Figure 5. Accumulation of reactive oxygen species (ROS) in tomato stem tissue.

ROS were determined in A: horizontally BW-resistant tomato H7996 and B: susceptible cv. Bonny Best 48 h after infection with Ralstonia solanacearum wild-type strain UW551 or UW551ΔepsB or water (mock-inoculated control). At 48 h post-inoculation, stem cross-sections containing 10⁵ CFU/g bacteria were stained with 50 µM dihydrorhodamine 123 (DHR 123) and fluorescence microscopy was used to visualize the green fluorescence of rhodamine 123 generated by oxidizing DHR 123 by ROS. Three independent experiments each contained eight plants per treatment; representative results are shown.