الفهرس 
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Abstract
The current study carried out to evaluate antibacterial activity of three synthetic nanoparticles (silver NPs, chromium III oxide NPs and zinc oxide NPs) within two levels in vitro and in vivo against the growth of soft rot bacterium of potato, Pectobacterium carotovorum subsp. carotovorum within the following steps and results: * Ten bacterial isolates of soft rot causal pathogen Pectobacterium carotovorum subsp. carotovorum (Pcc) were isolated from naturally infected potato tubers with soft rot symptoms and collected from different localities of Assiut and Sohag Governorates, Egypt. * Pathogenicity test showed all tested isolates were pathogenic to potato tubers with varied virulence. Isolate No.3 showed the highest disease severity (75.22%) Meanwhile, the lowest one was isolate No.2 with severity (4.06%). * On the other hand, three synthetic nanoparticles “silver nanoparticles (Ag NPs), chromium III oxide nanoparticles (Cr2O3 NPs) and zinc oxide nanoparticles (ZnO NPs)ˮ were screened, in vitro, to evaluate their inhibitory activities against P. carotovorum subsp. carotovorum isolate No. 3 comparing with standard control chloramphenicol. All three synthetic nanoparticles exhibited considerable inhibitory activities more than chloramphenicol and silver NPs was the most effective within highest inhibition zone at the lowest MIC (10.75mm/ 50 ppm) followed by chromium III oxide NPs and zinc oxide NPs (10.28mm/ 100 ppm and 10.08mm/ 150 ppm), respectively. Meanwhile, chloramphenicol was on the last ranking (9.34mm/ 150 ppm). * In vivo, controlled bacterial soft rot disease of potato performed with Ag NPs, Cr2O3 NPs and ZnO NPs within MBC (1800 ppm, 2200 ppm and 2600 ppm, respectively) in storage and greenhouse experiments. In the storage experiment including (0, 1, 2 and 3 months), three nanoparticles made complete control (100%) of soft rot disease development comparing with infected control exhibited gradual soft rot development (63.1%, 66.2%, 71.2% and 76.2%). * Moreover, these three nanoparticles with treatment A made complete soft rot disease with percentage 100%, with varied results by treatment B in greenhouse conditions exhibited significant decrease in the percentage of disease incidence and count number of diseased tubers, and increased in the percentage of efficacy and disease incidence reduction in the end of season compared with infected control. * Biochemically, three tested nanoparticles exhibited significant decrease in both enzymes polyphenol oxidase (PPO) and peroxidase (POD) compared with soft rot pathogen represented in infected control with preferable results exhibited by ZnO NPs acted as growth promoter with the lowest values of PPO and POD induction.