Figure 1: Titer evaluation of anti-Xoo antibodies using ELISA. ELISA plates were coated overnight with 0.2 μg of Xoo protein at 4°C. After blocking at 37°C with phosphate buffer containing 1% skimmed milk (w⁄v) for 2 h, plates were washed with phosphate buffer. Test sera were serially diluted with PBS, then added in duplicate to the plates and incubated for 1 h at 37°C. PBS buffer was used as the blank control and serum collected before immunization was used as the negative control (NS). After washing three times with the phosphate buffer, bound antibodies were detected with horseradish peroxidase-conjugated goat anti-rabbit antibodies, and revealed using 3’3’5’5’-tetramethylbenidine dihydrochloride and H2O2 in phosphatecitrate buffer. The color development was stopped by adding H2SO4. The optical density was recorded at 450 nm using a spectrophotometric microplate reader. Ab-s) Anti-Xoo antibody generated using protein isolated from sonicated Xoo cells as the immunogen. Ab-un: Anti-Xoo antibody generated using protein isolated from intact (un-sonicated) Xoo cells as the immunogen. PBS: PBS buffer; NS: negative sera.