The bacterial cultures were grown either from fire blight infectedbranches or from previously stored strains as glycerolstocks at −80 C. For bacterial isolation and culture from infectedbranches, approximately 2.5 cm of stem tissue surroundingthe visual symptoms of fire blight was used.Material was surface sterilized with 70% ethanol for 1 min,and treated afterwards with 10% Clorox bleach for 10 min.The sterilized samples were rinsed three times with water, andtheir barkwas skimmed off to expose the cambiumlayer. Thin(0.1 cm thickness × 0.5 cm length) layers of cambium weretaken from the healthy-infected transition zone and were platedonto the King’s B medium (King et al. 1954). The mediaplates were incubated at 24–26 °C for 2 days to grow thebacterial colonies. The resulting bacteria were either directlysuspended in water or kit buffer for fire blight infection experiments,or were used for quick DNA extraction to performvarious fire blight assays. The bacterial isolation and culturingwere done under sterile conditions in the laminar flow hood.