New research reveals which genes are needed to reinstate the rich, original flavor of tomatoes, now absent in many grocery shelf varieties of this fruit. The results are published in the 27 January issue of Science.
Over the years, tomatoes have been selectively bred for qualities such as size and firmness for shipping purposes, while selection for flavor has been overlooked, causing many modern varieties to lose their original taste.
Taste may seem like a quality that farmers and consumers would want to maintain; however the complex nature of flavor makes it difficult to detect changes produced by selective breeding over relatively short periods of time.
Harry Klee of the University of Florida, a researcher involved with the study, explained, "There is no single chemical that one can identify as a 'tomato' smell or taste. So gradual reductions in individual contributing chemicals almost certainly would not be noticed. Over time, however, the net effect can be large and that is what has happened."
To better understand the combination of compounds that humans enjoy, Klee and colleagues recruited a panel of people to taste and rate 160 tomato samples representing 101 modern, heirloom and wild varieties of tomato. The participants rated the samples based on qualities such as "overall liking" and "flavor intensity."
In this way, the researchers were able to identify 13 chemical compounds associated with flavor that were significantly reduced or lost in modern varieties relative to heirloom varieties. The researchers sequenced the genomes of nearly 400 tomato varieties to identify the corresponding genetic sequences, or alleles, which contribute to these compounds.
Among other results, the authors found that smaller fruit tended to have greater sugar content, suggesting that selection for more sizable tomatoes has come at the cost of sweetness and flavor.
"We need to move the good alleles back into these varieties to have a significant positive effect on flavor," said Klee. His team aims to accomplish this in their next stage of research, using molecular markers combined with traditional breeding methods.
Sanwen Huang of the Chinese Academy of Agricultural Sciences, a co-author of the study, explains the process. "We are talking about more than 10 genes. We need a comprehensive genome design that coordinates multiple flavor genes without sacrificing yield too much. We will start with the genes with major effects first."
He notes that it will require collaboration across a number of disciplines, involving geneticists, biochemists, breeders and consumers.
[Credit for associated image: Harry Klee/ University of Florida]