Antifungal Activity of Green and Chemically Synthesized ZnO Nanoparticles against Alternaria citri, the Causal Agent Citrus Black Rot

Citrus black rot is a serious disease of citrus plants caused by Alternaria citri. The current study aimed to synthesize zinc oxide nanoparticles (ZnO-NPs) by chemically or green method and investigate their anti -fungal activity against A. citri. The sizes of synthesized as measured by transmission electron microscope of ZnO-NPs were 88 and 65 nm for chemical and green methods, respectively. The studied prepared ZnO-NPs were applied, in vitro and in situ, at different concen-trations (500, 1,000, and 2,000 & mu;g/ml) in post-harvest treatment on navel orange fruits to verify the possible control effect against A. citri. Results of in vitro assay demonstrated that, at concentration 2,000 & mu;g/ml, the green ZnO-NPs was able to inhibit about 61% of the fungal growth followed by 52% of chemical ZnO-NPs. In addition, scanning electron microscopy of A. citri treated in vitro with green ZnO-NPs showed swelling and deformation of conidia. Results showed also that, using a chemically and green ZnO-NPs at 2,000 & mu;g/ml in situ in post-harvest treatment of orange, artificially -infected with A. citri, has reduced the disease severity to 6.92% and 9.23%, respectively, compared to 23.84% of positive control (non-treated fruits) after 20 days of storage. The out findings of this study may contribute to the development of a natural, effective, and eco-friendly strategy for eradicating harmful phytopatho-genic fungi.

Automated summary

This study synthesized zinc oxide nanoparticles (ZnO-NPs) using chemical or green methods and investigated their anti-fungal activity against citrus black rot caused by Alternaria citri. The results showed that green ZnO-NPs inhibited 61% of fungal growth at a concentration of 2,000 μg/ml, while chemical ZnO-NPs inhibited only 52%. Furthermore, post-harvest treatment of orange fruits infected with A. citri using green and chemical ZnO-NPs at a concentration of 2,000 μg/ml reduced the disease severity to 6.92% and 9.23%, respectively, compared to 23.84% in the untreated fruits.