Nanoparticles for the control of lettuce bacterial leaf spot (Xanthomonas hortorum pv. vitians)

Lettuce bacterial leaf spot, caused by Xanthomonas hortorum pv. vitians is one important pathogen of lettuce. The use of nanoparticles offers a new approach to controlling the disease. The objective of this work was to investigate the use of nanoparticles in the control of lettuce bacterial leaf spot and in seed treatment. Nanoparticles toxicity was evaluated by determining the in vitro bacterial growth inhibition zone. Lettuce seeds were inoculated with the bacteria and treated with CuO, NiO, ZnO:1.0Ag and ZnOCl:5.0Ag nanoparticles, the percentages of bacteria detected in the seeds, seed germination and seedlings emergence were determined. For the control of bacterial leaf spot, CuO, NiO, ZnO:1.0Ag and ZnOCl:5.0Ag nanoparticles were sprayed on lettuce plants in the preventive and curative application. In the preventive application, CuO, NiO, ZnO:1Ag, ZnOCl:5Ag, water and copper were sprayed, after three days, the plants were inoculated with a bacterial suspension (10 ⁸ CFU/mL). In the curative application, the plants were inoculated with the bacteria, and three days later sprayed with the nanoparticles. Disease severity was assessed and the area under the disease progress curve was calculated. ZnO:Ag, ZnO:Au, ZnOCl:Ag, CuO, and NiO nanoparticles inhibited bacterial growth in vitro . CuO, ZnO:1.0Ag, and ZnOCl:5.0Ag nanoparticles did not reduce the bacterium in inoculated lettuce seeds and did not reduce the seed germination and seedling emergence. The preventive and curative application of CuO, ZnO:1.0Ag, and ZnOCl:5.0Ag nanoparticles reduced the lettuce bacterial leaf spot severity. The nanoparticles are alternative to manage lettuce bacterial leaf spot.