Overview of the clubroot incidence and variation in the pathotypes of Plasmodiophora brassicae populations in Europe

Abstract: Plasmodiophora brassicae has recently become one of the most damaging pathogens to oilseed rape (OSR) cultivation in Europe. Questionnaires submitted by farmers and extension services revealed short rotation (once in 2-3 years) of the crop in 70% of fields. Frequency of OSR in the rotation significantly correlated with the incidence and prevalence of clubroot disease. Although there was a significant negative correlation between the disease index and soil pH, the occurrence of clubroot was not restricted to fields with highly acidic soils. Characterization of P. brassicae populations on the European Clubroot Differentials (ECD), and classification by the differential hosts of Williams or Somé et al. revealed that pathotypes: ECD 16/31/31 and 16/14/31; 4, 6 and 7; and P1 and P3, respectively, are predominant in central Europe. Several populations were found that could overcome the resistance of cv. Mendel, the first cultivar of OSR bred for resistance to clubroot.