Strategy for functional screening of P. infestans cDNAs using agroinfection with a binary potato virus X (PVX) vector. Pools of candidate cDNAs were ligated to the binary PVX vector, and electroporated into A. tumefaciens to generate infection-ready mini-libraries. Leaves of N. benthamiana plants were then toothpick-inoculated with individual clones. Clones inducing necrotic symptoms were identified by PCR amplification and sequencing.