Where does your potato come from?

Origins and domestication of crop plants is a fascinating scientific field, at the intersection of history, the natural history of a plant species crossing our own history. So does potato, or if you prefer, Solanum tuberosum. This now major crop originated from a complex of species, that is when species delineation is blurred up (if not upside down) by numerous ways to hybridize naturally, usually among specious entities differing in their ploidy level (the number of copies of each chromosome you find in a cell), resulting in special hybrids with a life of their own (and same differential but potential ability to intercross with other sister biological entities).

There are two independant origins of potato landraces, Andean, or Chilean Lowlands, for the ‘potato’ as known in Europe (of course, domestication gave many more species/crops in the Andes, but we are only dealing with the migrated crop in this post). And when potato was introduced to Europe (something that occured really slowly from the 16th to the 17th centuries), it’s long been thought it was from an Andean source. Well, this was the accepted dogma, over the last sixty years, though there was also a “Chilean Lowlands” school to argue botanically with. The real mess with this debate is that, after the blight epidemics which almost destroyed this crop in the 19th century, cultivars from Chilean origin were used in breeding experiments to restore and save the plant from its decline. It was therefore not possible to use genetics to find out the answer directly from modern cultivars…

Part of the Andean school argument was that remnant cultivars from the initial introduction in India and Canary Islands were of Andean origin. And this apparently turned out to be wrong, as shown in recent studies. This was just enough to renew the debate about early potato origins… (At least in some botanical circles :-)

How would deal with such a hot potato issue? Well, the answer came out recently, in a study* based on herbarium specimens. Sure, if we can’t use post-blight cultivars because they’ve been crossed with members from both origins, you can manage your genetic investigation from some old dried plants. And as a surprise, early potato migrants were of Chilean origins, contrary to the prevalent dogma. So if you weren’t already convinced… Herbarium and collection are really important components and tools of modern science.

If you wonder as to what use this science bit could hell have, here it is: some current potato breeding programs are trying to increase the pool of potentially useful genes, to improve the yield an resistance of modern cultivars. One way to do so is to recreate a pre-migration and pre-domestication pool of populations ready to use as genetic resources. These are the so-called “Neo-Tuberosum” pops. Since European potato was thought to originate from the Andes, so were chosen the founders of Neo-Tuberosum populations. But as it was hypothesized that this crop naturally evolved into long-day tuberizing plants, maybe Neo-Tuberosum won’t do as easily. Simply because the original European potatoes didn’t go that way, contrarily to what was previously thought.

On one hand, at least the odds are great that the gene pool of Neo-Tuberosum will really bring up some new alleles of interest for breeding. On the other hand, breeders will probably have to do some more work to ease the transition of this gene pool into plants that are able to produce tubercules under long-day conditions… But that’s another interesting genetic question.

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* Mercedes A. and D. M. Spooner. 2008. DNA from herbarium specimens settles a controversy about origins of the European potato. American Journal of Botany 95(2): 252–257.

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