Green Synthesized Zinc Oxide Nanoparticles: Antifungal Activity against Powdery Mildew Disease of Pepper (Capsicum annuum L.) and Genotoxicity Potentials

Powdery mildew, caused by Leveillula taurica, anamorph Oidiopsis taurica, is one of the most serious diseases affecting pepper (Capsicum annuum) under greenhouses and open fields in Egypt. The current study aimed to investigate the relative antifungal activity of chemically synthesized Zinc oxide (ZnO)-nanoparticles (CS-ZnO NPs) and green synthesized Zinc oxide (ZnO)-nanoparticles (GS-ZnO NPs) against pepper powdery mildew under greenhouse conditions. A controlled precipitation technique was used to produce CS-ZnO NPs, and aqueous leaf extract of Hibiscus sabdariffa was used to produce GS-ZnO NPs. ZnO NPs were characterized using transmission electron microscopy (TEM) and dynamic light scattering. The CS-ZnO NPs were 105.7 nm in size and with a zeta potential of -15.7 mV, whereas those of GS-ZnO NPs were 86.9 nm in size and zeta potential of -18.3 mV, respectively. TEM analyses of GS-ZnO NPs and CS-ZnO NPs confirmed their spherical shape. At 300 mg/L concentration, both types of NPs revealed a statistically significant (P < 0.05) decline in disease severity (DS) and area under the disease progress curve (AUDPC). The effectiveness of these NPs varied between 78.74 and 82.45%. However, penconazole exhibited the most significant effect, as evidenced by the lowest DS (9.5 and 11.72) and AUDPC (481.02 and 578.14) values when compared with GS-ZnO NPs and CS-ZnO NPs and control in both greenhouses. Pepper plants treated with GS-ZnO NPs and CS-ZnO NPs exhibited increased chlorophyll and carotenoid content, indicating a correlation with the dosage applied. Contrarily, the increased GS-ZnO NPs and CS-ZnO NPs concentration reduced the total phenol content (TPC). The treated pepper plants also exhibited the highest peroxidase and polyphenol oxidase levels at 100 mg/L. The findings revealed a dose-dependent increase of 9.6% and 9.4% in micronuclei and chromosomal aberrations. Our results implied that either GS-ZnO NPs or CS-ZnO NPs are capable of causing genotoxicity in bone marrow cells of rats, even at low dosages of 50 mg/kg after 14 days, and the effect gradually extended up to 28 days. The data suggests the cautious use of nano-products is inevitable, and the mitotic damage should be assessed before using such nano-products on a large scale.. KEYWORDS :Antifungal, Genotoxicity, Nanoparticles, Pepper, Powdery mildew, Zinc oxide