Discovery of Highly Effective Antibacterial Agents Based on Chalcone-Benzisothiazolinone against Plant Pathogens

In this study, a series of novel chalcone compounds containing 1,2-benzisothiazolin-3-one were designed, synthesized, and screened for the prevention and control of plant bacterial diseases. The results showed that most of the target compounds displayed excellent antibacterial activities. Especially, F17 (2-(3-(4-cinnamoylphenoxy)propyl)benzo[d]isothiazol-3(2H)-one) exhibited remarkable efficacy against Xanthomonas oryzae pv Oryzae in vitro, with a half effective concentration (EC₅₀) of 0.5 μg/mL, better than that of the commercial antibacterial agent thiodiazole-copper (TC, 56.1 μg/mL). Furthermore, F17 showed excellent effects against rice bacterial leaf blight in vivo, with protective and curative activities of 59.2% and 48.8% at 200 μg/mL, respectively, which were higher than those of TC (38.3% and 36.6%). Moreover, the bacteriostatic mechanism of F17 was elucidated through a series of biochemical experiments. The results indicated that F17 could inhibit the expression of multiple pathogenic factors and induce the host's resistance to disease by enhancing the activities of defense enzymes. Therefore, F17, which revealed the ability to combat plant bacterial diseases by orchestrating the control of multiple factors, might provide a new perspective for solving the problem of plant pathogen resistance. Overall, the results of this work demonstrated that chalcone compounds containing benzisothiazolinone as highly effective antibacterial candidates hold potential for the management of plant bacterial diseases.