Clubroot disease management challenges from a German perspective

Abstract

Clubroot research in Germany addresses a broad range of aspects of this disease, including host resistance and its genetic basis, different means of integrated control and basic studies of the physiological alterations in the host during infection. The intimate relationship between Plasmodiophora brassicae Wor. and its host leads to a dramatic change in hormone status, cellular development and source-sink relations. Apart from plant growth-promoting hormones, such as auxins and cytokinins, changes in secondary metabolites were also found to be associated with club development, exhibiting their effect either directly on growth hormones or indirectly via their general bioactive properties. Clubroot resistance is another focus of German research programmes. While clubroot has been a major concern of vegetable growers, now the disease has a significant impact on oilseed rape (Brassica napus L.). Accordingly, recent research addresses different aspects of clubroot control in this crop. The release of the clubroot resistant oilseed rape cultivar ‘Mendel’ by a German breeding company has been a milestone in clubroot management in oilseed rape worldwide. The efficacy of this resistance source is of key relevance and studies are being undertaken to characterize pathogenic variation. In addition to cultivar resistance, agronomical approaches, such as application of calcium cyanamide, are available, and integrated pest management strategies can address the prevention of the multiplication of P. brassicae inoculum. Clubroot resistance has been studied also in the model plant Arabidopsis thaliana. This work has resulted in the cloning of the resistance locus RPB1.