Improving the flavor of fresh fruits: genomics, biochemistry, and biotechnology

It is generally accepted that the flavor quality of many fruits has significantly declined over recent decades. While some of this decline can be linked to selection for certain traits, such as firmness and postharvest shelf life, that run counter to good flavor, a major contributing factor has been the challenge of breeding for such a complex quality trait. Flavor involves integration of sugars, acids and a set of 20 or more volatile chemicals. Together, these compounds involve a large number of primary and secondary metabolic pathways, many of which have only recently been established. This review describes recent advances in the understanding of the pathways and genes controlling synthesis of the volatile components of flavor. Because of tomato's unique role as a model for fruit development, the review emphasizes advances in this fruit. In the last decade we have literally advanced from a list of chemicals known to influence flavor to a detailed understanding of how and where they are made. However, our knowledge of the regulation of the critical metabolic pathways is still limited. Nonetheless, the pieces are in place for rapid advances to be made in the manipulation of flavor chemistry in the immediate future.