A genetic study has found that potatoes evolved through natural interbreeding in the wild between tomato plants and a potato-like species in South America about 9 million years ago.
Potatoes are a much-loved food around the world – from chips and fries to mash and roasts.
Peruvian woman preparing chuño, a freeze-dried potato, in the Andes. Credit: hadynyah / iStock / Getty Images Plus.
The origin of this golden vegetable has long been a mystery. It was first domesticated in the Andes Mountains of South America about 7,000–10,000 years ago before being introduced to Europe by Spanish colonisers in the 1500s.
But how did wild potatoes first emerge?
The new research, published in the journal Cell, shows that cross-breeding with wild tomato plants and a potato-like cousin led to the formation of the tuber – the enlarged underground structure that stores nutrients in potatoes, yams and taros.
“Our findings show how a hybridisation event between species can spark the evolution of new traits, allowing even more species to emerge,” says corresponding author Sanwen Huang of the Chinese Academy of Agricultural Sciences. “We’ve finally solved the mystery of where potatoes came from.”
Modern potato plants (Solanum tuberosum) are nearly identical to 3 species of potato-like plant called Etuberosum which are found in central Chile.
Etuberosum, however, do not carry tubers.
Adding even more confusion, phylogenetic analysis (how organisms are related evolutionarily) suggests that modern potatoes are more closely related to tomatoes (Solanum lycopersicum).
The new research sought to solve this riddle by analysing 450 genomes from cultivated potatoes and compared them to 56 from the wild Etuberosum plants.
“Wild potatoes are very difficult to sample, so this dataset represents the most comprehensive collection of wild potato genomic data ever analysed,” says first author Zhiyang Zhang of the Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences.
Every modern potato sample contained a stable mix of genetic material from tomato and Etuberosum. This suggests an ancient hybridisation of the 2 groups.
Further phylogenetic analysis showed that Etuberosum and tomatoes shared a common ancestor about 14 million years ago. The 2 species rekindled after about 5 million years to produce a hybrid – the wild ancestor of the modern, tuber-bearing potato.
Non tuberous and tuberous potato species. Credit: Yuxin Jia and Pei Wang.
The SP6A gene acts as a master switch telling the plant when to start producing tubers. The analysis showed that this gene came from the tomato side of the family.
But other key genes involved in the formation of tubers are a mix of genetic material from tomatoes and Etuberosum.
Another important gene, IT1, helps control the underground stems forming tubers. This came from the Etuberosum side.
Without IT1 or SP6A, the plant is incapable of forming tubers.
The evolution of tuber-bearing potatoes came toward the end of the Miocene epoch. This period of Earth’s history is marked by a cooling and drying of the global climate.
In South America, this also coincided with a rapid uplift of the Andes Mountain range between 10 and 6 million years ago. This occurred during a period of intensified activity between the Nazca and South American tectonic plates.
Today, the Andes are the highest mountain range outside Asia.
The researchers believe the evolution of tubers allowed these ancient plants to get a foothold in increasingly extreme weather and geological conditions.
“Evolving a tuber gave potatoes a huge advantage in harsh environments, fuelling an explosion of new species and contributing to the rich diversity of potatoes we see and rely on today,” Huang says.
So, just know that when you put some tomato ketchup on your potato fries, you’re reuniting an ancient plant family.