Stability of pathogen-derived Potato virus Y resistance in potato under field conditions and some aspects of their ecological impact

The results of three years of field experiments with transgenic potato clones resistant to Potato virus Y (PVY) are presented. The plants were transformed either with a truncated NIb gene of PVYN fused to the Enhanced Blue Fluorescent Protein gene or the coat-protein gene of a PVYN strain. It was demonstrated that their resistance to PVY can be overcome by several isolates of this virus. The spectrum of PVY strains infecting transgenic plants was different from that of control plants. On resistant clones the virulent strain (PVYW)-W-N prevailed while on control plants as well as on susceptible transgenic plants PVYN was the dominating strain. Susceptibility or resistance of the transgenic plants to several other viruses was altered too. Some of the clones were more attractive to aphids though the reproduction rate of the aphids on transgenic plants was not altered. Recombination was not observed between transgenic and viral RNAs but between RNAs of invading PVY isolates. We cannot rule out the possibility that the recombination rate between viral RNAs is enhanced in transgenic plants. The paper discusses why so far little use has been made of transgenic approaches for the induction of virus resistance.