Investigating the molecular genetic basis of antioxidants in lactuca sativa for the enhancement of its nutritional qualities

Consumer awareness of food nutritional properties has increased significantly. A healthy diet is now viewed as the first step towards the prevention of many age-related chronic diseases such as cancer and heart disease. In most cases oxidative damage is involved in the onset of these diseases, much of which can be prevented by a diet high in antioxidants. However, throughout hundreds of years of domestication, many crop species, such as lettuce, have been genetically manipulated with the purpose of increasing favourable traits. These selective processes have resulted in the unintentional decrease of the antioxidant nutritional content of species such as Lactuca sativa. This project aimed to use natural resources for the enhancement of lettuce nutritional properties through the introgression of genes from a close relative of L. sativa. Initially, the total antioxidant content of baby lettuce leaves was investigated, with particular focus on carotenoids, chlorophyll and phenolic compounds. Wild lettuce (L. serriola, acc. UC96US23) was found to produce higher levels of total antioxidants, chlorophylls and carotenoids than the lettuce cultivated variety, Salinas cv. Subsequently, these traits were analysed in a Recombinant Inbred Line mapping population obtained by crossing these two lettuce species. Considerable transgressive segregation was observed and this data was then used to map Quantitative Trait Loci (QTL) on the population, which showed an additive effect of both parents contributing to these beneficial traits. Subsequent analyses of key genes involved in the synthesis of carotenoids and phenolic compounds revealed the presence of single nucleotide polymorphisms. Understanding the processes involved in the synthesis of nutritional properties and identifying the genes underlying these traits is key to producing a better quality lettuce. This project demonstrates potential for the improvement of lettuce antioxidant nutritional qualities through breeding with a wild relative