Can knowledge about the molecular bases of plant disease and disease resistance help engineering resistance in crops ?

Knowledge regarding the plant-pathogen interactions is increasing steadily, with the common claim that this knowledge will help improving the control of diseases. Various ways to achieve this goal using biotechnologies will be discussed in the light of some examples in the field of plant viruses, as well as some of the biosafety issues associated. First, soon after the achievement of gene transfer to plants, it became evident that transgenic plants expressing portions of the virus genome were resistant to virus infection in a manner reminiscent of cross-protection, but without some of the adverse effects associated with inoculation of mild virus strains. Second, the recent isolation of natural virus resistance genes potentially enables their transfer to other plant species. However there are two classes of natural resistance genes, dominant and recessive, which differ so much in the mechanisms associated that the prospects to use them in plant biotechnology differ broadly, as well as the expected properties of the resulting virus resistance in the field.