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Molecular Plant Pathology

Heterologous Resistance to Potato Virus Y in Transgenic Tobacco Plants Expressing the Coat Protein Gene of Lettuce Mosaic Potyvirus. Sylvie Dinant, INRA, Station de Pathologie Végétale, Versailles 78026, France, Current address: Institute for Molecular Virology, University of Wisconsin, Madison 53706; Françoise Blaise, Chantal Kusiak, Suzanne Astier-Manifacier, and Josette Albouy. INRA, Station de Pathologie Végétale, Versailles 78026, France. Phytopathology 83:818-824. Accepted for publication 29 March 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/Phyto-83-818.

Heterologous protection can provide resistance against virus infection in transgenic plants and was evaluated with two potyviruses, potato virus Y (PVY) and lettuce mosaic virus (LMV). PVY causes a serious disease of tobacco. Transgenic plants, Nicotiana tabacum cv. Xanthi, containing a modified coat protein (CP) gene of LMV have been generated and tested for resistance against PVY. Half of the 34 independent R₀ transgenic plants tested accumulated detectable levels of LMV coat protein (LMV CP+). These LMV CP+ plants were resistant to infection following sap inoculation with a necrotic strain of PVY (PVY-NV). Moreover, R₁ populations of five LMV CP+ lines tested were resistant to PVY-NV and to four other PVY strains. Different phenotypes were observed, including 1) complete resistance in two lines, 2) delay and attenuation of symptoms in two lines, and 3) delay in symptoms with no modification of symptoms in one line. In cases 2 and 3, the number of plants showing symptoms was reduced, and the PVY accumulation was greatly decreased in the infected plants. These lines were considered to be partially resistant to PVY infection. Although PVY and LMV are clearly distinct potyviruses (their CPs share 66% amino acid sequence homology), the expression of the coat protein gene of LMV can confer a high level of heterologous protection against PVY in tobacco plants. Results are discussed regarding the possibility of different modes of resistance.