Effect of sugar beet variety resistance on the disease epidemiology of Cercospora beticola

Abstract

Background: Cercospora leaf spot (CLS), caused by Cercospora beticola, is the most destructive foliar disease in sugar beet. CLS is conventionally controlled with fungicide, but the emergence of fungicide-resistant populations reinforces the importance of developing and cultivating resistant varieties. Understanding the dynamics of CLS in different varieties is hence essential for sustainable CLS management.

Results: Field experiments (2022 and 2023) with four sugar beet varieties possessing different resistant properties were conducted to describe the relationship between the variety resistance and the disease epidemiology of C. beticola. For this purpose, spore flight and disease progression were assessed on a weekly basis. Disease severity (DS) and disease incidence (DI) were delayed in resistant varieties compared to the susceptible and moderately susceptible ones. This finding was further confirmed by a model-based analysis of DS and DI for all varieties. Weekly spore flight monitoring during the vegetation period showed a similar tendency of reduced spore quantity by the resistant varieties. This was probably due to the lower DS, as no differences were found when the amount of fungal DNA was determined in individual lesions from the different varieties. Analysis of relative yield loss further confirmed the advantage of growing resistant varieties.

Conclusion: Our results highlight that resistant varieties delay disease onset resulting in less severe symptoms and reduced spore flight. We also proved that aerial spore flight intensity could reflect the resistant property of each variety. These results provide a deeper insight into the interaction between variety resistance and CLS epidemiology, emphasizing variety-specific CLS management. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Keywords: Cercospora beticola; disease epidemiology; spore flight; sugar beet; variety resistance.

FIGURE 1

Mean value of disease incidence (DI) and disease severity (DS) (n = 108) and mean value of detected Cercospora beticola DNA (pg) (n = 3 plots) in 2022. For spore flight monitoring, varieties A, B, and D were selected for location Reinshof, while varieties A, C, and D were selected for location Weende. Error bars of DS data represent the standard deviation of three replicated plots of each variety. Error bars of C. beticola DNA represent the standard deviation of three field plots of qPCR. Small letters indicate the significant differences in DS among varieties (P < 0.05).

FIGURE 2

Correlation between cumulative DNA quantities in picograms detected from Cercospora beticola aerial spores and the disease severity (DS) at the corresponding time point. Data used for the correlation analysis in 2022 originated from the last sampling and rating time point. Data used for the correlation analysis in 2023 originated from the sampling and rating time point preceding the observation of severe regrowth [weeks post‐inoculation (wpi) = 13, corresponding to 9 June 2023].

FIGURE 3

Mean value of disease incidence (DI) and disease severity (DS) (n = 108) and mean value of detected Cercospora beticola DNA (pg) (n = 3 plots) in 2023. DI and DS data at 11 weeks post‐inoculation (wpi) were not recorded. For spore flight monitoring, varieties A, B, and D were selected for location Marienstein, while varieties A, C, and D were selected for location Weende. Error bars of DS data represent the standard deviation of three replicated plots of each variety. Error bars of C. beticola DNA represent the standard deviation of three field plots of qPCR. Small letters indicate the significant differences in DS among varieties (P < 0.05).

FIGURE 4

Mean value (n = 3) of relative loss in white sugar yield (%) in 2023 of four sugar beet varieties in (a) Marienstein and (b) Weende. Small letters denote the significant differences among varieties (P < 0.05). Error bars represent the standard deviation.

FIGURE 5

Boxplot of total DNA of Cercospora beticola on single lesion sampled from four different varieties (n = 30). Each jitter represents the mean value of three technical replicates of one sample.