Transgenic tobacco plants expressing the coat protein (CP) gene of tobacco rattle virus (TRV) strain TCM were found to be resistant to infection with the homologous virus but not to infection with the PLB strain of TRV. The amino acid sequence identity between the CP of TRV strains TCM and PLB is 39% and the two CP genes do not cross-hybridize. On the other hand, there is extensive cross-hybridization between the CP genes of TRV-TCM and a Dutch isolate of pea early browning virus (PEBV). The transgenic plants accumulating TRV-TCM CP showed a considerable resistance to infection with PEBV.