CERCOSPORA BETICOLA SACC AND ITS EFFECT ON SUGAR BEET PLANTS

Cercospora beticola was isolated during 1988 in Egypt. Produc‌tion of large number of conidia was attempted on different media and temperatures. Also, sugarbeet plant chemical composition was deter‌mined in relation to leaf spot infection by the fungus. Both potato dextrose agar and beet leaf extract media incubated under 25°C for 4 weeks, produce the greatest amount and number of conidia. Infection of sugarbeet leaves with the fungus caused a remark‌ble decrease in chlorophyll a and b. The reduction in chlorophyll was maximum with the variety "Trible" followed by "Ceres poly 3" , while the "Raspoly" variety was slightly affected. The total sugar content was inversely proportional to the infect‌ed area (disease index) of the leaf. Gradual decrease was noticed as the severity of infection increased. Also, sucrose in roots decreased as the severity of infection by C.beticola increased. This resulted in a negative coefficient value as correlated with the characters under investigation and the disease index caused by C.beticola. This decrease results in a 0.02, 0.01 and 0.01 tonnes sugar losses per feddan for each one per‌cent diseased area per plant for the three varieties, respectively.