Monitoring E. amylovora using real time PCR.

Fire blight, caused by the Gram-negative bacterium Erwinia amylovora is the most damaging bacterial disease of pome fruit world wide. Disease outbreak is only sporadic, disease outcome, however, can be devastating. Aside from physical factors like temperature and humidity, presence of the pathogen in sufficient amounts to cause infection is a crucial aspect in abatement of disease. We have refined a real time PCR based quantification of E. amylovora to be used in the field on a variety of environmental samples. This method allowed us to monitor pathogen abundance during blossom during the last four years. Integration of the amount of pathogen detected into refined prediction algorithms will most certainly improve applied forecasting models. The method also allows the quantification of pathogen outside the blooming period within or on the surface of different tissue, or plant organs. This may allow a monitoring of the pathogen population throughout the year and in the long run may facilitate timely countermeasures. Results also indicate a potential role of fruit mummies in overwintering and dissemination of the pathogen early in the growing season, as well as a role of non-host flowers in the built up of pathogen potential. The method is also capable of monitoring disease progression in infected, but symptomless tissue. Results from this set of experiments might improve recommendations for good cultural practice.