Researchers have discovered that the modern potato evolved from the hybridisation of tomato ancestors and etuberosum in South America. Photo / 123rf
They’re one of the world’s most important food crops and delicious roasted, mashed or fried, but the exact genetic origins of the humble potato have long been something of a mystery to scientists.
Now, researchers say the modern-day potato evolved from hybridisation of the ancestors of tomato plants and another potato-like plant, known as etuberosum, in South America up to 9 million years ago. The hybridisation created the petota lineage – which includes the cultivated potato seen in supermarkets around the world, as well as 107 wild potato species.
Sandra Knapp, a plant taxonomist at the Natural History Museum in London and an author of the study, said in an interview that while scientists had known potatoes, tomatoes and etuberosum were closely related, the exact relationship had been unclear as “different parts of the genome told us different stories”.
The new research, published in the journal Cell Press, was carried out by a team of scientists in China, the United States and the United Kingdom who focused on untangling this relationship.
Scientists conducted an intricate analysis of 128 genomes and found that “all members of petota exhibit a stable mixed genomic ancestry, derived from etuberosum and tomato lineages”. Researchers said they believe tomato and etuberosum share a common ancestor but diverged around 14 million years ago, before hybridisation between them resulted in the origin of petota around 8 to 9 million years ago.
The combination of two distinct genes in this “hybrid speciation” event led to a key innovation – the development of tubers in petota. Tubers, the edible part of the potato, allow the plant to reproduce without seeds or pollination as well as storing water and carbohydrates, meaning petota was able to thrive in different geographic niches and diversify into a large number of species, scientists added.
Knapp said while hybridisation in plants is nothing new, the resulting plants are often sterile, and it had previously been thought of as an “evolutionary dead-end”. The latest research showed that, in fact, “hybridisation is a really potent force in evolution,” she added.
Cultivated potatoes (Solanum tuberosum), with maize, rice, and wheat, make up around 80% of human calorie intake, the researchers said, and are renowned for being cheap, versatile, and packed with carbohydrates.
However, wild potatoes are difficult to sample, and the study is the “most comprehensive collection of wild potato genomic data ever analysed,” lead co-author Zhiyang Zhang, a genomics expert from the Agricultural Genomics Institute at Shenzhen, said in a statement.
Scientists detailed how this hybridisation event led to the creation of tubers through genes known as SP6A and IT1, derived from tomato and etuberosum, respectively.
The changes came at the same time as the Andes Mountains emerged between six and 10 million years ago, researchers said. Having a tuber to store nutrients allowed potatoes to survive harsh weather and spread throughout cold climates in the Andes and central Mexico.
While both petota and etuberosum have underground resprouting organs which allow them to reproduce without seeds, petota became more widespread than tomato or etuerosum species, as it was able to grow in areas such as grasslands, Alpine meadows and seasonally dry rainforests, the researchers added.
Now, scientists want to understand the effect of tuber-related genes on plants and how the exact “reshuffling” of genes in this case led to tuber formation, Knapp said, adding that it also raises the prospect of creating plants that can grow food faster, are more disease resistant, and environmentally friendly.
Studying the evolution of the potato also allows scientists to think about how the traits of wild species could be used on cultivated plants to boost biodiversity and mitigate the environmental impacts of agriculture, she said.
Zhang, meanwhile, said in an interview that he hoped the findings could help “generate a new species that maybe have a harvested fruit on the ground and a tuber in the ground”. One of his fellow researchers has joked that such a new species could be called “tomtatoes”.
Knapp suggested that the main benefit of the findings would be to build “better potatoes instead of building cool weird things”.
“If we’re going to optimise crops, what we want to do is optimise the thing we want from them, and usually when you get something that does two things, those two things are not as good as the one that does the one thing better,” she said.