FW-2.2 - A MAJOR QTL CONTROLLING FRUIT WEIGHT IS COMMON TO BOTH RED-FRUITED AND GREEN-FRUITED TOMATO SPECIES

We have shown that a major QTL for fruit weight (fw2.2) maps to the sa me position on chromosome 2 in the green-fruited wild tomato species, Lycopersicon pennellii and in the red-fruited wild tomato species, L. pimpinellifolium. An introgression line F-2 derived from L. esculentum (tomato) x L. pennellii and a backcross 1 (BC1) population derived fro m L. esculentum x L. pimpinellifolium both place fw2.2 near TG91 and T G167 on chromosome 2 of the tomato high-density linkage map.fw2.2 acco unts for 30% and 47% of the total phenotypic variance in the L. pimpin ellifolium and L. pennellii populations, respectively, indicating that this is a major QTL controlling fruit weight in both species. Partial dominance (d/a of 0.44) was observed for the L. pennellii allele of f w 2.2 as compared with the L. esculentum allele. A QTL with very simil ar phenotypic affects and gene action has also been identified and map ped to the same chromosomal region in other wild tomato accessions: L. cheesmanii and L. pimpinellifolium. Together, these data suggest that fw2.2 represents an orthologous QTL (i.e., derived by speciation as o pposed to duplication) common to most, if not all, wild tomato species . High-resolution mapping may ultimately lead to the cloning of this k ey locus controlling fruit development in tomato.