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Scientists Crack Tomato's Genetic Code

The tomato is the latest important food crop to yield its genetic secrets (Scott Bauer/USDA)

The tomato is the latest important food crop to yield its genetic secrets (Scott Bauer/USDA)

Scientists have unraveled the entire genetic code of the tomato, the world’s second-most valuable vegetable after the potato.

From pasta sauce to curry, this South American transplant has found itself at home in cuisines around the world. It is the latest important food crop to yield its genetic secrets, published in Nature.

This breakthrough provides a glimpse at how the genetic revolution is helping keep our favorite foods on the table.

Global effort

As befits this international vegetable, more than 300 scientists from 14 countries worked on the eight-year project.

Having a genetic map will provide a valuable starting point for breeders looking to make a better, hardier, more nutritious or simply tastier tomato.

“This will be facilitated now by the fact that we now know not only what genes are there, but their order,” says Giovanni Giuliano with the Tomato Genome Consortium and a researcher at the Italian national energy agency, which also does crop breeding.

Though it is the first tomato to have its DNA sequence decoded, Giuliano says there's nothing particularly special about the variety chosen for the project, known simply as Heinz 1706.

“It so happens that the day the person that made the first DNA library to be sequenced, they had Heinz 1706 seeds, and they started from that one. It is as simple as that.”

But it was not so simple to create this tomato -- or any new crop variety.

Ketchup story

Heinz, a U.S. food company, is famous for its tomato ketchup. It's the essential condiment for American staples like hot dogs and hamburgers.

But to make Heinz ketchup, not just any tomato will do.

Until the late 1960s, the tomatoes the company used had a nasty habit of cracking on the vine after a heavy rain. That can ruin the tomato.

So, “Heinz had set about trying to put together a variety of tomatoes that would resist that cracking,” says company research manager, Rich Ozminkowski.

It meant years of trial and error, mating different varieties, finding offspring that looked promising, mating those offspring with other varieties, and so on.

Complex traits

And it was not enough for the offspring to just resist cracking. Ozminkowski says the perfect ketchup tomato needs a whole list of other traits, too.

“Traits like sugars and, for Heinz, viscosity, or the juice thickness, and the redness of the tomatoes are all very critical traits for us," he says. "Those are all controlled by a lot of different genes within a tomato naturally.”

On top of all that, it had to be disease-resistant and easy to harvest mechanically.

Commercialized around 1967, Heinz 1706 fit the bill. Ozminkowski says creating that tomato would have been much easier if they had a genetic map to go by.

“The tools available back when 1706 was developed, it was all very, very conventional breeding." Breeders had to grow thousands of tomato plants and go looking for specific traits. "There were no genetic tools," he says. "You could not look at (DNA) sequences. You could not do comparisons. And that is what makes the genomic project and the technologies that have spun off of that so interesting.”

Less guesswork

Genome sequencing is such a powerful tool for breeders of all kinds of crops because it takes away much of the guesswork, says Heinz’s Rich Ozminkowski.

“By having the genome information, we can pick out those tomato plants that have more of those genes” for sweetness, redness, viscous juice, or whatever breeders are looking for.

And it’s not just about making better ketchup. Climate change will demand that many crops adjust to new conditions. Ozminkowski says researchers are already using the new genetic tools to help fight emerging plant diseases.

“This is going to give us even more [tools]," he says. That's important, he adds, "because there are new diseases that are becoming problems within California and around the world.”

So however you enjoy your tomatoes, or whatever you are eating, new genetic breakthroughs are helping keep them on your table for years to come.
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    Steve Baragona

    Steve Baragona is an award-winning multimedia journalist covering science, environment and health.

    He spent eight years in molecular biology and infectious disease research before deciding that writing about science was more fun than doing it. He graduated from the University of North Carolina at Chapel Hill with a master’s degree in journalism in 2002.