Using magnesium oxide nanomaterial as a novel tool for bacterial disease management

Bacterial spot of tomato is caused by four Xanthomonas species and is one of the most devastating bacterial diseases of tomato globally. In Florida, USA chemical control has been a challenge following the appearance of copper (Cu)-tolerant Xanthomonas strains. In recent years, numerous studies have demonstrated the greater antibacterial properties of nanomaterials. Some of these nanomaterials have better antibacterial activity toward copper-tolerant bacterial strains. Magnesium (Mg) is an important plant micronutrient for plants; over the past decade, micron-sized and nano-sized MgO (Nano-MgO) particles were shown to have antimicrobial activity against several mammalian and plant pathogens. In this study, Nano-MgO (20 nm) was evaluated for toxicity to a Cu-tolerant X. perforans strain in vitro by determining toxicity to living X. perforans cells. Viability assay demonstrated that Nano-MgO is bactericidal in nature against Xanthomonas perforans strains. Nano-MgO (20 nm) was also tested for control of bacterial spot disease of tomato in the field. In field studies, bacterial spot disease severity was significantly reduced by Nano-MgO compared to the untreated control (UT), whereas the grower standard treatment, a combination of a copper bactericide and ethylene-bis-dithiocarbamate (Cu-EBDC), was not significantly different from the UT (p=0.05). Based on the preliminary findings, Nano-MgO could be an effective alternative to the current grower standard.