Objective To screen highly effective fungicides against rice leaf blight caused by the new pathogen Pantoea ananatis.

Method Total 16 fungicides were screened via in vitro antibacterial experiments. The effects of three commercial agents on P. ananatis were systematically evaluated by apoptosis, reactive oxygen species (ROS) accumulation and in vivo efficacy.

Result Both 3 g/L tetramycin AS and 80% ( \omega) ethylicin EC had good antibacterial effects against P. ananatis, with EC₅₀ of 0.76 and 3.70 μg/mL, respectively. Further mechanism research found that 3 g/L tetramycin AS obviousily induced apoptosis of P. ananatis, increasing the early apoptosis rate to 55.89%, and markedly boosted the level of ROS, causing a marked rise in fluorescence intensity. In the efficacy test of rice bacterial leaf blight caused by P. ananatis, the protective activity of 80% ethylicin EC reached 73.18%, significantly outperforming 3 g/L tetramycin AS (60.71%). Conversely, 3 g/L tetramycin AS showed remarkable therapeutic activity at 69.32%.

Conclusion Tetracymycin can be used to treat the disease effectively by inducing apoptosis and ROS accumulation after the occurrence of the disease, while the outstanding protective activity of ethylicin is more suitable for early prevention.