SynopsisSome of the most successful early applications of genetic engineering in crop improvement have been in the production of virus-resistant plants. This has been achieved not by the transfer of naturally occurring resistance genes from one plant species or variety to another but by transformation with novel resistance genes based on nucleotide sequences derived from the viruses themselves or from virus-associated nucleic acids. Transformation of plants with a DNA copy of the particle protein gene of viruses that have positive-sense single-stranded RNA genomes typically confers resistance to infection with the homologous and closely related viruses. Transformation with a gene that is transcribed to produce a benign viral satellite RNA can confer virus-specific tolerance of infection. In addition, recent work with viral poly-merase gene-related sequences offers much promise, and research is active on other strategies such as the use of virus-specific ribozymes.Already the field trialling of plants incorporating transgenic virus resistance has begun, with encouraging results, and effects on virus spread are being studied. Deployment strategies for the resistant plants must now be devised and the conjectural hazards of growing them assessed. Genetically engineered virus resistance promises to make a major contribution to the control of plant virus diseases by non-chemical methods.
Genetic Engineering for Crop Virus Resistance