GAINESVILLE, Fla. -- Science is trying to build a better supermarket tomato.
At a laboratory here at the University of Florida’s Institute for Plant Innovation, researchers chop tomatoes from nearby greenhouses and plop them into glass tubes to extract flavor compounds – the essence of tomato, so to speak. These flavor compounds are identified and quantified by machine. People taste and rate the hybrid tomatoes grown in the university’s fields.
“I’m 98 percent confident we can make a tomato that tastes substantially better,” said Harry J. Klee, a professor of horticultural sciences. He hopes that the fruits of his labor will be available to commercial growers within four or five years and in supermarkets a couple of years after that. He thinks he can make seeds for better tomatoes available to home gardeners within a year or two.
The insipid-tomato problem is well known to salad lovers and scientists alike. For example, a gene mutation that tomato breeders love because it turns the fruit a luscious red also happens to make it blander. Refrigeration, transportation and other factors also take their toll. Over the decades, the average tomato has become not only less tasty but less nutritious.
Enter Klee, who helped found the Institute for Plant Innovation a decade ago and has been in a quest for a more flavorful and nutritious mass-market tomato ever since.
It is easy to find a better-tasting and more nutritious tomato: Go to a farmers market or grow one in the backyard. It is also easy to breed a plant that produces something tastier than a supermarket tomato – cross a sweet heirloom with the supermarket variety. But a hybrid also loses some of the qualities highly valued by commercial growers – it is not as fecund, not as resistant to disease, not as easily grown, not as pretty.
As growers are paid by the pound, a better-tasting but less productive tomato holds little economic appeal.
Klee’s goal is to tweak the tomato DNA – through traditional breeding, not genetic engineering – to add desired flavors while not compromising the traits needed for it to thrive commercially. “I figure that with approximately five key genes we could very significantly improve flavor,” he said. Three genes that control the production of key flavor compounds have already been located, he said. The next step is to identify versions of the genes that lead the tomato plant to produce more of them.
The chemistry of tomato flavor has three primary components: sugars, acids and what are known as volatile chemicals – the flavor compounds that waft into the air, carrying the fruit’s aroma. There are more than 400 volatiles in a tomato, and Klee and his collaborators first set out to determine which ones are the most important in making a tasty tomato.
This involved grinding up a lot of tomatoes, looking at what was in them, and asking a lot of people to taste them (unpulverized).
From there, Klee and his collaborators used statistics to correlate people’s preferences with the presence, or absence, of particular flavor compounds, to devise a chemical recipe for the ideal tomato.
The supermarket tomato – even when grown with care and picked ripe – did not excel. “The best it will do is middle-of-the-pack,” Klee said. Cherry Roma tomatoes were at the top of the charts, followed by heirloom varieties like Matina, Alisa Craig and Bloody Butcher.
Modern genetic engineering has provided tools to study the numerous compounds that enhance the flavor of tomatoes, which are one of the most common plants that plant geneticists study. Researchers can knock out particular compounds and see if they played a key role in flavor.
In the 1980s, plant geneticists at the University of California, Davis, just as frustrated by bland-tasting tomatoes, also tried to make a better tomato. That led to a biotechnology company, Calgene, in 1994, developing the Flavr Savr tomato, the first genetically engineered food of any kind in the supermarket, its DNA tweaked to inhibit a protein that turns a tomato mushy over time. While it sold well, Calgene foundered in the logistics of industrial agriculture and was bought by Monsanto, which discontinued selling the seeds.
The Florida team is not repeating the Flavr Savr game plan. Instead, the tomato would be created through traditional breeding techniques, but using genetic tests to determine which of the plants possess the desired genes.
Klee does not expect the improved tomato to taste as good as the best heirlooms. Supermarket tomatoes would still be grown in large quantities, picked green and shipped long distances before being gassed with ethylene to ripen. In addition, the tomatoes are often mishandled en route. Refrigeration, Klee notes, destroys the flavor compounds in even the best tomato.
Some traditional breeders are skeptical that Klee can do what he thinks he can as quickly as he predicts. “I don’t think the taste of tomatoes is going to be fixed by molecular biologists,” said David Francis, a professor at Ohio State University who has bred several tomato varieties, “because flavor is a lot more complicated than manipulating one or two genes.”