FM-568: A Promising\nPhenyl-Hydrazonomalononitrile\nAntibacterial Agent for the Sustainable Management of Citrus Canker

Citrus canker, caused by Xanthomonas citri subsp. <i>citri</i> (<i>Xcc</i>), poses a significant\nthreat to citrus production worldwide. To develop effective and eco-friendly\nantibacterial agents, we designed and synthesized phenyl-hydrazonomalononitrile\nderivatives using a scaffold-hopping strategy. Among these, <b>FM-568</b> emerged as a potent candidate, exhibiting broad-spectrum\nantibacterial activity <i>in vitro</i> against various phytopathogenic\nbacteria, including <i>Xcc</i>. Greenhouse experiments demonstrated\nthat <b>FM-568</b> achieved a control efficacy of 88.36% against\ncitrus canker at 400 μg/mL, with an EC<sub>50</sub> of\n26.68 μg/mL. Field trials in two major citrus-producing\nregions in China confirmed its effectiveness, yielding control efficacies\nof 86.60 and 77.87% at 400 μg/mL, outperforming conventional\nagents like zinc thiazole and thiadiazole copper. Density functional\ntheory calculations suggested that <b>FM-568</b>′s optimized\nscaffold and electronic properties contribute to its enhanced antibacterial\nactivity. These findings indicate that <b>FM-568</b> is a promising\neco-friendly alternative for managing citrus canker. Further studies\non its mechanism of action, safety profile, and formulation optimization\nare warranted to advance its development for sustainable citrus production.