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Characterization of Pseudomonas syringae pv. maculicola and Comparison with P. s. tomato. W. L. Wiebe, Former Graduate Student, Department of Plant Pathology, University of California, Davis 95616. R. N. Campbell, Professor, Department of Plant Pathology, University of California, Davis 95616. Plant Dis. 77:414-419. Accepted for publication 7 December 1992. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-0414.

Thirty strains of Pseudomonas syringae pv. maculicola and four of P. s. tomato were collected from diverse localities and compared for symptom expression, host range, temperature response, and plasmid profile. The P. s. maculicola strains induced one of three distinct lesion types on crucifer hosts: chlorotic, water-soaked, or necrotic. Each of five P. s. maculicola strains that caused chlorotic lesions synthesized coronatine as confirmed by bioassay and by gas chromatographic and mass spectrometric analyses of culture filtrates. Four other strains that caused either water-soaked or necrotic lesions did not synthesize coronatine. Plasmid profiles of 25 P. s. maculicola strains contained from zero to seven plasmids ranging from 11 to 105 kb. The strains were less variable in host range and temperature response, but the diversity in symptom expression, coronatine synthesis, and plasmid profile denoted a high degree of heterogeneity within the pathovar. The P. s. maculicola and P. s. tomato strains were similar in many of these traits, but P. s. maculicola infected both crucifers and tomatoes, whereas P. s. tomato did not infect crucifers.