Marine Actinobacteria Offer a Breakthrough in Tomato Salt Stress Tolerance
A new study published in BMC Plant Biology presents compelling evidence that rhizosphere-competent (RC) actinobacteria isolated from mangrove ecosystems can dramatically enhance tomato growth under high salinity conditions. The research team screened 68 isolates from mangrove rhizosphere soils and identified a powerful consortium of two strains—Streptomyces violaceus UAE1 (#36) and Streptomyces levis UAE1 (#53)—that outperform non-rhizosphere-competent bacteria in promoting growth and mitigating stress.
Why These Actinobacteria Matter
Both isolates possess complementary plant-growth-promoting traits:
- Isolate #36: High producer of phytohormones including auxins, cytokinins, gibberellins, and polyamines.
- Isolate #53: Strong ACC deaminase (ACCD) activity, breaking down the ethylene precursor ACC to prevent stress-induced ethylene buildup.
Under 200 mM NaCl—an extremely stressful condition for tomato plants—the RC consortium significantly enhanced shoot and root length, biomass, photosynthesis rates, and chlorophyll content compared to controls and NRC inoculations.
How They Reduce Salt Damage
The paper reports several biochemical and physiological mechanisms activated by the RC consortium:
- Lower leaf sodium accumulation
- Reduced lipid peroxidation (MDA)
- Enhanced peroxidase, catalase, and moderate antioxidant activity
- Elevated phytohormones (auxins, gibberellins, cytokinins, polyamines)
- Sharp reduction (~45%) in endogenous ACC under salt stress
Together, these processes help stabilize membranes, improve nutrient balance, and maintain photosynthesis under high salinity.
A Sustainable Approach for Salinity-Affected Regions
Given that salinity severely restricts agriculture in regions such as the UAE, these findings highlight an ecologically safe bioinoculant strategy. The RC consortium consistently outperformed NRC strains, demonstrating that rhizosphere competence is crucial for sustained colonization and plant benefit.
Conclusion
This study is the first to show the synergistic role of a rhizosphere-competent actinobacterial consortium in enhancing tomato salt tolerance through combined ACCD activity and phytohormone regulation. The results point to a promising future for microbe-based biofertilizers in saline agriculture.
Reference
Almazrouei, L.M., Purayil, G.P., Alnuaimi, L.S. et al. Rhizosphere-competent actinobacterial consortium alleviates salinity stress in tomato through plant growth-promoting traits and ACC deaminase activity. BMC Plant Biol 25, 1443 (2025). https://doi.org/10.1186/s12870-025-07446-1
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