Resistance gene Rpi-blb2 is broadly effective against Phytophthora infestans in potato, whereas Avrblb2, a known allele of the cognate effector, evades detection. In the August issue, Oliva and colleagues report their extensive analysis of the Avrblb2 gene family. They found that Avrblb2 is present in multiple copies and types in P. infestans isolates, which suggests that expansion of this family contributes to pathogen fitness.