Variations in Pseudomonas syringae Isolated from Grass Species Occurring in Woody Plant Nurseries in the Pacific Northwest. S. Baca, Graduate Research Assistant, Oregon State University, Corvallis 97331-2902. L. W. Moore, Associate Professor of Plant Pathology, Oregon State University, Corvallis 97331-2902. Plant Dis. 71:724-726. Accepted for publication 12 January 1987. 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, 1987. DOI: 10.1094/PD-71-0724.

High subpopulations of Pseudomonas syringae were detected from naturally occurring grass species on the edges of nursery production areas and from sudangrass and cereal ryegrass used as green manure and cover crops, respectively. Leaf samples obtained from diseased sudangrass and symptomless cereal ryegrass and roadside grass species in November yielded large populations of pathogenic and ice-nucleation-active strains of P. syringae. Populations approaching 10⁹ cfu/g of fresh tissue were isolated from sudangrass samples, whereas populations of 10⁶ cfu/g were obtained from ryegrass and roadside grass samples. Of 81 randomly selected strains from these isolations tested, 58 (72%) were similar to P. syringae; of these, 34 (59%) were ice-nucleation-active at –5 C. Thirty-one of the P. syringae strains (54%) induced a hypersensitive response in tobacco leaves, and 29 (50%) were pathogenic on green fruit of yellow pear tomato.

Keyword(s): hypersensitivity, LOPAT.