Objective  By measuring a series of index changes of Pseudomonas syringae pv. Actinidiae (Psa) after treatment with benzothiazolinone aqueous emulsion, the antibacterial mechanism of benzothiazolinone aqueous emulsion against Psa was revealed, which would provide a theoretical basis for the control of kiwifruit ulcer disease with benzothiazolinone.

Method  Psa was treated with benzothiazolinone diluted 10 times (X10), benzothiazolinone stock solution (Y) and sterile water (CK). The enzymatic activities of catalase (CAT) and superoxide dismutase (SOD) were determined by using kits and the soluble protein content was determined by Coomassie Brilliant Blue staining. Changes in the cell membrane structure of Psa were observed by fluorescence microscopy and scanning electron microscopy and cell cycle assays were performed by flow cytometry.

Result  The study showed that Psa growth and reproduction were significantly inhibited by benzothiazolinone treatment, which shortened the logarithmic growth period of Psa, caused cell membrane rupture, cell contents leakage and increased cell death, and the final amount of mycobacteria was only 5.5% of the control. Psa had oxidative stress response to benzothiazolinone, and the enzyme activities of Psa were significantly increased after treatment, showing a trend of increasing first and then decreasing. After treatment of benzothiazolinone, CAT enzyme activity reached a peak of 118.795 U/mg at 10 h and SOD enzyme activity reached a peak of 1 060.452 U/mg at 4 h. Bacterial protein content of X10 and Y differed significantly at 12 h compared with the control, decreasing by 47.1% and 73.4%, respectively. With the increase of the concentration of benzothiazolinone, more G0G1 phase cells piled up and the percentage of cells increased from 30.27% in the control group to 45.23% in treatment group Y. The percentage of S phase cells decreased from 58.84% in the control group to 41.86% in treatment group Y. The G0G1 phase cells in treatment group Y were 56.8% higher than those in CK and 23.7% lower than those in CK in S phase.

Conclusion  Benzothiazolinone ruptures bacterial cell membranes, causes oxidative stress response in Psa, and inhibits Psa growth by inhibiting DNA synthesis in bacterial cells. It can effectively prevent and control bacterial ulcer disease of kiwifruit.