Quantitative trait loci (QTLs) controlling phenotypic differences between cultivated sunflower and its wild progenitor were investigated in an F3 mapping population. Composite interval mapping revealed the presence of seventy-eight QTLs affecting the eighteen quantitative traits of interest, with two to ten QTLs per trait. Each QTL explained 3.0–68.0% of the phenotypic variance, although only four (corresponding to three of eighteen traits) had effects > 25%. Overall, fifty-one of the seventy-eight QTLs produced phenotypic effects in the expected direction, and for thirteen of eighteen traits the majority of QTLs had the expected effect. Despite being distributed across fifteen of the seventeen linkage groups, there was a substantial amount of clustering among QTLs controlling different traits. In several cases, regions influencing multiple traits harbored QTLs with antagonistic effects, producing a cultivar-like phenotype for some traits and a wild-like phenotype for others. Based on the directionality of QTLs, strong directional selection for increased achene size appears to have played a central role in sunflower domestication. None of the other traits show similar evidence of selection. The occurrence of numerous wild alleles with cultivar-like effects, combined with the lack of major QTLs, suggests that sunflower was readily domesticated.

Key words: domestication, Helianthus, QTL mapping, selection, sunflower