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Pathogenesis as Influenced by the Interaction of Two Virulent Strains of Pseudomonas solanacearum in Inoculated Tobacco Plants. Eldon I. Zehr, Former Graduate Assistant, Department of Plant Pathology, Cornell University, Ithaca, New York 14850, Present address: Department of Plant Pathology and Physiology, Clemson University, Clemson, South Carolina 29631; Phytopathology 61:987-989. Accepted for publication 18 March 1971. DOI: 10.1094/Phyto-61-987.

Tobacco plants were stem-inoculated with two Philippine isolates of Pseudomonas solanacearum virulent to tomato, but differing in virulence to tobacco. When the plants were inoculated near the shoot tip with mixtures of the two isolates, wilt was less severe than when tobacco plants were inoculated with the same number of cells of the more virulent isolate alone. The effect was most evident when the mixture contained a high percentage of cells of low virulence to tobacco, but was apparent even when the mixture contained equal numbers of cells of each isolate. However, when older plant tissues (stems) were inoculated with any proportion, disease severity was not reduced. When plants were inoculated near the shoot tip with the isolate of low virulence and in the lower stem with the more virulent isolate, wilt was less severe, but when the isolates were reversed in position, no such effect was observed.