الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Brown rot of potato tubers or wilt disease of potato plants is considered the most important agricultural quarantine disease worldwide. Countries of European Union do not allow to export any percentage of infected potato tubers by brown rot causal organism to their markets for consumption. For this reason they used strict agricultural quarantine system. This study was concerned with Ralstonia solanacearum isolated from different sources and localities. Identification of the isolated pathogen from different habitats by means of traditional bacteriological methods and recently developed techniques as well as disease control using different save methods (organic and mineral fertilizers, biological agents and biocides). Results revealed that, from 80 collected samples, fourteen pathogenic isolates were detected from tubers, weeds, water and soil. Ten isolates were from El-Monufiya governorate, four from El-Gharbia and non from El-Sharkia governorate. Pathogenic capabilities of those fourteen isolates were confirmed on tomato seedlings. Among obtained isolates, those of tubers, water, weeds and soil showed the highest disease severity on tomato seedlings were used in this study. The aforementioned fourteen pathogenic isolates were identified as Ralstonia solanacearum according to their biochemical and physiological properties detected, SMSA, King’s B and TZC plating media, immunofluorescence antibody assay (IFAS) test and Real Time PCR (Taq-Man . Two selected bacterial isolates (one from tuber [T4] and the second from water [W9]) of R. solanacearum showed the most virulence against tomato plants and potato tubers were used to detect the host range on different plants and their cultivars (tomato, eggplant, pepper, broad bean, groundnut, maize, onion, mallow, tobacco and amaranths). No wilt symptoms were induced by any bacterial isolate tested on broad bean, maize, groundnut, onion and tobacco . All the tested potato cultivars (pliny, draga, kara, alexant and mundial) were susceptible to the disease infection at different levels of both investigated isolates (T4 and W9). The effect of different compost types on potato brown rot incidence was evaluated. Animal, mixed1 and mixed2 compost reduced brown rot disease and increased total tuber yields, chlorophyll (a and b), polyphenoloxidase and peroxidase activity as compared with control treatment. The results also revealed that calcium superphosphate was effective on reducing the disease than other tested mineral fertilizers under greenhouse conditions. Biocide Rhizo-N, bioagent Bacillus subtililus and Pseudomonas fluorescence were the most effective agents on reducing the disease incidence and severity, increased weight of tubers, total tuber yields, chlorophyll (a and b), polyphenoloxidase and peroxidase activity as compared with control treatment.