chapter  18
20 Pages

Use of Genomics-Aided Breeding to Improve the Nutritional Content of Lettuce

The genetic improvement of plants began when man rst started gathering seeds from the wild, planting them, and harvesting these seeds. This repetitive cycle played out over hundreds to thousands of years and led to the domestication of most of the foods commonly eaten today. Cereals

Introduction .................................................................................................................................... 331 Domestication of Crops ................................................................................................................. 331 Early Crop Improvement ............................................................................................................... 332 The Road to Next-Generation Plant Breeding ............................................................................... 333 Why Lettuce? ................................................................................................................................. 336 Nutritional Value of Lettuce ........................................................................................................... 336 Improving the Antioxidant Content in Lettuce .............................................................................. 339 Future Prospects ............................................................................................................................. 342 References ...................................................................................................................................... 345

provide most of the food calories consumed worldwide, and they appear to be the rst in the domestication process pipeline (Balter 2007). The domestication of cereals, and likely most other crops, included a gathering stage followed by a predomestication cultivation stage, and nally the xation of genes responsible for domestication (Allaby 2010; Allaby et al. 2008). These domestication genes control a suite of traits that are advantageous for the plant to survive and evolve in the wild, but hamper its usefulness and therefore adoption, as a food source for humans. Almost without exception the traits affected include the loss of seed dormancy, loss of seed and fruit dehiscence, and the redirection of assimilates to reproductive structures (Hancock 2004). Archaeological evidence indicates cereal gathering as early as 23,000 years ago, predomestication cultivation approximately 13,000 years ago, and the xation of the traits occurring over long periods of time during the xation stage (Balter 2007). One of the key factors contributing to the length of time between gathering a plant species and the xation of an allele was to interrupt gene ow between the cultivated eld and the wild plants growing adjacent to the elds (Fuller et al. 2009; Kovach et al. 2007).