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An Ultraviolet-Induced Nontoxigenic Mutant of Pseudomonas phaseolicola of Altered Pathogenicity. Suresh S. Patil, Professor, Department of Plant Pathology, University of Hawaii, Honolulu, 96822; A. C. Hayward(2), and Rebecca Emmons(3). (2)(3)Visiting Professor, and former laboratory assistant, Department of Plant Pathology, University of Hawaii, Honolulu, 96822, (2)Present address: Department of Microbiology, University of Queensland, Brisbane, Australia. Phytopathology 64:590-595. Accepted for publication 23 September 1973. DOI: 10.1094/Phyto-64-590.

Cultures of a toxigenic isolate of Pseudomonas phaseolicola, which is capable of inducing typical halo blight symptoms in bean plants, were irradiated with ultraviolet light. One hundred and eight colonies were randomly selected and tested for their ability to induce halos in needle inoculations of trifoliolate leaves of ‘Red Kidney’ bean plants. One mutant isolate which in repeated tests failed to induce halos, and the parent isolate were compared with respect to multiplication in vivo, toxin production in culture, nutrition, physiology, and sensitivity to antibiotics. Except for toxin production in culture and the ability to cause systemic chlorosis and systemic invasion in inoculated plants, the mutant is indistinguishable from the wild type. It is proposed that toxigenicity of P. phaseolicola is intimately related to its ability to systemically invade susceptible bean plants.