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ARS Home » Midwest Area » Madison, Wisconsin » Vegetable Crops Research » Research » Publications at this Location » Publication #302190
Title: First report of bacterial blight of carrot in Indiana caused by Xanthomonas hortorum pv. carotae

Author
item DU TOIT, L - Washington State University Extension Service
item DERIE, M - Washington State University Extension Service
item CHRISTIANSON, C - Washington State University Extension Service
item HOAGLAND, L - Purdue University
item Simon, Philipp

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2014
Publication Date: 5/1/2014
Publication URL: http://handle.nal.usda.gov/10113/58835
Citation: Du Toit, L.J., Derie, M.L., Christianson, C.E., Hoagland, L., Simon, P.W. 2014. First report of bacterial blight of carrot in Indiana caused by Xanthomonas hortorum pv. carotae . Plant Disease. 98(5):685.

Interpretive Summary: Bacterial blight is an important disease of carrot caused by Xanthomonas hortorum pv. carotae. It damages leaves of growing plants and that usually spreads to roots, which subsequently usually rot either in the field or in storage. This disease has been observed widely around the world. This report confirms its first observation in Indiana. It is not expected to threaten carrot production in Indiana significantly, since it can be controlled by a simple seed treatment with hot water, but this report indicates that carrot seed planted in Indiana would benefit from routine application of this seed treatment. This information is of interest to carrot researchers and growers, and to plant pathologists.

Technical Abstract: In summer 2012, bacterial blight symptoms were observed on leaves of carrot plants in 7 out of 70 plots of carrot breeding lines at the Purdue University Meig Horticulture Research Farm, Lafayette, IN. Symptoms included small to large, variably shaped, water soaked to dry, necrotic lesions, with or without chlorosis. Microscopic examination of symptomatic leaf sections revealed bacterial streaming from the cut ends of each leaf piece. Colonies with morphology similar to that of isolate Car001 of Xanthomonas hortorum pv. carotae from Washington State were obtained consistently from all seven plots. All seven Indiana isolates and Car001 produced a 355 bp DNA fragment indicative of X. hortorum pv. carotae. Indian isolates were each tested for pathogenicity on 11-week-old carrot plants. Symptoms of bacterial blight were first observed 14 days after inoculation. To our knowledge, this is the first report of bacterial blight of carrot in Indiana.