The present invention concerns a method of genetic modification of a TGB-3 
wild type viral sequence for reducing or suppressing the possible deleterious effects of the agronomic properties of a transformed 
plant or 
plant cell by said TGB-3 
viral sequence, comprising the following successive steps: submitting said sequence to 
point mutation(s) which allow the substitution of at least one amino-acid into a different amino-acid; selecting genetically modified TGB-3 
wild type viral sequences having said 
point mutation(s) and which are not able to promote 
cell-to-
cell movement of a 
mutant virus having a dysfunctional TGB-3 
wild type viral sequence, when expressed in trans from a 
replicon; further selecting among said genetically modified TGB-3 viral sequences, the specifically genetically modified sequence which inhibits infection with a co-inoculated 
wild type virus when the 
mutant form was expressed from a 
replicon, and recovering said specifically genetically modified TGB-3 viral sequence. The invention further relates to genetically modified TGB-3 viral sequences suitable to induce 
gene silencing. In particular hairpin constructs based on such sequences proved highly efficient to induce a PTGS mechanism and degradation of the whole of 
RNA2 thereby. When plants are transformed accordingly the spread of the 
virus in the 
plant is significantly reduced or blocked.