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Novel Copper-Composites for Management of Bacterial Spot of Pepper Caused by Xanthomonas euvesicatoria

Qiurong Fan: University of florida

<div>Bacterial spot caused by <em>Xanthomonas euvesicatoria</em> is one of the most serious diseases of pepper in Florida and throughout the world. The widespread occurrence of copper tolerant strains of <em>X. euvesicatoria</em> have limited the efficacy of copper bactericide application, widely used for managing bacterial spot of pepper. In this study, we investigated the antibacterial effect of three novel copper-composites, Core-shell copper (CS-Cu), Mixed-valence copper (MV-Cu), and Fixed-quat copper (FQ-Cu) in <em>in vitro</em> and in greenhouse experiments against copper tolerant strains of <em>X. euvesicatoria</em>. All concentrations (100, 200, 500 and 1000 μg/ml) of CS-Cu and FQ-Cu effectively killed bacteria within 1 h and MV-Cu killed all the cells at 24 h, <em>in vitro</em>. In the first greenhouse experiment, plants treated with all copper-composites, at all concentrations (100, 200, and 500 μg/ml) had disease severity (AUDPC) statistically equivalent to or better than the growers’ standard copper-mancozeb. All three concentrations of FQ-Cu, 200 and 500 ppm of CS-Cu and 100 and 200 ppm of MV-Cu showed significantly less AUDPC compared to Kocide 3000. Phytotoxicity was observed at 500 ppm of CS-Cu and FQ-Cu. In the second greenhouse experiment, all concentrations of CS-Cu and 200 ppm of MV-Cu significantly reduced AUDPC compared to copper-mancozeb. FQ-Cu at all concentrations were statistically equivalent to copper-mancozeb. When compared to Kocide 3000, all three concentrations of CS-Cu, 200 and 500 ppm of MV-Cu and 500 ppm of FQ-Cu showed significantly less AUDPC. This study highlights the potential of copper-based nanomaterials for effective management of bacterial spot of pepper.</div>