The Potato's Secret Origin: A Tomato Was Its Mother
SHENZHEN, CHINA - In a surprising and monumental discovery that reshapes our understanding of one of the world's most important food sources, an international team of scientists has revealed that the humble potato is the result of an ancient hybridization event—a natural cross-breeding—between a tomato ancestor and a wild, non-tuber-bearing potato relative. The unlikely liaison, which occurred approximately 9 million years ago, not only gave birth to the potato lineage but also led to the accidental creation of a brand-new plant organ: the starchy, nutritious tuber that is now the world's third-largest staple crop.
The groundbreaking findings, published in the latest issue of the prestigious scientific journal Cell, were the result of a massive genetic investigation led by researchers at the Agricultural Genomics Institute in Shenzhen and the Chinese Academy of Agricultural Sciences. By conducting a comprehensive "DNA paternity test" on cultivated potatoes and their wild relatives, the team solved a long-standing evolutionary puzzle and provided a new roadmap for genetic potato breeding.
The Evolutionary Puzzle: A Plant with a Mysterious Past
For decades, the origin of the potato has been a source of scientific debate. On the surface, the modern potato plant looks almost identical to a wild, potato-like species called Etuberosum, which does not produce tubers. This visual similarity led many to believe it was the direct ancestor. However, a deeper look at the plant's family tree told a different, more confusing story: genetically, the potato is a "chip off the old tomato block," showing a closer relationship to its fruit-bearing cousin.
This created a paradox. How could the potato be genetically related to the tomato, yet look exactly like the non-tuber-bearing _Etuberosum_? And, most importantly, where did its unique and defining feature—the tuber—come from? This long-standing mystery is what the research team, led by renowned agricultural genomicist Huang Sanwen, set out to solve.
A Genetic Paternity Test: Unraveling the Potato's DNA
To get to the bottom of this botanical mystery, the research team undertook an unprecedented genetic analysis. They sequenced and analyzed 101 genomes and 349 re-sequenced samples from a wide variety of cultivated potatoes and 56 of their wild relatives.
The results were conclusive and stunning. They found that every potato they examined carried stable, balanced genetic contributions from both the ancient tomato lineage and the _Etuberosum_ lineage. This "mosaic" pattern of DNA was the smoking gun, proving that the potato was the hybrid offspring of both.
Using a "molecular clock" technique, their analysis showed that the ancestral lines of the _Etuberosum_ and the tomato began to diverge around 14 million years ago. Then, approximately 5 million years after they had become distinct species—around 9 million years ago—a natural cross-pollination event occurred. "The tomato served as the maternal parent of the potato, while the _Etuberosum_ was the paternal parent," Huang Sanwen explained.
The Accidental Invention of the Tuber
Even with the parentage confirmed, the biggest question remained: if neither parent had a tuber, how did their offspring get one? Huang's team proposed that the tuber was the accidental product of a genomic rearrangement following the hybridization event.
The team was able to trace the origins of the two key genes responsible for tuber formation:
- The Master Switch (from the Tomato): The SP6A gene, which acts like a master on/off switch that tells the plant when to start making tubers, came from the maternal tomato side of the family.
- The Growth Controller (from the _Etuberosum_): Another critical gene, IT1, which helps control the growth of the underground stems that form the tubers, came from the paternal _Etuberosum_ side.
Without either one of these genetic components, the hybrid offspring would have been incapable of producing tubers. It was only through this chance ancient marriage that both essential genes were brought together.
An Evolutionary Superpower: The Advantage of the Tuber
The accidental creation of the tuber gave the new potato lineage a massive evolutionary advantage, allowing it to thrive in the harsh, high-altitude environments of its native South America. The tuber is a biological survival kit. As an underground organ, it stores vast amounts of water and starch, helping the plant endure drought and cold. Furthermore, it provides a means of asexual reproduction, as new plants can sprout directly from the "eyes" or buds on a tuber.
"Evolving a tuber gave potatoes a huge advantage in harsh environments, fueling an explosion of new species and contributing to the rich diversity in the potatoes we see and rely on today," Huang said. This new, detailed understanding of the potato's genetic architecture provides a groundbreaking perspective for the future of potato breeding, which is critical for ensuring global food security.
Source(s): CGTN