The present invention relates to methods to alter the expression of a viral gene in a cell using sense and antisense RNA fragments of the gene. The sense and antisense RNA fragments are capable of pairing and forming a double-stranded RNA molecule, thereby altering the expression of the gene.The present invention also relates to cells, plants or animals, their progeny and seeds derived thereof, obtained using a method of the present invention. Preferably, such cells, plants or animals are resistant or tolerant to viruses.
