Replicase-Mediated Resistance To Potato Virus Y in Transgenic Tobacco Plants. Patrice Audy. Department of Plant Pathology, Cornell University, Ithaca, NY 14853 U.S.A. Peter Palukaitis, Steven A. Slack, and Milton Zaitlin. Department of Plant Pathology, Cornell University, Ithaca, NY 14853 U.S.A. MPMI 7:15-22. Accepted 29 September 1993. This article is in the public domain and nol copyrightable. II may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1994.

Nicatiana tabacum 'Turkish Samsun NN' plants were transformed with nuclear inclusion b (Nlb) gene sequences of potato virus Y, O strain (PVY^o). The full-length construct included an additional in-frame initiation codon contiguous to the putative N-terminal amino acid codon and a stop codon replacing the C-terminal amino acid codon. Of 13 independently transformed lines, four yielded 37 (out of 100) plants in the R₁ generation that were resistant to PVY° infection. Progeny of 13 out of 15 of R₁ plants tested expressed resistance in the R₂ generation. Conversely, 30 independently transformed tobacco lines expressing essentially the same sequence but deleted for the Gly-Asp-Asp (GDD) motif were not resistant. Two other constructs encoding either the 5'-deIeted or 3'-truncated Alb gene, but harboring (he GDD) motif, conferred resistance to PVY^o in some tobacco plants. Despite the high level of nucleotide and amino acid identity shared by strains PVY^o and PVY^N Tor the Alb gene, PVY^N replication was found in all PVY^°-resistant plants. However, plants of one R₂ line showed reduced PVY^N replication