To explore natural biodiversity we developed and examined introgression lines (ILs) containing chromosome segments of wild species ( Solanum pennellii ) in the background of the cultivated tomato ( S. lycopersicum ). We identified Brix9-2-5 , which is a S. pennellii quantitative trait locus (QTL) that increases sugar yield of tomatoes and was mapped within a flower- and fruit-specific invertase ( LIN5 ). QTL analysis representing five different tomato species delimited the functional polymorphism of Brix9-2-5 to an amino acid near the catalytic site of the invertase crystal, affecting enzyme kinetics and fruit sink strength. These results underline the power of diverse ILs for high-resolution perspectives on complex phenotypes.

Zooming In on a Quantitative Trait for Tomato Yield Using Interspecific Introgressions