Early Defense Mechanisms of in Response to Attack by pv. .

Black rot disease, caused by pv. (), results in significant yield losses in crops worldwide. To find black rot disease-resistant cabbage lines, we carried out pathogenicity assays using the scissor-clipping method in 94 different lines. By comparing the lesion areas, we selected a relatively resistant line, Black rot Resistance 155 (BR155), and a highly susceptible line, SC31. We compared the two cabbage lines for the -induced expression pattern of 13 defense-related genes. Among them, the -induced expression level of and antioxidant-related genes (, , , , and ) were more than two times higher in BR155 than SC31. Nitroblue tetrazolium (NBT) and diaminobenzidine tetrahydrochloride (DAB) staining analysis showed that BR155 accumulated less -induced reactive oxygen species (ROS) than did SC31. In addition, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assays showed that BR155 had higher antioxidant activity than SC31. This study, focused on the defense responses of cabbage during the early biotrophic stage of infection, indicated that -induced ROS might play a role in black rot disease development. We suggest that non-enzymatic antioxidants are important, particularly in the early defense mechanisms of cabbage against .