Response of central European Pyrus germplasm to natural fire blight infection and artificial inoculation.
Of 133 Pyrus accessions (predominantly P. communis) collected in Central Europe and previously rated in the resistant (USDA) blight scores 10-6, only 77 (57.0%) remained in these scores afer an additional 5 years of exposure to Erwinia amylovora. Of these, 24 originated from 3 states in the former Yugoslavia. Following several years of severe blight epiphytotics, only 5 (10.4%) of 52 accessions released from quarantine since 1986 and planted at the Appalachian Fruit Research Station scored 6 or above. All accessions were highly susceptible to artificial blossom inoculation, and only 10 accessions were at least moderately resistant to artificial shoot inoculations.