SUMMARY

Agrobacterium-mediated transformation of leaf discs of N. benthamiana and N. occidentalis with constructs containing the coat protein (CP) genes of grapevine virus A (GVA) or grapevine virus B (GVB), produced several lines of transgenic plants. Some of the transfor-mant lines (GVAcp+ and GVBcp+) growing on a selec-tive kanamycin-containing medium were assayed in R1 generation for the expression of transgenic mRNAs and coat proteins. Some of the plants that hybridized specif-ic digoxigenin-labeled riboprobes to both viruses, con-tained detectable amounts of viral CP as shown by Western blot analysis, whereas others did not. The be-haviour of R1 seedlings following challenge inoculation with homologous viruses at a concentration of 1 µg ml-1 was monitored by TAS-ELISA up to 18 days post inoc-ulation. Various levels of resistance to both viruses were observed, as expressed by reduction of virus accumula-tion. Some of the GVAcp+ lines also showed a 3-4 day delay in symptom appearance