Comparative account of antifungal activity of green and chemically synthesized Zinc Oxide nanoparticles in combination with agricultural fungicides

The present study aims at study on combined effect of zinc oxide nanoparticles (ZnO) with common agricultural fungicides. Nanoparticles were synthesized using chemical reduction process and characterized through UV-Visible spectroscopy, X-ray diffraction (XRD), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM). Synthesized nanoparticles were observed to be in size range of 12-63 nm as confirmed by TEM micrograph. DLS established polydisperse nature of nanoparticles and provided effective hydrodynamic diameter of 76.15 nm, confirming the hypothesis of particles being in nano range. Nanoparticles were tested against fungal phytopathogens, namely A. alternata, A. niger, B. cinerea, F. oxysporum and P. expansum. Nanoparticles used in the study exhibited good antifungal activity. Both classes of nanoparticles (green and chemically synthesized) were individually tested against fungal phytopathogens and in combination with fungicides. Nanoparticles positively influenced the inhibitory effects of fungicides. P. expansum was observed to be the most sensitive fungus. It exhibited sharp decrease in MIC values from 2 μg/mL for carbendazim and 4 μg/mL for thiram to 0.25 μg/mL when carbendazim and thiram were used in combination with green ZnO NPs. Mean MIC value (mean ± sd) for combination of all three fungicides with green ZnO NPs was 0.83 ± 0.4 μg/mL and for chemical ZnO NPs was 1.17 ± 0.7 μg/mL. Hence, green ZnO NPs showed better inhibition of test fungi when compared to chemically synthesized ZnO NPs. In summary, the study reports synthesis of ZnO nanoparticles with good antimicrobial potential and amelioration of activity of fungicides was observed when used in combination with nanoparticles.