A strategy for interfering with vital development in transgenic plants using random potato virus Y cDNA sequences has been investigated. A representative expression library of the pathogen genome has been established in an host plant and screened for resistance phenotypes. Among 53 independent transgenic plants, five were found to display an altered response to the viral infection each one expressing a different part of the viral genome. This approach to generate new types of pathogen derived resistance can theoretically be applied to any virus.