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Etiology

Etiology of Watermelon Rind Necrosis. D. L. Hopkins, Associate Professor of Plant Pathology, University of Florida, Agricultural Research Center, Leesburg, FL 32748; G. W. Elmstrom, Associate Professor of Horticulture, University of Florida, Agricultural Research Center, Leesburg, FL 32748. Phytopathology 67:961-964. Accepted for publication 2 March 1977. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-961.

Bacteria were isolated consistently from healthy watermelons and from melons with watermelon rind necrosis (WRN). No single bacterial species was isolated consistently from WRN tissue. The diversity of the internal bacterial flora of melons with WRN was similar to that of healthy melons. However, enterobacteria were isolated more frequently from melons with WRN than from healthy melons. Most of the bacteria isolated produced localized rind necrosis when injected at high concentrations but at low concentrations some bacteria were more effective than others. With some isolates a systemic rind necrosis was produced which resembled that often observed in natural infections. In field studies, foliar sprays of mineral nutrients did not affect WRN incidence. It is hypothesized that the WRN symptoms result from the multiplication of one of the resident bacteria to a level high enough to induce a necrotic reaction in the watermelon.