Genetic analysis of fruit quality in tomato

Abstract

This thesis focused on two important fruit quality aspects, fruit shelf life and fruit flavour by utilisation of two sources of genetic variation: (1) segregating populations based on cultivated tomato germplasm and (2) a diverse tomato core collection that consist of wild relatives, land races and old cultivars. In chapter 2 and 3 of this thesis we have evaluated a tomato core collection consisting of 122 landraces, heirloom varieties and wild accessions for variation in several plant growth and fruit quality-related traits. This collection provided a good resource of superior alleles to incorporate in future breeding programs. 66 of the 88 cultivated accessions of this collection have been sequenced and explored for the presence of known mutations or sequence variations in key genes underlying important domestication and agronomic traits. In chapter 3, the 88 cultivated accessions of this collection plus two additional modern genotypes have been characterised in more detail for post-harvest shelf-life and thus we have now uncovered in that material novel sources for fruit shelf-life improvement. in chapter 4 and 5 of this thesis, we have investigated two metabolite QTLs involved in flavour of tomato by using a segregating population based on cultivated tomato genotypes. In chapter 4 we have fine mapped a major QTL for a volatile organic compound (2-phenyethanol) which is highly associated with consumer liking and flavour intensity (Knudsen et al., 1993; Tieman et al., 2007; Tieman et al., 2017). In chapter 5 we have identified and fine mapped the genomic region controlling the amino acid glutamate, which is a flavour enhancer and key factor conferring umami taste in tomato (Yilmaz, 2000). These results facilitate the molecular breeding of cultivars with improved flavour and also lead to a better understanding of the biosynthesis pathway underlying these two metabolites.