Enhancing tomato resilience: Bacillus sp. H2R10 stimulates defense responses and promotes plant growth against Fusarium wilt

Fusarium wilt is a destructive disease that reduces tomato production. Developing effective bioagents for disease management and growth promotion is crucial for food safety, security, and sustainability. In this study, 48 endophytes were isolated from six different wild plants collected from Alexandria and Dakahlia governorates in Egypt and screened for their antifungal activity against Fusarium oxysporum forma specialis lycopersici HSR3. The bacterial endophyte H2R10 exhibited the highest growth inhibition (88.48%) and was subsequently identified through molecular analysis as Bacillus sp. H2R10. Antifungal activity tests of the diffusible and volatile metabolites produced by Bacillus sp. H2R10 showed significant inhibition of 87.40 and 18.50%, respectively, against the growth of F. oxysporum HSR3. Scanning electron microscopy revealed disintegration, lysis and collapse of F. oxysporum HSR3 mycelia when exposed to the metabolites of Bacillus sp. H2R10. Gas chromatography–mass spectrometry (GC-MS) identified various antifungal compounds produced by Bacillus sp. H2R10, including palmitic acid, citric acid, and other antifungal compounds. Results from two field experiments demonstrated strong biocontrol activity, reducing disease severity by 48%, compared with untreated control. In addition, treatment of tomato plants with Bacillus sp. H2R10 upregulated defense-related genes JERF3, CHI II, PAL1, and F3H by 6.41-, 18.12-, 10.01-, and 8.27-fold, respectively. An increase in phenolic content and in the activity of antioxidant enzymes POD and PPO was also observed. Furthermore, Bacillus sp. H2R10 promoted tomato plant growth and enhanced chlorophyll content in tomato leaves. These findings suggest that Bacillus sp. H2R10 is a promising biocontrol agent for combating Fusarium wilt in tomato and a potent promoter of plant growth.