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Immunofluorescent Stain Procedures for Detection and Identification of Erwinia carotovora var. atroseptica. Elizabeth Allan, Specialist, Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706; Arthur Kelman, Professor, Department of Plant Pathology, University of Wisconsin-Madison, Madison, WI 53706. Phytopathology 67:1305-1312. Accepted for publication 30 March 1977. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-1305.

A fluorescent antibody stain (FAS) was effective in the identification of isolates of Erwinia carotovora var. atroseptica (Eca) from different geographic areas. The antiserum for the FAS was prepared using bacterial cells (Wisconsin isolates - SR-8) fixed in 2% glutaraldehyde. All U.S. isolates of Eca from potato, which were confirmed by physiological tests, reacted with the FAS. Three isolates of Eca from potato (Scotland) and all the isolates of Eca from sunflower (Mexico), sugarbeets (U.S.), iris (England), and tomato (England) did not give a positive reaction. All other isolates of Erwinia spp. that were tested did not react with the FAS with the exception of one potato isolate of E. carotovora var. carotovora (Ecc) from The Netherlands. Fluorescing Eca cells were detected on prepared slides in mixed populations containing as few as 500 cells/ml mixed with 10⁸ cells/ml of Ecc. Cells of Eca also were detected in soils to which as few as 10 cells/gm had been added and on potato leaves previously sprayed with bacterial suspensions. The FAS procedure also was effective in detecting Eca in tissues of infected and/or decaying potato tubers and in artificially contaminated adult fruit flies (Drosophila melanogaster).