially caused by climatic change may become a major threat to global agriculture, reducing crop production, with drastic economic results (Ipek et al, 2019;Mukhtar et al, 2020). Beneficial microorganism inoculation is efficient in enhancing plat growth and mitigating adverse stresses caused by extreme temperature, as Pseudomonas putida in Triticum sp.…”

“…Beneficial microorganism inoculation is efficient in enhancing plat growth and mitigating adverse stresses caused by extreme temperature, as Pseudomonas putida in Triticum sp. (Ali et al, 2011) and Bacillus cereus in Solanum lycopersicum (Mukhtar et al, 2020) under high temperature. Fernandez et al (2012) related that under low temperature Burkholderia sp.…”

“…Extreme temperatures are recognized stress in agriculture, reducing seed germination, seedling growth, yield and altering plant metabolism (Ipek et al, 2019;Mukhtar et al, 2020). Temperature impacts morphological, biochemical and physiological attributes of plants, interfering with plant-PGPM interaction by changing root exudation composition (Ali et al, 2011;Meena et al, 2015;Ipek et al, 2019).…”

Bioinoculants in Technological Alleviation of Climatic Stress in Plants

“…The bacterial strain Bacillus cereus capable of producing ACC-deaminase (0.76-C0.9 μM/mg protein/h) can cleavage ACC to α-ketobutyrate and ammonia to increase heat tolerance in tomato (Solanum lycopersicum L.). Moreover, increase in synthesis of exopolysaccharide (0.66-C0.91 mg/mL) showed promising plant growth in tomato [9] (Table 2). Moreover, the presence of enzymatic antioxidants such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and accumulation of metabolites such as amino acids and proline had boosted the scavenging activity against ROS under heat stress.…”

“…Bacillus cereu/Solanum lycopersicum Heat stress Increased production of exopolysaccharide, cleavage of ACCdeaminase [9] Bacillus amyloliquefaciens, Agrobacterium fabrum/Triticum aestivum Water stress Increase in biomass and grain yield [10] Aneurinibacillus aneurinilyticus, Paenibacillus sp./Phaseolus vulgaris…”