Designing Biaryl Pyrazole Derivatives for Antibacterial Activity against Plant Pathogenic Bacteria

Plant bacterial diseases severely threaten global agricultural production. In this study, a series of biaryl pyrazole derivatives (Series I–III) were synthesized and evaluated for their activity against five major phytopathogens, including Xanthomonas oryzae pv. oryzae (Xoo), Pseudomonas syringae pv. actinidiae (Psa), Xanthomonas citri subsp. citri (Xcc), Acidovorax citrulli (Ac), and Ralstonia solanacearum (Rs). Among them, compound II-28 exhibited potent broad-spectrum antibacterial activity, with an MIC value as low as 12.5 μg/mL. In vivo trials demonstrated that II-28 effectively controlled rice bacterial blight and kiwifruit canker, performing comparably to thiodiazole copper. Preliminary mechanistic studies suggested that II-28 may target the LolCDE complex, modulates the expression of relevant genes, disrupts lipoprotein transport, and inhibits bacterial division. This work identifies biaryl pyrazoles as promising bactericidal leads and suggests LolCDE as a potential novel target for managing plant bacterial diseases.