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Characterization of Hypersensitivity in Capsicum annuum Induced by the Tomato Strain of Xanthomonas vesicatoria. A. A. Cook, Department of Plant Pathology, University of Florida, Gainesville 32601; Phytopathology 63:915-918. Accepted for publication 25 January 1973. DOI: 10.1094/Phyto-63-915.

The hypersensitive response induced in two cultivars of Capsicum annuum by isolates of the tomato strain of Xanthomonas vesicatoria were characterized according to several criteria. Response to inoculation in leaves of both pepper cultivars was not visibly evident until after ca. 15-hr incubation at 30 C and 24 hr at 25 C. An initial decrease in bacterial concentration in vivo was found after 6-hr incubation at the higher temperature, but this was followed by a progressive increase in concentration for the next 18 hr. Electrolyte-loss patterns from both pepper cultivars intermediate to those induced by pepper strain, race 2 of the bacterium were induced by six isolates of the tomato organism. Although electrolyte losses from both pepper types induced by tomato isolate 71-14 were consistently lower than for five other isolates of the tomato pathotype, they generally followed the same pattern. Incubation at 25 C, rather than 30 C, retarded electrolyte loss from leaves inoculated with the tomato strain of the bacterium but incubation of leaves in darkness, as opposed to light, enhanced electrolyte loss at both temperatures. Introduction of bacterial cells suspended in 0.15 N Ca(NO3)2 instead of sterile distilled water also enhanced electrolyte loss, more in one pepper cultivar than in the other. These results provide evidence that distinct forms of hypersensitivity may be induced in pepper by inoculation with different pathotypes of X. vesicatoria.

Additional keywords: light.