On the tomato trail: in search of ancestral roots

A profile of Roger Chetelat, the director of the C.M. Rick Tomato Genetics Resource Center at the University of California, Davis. Chetelat maintains one of the largest collections of tomato seeds in the world. Many of those seeds come from wild tomato species that Chetelat and his associates collect on field research trips to the dry coastal areas of Chile, Peru, and Ecuador. Wild tomatoes are tough, versatile organisms that have evolved resistance to virtually all common tomato diseases and pests and stubbornly tolerate extreme environmental conditions. Some boast extraordinarily high levels of sugars, beta carotene, vitamin C, lycopene, and antioxidants. Chetelat has dedicated his career to finding and preserving these genetic riches. Modern cultivated tomatoes are a frail, inbred lot. They all trace their origins to a single, wild tomato plant that underwent a random mutation sometime in prehistory. Because of this genetic fluke, that plant's fruits were plump, juicy, and many, many times larger than the output of its progenitors. Offspring from that tomato were taken away from the Andes and domesticated in what is present-day Mexico, becoming severed from their wild ancestors and the vast pool of genetic diversity that tomatoes had evolved over the millennia. Botanists call this a “bottleneck.” It leaves subsequent generations susceptible to disease and unable to adjust to rapid climate changes. The stored wild seeds at the Rick Center enable plant breeders to re-incorporate desirable wild traits into new tomato varieties, literally reconnecting them to their ancestral roots, ensuring that this vast reservoir of genetic diversity will be available when it is needed.