The present invention is directed to a DNA construct comprising a first DNA
molecule having a length insufficient to independently impart resistance
to papaya ringspot virus to plants transformed with said first DNA
molecule, wherein the first DNA molecule is from a DNA molecule encoding a
papaya ringspot virus coat protein 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 papaya ringspot
virus. Alternately, the DNA construct can comprise a plurality of DNA
molecules each of which is at least 110 nucleotides and at least one of
which is from a DNA encoding a papaya ringspot viral coat protein and is
insufficient in length to independently impart resistance to papaya
ringspot virus to plants.
