Fig. 5. Activation of induced systemic resistance (ISR) against Ralstonia solanacearum in HRS samples by the spore-forming Firmicutes and Actinobacteria.

a Co-cultivation of HRS-specific Firmicutes bacteria and bacterial wilt pathogen R. solanacearum on TSA agar medium. Four selected bacterial strains (50 μL; OD₆₀₀ = 1), gentamycin (GM; 0.5 mg/mL; positive control), or sterile distilled water (Control; negative control) were dispensed on a lawn of R. solanacearum on TSA agar plates, and photographs were captured after 2 days. b Spatial separation system. A suspension of R. solanacearum (50 µL; OD₆₀₀ = 1) was injected into the tomato stem 7 days after the root system was treated with each of the four selected Firmicutes strains. Severity of bacterial wilt disease caused by the injection of R. solanacearum suspension into the stems of tomato plants treated with HRS-specific Firmicutes bacteria (c), or with HRS and DRS fractions (d). Data represent mean ± SEM (n = 12 plants per treatment). Asterisks indicate significant differences (*P < 0.05, **P < 0.01, ***P < 0.001).