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Disease Note.

Leaf Spot of Cilantro in California Caused by a Nonfluorescent Pseudomonas syringae. D. A. Cooksey, Department of Plant Pathology, University of California, Riverside 92521. H. R. Azad, A. O. Paulus, and S. T. Koike. Department of Plant Pathology, University of California, Riverside 92521, and UC Cooperative Extension, 118 Wilgart Way, Salinas, CA 93901. Plant Dis. 75:101. Accepted for publication 4 September 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0101D.

A leaf spot disease of field-grown, sprinkler-irrigated cilantro (Coriander sativum L.) was observed in 1988 and 1990 in southern California and in Monterey County in 1990. Leaves had dark brown, vein-delimited lesions. The disease was randomly distributed throughout fields and occurred on at least two cultivars, Santo and Romanian. Nonfluorescent strains of Pseudomonas syringae van Hall were consistently isolated from lesions in several independent samples of diseased cilantro during both 1988 and 1990. The bacteria were gram-negative aerobic rods with polar flagella and produced negative reactions for oxidase, arginine dihydrolase, nitrate reduction, and gelatin hydrolysis. Reactions for production of levan and hypersensitivity in tobacco were positive. The bacteria were identified as P. syringae based on carbon source utilization patterns in Biolog MicroPlates and comparison to the MicroLog database (Biolog, Inc., Hayward, CA). Leaf spot symptoms developed on spray-inoculated cilantro and parsley. This disease has not been previously reported in the United States, but a similar disease was reported in England (1), where both fluorescent and nonfluorescent strains of P. syringae were isolated.

Reference: (1) J. D. Taylor and C. L. Dudley. Plant Pathol. 29: 117, 1980.