evaluation of commercial sugar beet cultivars for resistance to cercospora leaf spot under field condition

resistance of 16 sugar beet cultivars to cercospora leaf spot was evaluated in ghaemshahr region. the experiment was conducted in a complete block design with 6 replications, and, disease severity of cultivars was measured two times. root yield of cultivars, as well as their disease severity, was compared with each other under natural cercospora infection in dezful area (winter crop). in dezful, the experiment was carried out in complete block design with 4 replications. reaction of sugar beet cultivars to cercospora leaf spot was almost similar in ghaemshahr and dezful areas. the most resistant and susceptible cultivars to cercospora leaf spot were palma and 191, respectively. the cultivars palma, canaria, 4k21 and hi0152 produced highest sugar yield in dezful area and showed highest resistance to the disease in the two regions. the lowest amount of sugar was produced by genotypes 191 and br1. it seems that for introducing appropriate cultivars to the region, yield of the crop under stress condition should be considered as well as the resistance to the disease.