Epidemiology of bacterial ring rot of potato in plant and soil–consequences for disease management

Abstract

In five field experiments, carried out from 2002 to 2004, the infestation of potato plants and the contamination of soil with Clavibacter michiganensis subsp. sepedonicus, the causal agent of bacterial ring rot of potato, were investigated throughout the growing season. Aiming at a detailed description of disease progress, for the first time potato tubers, stems and roots as well as soil were examined in parallel. The development of bacterial populations in plant organs and soil differed considerably within and between the experiments. Roots showed the highest and tubers the lowest incidence of infection of plant organs based on polymerase chain reaction (PCR) and immunofluorescence antibody staining (IFAS). Logistic regression analyses indicated a significant increase in the probability of infestation (in the case of soil: contamination) during the growing season for all investigated plant parts of highly infected plants and the respective soil samples. Results were discussed in terms of the suitability of particular plant organs and the determination of the best sampling time point for official testing. Furthermore, the risks are evaluated to contaminate machinery on the field and to spread bacterial ring rot through soil.