Salt Tolerance Mechanism of the Rhizosphere Bacterium JZ-GX1 and Its Effects on Tomato Seed Germination and Seedling Growth

Abstract

Salinity is one of the strongest abiotic factors in nature and has harmful effects on plants and microorganisms. In recent years, the degree of soil salinization has become an increasingly serious problem, and the use of plant growth-promoting rhizobacteria has become an option to improve the stress resistance of plants. In the present study, the salt tolerance mechanism of the rhizosphere bacterium Rahnella aquatilis JZ-GX1 was investigated through scanning electron microscopy observations and analysis of growth characteristics, compatible solutes, ion distribution and gene expression. In addition, the effect of JZ-GX1 on plant germination and seedling growth was preliminarily assessed through germination experiments. R. aquatilis JZ-GX1 was tolerant to 0–9% NaCl and grew well at 3%. Strain JZ-GX1 promotes salt tolerance by stimulating the production of exopolysaccharides, and can secrete 60.6983 mg/L of exopolysaccharides under the high salt concentration of 9%. Furthermore, the accumulation of the compatible solute trehalose in cells as the NaCl concentration increased was shown to be the primary mechanism of resistance to high salt concentrations in JZ-GX1. Strain JZ-GX1 could still produce indole-3-acetic acid (IAA) and siderophores and dissolve inorganic phosphorus under salt stress, characteristics that promote the ability of plants to resist salt stress. When the salt concentration was 100 mmol/L, strain JZ-GX1 significantly improved the germination rate, germination potential, fresh weight, primary root length and stem length of tomato seeds by 10.52, 125.56, 50.00, 218.18, and 144.64%, respectively. Therefore, R. aquatilis JZ-GX1 is a moderately halophilic bacterium with good growth-promoting function that has potential for future development as a microbial agent and use in saline-alkali land resources.

The Endophytic Strain ZS-3 Enhances Salt Tolerance in Arabidopsis thaliana by Regulating Photosynthesis, Osmotic Stress, and Ion Homeostasis and Inducing Systemic Tolerance

“…This indicates that ZS-3 has an additional mechanism to limit plant Na + accumulation. The concentrations of intracellular and extracellular Na + were lower in Rahnella aquatilis JZ-GX1 inoculated with LB liquid medium (CK) under salt stress, indicating that the bacteria can consume Na + in the medium ( Li et al, 2021 ). ZS-3 is a salt-tolerant strain that tolerates 8% salt in LB, corresponding to moderate salt stress ( Lu et al, 2018 ).…”

Volatile Organic Compounds of the Plant Growth-Promoting Rhizobacteria JZ-GX1 Enhanced the Tolerance of Robinia pseudoacacia to Salt Stress

“…Rahnella aquatilis JZ-GX1 is a strain of plant-promoting bacteria that was isolated from the rhizosphere of Pinus massoniana in our previous study ( Li and Wu, 2014 ). A previous study showed that JZ-GX1 significantly increased the germination rate, germination potential, fresh weight, primary root length and stem length of tomato seeds under salt stress, and it is a moderately salinophilic bacterium with good growth-promoting function ( Li et al, 2021 ). However, it is not clear whether VOCs from this strain can promote plant growth under salt stress.…”

Seed Germination and Seedling Growth of Dendrocalumus brandisii in vitro, and the Inhibitory Mechanism of Colchicine

“…The germination rates of seeds in media supplemented with different concentrations of colchicine were recorded every day, until the 21st day, when the seeds did not germinate anymore. Starting on the 2nd day of observation on culture tubes, the germinated seeds based on a radicle length of 0.2 cm were used as the germination standard (Li et al, 2021 ). The germination rate reached its highest values on the 4th day, and then the germination potential was calculated based on the number of germinated seeds by Day 4.…”