On the Tomato Trail: Researchers Scour Remote Andean Deserts in Search of Wild Ancestors of Domestic Tomatoes. The Popular Fruit’s Future May Depend on Their Success

Beefsteaks' Contry Cousins. Photo by Carl Jones

A chilean soldier was guarding a lonely garrison in the Attacama Desert near the Peruvian border when American geneticist Roger Chetelat and his field research team arrived there in 2005. The soldier obligingly provided what should have been straightforward directions to their destination: Follow the road beside the railroad tracks. As an afterthought, the sentry quietly suggested that they stay on the road, adding with a knowing nod, “landmines.”

Chetelat, an athletic fifty-two-year-old, could be mistaken for a high-school gym teacher. In fact he is the director of the prestigious C.M. Rick Tomato Genetics Resource Center at the University of California, Davis, the world’s foremost repository of wild tomato plants and their seeds. The Center houses a collection of tough, versatile organisms that have evolved disease resistance and tolerance to extreme environmental conditions—genetic traits that researchers can incorporate into cultivated tomatoes, a feeble, inbred lot that, like some royal families in the Middle Ages and certain dog breeds that have become too popular, need all the genetic help they can get. The Center acts like a lending library, nurturing and preserving its 3,600-specimen collection but also making it readily available to scholars and plant breeders worldwide who want to “check out” seeds for their own experiments. “If it wasn’t for the genes of these wild species, you wouldn’t be able to grow tomatoes in a lot of areas,” explains Chetelat. “I don’t think there is a cultivated plant for which the wild relatives have been more critical.”

Drop by nearly any farmer’s market on a summer Saturday, and displays of cultivated tomatoes all but scream out the word diversity. Their descriptive names say it all: Big Beef, Orange Blossom, Pruden’s Purple, Striped German, Green Zebra, Great White, Yellow Pear, Red Grape, White Cherry, Black Cherry, Matt’s Wild Cherry. But all that variety is literally only skin deep. Botanists have but one name for all those oddball cultivated tomatoes: Solanum lycopersicum. “Most of the variation you are seeing is from a few genes that control color, shape, and size,” says Chetelat. “There is very little genetic variation.”

On that day in the desert five years ago, Chetelat and his group, which included scientists from the Universidad de Chile in Santiago, had been retracing a trail that had been cold for fifty years, its route filed away in the records of a Chilean herbarium. With luck—lots of it—the stale information might lead them to a few remote clumps of a wild tomato species called S. chilense. If the team was successful, seeds from those plants, which had never before been collected in that area, would become a valuable addition to the Center’s collection.

But that was a big “if.”

Continue reading the rest of the article in the Spring 2010 issue of Gastronomica.

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