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Resistance

Effects of Local Infection of Cucumber by Colletotrichum lagenarium, Pseudomonas lachrymans, or Tobacco Necrosis Virus on Systemic Resistance to Cucumber Mosaic Virus. G. C. Bergstrom, Graduate research assistant, Department of Plant Pathology, University of Kentucky, Lexington 40546, Current address of senior author: Department of Plant Pathology, Cornell University, Ithaca, NY 14853; M. C. Johnson(2), and J. Ku?(3). (2)(3)Research associate, and professor, respectively, Department of Plant Pathology, University of Kentucky, Lexington 40546. Phytopathology 72:922-926. Accepted for publication 26 January 1982. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-922.

Inoculation of leaves 1 and 2 of cucumber cultivar Marketer with Colletotrichum lagenarium, Pseudomonas lachrymans, or tobacco necrosis virus (TNV) induced systemic resistance to challenge inoculation with cucumber mosaic virus (CMV) rubbed onto leaf 3. Induced resistance was expressed as a decrease in the number of chlorotic, primary lesions on CMV-inoculated leaves and as a delay in the time of appearance of systemic mosaic symptoms in plants with induced resistance compared to that of control plants. Differences between TNV-induced and control plants were most pronounced with dilute CMV inocula. Local lesions of TNV enhanced the moderate resistance of cultivar Wisconsin SMR-58 cucumber to CMV. Resistance also was induced in plants challenged with CMV transmitted by melon aphids, the natural vectors of CMV. Induced resistance to CMV resembled klendusity, the tendency to escape infection. To our knowledge, this study provides the first report that localized infections by fungi, viruses, and bacteria nonspecifically induce systemic resistance in a plant against a systemic virus.