Gazpacho is a traditional Spanish drink and Italians could not imagine their cuisine 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 consumed by the Aztecs into Spain. The first known description of the plant is by Pietro Mattioli, an Italian naturalist, who wrote it in 1544, but its use in his country’s cuisine did not come until a century and a half later. The resemblance of the tomato to other poisonous plants with which it shares a family, such as the mandrake or belladonna, meant that for a long time it was only used as an ornament. As of 2020, it is the second most important vegetable in the world after the potato.
This history of conquering world tables began many tens of thousands of years ago on the west coast of South America, in that area where the high peaks of the Andes are separated by a few kilometers from the beaches of the Pacific. This week, a team from the University of Massachusetts at Amherst (USA) published in the journal Molecular Biology and Evolution an article in which they reconstruct the evolutionary history of the tomato.
For a century and a half, in Italy, the tomato was used only as a decorative plant due to its resemblance to poisonous plants
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 on 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. cherry-shaped), says the main author of the study, Ana Caicedo, was used by the inhabitants of the region thousands of years ago, and “they have characteristics similar to those of a domesticated fruit, similar acids and sugars.”
That made us think that those responsible for that transformation in the ancestral tomatoes had been humans. However, Caicedo and his colleagues, using complete genome sequences from 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 in the Americas. When the immigrants arrived on the continent they found the job done.
Researchers from the University of Massachusetts found some other surprise on the way of wild tomatoes to what is now Mexico, where there is the first evidence of domestication of the tomatoes that are the basis of the current ones (S. lycopersicum L. var. lycopersicum). “Upon migrating north, tomatoes that were the size of cherry tomatoes became smaller, possibly because when they changed latitude and environment they had to evolve and acquire other characteristics to survive,” says Caicedo. These small fruits “still grow in the milpas [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 small tomatoes were later the basis on which the ancient Americans worked to select varieties and create the tomatoes that would eventually reach Europe and conquer the world.
The first humans who arrived in America already found tomatoes the size of the cherry we know today
In addition to knowing the evolutionary history of such an important plant, the research carried out by the team led by Caicedo can be useful for improving current tomato crops. The genetic study has made it possible to identify variants that improve resistance to certain diseases or to drought and this knowledge can be used to create tomatoes with these virtues. In other intermediate populations of the plant, which has varied to adapt to a large number of environments between the Andean region, Central America and Mexico, populations have been identified that produce a greater amount of sugar or beta carotene, two interesting characteristics because they make the tomatoes have a better flavor or a more attractive color.
All over the world there are efforts to return tomatoes to being a tasty fruit as it was not so long ago. The selection of the producers, who preferred to grow larger tomatoes or with a brighter skin, neglected its flavor and now there are projects to recover it. In 2017, a team in which Antonio Granell, a researcher at the Institute of Molecular and Cell Biology of Plants, in Valencia, participated, sequenced the complete genome of 398 tomato varieties, including modern, traditional or wild varieties 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 by the Pacific to global success, science wants to help the tomato recover part of its essence.