Halotolerant Bacillus spizizenii FMH45 promoting growth, physiological, and antioxidant parameters of tomato plants exposed to salt stress

Authors: MASMOUDI, FATMA - University Of Sfax; TOUNSI, SLIM - University Of Sfax; Dunlap, Christopher; TRIGUI, MOHAMED - University Of Sfax

Submitted to: Plant Cell Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2021
Publication Date: 5/13/2021
Citation: Masmoudi, F., Tounsi, S., Dunlap, C.A., Trigui, M. 2021. Halotolerant Bacillus spizizenii FMH45 promoting growth, physiological, and antioxidant parameters of tomato plants exposed to salt stress. Plant Cell Reports. 40:1199-1213. https://doi.org/10.1007/s00299-021-02702-8.
DOI: https://doi.org/10.1007/s00299-021-02702-8

Interpretive Summary: An ARS researcher from Peoria, Illinois collaborated with scientists from a University in Tunisia to characterize a novel isolate of Bacillus spizizenii from a high salt environment. High salt contamination is a significant problem worldwide in irrigated agricultural lands. This strain was determined to increase salt tolerance and enhance plant yield in tomatoes. The current study evaluated the role of secondary metabolites and enzyme activities in tomatoes irrigated with different salt concentrations. The results showed treatment with the strain enhanced several plant traits while grown under salt stress. Future research will evaluate the potential of the strain in larger fields trials in areas with salt stress. The research benefits U.S. farmers and consumers who rely on irrigated vegetable crops.

Technical Abstract: Agricultural soil salinization is a serious issue worldwide affecting agricultural yield. Plant growth promoting bacteria can enhance salt tolerance and plant yield. Bacillus spizizenii FMH45 has been shown to inhibit fungal attacks in tomato fruits and to augment tomato seed germination in presence of abiotic stresses. During this study, we reported for the first time B. spizizenii as a salt-tolerant bacterium able to alleviate salt stress in tomato plants. B. spizizenii FMH45 was examined in vitro for its potential to produce several plant growth promoting characters (siderophores, IAA, and phosphate solubilization) and hydrolytic enzymes (cellulase, glucanase and protease) in the presence of saline conditions. FMH45 was also investigated in vivo in pot experiments to evaluate its ability to promote tomato plant growth under salt stress condition. FMH45 inoculation, enhanced tomato seedling length, vigor index, and plant fresh and dry weights when compared to the non-inoculated controls exposed and not exposed to a regular irrigation with salt solutions containing: 0; 3.5; 7; and 10 g L-1 of NaCl. FMH45-treated plants also presented improved chlorophyll content, membrane integrity (MI), and phenol peroxidase (POX) concentrations, as well as reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) levels under saline conditions with a significant salinity'×'strain interaction. Furthermore, FMH45 inoculation significantly decreased endogenous Na+ accumulation, increased K+ and Ca2+ uptake, and thereby improved K+/Na+ and Ca2+/Na+ ratios. This study proves that bio-inoculation of FMH45 efficiently increases salt tolerance in tomato plants. This sustainable approach can be applied to other stressed plant species in affected soils.