الفهرس 
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Abstract
In this study, three deferent Fusarium species were isolated from tomato plants infected with wilt disease, the infected plants were collected from three different fields in Bolkeina village - El Mahalla El Kobra – Gharbia governorate, these three isolates were tested for biosynthesizing of Silver Nanoparticles, it was found that Fusarium oxysporum f.sp lycopersici capable of synthesizing nanosilver efficiently. The first step was the production of fungal biomass by culturing it in MGYP medium under an aerobic condition, the separated fungal filtrate was used as a biocatalyst for production of nanosilver by addition of Silver Nitrate under dark condition. At the next stage the biosynthesized nanosilver was characterized physically for detection of the specific absorbance band for nanosilver biosynthesis, transmission electron microscopy is used for shape and size range detection, it was found that nanosilver particles were spherical in shape and had size distribution range from 0.5 to 50 nm, by the same instrument it was found that nanosilver particles were crystalline in structure, nanocolloidal solution was stable for long time, the size distribution range was homogenous and the average size of particles was higher than that detected by TEM, this indicated the presence of surrounding capping protein layers. Nanosilver particles have an efficient bactericidal effect as proved by a decreasing in bacterial growth with increasing of nanocolloidal solution concentration, nanosilver affect on bacterial ultrastructure and protein synthesis , so nanosilver is an efficient as a bactericidal agent as it targeting many components within bacterial cells, so the emergence of bacterial species resistant to nanosilver was difficult.