الفهرس 
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Abstract
This work was conducted over the 2017-2019 growing seasons for screening the root and stem rot diseases that occurred prevalently in the grafted and non-grafted cucumber greenhouses in Egypt. Several cucumber greenhouses were investigated to determine the main causes of infection. Fusarium spp. was the most common pathogen isolated from grafted and non-grafted Cucumber. Pathogenicity test confirmed the pathogenic capabilities of the isolated fungi and proved thatFusarium proliferatum(MW242871) and Fusarium equiseti(MW216971.1), with the highest virulence to the tested cucumber cultivar and the majority of the inspected rootstocks. Cucumber seedlings grafted onto Strongtosa rootstock were superior in reducing the infection with both Fusarium spp. Fusarium equisetiremarkably affected the graft union area causing tissue discoloration and decay. Grafting cucumber onto a resistant rootstock using the splice technique,enhanced the histological, physiological and molecular defense response of the grafted seedling.The grafted cucumber root exudates proved to contain higher concentrations (µg/g) of 12 phenoic compounds, compared with the self- rooted cucumber. Trichoderma sp.(T1) and Bacillus subtilis (B3), isolated from Strongtosa rootstock rhizosphere, significantly exhibited the strongest antagonism and antibiosis against Fusarium spp., in vitro.The crude vermicompost extract showed also high reduction percentages of both Fusarium spp. Thus they were applied under greenhouse conditions to evaluate their impact on reducing the root and stem rots of grafted and self-rooted cucumber comparing with the chemical treatment. The results of the greenhouse experiment indicated that, the grafted cucumber treated with vermicompost significantly reduced the disease incidence and severity as well as resulted the best vegetative parameters.