DescriptionRutgers Scarlet Lettuce (RSL), a dark red lettuce variety with an exceptionally high content of health-promoting dietary polyphenols, was selected as the starting material to develop new and non-transgenic varieties of lettuce with an improved nutritional content, through the use of ethyl methanesulfonate (EMS) seed mutagenesis followed by phenotype screening. The project focused specifically on identification of a green phenotype which retained the high polyphenol content of its red RSL parent. An in-house approach for simple, cost-effective and large-scale production, identification and chemical analysis of mutagenized candidate plants was established and optimized. This approach generated a large seed collection from 2000 individual M2 families with the potential to express both dominant and recessive mutations, which are being screened for traits of interest. A number of green plants were identified and chemically characterized and one of them was found to retain the high polyphenol trait. Successful self-pollination of this plant produced a valuable collection of approximately 10000 seeds of green high polyphenol lettuce. Analysis of their phytochemical profile suggests an accumulation of colorless anthocyanin precursors brought on by blocking one of the later steps in the anthocyanin biosynthetic pathway.