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Physiology and Biochemistry

Different Induction Periods for Hypersensitivity in Pepper to Xanthomonas vesicatoria Determined with Antimicrobial Agents. M. E. Meadows, Graduate research assistant, Plant Pathology Department, University of Florida, Gainesville 32611; R. E. Stall, professor, Plant Pathology Department, University of Florida, Gainesville 32611. Phytopathology 71:1024-1027. Accepted for publication 22 January 1981. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-1024.

The minimum inhibitory concentration (MIC) of 12 antimicrobial agents to Xanthomonas vesicatoria was determined for growth in nutrient broth and for induction of the hypersensitive reaction (HR) in pepper leaves. The latter was determined by additions of an agent to inoculum or to inoculated leaves. The MICs for growth and induction of HR were similar for chloramphenicol (chl), rifampicin (rif), and tetracycline, but much lower for growth than for induction of HR for the other antimicrobial agents. The longest period of time between inoculation of pepper leaves with an incompatible strain of X. vesicatoria and infiltration with an agent that prevented cell collapse (induction period) was variable with the 12 antimicrobial agents. The longest estimate of an induction period, 3 hr when cell collapse began near 5 hr after inoculation, was obtained with chl and rif. Mutants resistant to chl and rif induced HR when mixed with the chemicals to which they were resistant.