This experiment aimed to study the effect of three species of plant growth promoting rhizobacteria (Frateuria aurantia, Bacillus megaterium and Azotobacter chroococcum) inoculated to seeds and shoots of tomato plants on Cucumber mosaic virusdisease severity, salicylic acid and peroxidase activity content and their ability to suppress the effect of CMV in a plastic tunnel in Tartus-Syria. The results showed that, the treatment with single bacteria Frateuria aurantia produced significant reduction in disease severity and higher infree salicylic acid and peroxidase activity contents compared with Bacillus megaterium or Azotobacter chroococcumin CMVinfected or healthy controls. Mixed treatments with three bacterial species gave the highest reduction in disease severity and increasedof free salicylic acid and peroxide activity contained in both CMV-infected and healthy tomato plants. Such increase in free salicylic acid and peroxidase activity contents suggested the potential ability of rhizobacteria to stimulate mechanisms of systemic resistance and reduces the effect of CMV infection on tomato plants.

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