AN INTROGRESSION LINE POPULATION OF LYCOPERSICON PENNELLII IN THE CULTIVATED TOMATO ENABLES THE IDENTIFICATION AND FINE MAPPING OF YIELD-ASSOCIATED QTL

Methodologies for mapping of genes underlying quantitative traits have advanced considerably but have not been accompanied by a parallel dev elopment of new population structures. We present a novel population c onsisting of 50 introgression lines (ILs) originating from a cross bet ween the green-fruited species Lycopersicon pennellii and the cultivat ed tomato (cv M82). Each of the lines contains a single homozygous res triction fragment length polymorphism-defined L. pennellii chromosome segment, and together the lines provide complete coverage of the genom e and a set of lines nearly isogenic to M82. A field trial of the ILs and their hybrids revealed at least 23 quantitative trait loci (QTL) f or total soluble solids content and 18 for fruit mass; these estimates are twice as high as previously reported estimates based on tradition al mapping populations. For finer mapping of a QTL affecting fruit mas s, the introgressed segment was recombined into smaller fragments that allowed the identification of three linked loci. At least 16 QTL for plant weight, 22 for percentage green fruit weight, 11 for total yield and 14 for total soluble solids yield were identified. Gene action fo r fruit and plant characteristics was mainly additive, while overdomin ance (or pseudo-overdominance) of wild species introgressions was dete cted for yield.