Tomato is the mother of potato says genome biologist and plant breeder Sanwen Huang, who led the new research. That hybridisation, the authors argue, helped the first potatoes diversify into new regions and climatic conditions — from warm grasslands to cold mountain meadows — that neither of its ancestor lineages could inhabit so well.
Early tomato plants hybridised with another ancestral group about nine million years ago — a tryst that yielded hybrid offspring with just the right combination of genes to make tubers.
Previous genomic studies had revealed that tomatoes are potatoes’ closest living relatives and that a separate group of three ancestral species, known as Etuberosum, is eerily potato-like.
However, Etuberosum plants don’t grow tubers.
Intrigued by this discrepancy, Huang and his colleagues sequenced the genomes of 44 wild potato species, the three Etuberosum species, and 15 species of wild tomato.
Huang’s team found that the wild potatoes have a uniform blend of genes from tomatoes and Etuberosum — “a signal of ancient hybridisation,” Huang says. The potato genomes suggest the two lineages successfully hybridised about nine million years ago.
This crossing is what gave proto-potatoes the genetic knack for making tubers, Huang and his colleagues believe. Tubers store nutrients, which can help a plant endure tough conditions.
They also let plants reproduce vegetatively — without pollinators or even sexual reproduction — which probably helped the new lineage overcome any lingering fertility problems. The researchers also suspect that tubers helped this early potato lineage diversify into many new species.
Huang is looking to the future. He thinks the findings could inform the creation of new potato varieties propagated by seed. For example, plant scientists might transform a tomato into a tuber-bearing species by adding IT1 and other genes from potato.
Such an approach would, in some respects, simply riff on evolution’s original handiwork in the foothills of the rising Andes. “Next time you eat potatoes,” Huang says, “thank a tomato.”
