Pathogenicity assays on Arabidopsis thaliana infected with Xanthomonas campestris pv. campestris seize aggressiveness variation at the race and isolate levels

Black rot of crucifers caused by Xanthomonas campestris pv. campestris (Xcc) is one of the most destructive diseases affecting vegetable Brassica crops, as well as the model plant Arabidopsis thaliana. Although the interaction between both model organisms has been studied, there is still a gap in knowledge regarding the characterization of the response of different races of Xcc. The objective of this study was to screen out the pathogenicity of Xcc Brazilian isolates, representing different races and collected from different Brassica fields, in the model plant A. thaliana. Six Xcc isolates comprising five different races were pressure infiltrated on A. thaliana leaves. Plants were phenotyped for the percentage of lesion area and in planta bacterial population growth. We report a great variation in the pathogen aggressiveness at race and isolate levels, characterized mostly by trade-offs between disease severity and in planta survival rate. Our data provide a valuable piece of knowledge about Xcc phenotypic responses at race and isolate levels. These results contribute for further functional studies in the model plant A. thaliana, besides providing a better understanding of Xcc race structure complexity.