Sub-project 5 of BIOEXPLOIT aims to design durable disease resistance through marker-assisted breeding by converting existing markers for high-throughput application, developing and validating high-throughput marker technologies and pyramiding major R genes and/or quantitative trait loci into elite material. Activities include (1) the fine mapping of the quantitative trait locus PiXspg which accounts for a large proportion of the variation in late blight resistance, (2) converting SNP-based markers and an AFLP marker to easy-to-use-markers, (3) testing of progenies with combined sources of late blight resistance for presence of R genes and agronomic features, (4) backcrossing new sources of resistance to S. tuberosum and molecular screening of breeding materials with marker GP94 linked with gene Rpi-phu1 conferring late blight resistance, (5) evaluating potato clones with enhanced resistance against Phytophthora infestans under field conditions of Toluca (México), and (6) developing populations and marker-assisted breeding for disease resistance.