A recombination hotspot delimits a wild-species quantitative trait locus for tomato sugar content to 484 bp within an invertase gene

In nature, genetic Variation usually takes the form of a continuous phenoty pic range rather than discrete classes. The genetic variation underlying qu antitative traits results from the segregation of numerous interacting quan titative trait loci (QTLs), whose expression is modified by the environment . To uncover the molecular basis of this variation, we characterized a QTL (Brix9-2-5) derived from the green-fruited tomato species Lycopersicon penn ellii, The wild-species allele increased glucose and fructose contents in c ultivated tomato fruits in various genetic backgrounds and environments. Us ing nearly isogenic lines for the QTL, high-resolution mapping analysis del imited Brix9-2-5 to a single nucleotide polymorphism-defined recombination hotspot of 484 bp spanning an exon and intron of a fruit-specific apoplasti c invertase, We suggest that the differences between the Brix9-2-5 alleles of the two species are associated with a polymorphic intronic element that modulates sink strength of tomato fruits. Our results demonstrate a link be tween naturally occurring DNA variation and a Mendelian determinant of a co mplex phenotype for a yield-associated trait.