Gazpacho is a lifelong Spanish drink and Italians could not imagine their cooking without tomato dressings. However, its arrival in Europe is relatively recent and its use as food is even more so. Hernán Cortés conquered Tenochtitlan in 1521 and it is likely that it was some member of that expedition who introduced the yellow tomatoes that the Aztecs consumed in Spain. The first description of the plant that is known is by Pietro Mattioli, an Italian naturalist, who wrote it in 1544, but the use in the kitchen of his country did not come until a century and a half later. The resemblance of the tomato with other poisonous plants with which it shares a family, such as the mandrake or the belladonna, meant that for a long time it was only used as an ornament. In 2020, it is the second vegetable most important in the world after the potato.
This history of conquering the world tables began many tens of thousands of years ago on the west coast of South America, in that terrain where the high peaks of the Andes are separated by a few kilometers from the Pacific beaches. This week, a team from the University of Massachusetts in Amherst (USA) publishes in the magazine Molecular Biology and Evolution an article in which they reconstruct the evolutionary history of tomato.
It all started with some small wild fruits (Solanum pimpinellifolium L.) the size of a blueberry, the type of vegetable that human ancestors would have fed hundreds of thousands of years ago. Except that in America, according to the latest data, our species did not reach, at most, 40,000 years. The next step in the long process of domestication was an increase in the size of the fruit, which about 80,000 years ago, in what is now Ecuador, reached the size of a cherry tomato. This variety (S. lycoperiscum L. var. cerasiform), says the lead author of the study, Ana Caicedo, was employed by the inhabitants of the region thousands of years ago, and “they have similar characteristics to those of a domesticated fruit, similar acids and sugars.”
That made think that those responsible for that transformation in ancestral tomatoes had been humans. However, Caicedo and his colleagues, using complete genomic sequences of 166 samples of wild, intermediate and domesticated tomatoes to reconstruct the history of that domestication, place the event at least 400 centuries before the arrival of the first humans to America. When immigrants arrived on the continent they found work done.
Researchers at the University of Massachusetts found some other surprise on the way of wild tomatoes to what is now Mexico, where there are the first tests of domestication of tomatoes that are the basis of current (S. lycopersicum L. var. lycopersicum). “When migrating to the north, tomatoes that were the size of the cherry became smaller, possibly because when changing latitude and environment they had to evolve and acquire other characteristics to survive,” says Caicedo. These little fruits “still grow in the cornfields [lugares de cultivo] from Mexico, where people eat them even if they don’t grow them on purpose, ”explains Hamid Razifard, another of the authors of the work. These little tomatoes were later the base on which the ancient Americans worked to select varieties and create the tomatoes that would eventually reach Europe and conquer the world.
In addition to knowing the evolutionary history of such an important plant, the research of the team led by Caicedo can be useful to improve current tomato crops. The genetic study has allowed to identify variants that improve resistance to certain diseases or drought and that knowledge can be used to create tomatoes with these virtues. In other intermediate populations of the plant, which varied to adapt to a large number of environments between the Andean region, Central America and Mexico, populations that produce a greater amount of sugar or beta carotene have been identified, two interesting characteristics because they make them Tomatoes taste better or have a more attractive color.
Throughout the world there are efforts to make tomatoes again a tasty fruit as it was not so long ago. The selection of producers, who preferred to grow larger tomatoes or with a brighter skin, neglected their flavor and now there are projects to recover it. In 2017, a team in which I participated Antonio Granell, a researcher at the Institute of Molecular and Cellular Biology of Plants, in Valencia, sequenced the complete genome of 398 tomato varieties, including modern, traditional or wild such as those that appeared in South America tens of thousands of years ago. Then, the genetic basis of the production of 13 chemical compounds associated with flavor that abound in ancestral varieties and are scarce in those found in the supermarket were identified. After such a long journey, from smallness in its cradle along the Pacific to global success, science wants to help the tomato recover some of its essence.