Alternaria brassicae is a necrotrophic fungus causes Alternaria blight disease in oilseed mustard crop. There is a 47% loss of the mustard crop due to the Alternaria blight disease. To control this disease, various chemical fungicides have been used till date which are harmful to our environment. Zinc oxide (ZnO) nanoparticles synthesized from Terminalia bellerica have been reported to have significant antifungal potential against A. brassicae at 200 ppm concentration. In the present study, the effect of green synthesized zinc oxide (Tb-ZnO) nanoparticles, chemically synthesized ZnO nanoparticles, and chemical fungicides on A. brassicae has been anticipated by analysing changes in cytomorphology characteristics, biochemical constituent, and stress enzymes of A. brassicae. Cytomorphological studies by transmission electron microscopy and scanning electron microscopy have shown the complete disintegration of cell wall, cell membrane, and cytoplasmic content at 200 ppm concentration of Tb-ZnO nanoparticles. Decrement in biochemical constituents and changes in activity of stress enzymes in Tb-ZnO nanoparticles treated cell confirm the toxicity of nanoparticles at 200 ppm concentrations. Hence, on the basis of all these results, the mechanism of action of Tb-ZnO nanofungicides on A. brassicae has been hypothesized in the present study. This study confirms how nanoparticles inhibit the growth of A. brassicae and suggested the use of nanofungicides.
Plant pathogens resistant to the commercially available fungicides and bactericides even at higher concentrations are the biggest challenge for the farmers to control the losses due to plant diseases. The antibacterial and antifungal potential of nanomaterials makes them a suitable candidate for the control of plant diseases. Thus, the present study reports the phytofabricated zinc oxide nanoparticles (ZnO Np's) using aqueous plant leaf extract of Terminalia bellerica (Baheda). Characterization of ZnO nanoparticles was done by ultraviolet-visible (UV-Vis) studies, X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infra-red (FT-IR) analysis, and transmission electron microscopy (TEM). The presence of pure hexagonal wurtzite crystalline structure of ZnO nanoparticles was confirmed by XRD analysis. The TEM images revealed the spherical to hexagonal shaped ZnO nanoparticles with sizes ranging from 20 to 30 nm. The stabilization of synthesized ZnO nanoparticles through the interactions of terpenoids, steroids, phenylpropanoids, flavonoids, phenolic acids, and enzymes present in the leaf extract was suggested by FTIR analysis. The mechanism of the formation of ZnO nanoparticles using Terminalia bellerica (Baheda) (Tb-ZnO Np's) as a bioactive compound is proposed. These phytofabricated ZnO nanoparticles (Tb-ZnO Np's) have shown significant antifungal potential against Alternaria brassicae the causal agent of Alternaria blight disease/leaf spot disease in Brassica species. The microscopic results confirm the changes in mycelium morphology and reduction in the number of spore germination at 0.2 mg/mL concentration Tb-ZnO Np's.
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