Erwinia amylovora expresses fast and simultaneously hrp/dsp virulence genes during flower infection on apple trees.

Background: Pathogen entry through host blossoms is the predominant infection pathway of the gram-negative bacterium Erwinia amylovora leading to manifestation of the disease fire blight. Like in other economically important plant pathogens, E. amylovora pathogenicity depends on a type III secretion system encoded by hrp genes.