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Isolation of Pectolytic Fluorescent Pseudomonads from Soil and Potatoes. Diane A. Cuppels, Former graduate research assistant, Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706, Present address of senior author: Agriculture Canada Res. Inst., Univ. Sub Post Office, London, Ont., Canada. N6A 5B7; Arthur Kelman, professor, Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706. Phytopathology 70:1110-1115. Accepted for publication 17 May 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1110.

Fluorescent pectolytic pseudomonads capable of causing soft rot of fleshy vegtables were isolated frequently from the surfaces and lenticels of stored potato tubers. On crystal violet pectate medium (CVP), colonies examined with oblique light appeared pink and slightly translucent and were surrounded by wide, shallow depressions. Pseudomonads of this colony morphology also were detected in the root zones of potato plants, washwater from a potato chip processing plant, field soils, a Wisconsin river and lake, and from decaying carrot and cabbage heads. Strains were found in Wisconsin soils just after the spring thaw and thus probably overwintered there. When inoculated into potato tuber and carrot slices, these strains rapidly produced a soft rot which fluoresced under ultraviolet light. When inoculated into stems of potato plants or lettuce heads, they caused a localized browning and softening of tissue. On the basis of the biochemical and physiological properties of 62 strains (including 45 from potato tuber surfaces), these bacteria were identified as strains of Pseudomonas marginalis.

Additional keywords: bacterial soft rot of carrot and cabbage.