الفهرس 
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Abstract
The present work has been carried out at laboratory, greenhouse and farm of plant pathology of the faculty of agriculture, Minia University during 2011, 2012 and 2013 growing seasons to isolate and identify some viruses affecting some vegetable crops causing severe losses in yield. During this investigation three viruses were isolated the first virus cucumber mosaic virus (Cucumoviridae- cucumovirus) which causes severe losses to naturally infected plants. The second virus was hibiscus chlorotic ring spot virus (Tombusviridae - tombusvirus) HCRSV was isolated from naturally infected okra (Hibiscus esculantus L.) exhibiting chlorotic spots, mosaic. Symptoms produced by mechanical inoculation, ranged from chlorotic to necrotic. The third virus was potato virus Y (Potyviridae) it was isolated originally from naturally infected pepper (Capsicum annum L.) exhibiting symptoms of mosaic, chlorosis, vein banding and severe crinkling.
Physical properties of the isolated viruses recorded as follows. Thermal inactivation point for CMV, HCRSV and PVY were 60, 70 and 60 c◦ respectively. While dilution end point were 10-3 -10-4, 10-8-10-9 and 10-5 -10-6. With regards to infectivity of the viruses CMV, HCRSV and PVY at room temperature were found 10-11 days, 2-3 days and 13-14 days respectively. As far as the effect of different types of compounds in controlling virus diseases under this investigation. It has been indicated that application of some antioxidants including ascorbic, benzoic, citric and salicylic acids individually at different concentrations (50,100 and 200 ppm) as soaking or spraying markedly decreased number of local lesion and hereby controlled the disease caused by the three tested viruses (CMV, HCRSV and PVY) particularly when these antioxidants applied before inoculation or sprayed more than one time and at older ages.
Aqueous extracts of olive, rose, garlic, moringa, neem, guava and bougainvilla showed marked inhibitory effect particularly if sprayed before inoculation at older ages. There were no significant difference between sprayed the tested extracts pre-or post-inoculation with viruses isolate CMV, HCRSV and PVY.As far as the authors are aware. Occurrence of the isolated virus HCRSV during this study, suggested HCRSV was the first record in Egypt.