Endophytic halotolerant Bacillus velezensis FMH2 alleviates salt stress on tomato plants by improving plant growth and altering physiological and antioxidant responses

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

Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2021
Publication Date: 5/21/2021
Citation: Masmoudi, F., Tounsi, S., Dunlap, C.A., Trigui, M. 2021. Endophytic halotolerant Bacillus velezensis FMH2 alleviates salt stress on tomato plants by improving plant growth and altering physiological and antioxidant responses. Plant Physiology and Biochemistry. 165:217-227. https://doi.org/10.1016/j.plaphy.2021.05.025.
DOI: https://doi.org/10.1016/j.plaphy.2021.05.025

Interpretive Summary: An ARS researcher from Peoria, IL, collaborated with scientists from a University in Tunisia to characterize the ability of a novel bacterial isolate to mitigate salt stress in tomato plants. The bacterium was isolated from a high salt environment and shown to colonize the internal tissues of tomato plants. 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 effect of the bacterial isolate on plant physiological responses when 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: Salinity stress has significant deleterious effects on agricultural lands and plant yields. Plants undergo a series of physiological and molecular changes to reduce salt-induced damage. However, these mechanisms remain insufficient. The inoculation of plant growth promoting bacteria to improve plant health under stress conditions offers promise. Bacillus velezensis FMH2 has been shown to protect tomato fruits against black mold disease and to improve seed tolerance to abiotic stresses. During this study, the major physiological and metabolic changes connected with FMH2 mitigation of abiotic stress tolerance in tomato plants were explored. In presence of different salt levels, FMH2 showed a high potentiality to colonize internal plant tissues and to produce several plant growth promoting metabolites such as siderophores, indole acetic acid, and hydrolytic enzymes. FMH2 inoculation promoted plant growth (root structure, plant elongation, leaf emission, fresh and dry weights, water content, etc.) in absence as well as in presence of salt stress. FMH2 treatment decreased endogenous Na+ accumulation and increased K+ and Ca2+ uptake. Furthermore, B. velezensis FMH2 inoculation improved chlorophyll contents, membrane integrity and phenol peroxidase concentrations, and reduced malondialdehyde and hydrogen peroxide levels under saline conditions with a significant salinity × strain interaction. The present study suggests the endophytic strain FMH2 involved different mechanisms and regulatory functions to enhance plant oxidative systems and regulates ion uptake mechanisms supporting both growth and stress management.