You Say Tomato and I Say Potato

You know the old song lyric, “you say tomayto and I say tomahto?” Well, a new study has Dave and me saying, “you say tomato and I say potato.” That’s because the tomato plant may be the ancestor to potato plants. At some point, the tomato genome joined with an ancestral form of a tuberless potato plant to form today’s potato in South America’s Andes mountains about 9 million years ago.  

The ancestral tuberless potato plant is called Etubersum. It had been a scientific mystery how this plant’s stem began enlarging into potatoes until a Chinese research group did molecular analysis on more than 40 wild potato species and a dozen species of wild tomato plants. They found that wild potatoes have a genome that’s the combination of tomato and Etubersum genes.  And the mixing is extensive which means large presence of both genes, implying the potato wasn’t the result of simple mutations.   

Instead, the theory is that the genomes hybridized together to form the modern potato. A single gene called SPAsix might be the genetic switch that creates tubers in potatoes. And a second gene called IT-one directs the underground stems to develop into potatoes. Today, more than 100 potato species grow in the wild and form potatoes of various shapes and colors. 

Results from the new study may help scientists grow hardier potatoes, which will be important as the earth warms and crops will need to adapt.