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The Effect of Removing Leaf Surface Components with Acetone from Immunized and Nonimmunized Resistant Tobacco Plants on Their Susceptibility to Blue Mold. S. Tuzun, Department of Plant Pathology, University of Kentucky, Lexington 40546; M. Reuveni(2), M. R. Siegel(3), and J. Kuc(4). (2)Plant Biotech Industries Ltd., Mobile Post Ashrat 25201, Israel; (3)(4)Department of Plant Pathology, University of Kentucky, Lexington 40546. Phytopathology 79:1024-1027. Accepted for publication 4 May 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-1024.

The involvement of leaf surface compounds in resistance to blue mold was studied in three tobacco cultivars (Ovens 62, Incekara, and Izmir Ozbaz), bred for resistance to blue mold, and susceptible burley tobacco cultivar Ky 14. In general, plants became more resistant to blue mold with age. A leaf-disk assay supported the results of the whole-plant assays. Dipping leaf strips in acetone significantly increased their susceptibility to blue mold. Stem injection of sporangiospores of Peronospora tabacina into Ky 14 plants induced systemic resistance against blue mold (immunized). The susceptibility of immunized and nonimmunized resistant leaf strips was increased after they were dipped in acetone; however, the susceptibility did not reach that of water-injected Ky 14 plants (controls) of the same age that were dipped in acetone. The levels of fungitoxic leaf surface compounds, the duvatrienediols (DVT), on the two resistant varieties Incekara and Izmir Ozbaz were similar to those on Ky 14. The levels of DVT were approximately twice as great on the most resistant variety Ovens 62 and on immunized plants as compared to controls. More than 90% of the DVT was removed by a 1-sec dip in acetone. Duvatrienediols may have a role in resistance of Ovens 62 and immunized plants; however, they are not the sole determinant of resistance or immunization.