FIGURE 2.

Xanthomonas aurantifolii (Xa)‐induced protection against Xanthomonas citri (Xc) infection is time‐dependent. Natal leaves were sprayed with a suspension of Xa (OD₆₀₀ = 0.1) and after 4 h, 24 h, or 5 days, Xc (OD₆₀₀ = 0.1) was infiltrated into the leaves (areas surrounded by dashed lines). Canker symptoms were recorded 10 days after Xc inoculation. Xa prevented canker formation when Xc was inoculated 24 h after Xa application. No protection was observed when Xc was inoculated 4 h or 5 days after the Xa treatment, indicating that the Xa‐induced protection response has a short time frame of a few hours and requires bacterial penetration into the leaf mesophyll to occur. The images presented are representative of the phenotype observed in most infiltrated leaves