VIEW ARTICLE

Ecology and Epidemiology

Atmospheric Dispersal of Ice Nucleation-Active Bacteria: The Role of Rain. H. A. Constantinidou, Department of Plant Pathology and Agricultural Research Service, U.S. Department of Agriculture, University of Wisconsin, 1630 Linden Drive, Madison 53706, Present address: Laboratory of Agricultural Chemistry, Department of Agriculture, Aristotelian University of Thessaloniki, University Box 251, Thessaloniki, Greece; S. S. Hirano, L. S. Baker, and C. D. Upper. Department of Plant Pathology and Agricultural Research Service, U.S. Department of Agriculture, University of Wisconsin, 1630 Linden Drive, Madison 53706. Phytopathology 80:934-937. Accepted for publication 17 April 1990. 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, 1990. DOI: 10.1094/Phyto-80-934.

A strong net downward flux of bacteria was measured in a soybean field during two different rain events. The ice nucleation-activity and phytopathogenic host range of strains of Pseudomonas syringae isolated from rainwater and aerosols present during rain differed from those of the bacteria present on the soybeans. Bacteria that produced fluorescent pigments on an iron-deficient medium were 3?8%, 5?9%, and 81% of those isolated from aerosols during rain, from rain, and from the soybean leaves, respectively. These two observations?net downward flux and bacteria in the rain and air being different from those on the leaves?were interpreted to mean that the bacteria being delivered to the canopy came from a source outside the soybean field.