Western Blot Detection of Xanthomonas Oryzae pv. Oryzae in Rice

Bacterial blight, caused by Xanthomonas oryzae pv. oryzae (Xoo), is a severe rice disease, and rice-Xoo interactions form a model system in plant disease resistance research. To establish immuno-techniques for Xoo detection, a Xoo-specific polyclonal antibody was generated using the total Xoo protein as the immunogen. A western blot procedure, which can detect as few as 3,500 Xoo cells, was established. Xoo can be detected in rice at 1-day post-inoculation (dpi) and a significant difference between the number of Xoo cells in resistant and susceptible reactions was found at 2 dpi. In the incompatible rice-Xoo interaction, Xoo can be detected within 6 cm of the inoculated site at 10 dpi. In the compatible interaction, Xoo can be detected within 12 cm of the inoculation site, while no Xoo signal was detected beyond that area in inoculated leaves and uninoculated leaves, supporting the hypothesis that rice plants harboring resistance genes have stronger inhibitory effects on Xoo propagation. This method is expected to replace the traditional manner of counting bacterial cells in laboratories and of inspecting Xoo-infected rice in paddy fields.