LAUSR

BACKGROUND Controlling bacterial infections in plants is a major challenge due to the appearance of resistant strains. As a physical barrier, the bacterial biofilm helps bacterial infections acquire drug resistance by enabling bacteria to accommodate complex and volatile environmental conditions and avoid bactericides' effects. Thus, developing new antibacterial agents with antibiofilm potency is imperative. RESULTS A series of simple triclosan derivatives containing isopropanolamine moiety were elaborately designed and assessed for antibacterial behavior. Bioassay results showed that some title compounds had excellent bioactivity against three destructive bacteria Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas axonopodis pv. citri (Xac), and Pseudomonas syringae pv. actinidiae (Psa). Notably, compound C8 displayed high bioactivities toward Xoo and Xac, the related EC50 values were 0.34 and 2.11 μg mL-1 , respectively. In vivo trials revealed that compound C8 exhibited excellent protective activities against rice bacterial blight and citrus bacterial canker at 200 μg mL-1 , with a control effectiveness of 49.57% and 85.60%, respectively. Compound A4 had remarkably inhibitory activity toward Psa, with an EC50 value of 2.63 μg mL-1 , and demonstrated outstanding protective activity with a value of 77.23% against Psa in vivo. Antibacterial mechanisms indicated that compound C8 dose-dependently prevented biofilm formation and extracellular polysaccharide production. C8 also significantly weakened the motility and pathogenicity of Xoo. CONCLUSION This study contributes to the development and excavation of novel bactericidal candidates with broad-spectrum antibacterial activity by targeting bacterial biofilm to control refractory plant bacterial diseases. This article is protected by copyright. All rights reserved.