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Detection of Xanthomonas campestris pv. carotae in Carrot Seed. T. -L. Kuan, Asgrow Seed Company, P.O. Box L, San Juan Bautista, CA 95045. G. V. Minsavage, Asgrow Seed Company, P.O. Box L, San Juan Bautista, CA 95045, and R. L. Gabrielson, Western Washington Research and Extension Center, Washington State University, Puyallup 98371. Plant Dis. 69:758-760. Accepted for publication 17 March 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-758.

A method has been developed to isolate Xanthomonas campestris pv. carotae (X. c. carotae) in carrot seed lots. The method consists of a low-temperature (5 C) stationary aqueous soak of carrot seed in darkness for 18 hr followed by a vigorous shaking of the seed in water containing Tween 20, concentration of bacterial cells by centrifugation (7,796 g for 15 min), and plating of a dilution series of these cells onto a modified Kado and Heskett’s D5 medium. The method yielded repeatable and consistent results in replicated testing of seed lots. The bacterium was detected in 34 of 35 seed samples from infected fields and zero of six seed samples from healthy fields. One naturally infected seed in 10,000 seeds can be detected by this method. This is the first report of direct isolation of X. c. carotae from carrot seed.