Nematode-tolerant sugar beet varieties – resistant or susceptible to the Beet Cyst Nematode Heterodera schachtii?

Abstract

The beet cyst nematode Heterodera schachtii (BCN) is an important parasite compromising yield of sugar beet. Standard sugar beet varieties are susceptible to BCN and strongly support BCN reproduction. Another type of variety is resistant to BCN. Although resistance leads to reduced nematode infestation levels, the yield potential of available resistant varieties is low. Tolerant varieties form a third type; high yield is produced with and without BCN infestation. However, so far it has remained unknown whether tolerant sugar beet varieties support or reduce BCN infestation and reproduction under field conditions. In order to address this question, the impact of five tolerant beet varieties on BCN population levels was investigated at 15 locations during a period of three years and compared to a resistant and a susceptible variety. The results demonstrate that all tolerant varieties led to population levels that ranged between that of the susceptible and that of the resistant variety. According to the respective BCN reproduction, the different varieties were classified as moderately susceptible (MS) or highly susceptible (HS) or as moderately resistant (MR) or highly resistant (HR). Tolerant varieties differed in their host status but tended to respond moderately resistant. In conclusion, it is suggested to include the analysis of resistance level either in the official registration procedure for BCN-tolerant sugar beet varieties or to perform this analysis for all registered varieties as a kind of risk assessment.