We have tested a new strategy for engineering fungal disease resistance in crops which is based on inhibition of fungal growth and reproduction by controlled generation of necrotic lesions at infection sites, analogous to the naturally occurring hypersensitive cell death. The approach relies on the use of two chimeric genes. On the one hand, a promoter fragment of the potato prp1-1 gene which mediates rapid and localized transcriptional activation selectively in response to pathogen attack is used to drive the expression of the bacterial ribonuclease, barnase. On the other hand, transgenic plants express barstar, a specific inhibitor of barnase, to minimize the detrimental effects of potential background barnase synthesis in non-infected tissue. Sporulation of the late-blight fungus Phytophthora infestans was considerably reduced on leaves from transgenic potato lines harboring this two-component system. Treatment of leaves from such plants with ethylene, a chemical stimulus of prp1-1 promoter activity, resulted in rapid tissue destruction, indirectly indicating the inducibility and action of barnase. Furthermore, the reduction of fungal sporulation cosegregated with the transgenes in an F1 population.