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Resistance

Further Characterization of Mycolaminaran-Induced Resistance: Temperature Sensitivity Against Tobacco Mosaic Virus and Function Against Cauliflower Mosaic Virus and Tomato Spotted Wilt Virus. Christina M. Heinkel, Plant Molecular Biology Center and Department of Biological Sciences, Northern Illinois University, DeKalb 60115; M. E. S. Hudspeth, R. Meganathan, and Thomas M. Zinnen. Plant Molecular Biology Center and Department of Biological Sciences, Northern Illinois University, DeKalb 60115. Phytopathology 82:637-641. Accepted for publication 15 January 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-637.

Mycolaminaran, a β-1,3-glucan from Phytophthora megasperma, inhibits initial tobacco mosaic virus (TMV) infection in greenhouse-grown Nicotiana tabacum and N. glutinosa when mixed at 100–500 µg/ml with inoculum. TMV inoculum amended with 250 µg/ml mycolaminaran produced fewer than 10% as many lesions as unamended control inoculum when applied to Datura stramonium, another member of the Solanaceae. Mycolaminaran similarly inhibited the infection of D. stramonium by four strains of cauliflower mosaic virus (Cabb-B, D4, CM1841, W260). Tomato spotted wilt virus inoculum amended with 250 µg/ml mycolaminaran also produced fewer than 10% as many lesions as unamended inoculum when applied to N. glutinosa. When plants (N. tabacum ‘Xanthinc’ or N. glutinosa) were kept at 32 C for 24–48 h before inoculation, TMV inoculum amended with mycolaminaran produced 80–100% as many lesions as unamended controls. At 30 C, the induced resistance was observed on developing leaves but not on fully expanded leaves of Xanthinc tobacco. The resistance induced by mycolaminaran is general, temperature sensitive, and not restricted to RNA plant viruses.