A COAT PROTEIN TRANSGENE FROM A SCOTTISH ISOLATE OF POTATO MOP-TOP VIRUS MEDIATES STRONG RESISTANCE AGAINST SCANDINAVIAN ISOLATES WHICH HAVE SIMILAR COAT PROTEIN GENES

Resistance tests were made on seedlings of transformed lines of Nicoti ana benthamiana which contain a transgene encoding the coat protein (C P) gene of a Scottish isolate of potato mop-top virus (PMTV). This tra nsgene has been reported to confer strong resistance to the PMTV isola te from which the transgene sequence was derived and also to a second Scottish isolate. Plants of lines of the transgenic N. benthamiana wer e as resistant to two Swedish and two Danish PMTV isolates as to a Sco ttish isolate, and of five lines tested, greater than 93.5% of transge nic plants were immune. The coat protein gene sequences of these foul Scandinavian isolates were very similar to those of the two Scottish i solates. The greatest divergence between the isolates was three amino acid changes and there was less than 2% change in CP gene nucleotide s equence. It is concluded that the PMTV CP transgene used in these expe riments could confer resistance against isolates from different geogra phical areas because it is bt coming apparent that the CP genes of PMT V isolates are highly conserved.