Abstract
Secondary metabolites, also known as phytochemicals, represent a large subset of plant molecules that include compounds with health-promoting effects. Indeed, a number of epidemiological studies have shown that, when taken regularly and in adequate amounts, these molecules can have long-term beneficial effects on human health, through reduction of the incidence of degenerative diseases, such as cardiovascular diseases, obesity, diabetes, and cancer. As the dietary intake of these phytochemicals is often inadequate, various strategies are in use to improve their content in staple crops, and the end-products thereof. One of the most effective strategies is crop improvement through genetic approaches, as this is the only way to generate new cultivars in which the high accumulation of a given phytochemical is stably fixed. Efforts to genetically improve quality traits are rapidly evolving, from classical breeding to molecular-assisted approaches; these require sound understanding of the molecular bases underlying the traits, to identify the genes/alleles that control them. This can be achieved through global analysis of the metabolic pathway responsible for phytochemical accumulation, to identify the link between phytochemical content and the activities of key enzymes that regulate the metabolic pathway, and between the key enzymes and their encoding genes/alleles. Once these have been identified, they can be used as markers for selection of new improved genotypes through biotechnological approaches. This review provides an overview of the major health-promoting properties shown to be associated with the dietary intake of phytochemicals, and describes how molecular approaches provide means for improving the health quality of edible crops. Finally, a case study is illustrated, of the identification in durum wheat of the Lipoxygenase-B1 genes that control the final carotenoid content in semolina-based foods, such as pasta products.
Highlights
The secondary metabolites from plants, which are known as phytochemicals, represent a large subset of plant chemicals, but their importance in both plant metabolism and human health has only been recognized more recently
In human nutrition attention has been focused for years on the energy demand that needs to be satisfied through the correct combination of carbohydrates, lipids, and proteins in the diet, whereas the impact of secondary metabolites on human health has been ignored for a long time
To choose the breeding strategy that is more adapted for improvement of the phytochemical content in a crop of interest, a metabolite analysis has to be performed that determines the natural variability of the trait in the genotypes of a large germplasm collection
Summary
The secondary metabolites from plants, which are known as phytochemicals, represent a large subset of plant chemicals, but their importance in both plant metabolism and human health has only been recognized more recently. One approach is to increase the content of health-promoting compounds in staple crops and their end products This can be effectively achieved by genetic improvement of crops through proper breeding programs, which represent the only certain way to generate new cultivars in which a desirable phytochemical content is stably fixed. Over the years, with the advent of molecular genetics, crop improvement has rapidly evolved from classical breeding approaches to biotechnological breeding approaches, such as marker-assisted selection (MAS) [5], genetic transformation [6], and very recently, genome editing [7] These advanced technologies require sound understanding of the molecular bases underlying the accumulation of a bioactive compound in a given crop, to be able to identify the candidate gene that controls its levels.
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