The sterilized samples were rinsed three times with water, and their bark was skimmed off to expose the cambium layer. Thin (0.1 cm thickness × 0.5 cm length) layers of cambium were taken from the healthy-infected transition zone and were plat ed onto the King's B medium (King et al. 1954). The media plates were incubated at 24-26 °C for 2 days to grow the bacterial colonies. The resulting bacteria were either directly suspended in water or kit buffer for fire blight infection exper iments, or were used for quick DNA extraction to perform various fire blight assays. The bacterial isolation and culturing were done under sterile conditions in the laminar flow hood.