Field resistance to late blight - a fungal disease caused by Phytophthora infestans - has been genetically characterized by analyzing trait-marker association in a Solanum phureja (phu)xdihaploid Solanum tuberosum (dih-tbr) population. Trait data were developed at three locations over a 3-year period under natural infection pressure. RAPD (random amplified polymorphic DNA) and AFLP (amplified fragment length polymorphism) markers were used to develop anonymous genetic linkage groups subsequently anchored to potato chromosomes using mapped RFLP (restriction fragment length polymorphism), SSR (single sequence repeats) and AFLP markers. RFLP and SSR markers achieved the most-accurate anchoring. Two genetic maps were obtained, with 987.4 Cm for phu and 773.7 Cm for dih-tbr. Trait-marker association was revealed by single-marker and interval mapping analyses. Two important QTLs (quantitative trait loci) were detected on chromosomes VII and XII as a contribution from both parents, totalling up to 16% and 43%, respectively, of the phenotypic variation (PH). One additional QTL was detected on chromosome XI (up to 11% of the PH) as a contribution from the phu parent, and three others were detected on chromosome III (up to 13% of the PH), chromosome V (up to 11% of the PH) and chromosome VIII (up to 11% of he PH) as a contribution from the dih-tbr parent. Our results reveal new genetic loci of the potato genome that contribute to resistance to late blight. We postulate that some of these loci could be related to plant growth under short-day conditions. © Springer-Verlag 2001.