Disease Note

First Report of Natural Infection of Arabidopsis thaliana by Xanthomonas campestris pv. campestris. J. Tsuji, MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing 48824-1312. S. C. Somerville, MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing 48824-1312. Plant Dis. 76:539. Accepted for publication 13 November 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0539A.

Semioval necrotic and chlorotic lesions were Observed on the margins of leaves of the cruciferous weed Arabidopsis thaliana (L.) Heynh. growing along a roadside in Kalamazoo, Michigan. A gram-negative, rod-shaped bacterium was isolated from diseased tissue and identified as Xanthomonas campestris pv. campestris (Pammel) Dowson by the following criteria: yellow mucoid colonies on YDC, growth on SX, xanthomonadin pigment production, growth at 35 C, protease activity, and ability to cause black rot disease on turnip (Brassica campestris L. subsp. campestris) from Bentley Seed Co. (Cambridge, NY). To fulfill Koch's postulates, we sprayed guttating leaves of 3-wk-old A. thaliana race PrO with the bacterium. Symptoms identical to those described above were observed 1-2 wk after inoculation, and the same bacterium was reisolated from the diseased leaves. No blackened veins were observed on either naturally infected or artificially inoculated leaves. This is the first report of natural infection of A. thaliana by X. c. campestris and further extends the range of cruciferous weeds that are alternative hosts for this bacterium.