The present invention provides a new nucleic acid molecule which encodes a polypeptide that is able to convey a resistance to a pathogen, in particular to “Beet Necrotic Yellow Vein Virus” in a plant, in particular a plant of the Beta genus, in which the polypeptide is expressed, and also a preferred nucleic acid molecule encoding the RZ-3 gene of Beta maritima, derivatives and homologues thereof. Further aspects of the invention include vectors, transgenic plant cells, transgenic plants, methods for production thereof, and methods for identifying a resistance-conveying nucleic acid molecule.