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Ecology and Epidemiology

Overwintering of Pseudomonas syringae pv. glycinea in the Field. E. W. Park, Graduate research assistant, Department of Plant Pathology, University of Illinois at Urbana-Champaign, Urbana 61801; S. M. Lim, professor, (also research plant pathologist, Agricultural Research Service, U.S. Department of Agriculture), Department of Plant Pathology, University of Illinois at Urbana-Champaign, Urbana 61801. Phytopathology 75:520-524. Accepted for publication 6 November 1984. 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, 1985. DOI: 10.1094/Phyto-75-520.

Overwintering of Pseudomonas syringae pv. glycinea (PSG) associated with soybean leaves in the field was evaluated with a streptomycin-rifampicin resistant mutant (PRS-81) of the bacterium. In 1981- 1982, PRS-81 was recovered from buried samples (10, 20, and 30 cm below the surface) until February 1982 and from soil surface samples until March 1982. It was not detected after April. In 1982- 1983, survival of the bacterium was not affected by depths at which samples were placed. Viable cells were detected from all samples until March. Soil temperature and moisture greatly influenced survival of the bacterium associated with soybean leaves. PRS-81 survived better under dry, cold conditions than under wet, warm conditions. Effects of soil temperature and moisture on survival of PRS-81 appeared to interact. Effects of soil moisture were more apparent at 4 C than at 12 or - 12 C. Considering technical limitations in detecting PSG in soil and influences of soil temperature and moisture on its survival, it is concluded that PSG associated with soybean leaf tissue could overwinter on the soil surface in central Illinois if the weather is cold and dry.