Green-synthesized copper nanoparticles as a potential antifungal against plant pathogens

Abstract

The fabrication of fungicides in cost-effective and eco-friendly ways is particularly important for agriculture. Plant pathogenic fungi produce many economic and ecological problems worldwide, which must be controlled with potent fungicides. Here we propose the green synthesis of fungicides, which consist of copper nanoparticles (Cu-NPs) prepared in aqueous media. Through in vitro experiments, the antifungal efficacy against Fusarium solani, Neofusicoccum sp., and Fusarium oxysporum was investigated. Although the antifungal activity differs for each fungal species, it was found that the Cu-NPs induce strong morphological changes in the mycelium. Additionally, the damage of the cell membranes of the pathogens was revealed by microscopic observations. For the three evaluated fungi, fluorescence microscopy demonstrated the intracellular generation of reactive oxygen species in the mycelium. This work proves that the green-synthesized Cu-NPs are potential fungicides against F. solani, Neofusicoccum sp., and F. oxysporum.

Fig. 1. (a) X-ray diffraction pattern of Cu-NPs. (b) TEM micrograph of the Cu-NPs, the inset shows a high resolution TEM image of the border of a Cu-NP. (c) The fitted XPS spectrum of the Cu-NPs.

Fig. 2. Antifungal activity of Cu-NPs against: (a) Fusarium solani, (b) Neofusicoccum sp. and (c) Fusarium oxysporum. The columns indicate different concentrations of Cu-NPs: (I) 0 (controls), (II) 0.1, (III) 0.25, (IV) 0.5, (V) 0.75 and (VI) 1.0 mg mL⁻¹ of Cu-NPs.

Fig. 3. Inhibition of radial growth (IRG) (%) of Cu-NPs against Fusarium solani, Neofusicoccum sp., and Fusarium oxysporum. The quantitative data are expressed as the mean ± SD (n = 3). (*) indicates significant differences (P < 0.05) in comparison to their controls (treatments without Cu-NPs).

Fig. 4. SEM micrographs of Fusarium solani, (a) control. The treatments with different concentrations of Cu-NPs: (b) 0.1 mg mL⁻¹, (c) 0.25 mg mL⁻¹, and (d) 0.5 mg mL⁻¹.

Fig. 5. SEM micrographs of Neofusicoccum sp., (a) control. The treatments with different concentrations of Cu-NPs: (b) 0.1 mg mL⁻¹, (c) 0.25 mg mL⁻¹, and (d) 0.5 mg mL⁻¹.

Fig. 6. SEM micrographs of Fusarium oxysporum, (a) control. The treatments with different concentrations of Cu-NPs: (b) 0.1 mg mL⁻¹, (c) 0.25 mg mL⁻¹, and (d) 0.5 mg mL⁻¹.

Fig. 7. The effect of Cu-NPs on the cell viability by analyzing the PI influx in F. solani, Neofusicoccum sp., and F. oxysporum. (a–c) Controls and (d–f) treatments of Cu-NPs at a concentration of 0.5 mg mL⁻¹.

Fig. 8. The effect of Cu-NPs on the production of intracellular ROS in F. solani, Neofusicoccum sp., and F. oxysporum. (a–c) Controls and (d–f) treatments of Cu-NPs at a concentration of 0.5 mg mL⁻¹.