Fine Mapping of fw6.3 , a Major-Effect Quantitative Trait Locus That Controls Fruit Weight in Tomato.

Tomato ( Solanum lycopersicum ) is a widely consumed vegetable, and the tomato fruit weight is a key yield component. Many quantitative trait loci (QTLs) controlling tomato fruit weight have been identified, and six of them have been fine-mapped and cloned. Here, four loci controlling tomato fruit weight were identified in an F 2 population through QTL seq.; fruit weight 6.3 (fw6.3 ) was a major-effect QTL and its percentage of variation explanation (R 2 ) was 0.118. This QTL was fine-mapped to a 62.6 kb interval on chromosome 6. According to the annotated tomato genome (version SL4.0, annotation ITAG4.0), this interval contained seven genes, including Solyc06g074350 (the SELF-PRUNING gene), which was likely the candidate gene underlying variation in fruit weight. The SELF-PRUNING gene contained a single-nucleotide polymorphism that resulted in an amino acid substitution in the protein sequence. The large-fruit allele of fw6.3 ( fw6.3 HG ) was overdominant to the small-fruit allele fw6.3 RG . The soluble solids content was also increased by fw6.3 HG . These findings provide valuable information that will aid the cloning of the FW6.3 gene and ongoing efforts to breed tomato plants with higher yield and quality via molecular marker-assisted selection.