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Submitted to: Genetic Improvement of Solanaceous Crops, Vol 2: Tomato
Publication Type: Book / Chapter Publication Acceptance Date: 12/5/2005 Publication Date: 12/1/2006 Citation: Stommel, J.R. 2006. Genetic enhancement of tomato fruit nutritive value. Genetic Improvement of Solanaceous Crops. 2:193-238. Interpretive Summary: This book chapter reviews research on the use of plant breeding and genetics to improve the nutritive value of tomatoes. Tomatoes are a major dietary source of vitamins A and C and the antioxidant lycopene. Lycopene accounts for the red pigmentation of tomato fruit and is also an important determinant of fruit quality. In addition to these well-known vitamins and antioxidants, considerable genetic variation exists in tomato for other micronutrients with antioxidant activity. A number of these micronutrients, particularly carotenoids (fruit pigments), have been the subject of considerable research due to their contribution to the quality of fresh and processed tomato products. Increased recognition of their health promoting properties has stimulated new research and provided added justification for research in this area. Tomatoes also contribute macronutrients to the diet including carbohydrates and fiber. In tomato, these constituents have been studied principally for their effects on fruit quality. Little attention has been given to their contribution to fruit nutritive value. There is a wealth of variability within modern and heirloom tomato varieties and wild tomato relatives that can be utilized for improvement of fruit nutritive value. Where existing variation is insufficient or difficult to introduce into improved varieties, genes from other organisms may be introduced into tomato and transgenic plants produced that synthesize compounds which contribute to fruit nutritive value. Detailed knowledge of the biochemical pathways for a number of nutritional compounds has assisted researchers in identifying genes of importance for improving fruit nutritional value. As consumers gain increased knowledge of the nutrients of fruits and vegetables and recognize the value of these products, markets for nutritionally enhanced varieties will expand. Technical Abstract: During the twentieth century, plant breeding and genetics have improved the nutritive value of horticultural and agronomic crops. Tomatoes are a major dietary source of vitamins A and C and lycopene. In addition to these well-known vitamins and antioxidants, other compounds in tomato fruit with antioxidant properties include chlorogenic acid, rutin, plastoquinones, tocopherol, and xanthophylls. Tomatoes also contribute carbohydrates, fiber, flavor compounds, minerals, proteins, and glycoalkaloids to the diet. Considerable genetic variation exists in tomato for micronutrients with antioxidant activity. A number of these micronutrients, particularly carotenoids, have been the subject of considerable research due to their contribution to the quality of fresh and processed tomato products. Increased recognition of their health promoting properties has stimulated new research and provided added justification for research in this area. Plants also contribute to the availability of dietary macronutrients including protein, fats, and carbohydrates. In tomato, these constituents have been studied principally for their effects on fruit quality. Little attention has been given to their contribution to fruit nutritive value. There is a wealth of genetic variability within modern and heirloom tomato cultivars, land races, and wild species for improvement of fruit nutritive value. Where existing genetic variability for phytonutrient content is insufficient or difficult to introduce into adapted materials due to crossing barriers, appropriate gene constructs relevant to the biosynthesis of a specific phytonutrient or class of phytonutrients may be developed and genetically modified plants produced. Development of gene-specific probes and identification of markers tightly linked to phytonutrient constituent loci enables implementation of marker-assisted selection strategies for genotypic selection of well-studied traits. Detailed knowledge of the biochemical pathways for a number of phytonutrients has assisted in identification of structural and regulatory genes responsible for metabolite accumulation. As consumers gain increased knowledge of the nutrients of fruits and vegetables and recognize value-added products, markets for enhanced phytonutrient enriched crops will expand. The present chapter reviews the historical literature and highlights new applications of molecular genetics to enhancement of tomato nutritive value. |
