Co-Authors:
Levy, A., Virus Laboratory, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel
Loebenstein, G., Virus Laboratory, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel
Smookler, M., Virus Laboratory, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel
Drori, T., Virus Laboratory, Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel
Abstract:
Shortwave UV (2540 Å) significantly enhanced cucumber mosaic virus (CMV) multiplication in cotyledons of a resistant cucumber (Cucumis sativus L.) cultivar (Elem) when applied 1-3 days after inoculation. Compared with nonirradiated controls, infectivity increased 4-8 times when cotyledons were irradiated with dosages of 11,000-18,000 ergs mm-2 at a distance of 10 cm, 1-2 days after inoculation. Irradiations after longer intervals were less effective and irradiations with longwave UV (3600 Å) had no effect. Irradiations before inoculation reduced extractable infectivity markedly. No difference in infectivity titer was obtained when cotyledons of a susceptible cucumber variety were irradiated. The number of virions, observed with an electron microscope, in extracts of cotyledons irradiated 48 hr after inoculation, was also significantly higher than in control extracts. The action spectrum for the suppression of the resistance (dose scale factor of 28-42) was between that of tobacco mosaic virus (TMV) (40-60) and that of TMV-RNA (15-20), used as biological "dosimeters" for nucleoproteins and nucleic acids, respectively, and differed markedly from that of a protein (4-5). It is suggested that the resistance mechanism is activated by the virus, and suppressed by shortwave UV, which probably blocks transcription by the formation of thymine dimers. © 1974.
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