ABSTRACT
Successful infection of fruit trees by plant pathogenic bacteria involves movement of the pathogen to the host, attachment to the host surface, entry, multiplication, and establishment in the host. For a general account of these events, the reader is referred to several publications. This chapter describes the pathological anatomy of infection and systemic invasion of fruit trees by bacterial pathogens. Motile strains of bacterial pathogens of fruit trees probably occur much more commonly than do nonmotile strains. The role of bacterial motility in infection has been examined extensively with the peritrichously flagellated E. amylovora. In vitro studies showed that virulent strains of E. amylovora had their full complement of normal-sized flagella after 10 h. Infection is more likely to occur if plant pathogenic bacteria follow a chemical gradient. E. amylovora is attracted chemotactically to nectar extracts of apple blossoms. In this system, chemotaxis is dependent on temperature (20 to 28°C) and pH (6 to 8).
