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Ecology and Epidemiology

Role of Motility in Apple Blossom Infection by Erwinia amylovora and Studies of Fire Blight Control with Attractant and Repellent Compounds. Rizaldo G. Bayot, Former graduate student, Department of Plant Pathology, University of Illinois at Urbana-Champaign 61801; Stephen M. Ries, associate professor, Department of Plant Pathology, University of Illinois at Urbana-Champaign 61801. Phytopathology 76:441-445. Accepted for publication 15 October 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-441.

A nonmotile strain (Nm22) and its motile revertant (Mr22) of Erwinia amylovora were obtained after treating cells of the wild type with 0.3 M ethyl methanesulfonate. Pathogenicity of both strains was similar to that of the wild type on young Jonathan apple (Malus domestica) seedlings. Significantly more infection was recorded in blossoms inoculated with Mr22 than with Nm22 at inoculum concentrations of 5 x 10⁵ and 1 x 10⁷ colony-forming units per milliliter. Neither the repellents, sodium benzoate or sodium salicylate, nor the attractants, sodium malate or sodium tartrate, applied to apple blossoms as 10^-2 or 10^-3 M solutions, provided consistent protection against infection by E. amylovora. Negative chemotaxis of E. amylovora was constitutive for benzoate and salicylate but inducible for l-isoleucine, l-leucine, and l-phenylalanine.