Evaluation of sugar beet resistance to Cercospora beticola using detached leaf disks

In order to determine possibility of using detached leaf disks for evaluating resistance to Cercospora beticola, the causal agent of leaf spot in sugar beet, twelve sugar beet cultivars exhibiting different levels of resistance to Cercospora leaf spot were evaluated under field and laboratory conditions. The field experiment was conducted in a complete randomized block design with six replicates in Ghaemshahr region, where conductive and favorable climatic conditions for disease development existed. In the laboratory experiment, levels of resistance of the cultivars were determined by assessing of disease severity of detached leaf disks laid in rows on top of 1.5% water agar in 20×30 cm Pyrex plates. The results of this study indicated that there was a high correlation between both evaluation methods. Therefore, the evaluation of resistance would be reliable through each of these methods. The leaf disk assay is a very rapid and useful evaluation method enabling the evaluation of a lot of plant materials within a short period in the laboratory independent of climatic conditions.