The present invention is directed to a DNA construct comprising a first DNA molecule
having a length insufficient to independently impart resistance to a virus to plants
transformed with said first DNA molecule, wherein the first DNA molecule is from
a viral coat protein gene and is at least 110 nucleotides in length. The construct
also comprises a second DNA of at least 400 nucleotides in length, which is coupled
to the first DNA molecule so that the first and second DNA molecules collectively
achieve post-transcriptional silencing and impart resistance to the virus. Alternately,
the DNA construct can comprise a plurality of DNA molecules each of which is at
least 110 nucleotides in length and from a viral gene, wherein the plurality of
DNA molecules are at least 510 nucleotides in length.
