Abstract
Cercospora leaf spot disease (CLS), caused by the hemibiotrophic fungus Cercospora beticola, is one of the most severe sugar beet diseases causing a significant yearly loss in total sugar yield in the US. Identifying genetic resistance has long been an important goal for sugar beet breeding companies and has resulted in two types of genetic resistance; monogenic and multigenic. Experience from other monogenic resistance traits shows that monogenic resistance is easily overcome by the pathogen by drastically changing the selection pressure. In order to achieve sustainable CLS resistance for the US market multigenic is required. In this work, we present the genetic background of several novel multigenic resistance sources and a strategy for introducing a genetic defence-in-depth approach for long term resistance against CLS in the US sugar beet market.