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Field Evaluations of the Interactions Among Fluorescent Pseudomonads, Erwinia carotovora, and Potato Yields. G. -W. Xu, Department of Plant Pathology, Washington State University, Pullman 99164-6430; D. C. Gross, Department of Plant Pathology, Washington State University, Pullman 99164-6430. Phytopathology 76:423-430. Accepted for publication 3 October 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-423.

Fluorescent pseudomonad strains that inhibited Erwinia carotovora in vitro and which reduced potato seed piece decay in the greenhouse were tested in the field for ability to colonize potato roots and increase yield. Some strains colonized roots with populations exceeding 105 colony-forming units per gram (fresh weight) and were detected throughout the growing season. In 1982, the population of E. carotovora on roots of pseudomonad-treated potatoes (cultivar Russet Burbank) was only 1-8% of that on the untreated check; in 1983, it was less than 25% of that on the check. Strain W4P63 of Pseudomonas putida increased the yield of Russet Burbank by 11.7% in 1982 and by 10.2% in 1983; in both years it suppressed the soft rot potential of the tubers.

Additional keywords: bacterial soft rot, blackleg, siderophore.