Selenium-induced rhizosphere microorganisms endow salt-sensitive soybeans with salt tolerance

Area of Science:

• Agricultural Science
• Environmental Science
• Microbiology

Background:

• Soil salinization is a major abiotic stress limiting soybean production worldwide.
• Rhizosphere microorganisms can enhance plant stress resistance, but their role in selenium-mediated salt tolerance is unclear.
• Selenium's impact on rhizosphere microbial communities and subsequent plant salt tolerance requires further investigation.

Purpose of the Study:

• To investigate the effect of selenium application on soybean rhizosphere microbial community structure under salt stress.
• To isolate and evaluate salt-tolerant bacteria from selenium-fertilized soybean rhizosphere for their ability to enhance salt tolerance in sensitive soybean varieties.
• To elucidate the combined role of selenium and specific rhizosphere bacteria in mitigating salinity stress in soybean.

Main Methods:

• Pot experiments were conducted using salt-tolerant and salt-sensitive soybean varieties under varying salt stress levels with and without selenium application.
• Rhizosphere microbial community structure was analyzed using high-throughput sequencing of the 16S ribosomal RNA gene.
• Four isolated salt-tolerant bacteria were inoculated into salt-sensitive soybean to assess their impact on plant growth, physiological parameters, and ion content under salt stress.

Main Results:

• Selenium application improved soybean salt tolerance by optimizing rhizosphere microbial community structure and enhancing soil enzyme activities in both soybean varieties.
• Inoculation with the four isolated bacteria significantly increased plant height, aboveground fresh weight, SPAD value, and K+ content in salt-sensitive soybean under salt stress.
• Bacterial inoculation also reduced proline, MDA, and Na+ content in salt-sensitive soybean, indicating enhanced stress mitigation and ion homeostasis.

Conclusions:

• Selenium application effectively modulates the rhizosphere microbial community, contributing to enhanced soybean salt tolerance.
• The isolated salt-tolerant bacteria are promising bio-agents for improving the salt tolerance of sensitive soybean varieties.
• Combining selenium application with beneficial rhizosphere microorganisms presents a viable strategy for alleviating salinity stress in soybean cultivation.