The potato is a staple in many households around the world, whether mashed, baked, or fried. It represents the essence of ordinary yet has a rich and complex genetic history that has intrigued scientists for years. Sandy Knapp, a botanist from the Natural History Museum in London, explains that the lineage of the potato and its wild relatives has been shrouded in mystery. "We didn't know where the whole potato lineage came from," she states.
Researchers have long established that potatoes are most closely related to two groups of plants: tomatoes and a cluster known as Etuberosum. Knapp describes these plants as "very cute" with their lovely purple flowers. However, a puzzling conundrum has emerged; certain genes indicate a closer relationship to tomatoes, while others suggest a connection to Etuberosum. This genetic uncertainty has hindered the ability to construct a clear family tree for potatoes and their relatives. "When something doesn't quite fall out right, that's where the exciting biology is," says Knapp.
In a groundbreaking study published in the journal Cell, Knapp and her team propose that the confusion surrounding the potato's ancestry stems from an ancient interbreeding event between the ancestors of tomatoes and Etuberosum. This fusion occurred at a pivotal moment when new high-elevation habitats were forming in the Andes. The researchers aim to leverage these findings to develop a "greater tater"—a potato variety engineered to thrive in the face of challenges like disease and climate change.
Knapp highlights a humble potato from her kitchen, noting the diversity among potatoes we consume today—ranging from small red varieties to large ones used for chips. All these potatoes derive from a single domesticated species that originated in the Americas, where a staggering 107 wild species exist. The underground tubers of these plants serve as a starch storage mechanism, allowing them to survive adverse growing seasons. Interestingly, neither tomatoes nor Etuberosum produce tubers, leading researchers to dig deeper into this genetic enigma.
The research team sequenced the genomes of various Etuberosum plants, tomatoes, and a wide array of wild and domesticated potatoes, marking the most extensive analysis of potato genomes to date. The results revealed a balanced mix of genes from both tomatoes and Etuberosum, implying that these ancestors hybridized to give rise to a new type of plant capable of producing tubers—a crucial evolutionary advantage.
"Tuberization is a complex trait controlled by multiple genes," Knapp explains, with findings suggesting that this interbreeding event occurred approximately 9 million years ago. This timing coincided with the formation of the Andes, creating cold and dry high-elevation habitats. Unlike their ancestors, which struggled in such environments, the new potato lineage thrived, leveraging its tubers to store energy and endure harsh conditions. "If there's a plant that can invade and take advantage, then off it goes," observes Knapp.
About 6,000 to 7,000 years ago, humans near Lake Titicaca began to domesticate a single potato species, leading to the vast array of potato varieties we enjoy today. This transformation turned the humble tuber into a vital resource for human consumption.
The research may also have practical implications for potato farming. Currently, farmers propagate potatoes by planting small pieces of the tuber, resulting in genetically identical plants that are vulnerable to diseases. Knapp suggests that this study could pave the way for innovative genetic engineering approaches using tomatoes or Etuberosum to develop potato varieties capable of producing seeds. This advancement could lead to healthier potatoes resilient to pests and climate fluctuations.
The findings underscore the significant role of hybridization in plant evolution. Iris Peralta, an agronomist from the National University of Cuyo in Argentina, emphasizes the importance of modern genomic tools in uncovering the potato’s origin story. "It's a pattern we can assume is an important mechanism to generate variability," she states. The authors agree that hybridization can produce numerous new combinations rapidly, which is essential for adapting to changing environments.
In conclusion, while not all interbreeding events yield successful outcomes, the potato serves as a remarkable example of how evolutionary processes can create new and beneficial plant lineages. The potato's journey from a simple tuber to a global staple is a testament to nature's complexity and resilience.
