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Disease Note.

First Report of Black Chaff of Wheat Caused by Xanthomonas campestris pv. translucens in Washington State. T. D. Murray, Department of Plant Pathology, Washington State University, Pullman 99164-6430. O. C. Maloy, Department of Plant Pathology, Washington State University, Pullman 99164-6430. Plant Dis. 74:183. Accepted for publication 16 November 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0183C.

Wheat (Triticum aestivum L. 'Bronze Chief') plants grown under sprinkler irrigation near Touchet, Washington, were collected in June 1988 from a field where nearly 100% of the plants showed extensive necrosis on leaves, peduncles, and glumes. A diagnosis of black chaff of wheat caused by Xanthomonas campestris pv. translucens (J. J. & R.) Dye was made based on obvious symptoms and the presence of dried exudate. A yellow mucoid, gram-negative bacterium was isolated in nearly pure culture from leaves and glumes ground in sterile water, spread on YDC agar, and incubated at 30 C. Growth of individual colonies on a medium specific for X. c. pv. translucens (1) and development of black chaff symptoms in T. durum Desf. 'WAID' seedlings injected at the four-leaf stage with 102 cfu/ml washed bacterial cells were evidence for identification of X. c. pv. translucens. Necrosis developed in all inoculated plants after incubation for 10-13 days at 23 3 C. A sample of seed (origin unknown) used to establish the field was sent to the University of Idaho Seed Pathology Laboratory and yielded 270 cfu of X. c. pv. translucens per gram of seed. Although X. c. pv. translucens was isolated from a seed lot grown in Washington (1), this is the first known report of black chaff on wheat in that state.

Reference: (1) N. W. Schaad and R. L. Forster. Phytopathology 75:260, 1985.