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Etiology

Characterization of the Bacterium Inciting Bean Wildfire in Brazil. R. de L. D. Ribeiro, Research assistant, Department of Plant Pathology, University of Wisconsin, Madison 53706; D. J. Hagedorn(2), R. D. Durbin(3), and T. F. Uchytil(4). (2)Professor, Department of Plant Pathology, University of Wisconsin, Madison 53706; (3)Research leader, Plant Disease Resistance Research Unit, SEA, USDA, University of Wisconsin, Madison 53706; (4)Professor, Department of Plant Pathology, and microbiologist, Plant Disease Resistance Research Unit, SEA, USDA, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 69:208-212. Accepted for publication 4 October 1978. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1979. DOI: 10.1094/Phyto-69-208.

The bacterium that incites bean wildfire and a foliar blight of garden peas in Brazil was identified as a strain of Pseudomonas tabaci. The organism conformed with this nomenspecies on the basis of in vitro biochemical properties, including the type of phytotoxins formed (tabtoxins). The Brazilian pathogen and a strain of P. tabaci originally isolated from soybean induced typical wildfire lesions on bean but were avirulent on tobacco. However, all the tobacco wildfire stains tested induced a hypersensitive response on bean. Cowpea, lima bean, and soybean developed wildfire symptoms with all strains of P. tabaci, regardless of their original hosts. The P. tabaci strains reached populations substantially higher in cowpea leaves than in leaves of their respective natural hosts (tobacco and bean). The bean wildfire organism multiplied in tobacco leaves much less than did the tobacco wildfire pathogen. The bean wildfire bacterium did not infect bean seeds. Differential symptoms produced on inoculated bean pods were useful in distinguishing between bean wildfire and bean halo blight, because the foliar symptoms of the two diseases were similar. The Brazilian pathogen and other strains that can induce wildfire symptoms on Phaseolus bean and are avirulent on wildfire-susceptible tobacco cultivars constitute a separate group within P. tabaci.