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Etiology

White Blotch Incited in Wheat by Bacillus megaterium pv. cerealis. R. M. Hosford, Jr., Professor, Department of Plant Pathology, North Dakota State University, Fargo 58105; Phytopathology 72:1453-1459. Accepted for publication 30 March 1982. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1982.. DOI: 10.1094/Phyto-72-1453.

White blotch of wheat is characterized by severe white to very light tan blotches and streaks on leaf blades, sheaths, and culms. It has occurred with increased frequency on hard red spring, hard red winter, and durum wheats throughout North Dakota since 1975. Bacillus megaterium pv. cerealis was consistently isolated from these blotches and from 2 to 14% of seed of severely affected cultivars. Koch’s postulates were completed with 12 strains of the bacterium. On susceptible cultivars, disease symptoms began as small white or yellow diffuse blotches without water congestion and developed into severe spots within 2–20 days after inoculation. Symptom expression was accelerated by high temperatures and high light intensities. Pseudomonas syringae pv. syringae caused similar white blotches and streaks, but differed in that the lesions first appeared as transient water-soaked streaks and in the reported degree of virulence on some cultivars.