Control of Tomato yellow leaf curl virus disease by Enterobacter asburiae BQ9 as a result of priming plant resistance in tomatoes

Enterobacter asburiae BQ9, a plant-growth-promoting rhizobacterium, was shown to promote tomato plant growth and induce resistance to Tomato yellow leaf curl virus (TYLCV) under greenhouse conditions. Compared with mock-treated tomato plants, plants that were pretreated with BQ9 had increased fresh mass and significantly reduced disease severity and 52% biocontrol efficacy was achieved 30 days after inoculation. The expression of defense-related genes PR1a and PR1b and the H2O2 burst were quickly induced in BQ9 pretreated plants. Antioxidase activity analysis showed that the activities of phenylalanine ammonia lyase, peroxidase, catalase, and superoxide dismutase increased significantly in BQ9 pretreated plants. Our results suggest that the plant-growth-promoting rhizobacterium BQ9 induced a priming of the plant defense responses to TYLCV by increasing the expression of defense response genes, and the induced resistance was mechanistically connected to the expression of antioxidant enzymes and the production of H2O2.