Bird's Eye Lesions of Tomato Fruit Produced by Aerosol and Direct Application of Clavibacter michiganensis subsp. michiganensis.

Development of the bird's eye fruit lesion of tomato was studied by inoculating flowers and the surface of young tomato fruit with strains of Clavibacter michiganensis subsp. michiganensis. Flowers were sprayed once or twice with C. michiganensis subsp. michiganensis at 108 CFU/ml. The maximum incidence (80%) and severity (12 spots/fruit) of spotted fruit resulted when inoculum was sprayed twice, 3 days apart. Flowers were most susceptible to infection 2 days after anthesis. When a paintbrush was used to apply inoculum to the surface of small fruit, a large number of fruit spots (≤456 spots/fruit) resulted. Even strains determined to be avirulent based on a tomato stem inoculation assay and a hypersensitive response on four-o'clock leaves (Mirabilis jalapa) were able to produce fruit spots, although at a reduced level. The inoculation methods developed in this study can provide opportunities to observe subtle host-pathogen interactions between C. michiganensis subsp. michiganensis strains and tomato and to help formulate methods to quantify infection.