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Physiology and Biochemistry

Chlorosis and Ethylene Production in Pepper Leaves Infected by Xanthomonas campestris pv. vesicatoria. R. E. Stall, Professor, Department of Plant Pathology and Department of Vegetable Crops, University of Florida, Gainesville 32611; C. B. Hall, professor, Department of Plant Pathology and Department of Vegetable Crops, University of Florida, Gainesville 32611. Phytopathology 74:373-375. Accepted for publication 3 November 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-373.

An unusual pepper (Capsicum annuum) line, designated P-107, was selected from descendants of a cross between a plant of PI 271322 and cultivar Early Calwonder (ECW). Leaves of P-107 yellowed rapidly compared to leaves of ECW after inoculation with the bacterial spot pathogen (Xanthomonas campestris pv. vesicatoria). Ethylene evolution, multiplication of the bacterium, and electrolyte leakage increased in leaves of P-107 and ECW after inoculation. The pattern of increase for each parameter was similar in both pepper types. However, chlorosis occurred more rapidly in P-107 leaves than in ECW leaves after exposure to ethylene or infiltration with ethephon. The differential rate of chlorosis of the two pepper types after exposure to ethylene and after inoculation with X. campestris pv. vesicatoria is evidence that the chlorotic zone surrounding necrotic lesions of bacterial spot is associated with ethylene production in the diseased leaves.