Study on amount of losses and factors effects on severity infection

The curly top virus disease is one of the most imprtant disease in sugar beet production areas. The effect of this disease on sugar beet yield is severe, and it has been known as a common virus disease in the American, European and Asian countries. In the Fars province sugar beet farms, particularly in Fasa area, Isfahan and Kerman cities,it has caused severe damages to sugar beet root yield The primary estimates of this diseasse damages showed that if sugar beet farm is infected by 80% , then the root yield would be decreased by 40% . In 1967, Gibson had reported the presence of this disease in Iran. By that time, the sugar beet research institute attempted to purchase the seeds of parent commerical cultivar known as H5505 from the Netherlands and USA, and started to release the cultivars which are tolerant to curly top disease. Considering in mind that there is no exact data showing the severity of this disease on sugar beet root yield , an experiment was conducted in Fasa area to determine the degree of disease damage. In this respect , two separate plots were chosen in Fasa sugar beet farms. In the first plot,the disinficted seeds by Gaucho of Ic1 cultivar were sown in 20 rows each 50 meter long. During the growing season this plot was sprayed repeatedly in order to maintain the least infection . in the second plot, the seeds of the same cultivar were sown but without disinfection and the plot was not sprayed during the growing period in order to maintain the maximum infection. The root yield and yield components such as sugar content , percent of white sugar, impurrities, mellas sugar, white sugar yield and purity of raw extract were determined during four years. The results of ANOVA showed that there is a highly significant difference between root yield and infection percent between two plots(infection vs disinfection ). The least infection percent and maximum root yield was obtained from the disinfected pl o t equal to 15.02% and 46.61%T.ha-1 respectively. From the stundpoint of yield components (sugar content, percent of white sugar, impurities, alcaline inder and mellus sugar)these was not significant difference between the infected vs disinfected plots. But, based on white sugar yield and purity of raw extracted there was a significant difference between the two plots(at 5% level of probability ).The maximum amount of white sugar yield 19 and purity of raw extract was obtained from the isinfected plot equal to 5.33 T.ha-1 and 80.83% respectively.