Together with the breeding for better yield the introduction of new resistance properties is one of KARNAs most important activities. From the foundation of KARNA onwards breeding for resistance to potato cyst nematode (Globodera rostochiensis and G. pallida) and wart disease (Synchytrium endobioticum) has had a high priority in the breeding program. Also research on late blight (Phytophthora infestans) and a number of virus diseases (PVY, PLRV, PVX, PVS) are important aspects at the KARNA breeding station. To test the breeding material thousands of resistance tests in the greenhouse, laboratory and trial fields are carried out. A few years ago the Dutch Plant Protection Service has certified KARNA to perform resistance tests on Globodera and Synchytrium for official use in the Dutch Variety List. Also new varieties from other breeders are tested in the KARNA laboratories. To be sure no disease can break out a special quarantine laboratory has been built.