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Cytology and Histology

Scanning Electron Microscopy of Infection Sites and Lesion Development on Tomato Fruit Infected with Pseudomonas syringae pv. tomato. S. Getz, Graduate research assistant, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; D. W. Fulbright(2), and C. T. Stephens(3). (2)(3)Assistant professors, respectively, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. Phytopathology 73:39-43. Accepted for publication 25 May 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-39.

Tomato ovary and fruit surfaces inoculated with Pseudomonas syringae pv. tomato (= P. tomato) were examined with a scanning electron microscope to observe possible infection sites and to follow lesion development. Bacteria were detected on both glandular and nonglandular trichomes present on ovaries during anthesis. Following anthesis, trichomes were gradually lost, leaving openings in the young fruit epidermis. Swollen areas of the epidermis that resembled trichome bases were filled with bacteria, suggesting that open trichome bases may serve as fruit infection sites. Mature lesions were either sunken or raised, and masses of bacteria were extruded from cracks in the lesion surface.