Magnesium Oxide Nanomaterial, an Alternative for Commercial Copper Bactericides: Field-Scale Tomato Bacterial Spot Disease Management and Total and Bioavailable Metal Accumulation in Soil

Abstract

Copper (Cu) is the most extensively used bactericide worldwide in many agricultural production systems. However, intensive application of Cu bactericide have increased the selection pressure toward Cu-tolerant pathogens, including Xanthomonas perforans, the causal agent of tomato bacterial spot. However, alternatives for Cu bactericides are limited and have many drawbacks including plant damage and inconsistent effectiveness under field conditions. Also, potential ecological risk on nontarget organisms exposed to field runoff containing Cu is high. However, due to lack of alternatives for Cu, it is still widely used in tomato and other crops around the world in both conventional and organic production systems. In this study, a Cu-tolerant X. perforans strain GEV485, which can tolerate eight tested commercial Cu bactericides, was used in all the field trials to evaluate the efficacy of MgO nanomaterial. Four field experiments were conducted to evaluate the impact of intensive application of MgO nanomaterial on tomato bacterial spot disease severity, and one field experiment was conducted to study the impact of soil accumulation of total and bioavailable Cu, Mg, Mn, and Zn. In the first two field experiments, twice-weekly applications of 200 μg/mL MgO significantly reduced disease severity by 29–38% less in comparison to a conventional Cu bactericide Kocide 3000 and 19–30% less in comparison to the water control applied at the same frequency (p = 0.05). The disease severity on MgO twice-weekly was 12–32% less than Kocide 3000 + Mancozeb treatment. Single weekly applications of MgO had 13–19% higher disease severity than twice weekly application of MgO. In the second set of two field trials, twice-weekly applications of MgO at 1000 μg/mL significantly reduced disease severity by 32–40% in comparison to water control applied at the same frequency (p = 0.05). There was no negative yield impact in any of the trials. The third field experiment demonstrated that application of MgO did not result in significant accumulation of total and bioavailable Mg, Mn, Cu, or Zn in the root-associated soil and in soil farther away from the production bed compared to the water control. However, Cu bactericide contributed to significantly higher Mn, Cu, and Zn accumulation in the soil compared to water control (p = 0.05). This study demonstrates that MgO nanomaterial could be an alternative for Cu bactericide and have potential in reducing risks associated with development of tolerant strains and for reducing Cu load in the environment.

Surface Coated Sulfur Nanoparticles Suppress Fusarium Disease in Field Grown Tomato: Increased Yield and Nutrient Biofortification

“…Field trials demonstrated that ZnO NPs reduced grapefruit canker incidence to a greater extent than did cuprous oxide and cuprous oxide/zinc oxide bactericides. Liao et al demonstrated in a field experiment that twice-weekly applications of 200 μg/mL nanoscale MgO significantly reduced disease severity of tomato bacterial spot caused by Xanthomonas perforans by 29–38% compared to the conventional Cu bactericide Kocide 3000 …”

Adding exogenous protein relieves the toxicity of nanoparticles to anammox granular sludge by adsorption and the formation of eco-coronas

“…Zhang et al 41 discovered that 5.0 mg L −1 Cu NPs decreased the metabolic activity and abundance of anammox bacteria. According to Liao et al , 42 MgO NPs are considered alternative materials for copper-based bactericides. Furthermore, the United States Food and Drug Administration (FDA) states that MgO NPs are a safe material, which indicates that the amount of used MgO NPs will greatly increase in the future.…”

Bacterial Spot of Tomato and Pepper in Africa: Diversity, Emergence of T5 Race, and Management

“…Perhaps, the absence of streptomycin and copper-resistant strains in some countries in Africa provides a window for the careful deployment of antibiotics and copper-based formulations in bacterial spot disease management. Recent advances in small molecules and nano-formulations may provide additional opportunities for the management of bacterial spot disease in the future ( Liu et al, 2019 ; Liao et al, 2021 ; Qiao et al, 2021 ; Srivastava et al, 2021 ).…”