Evaluation of sugar beet cultivars for resistance to curly top disease under field condition

To evaluate resistance of new sugar beet hybrids and cultivars against curly top disease in field condition, an experiment was carried out in a randomized complete block design with four replications in the year 2008 in Zarghan area with twelve treatments. Each plot included a cultivar which was planted in three rows with eight meters lenght and 50cm interval. After weeding and first thinning, about 60 days after planting, the number of infected and uninfected young plant were recorded, considering the morphological characteristics of the young plants, disease percentages were calculated. Also, severity of infection was evaluated in each treatment using related index. At the end of growing period, quantity (root yield and white sugar yield) and quality (sugar content) of all treatments were measured and compared using ANOVA analysis and LSD (Least Significant Different). The results showed that there was a significant difference in the infection percentage cultivars under study (at á=1%). Index of infection severity was non- significant. Between the cultivars, three cultivars F-20511 (Check) and F-20717 and F-20510 Bronco(Check), together had lowest infection percentage and disease severity (2.370%, 1.010 and 3.800%, 1.013 and 4.612%, 1.016 respectively). Also, there was a significant difference among cultivars regarding root and white sugar yield (at á=1%). Cultivars sugar content wasn't significant. Highest root yields (97.38 and 86.90 tha-1) and white sugar yield (13.34 and 11.37 tha-1) were recorded for F-20718 and F-20510 (Check) cultivars, respectively. Considering the results, among the cultivars, cultivar F-20718 had the lowest infection to curly top and the maximum white sugar yield (13.34 tha-1). Therefore, maximum root yield, white sugar yield obtained from cultivar F-20718. This cultivar is recommended as a tolerant cultivar to curly top for cultivation in infected areas.