STREPTOMYCIN-RESISTANT BACTERIA ASSOCIATED WITH FIRE BLIGHT INFECTIONS

Streptomycin-resistant strains of Erwinia amylovora were not detected from samples of 357 fire blight infected apple and pear tissues collected from 38 orchards in New York State. Streptomycin-resistant strains of other species were detected in the fire blight-infected tissues from four apple (cv. Crispin) orchards. These included strains of oxidase-positive and oxidase-negative Pseudomonas spp. and strains of Pantoea agglomerans. DNA from eight of the 18 streptomycin-resistant strains hybridized with a DNA probe, SMP3, that was previously cloned from a streptomycin-resistant strain of Pseudomonas syringae pv. papulans and shown to share sequence homology with DNA from several strains of streptomycin-resistant bacterial plant pathogens and saprophytic epiphytes. All of the strains that contained sequences homologous to SMP3 carried the streptomycin resistance determinant on plasmids of varying sizes. The frequency of resistance development appears to be associated with streptomycin use patterns.