Improving the nutritional quality and shelf life of baby leaf lettuce (Lactuca sativa)

Abstract

There is a pressing need to progress the focus in crop breeding to consider post-harvest quality, if the concept of sustainable intensification is to materialise. Lettuce (Lactuca sativa L.) is widely consumed worldwide; however it has a relatively low nutrient density and a short shelf life, which result in considerable amounts of food and resource waste. Improvements to the nutritional quality of lettuce could substantially boost phytonutrient intake, contributing to health by reducing the incidence of chronic diseases. Improving shelf life could not only reduce the wastage of food, but also finite resources such as land, energy and water used in crop production. Chapters 2 and 4 are dedicated to determining the genetic basis of lettuce nutritional quality and shelf life, respectively, using a quantitative trait loci (QTL) mapping approach. QTL for nutrition and shelf life-related traits were identified and for the first time, candidate genes underlying these post-harvest traits have been described for lettuce, using the recently published genome. In Chapter 3, attempts to introgress QTL for nutritional quality into an elite cultivar by marker-assisted breeding led to the development of a novel green leaf variety, demonstrating ~50% higher antioxidant content in comparison to a standard green cultivar. Chapter 4 describes efforts to refine candidate gene lists for shelf life utilising a candidate gene association mapping approach, performed using a panel of baby leaf lettuce cultivars, detecting significant marker-trait associations in this different genetic background. Finally, in Chapter 5, the revolutionary CRISPR/Cas genome editing technology was employed, to knockout promising candidate genes for shelf life in an attempt to functionally validate candidate genes. This research fundamentally enhances our knowledge of the genetic basis of important quantitative traits for a food crop of global significance.

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