الفهرس 
Introduction
DiscussionOnly 14 pages are availabe for public view
 |  | from | 152 |  |  |
| | | from | 152 | | |
Abstract
Cercospora leaf spot disease caused by C. beticola Sacc. is the most destructive foliage disease for sugar beet in Egypt. This study was conducted to study the integrated management of the disease. The obtained results from this study indicated the follows: Pathogenicity test in greenhouse indicated that from 18 isolates of C. beticola isolated form 7governorates, the most virulence isolates no. 6 (Sharkia) and isolate no. 3 (Behaira). They decreased the root weight and sucrose percentage compared to control. Cercosporin toxin was produced by all the tested seven isolates of C. beticola and it ranged from 0.76 to 3.03g/g. Increasing the conc. of toxin led to increasing of the chlorosis and necrosis in sugar beet leaves. Out of 18 sugar beet cultivars, Oscar poly, 9001 and Sultan gave the highest response to cercospora leaf spot disease. While the reverse was true with Gloria, Desperz and Kawamera under natural infection through the two tested successive seasons. The disease severity of cercospora leaf spot disease was decreased by spraying the sugar beet plant with the tested dry plant extract. The best treatment was C. proximus at the rate (1: 4 v/v) during two tested seasons under the field conditions compared to fungicide eminent and control. This treatment increased the root weight and improved the sucrose percentage. from 8 fresh plant extracts, A. sativum and L. camara extracts were the most effective against cercospora leaf spot disease under the field conditions and improved the yield and sucrose content during the two tested seasons. Under field conditions all tested oils decreased the cercospora leaf spot disease. The best effects were obtained with C. syminum at 1500 and 2500 ppm and A. sativum at 2500 ppm in two tested years, these oil concentrations were non phytotoxic but they are fungicidal. In greenhouse experiments, the treatments with bioagents of Saccharomyces spp. (no. 5), P. fluorescens and Rhodotorula spp.(no. 8 and 9) decreased the disease severity of cercospora leaf spot disease and increased TSS%, sucrose percentage, purity and root weight (yield). In vitro, antioxidants reduced the linear growth of C. beticola and the most effective one was acetic acid specially at 15 mM which prevent the fungal radial growth as eminent (fungicide) did. Antioxidant compounds, i.e. lactic acid and sodium benzoate at 10 and 20 mM were the most effective ones against cercospora leaf spot disease and resulted in increasing sucrose content. Sodium salicylate had phytotoxic effect to sugar beet leaves under field conditions. Commercial products like ElKanz, blight stop, Aman at concentration 2.5 and 3.5 cm/L were tested against cercospora leaf spot disease in the field under natural infection. ElKanz was the best ones. It has the best efficiency in decreasing the disease severity. Laboratory experiments indicated that, peroxidase enzyme activity was found in high levels in resistant cultivar especially at age 120 days than in the susceptible one and may play a role in resistance to cercospora leaf spot disease.