Bacterial Mosaic of Wheat in Illinois. R. J. Chang, USDA-ARS Crop Protection Research Unit, University of Illinois, Urbana 61801. S. M. Ries, A. D. Hewings, and C. J. D’Arcy. USDA-ARS Crop Protection Research Unit, and Department of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 74:1037. Accepted for publication 4 September 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-1037E.
A foliar disease of wheat (Triticum aestivum L. 'Caldwell'),
characterized by yellow lesions with indefinite margins, was found
in Gallatin and Clay counties, Illinois, in May 1990. A diagnosis of
bacterial mosaic of wheat caused by Clavibacter michiganense subsp.
tessellarius (Carlson & Vidaver) Davis et al was made based on the
distinctive mosaic symptoms and the isolation of bacteria that formed
apricot-orange colonies on CNS medium (1). The gram-positive
coryneform bacterium was isolated from diseased tissues that were
ground in sterile water and streaked on NBY medium. Orange, mucoid
colonies with entire margins were visible on NBY plates incubated
for 3 days at 25 C. A sterile needle and syringe were used to inoculate
plants of wheat cv. Michigan Amber at the four-leaf stage with washed
bacterial cells. Small, yellow lesions that sometimes coalesced into
streaks were observed in all inoculated plants after incubation for
14 days at 25 C. The bacterium was reisolated from inoculated leaves.
A hypersensitive reaction was not observed on tobacco leaves that
had been injected with a bacterial suspension. This is the first report
of bacterial mosaic of wheat in Illinois.