Fire blight susceptibility tests on old apple varieties under controlled climatological conditions

The fire blight susceptibility of old apple varieties was tested in order to select resistant plant material. In a first experiment, seven old apple varieties and four commercial varieties were evaluated by artificial shoot and blossom inoculations. After an incubation time under controlled climatological conditions, the trees were evaluated on fire blight symptoms and classified in three groups according to their susceptibility. In a second experiment, grafts of eleven other old varieties were screened by artificial shoot inoculations. In all the grafts necrosis was formed to a various extent. In this experiment it was not possible to classify the used varieties according to their fire blight susceptibility, due to the low amount of grafts and the variability between the grafts of the same variety. The pathogenicity of the Erwinia amylovora strain that was used in these experiments was previously checked in host and non-host interactions.