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Ecology and Epidemiology

Population Dynamics of Pseudomonas syringae pv. syringae on Spring Wheat. W. W. Shane, Former research fellow, Department of Plant Pathology, University of Minnesota, St. Paul 55108, Present address: Department of Plant Pathology, Ohio State University, Columbus 43210-1087 ; J. S. Baumer, Former assistant professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108, Present address: Land O’Lakes Research Farm, RR 2, Webster City, IA 50595. Phytopathology 77:1399-1405. Accepted for publication 31 March 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1399.

Resistance of spring wheat genotypes to Pseudomonas syringae pv. syringae was investigated in growth chamber studies. Population growth and symptom development were monitored after introduction of bacterial suspensions (5 × 10⁶ cfu ml^–1) into leaf intercellular spaces and incubation at 18–20 C under light mist. Spray, wound, or vacuum infiltration were inappropriate inoculation methods. P. s. pv. syringae is a weak pathogen that requires moist conditions during the incubation period for significant infection. Foliar symptoms and log₁₀ bacterial populations 3 days after inoculation were positively correlated (r² = 0.54). Genotypes Len, Marshall, Nowesta, Red River 68, Bonanza, Bounty 208, and Alex were relatively resistant; Polk, Angus, Chris, Oslo, and Lark were moderately susceptible; and Bounty 309 and L1 were susceptible to P. s. pv. syringae as measured by symptom development and bacterial populations.