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Evidence Against the Involvement of Hydrogen Peroxide in Bacterial Leaf Spot of Pepper. Myron Sasser, Assistant Professor, Department of Plant Science, University of Delaware, Newark 19711; Phytopathology 64:793-796. Accepted for publication 26 December 1973. DOI: 10.1094/Phyto-64-793.

Hydrogen peroxide (H2O2) was found to be highly toxic to Xanthomonas vesicatoria and to Xanthomonas phaseoli in vitro, but did not cause visible damage when injected into pepper leaves. Isolation of bacteria from inoculated pepper leaves was not affected by subsequent injections of H2O2, an enzymatic generator of H2O2, catalase, manganese chloride, or malate. Extracts of intercellular space fluid from healthy pepper leaves had H2O2-decomposing ability which was lost within 48 h following inoculation with bacteria. The lack of sensitivity in vivo by the plant or the bacteria, suggest that H2O2 is not a major causal factor in either pathogenesis or disease resistance in the system studied.

Additional keywords: disease physiology.