SENSE AND ANTISENSE RNA-MEDIATED RESISTANCE TO POTATO LEAFROLL VIRUS IN RUSSET BURBANK POTATO PLANTS

Three constructs of the potato leafroll virus (PLRV) coat protein gene were efficiently inserted into the commercial potato cultivar Russet Burbank via Agrobacterium tumefaciens-mediated gene transfer. One construct possessed 12 nucleotides of the untranslated leader sequence 5' to the coat protein gene AUG, the second construct had 192 nucleotides from this leader sequence, and the third construct was the same as the second construct except that it was inserted in the reverse orientation. Introduced as chimeric genes under the control of the duplicated cauliflower mosaic virus 35S promoter, both positive- and negative-sense constructs showed high levels of transcription but coat protein was not detectable in any of the plants. Results show that significant levels of sustained resistance were obtained with each construct, resulting in PLRV titers as low as 1% of the level observed in controls. Both the pattern and level of protection were the same for constructs producing positive- and negative-sense RNA, suggesting a similar mechanism of resistance. Aphid transmission of virus from PLRV-inoculated transgenic Russet Burbank potato plants was reduced significantly when PLRV titers were reduced by at least 95%.