fw 2.2:a major QTL controlling fruit weight is common to both red- and green-fruited tomato species

Abstract

We have shown that a major QTL for fruit weight (fw2.2) maps to the same 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 F2 derived from L. esculentum (tomato) x L. pennellii and a backcross 1 (BC1) population derived from L. esculentum x L. pimpinellifolium both place fw2.2 near TG91 and TG167 on chromosome 2 of the tomato highdensity linkage map. fw2.2 accounts for 30% and 47% of the total phenotypic variance in the L. pimpinellifolium 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 fw 2.2 as compared with the L. esculentum allele. A QTL with very similar phenotypic affects and gene action has also been identified and mapped 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 opposed to duplication) common to most, if not all, wild tomato species. High-resolution mapping may ultimately lead to the cloning of this key locus controlling fruit development in tomato.

High-Resolution Mapping of a Fruit Firmness-Related Quantitative Trait Locus in Tomato Reveals Epistatic Interactions Associated with a Complex Combinatorial Locus

“…For example, Chen and Tanksley (2004) identified 123 recombinants from 1,535 F2 individuals within the S. pennellii IL 2-5 region for the fine-mapping of se2.1 on chromosome 2. Recombination suppression varies across Solanaceae genomes and chromosomal locations (Alpert et al, 1995;Ku et al, 1999;Monforte and Tanksley, 2000;Gorguet et al, 2008), and in some regions, recombination hotspots have been identified, including on S. pennellii chromosome 9 (Fridman et al, 2000).…”

Generation and Analysis of an Artificial Gene Dosage Series in Tomato to Study the Mechanisms by Which the Cloned Quantitative Trait Locus fw2.2 Controls Fruit Size

“…TA1589, from tomato (Lycopersicon esculentum), is a nearly isogenic line homozygous for the small-fruit allele from Lycopersicon pennellii, LA716, at the endogenous fw2.2 locus (Alpert et al, 1995); TA1616 is homozygous for the large-fruit allele at the endogenous fw2.2 locus and homozygous for the small-fruit allele, also from L. pennellii, introduced into an unlinked site through transgenesis (Frary et al, 2000). A series of stocks carrying zero, one, two, three, or four copies of the small-fruit alleles were selected from the progeny of a cross between TA1589 and TA1616.…”

Mapping quantitative trait loci in inbred backcross lines ofLycopersicon pimpinellifolium(LA1589)

“…The map positions of the two QTL identified in this study were also found to be associated with FW in several previous studies (reviewed in Grandillo et al 1999;Chen et al 1999). Of these, fw2.2 has been reported to be conserved among the wild tomato species and is considered to be a major fruit weight QTL (Alpert et al 1995). fw2.2 was recently isolated via mapbased cloning .…”