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A paper published recently* by David M. Spooner, a research botanist employed by the USDA Agricultural Research Service working at the University of Wisconsin in close collaboration with the Scottish Crop Research Institute, goes a long way towards resolving the question, by using genetic analysis of wild species and landraces found throughout the Andes. The paper concludes that there was a single point of origin of the cultivated potato to the north of Lake Titicaca in southern Peru. challenging all previous theories of multiple origins.
“This paper is a good piece of work,” said Willy Roca, the head of CIP’s genebank. “The evidence clearly shows that the potato had a single origin.”
Since 1998, through careful study of the morphology of wild species and landraces, Alberto Salas, an agronomist in CIP’s Biodiversity Complex, has been assembling evidence that supports Spooner’s conclusions. “He has used the right material to prove the relationships,” said Salas. “It contradicts earlier studies and even goes against Spooner’s own previous beliefs.”
The cultivated potato traces its origin to landraces developed by pre-Columbian farmers from species growing in the wild. Archeological evidence puts the earliest signs of cultivation at 7000 years ago around Lake Titicaca, centering on a group of about 20 morphologically similar wild species referred to as the Solanum brevicaule complex. This is distributed from central Peru to northern Argentina.
Native cultivated potatoes or landraces are distributed widely in the Andes, although the Chilean ones are derived from secondary hybridization with most likely Bolivian and/or Argentinean wild species. All previous hypotheses had proposed that the cultivated potato had developed in a number of different points from a variety of wild species.
Spooner et al. analyzed the genetic makeup of 365 landraces, their putative progenitors and associated groups, using a molecular technique called amplified fragment length polymorphism. The evidence showed all the cultivated potatoes to be derived from a single origin in the northern part of the S. brevicaule complex, rather than the “?multiple independent origins from various northern and southern members,” as Spooner writes in the paper.
“They used the actual varieties that other groups had used in their multipoint theories and still came up with the single point of origin,” said Willy Roca.
Marc Ghislain, a molecular biologist at CIP, has been studying potato origins at the molecular level. “Our data confirm the origin in that area very clearly,” he said. However, he has some reservations. “We have done a large study using another type of molecular marker that may indicate independent domestication events for three groups of landraces, also known as the bitter potatoes, that were not present in the sample used by Spooner’s group,” he noted. “I think that it is premature to also include them in the single point concept.”
“I think this work highlights the value of the genetic resources CIP is maintaining in its genebank,” said CIP’s Oscar Hidalgo. “CIP has been able to capture and maintain these 7000 year old resources yet we should also recognize the dedication that the farmers have put in to conserving this material for their own use and that of future generations.”
* Spooner, DM et al. Proc Natl Acad Sci 14694-14699 Oct 11 2005 102 41
