Species of Potatoes

The major species grown worldwide is Solanum tuberosum (a tetraploid with 48 chromosomes), and modern varieties of this species are the most widely cultivated.

There are also four diploid species (with 24 chromosomes): S. stenotomum, S. phureja, S. goniocalyx, and S. ajanhuiri.

There are two triploid species (with 36 chromosomes): S. chaucha and S. juzepczukii.

There is one pentaploid cultivated species (with 60 chromosomes): S. curtilobum.

There are two major subspecies of Solanum tuberosum: andigena, or Andean; and tuberosum, or Chilean.

The Andean potato is adapted to the short-day conditions prevalent in the mountainous equatorial and tropical regions where it originated.

The Chilean potato is adapted to the long-day conditions prevalent in the higher latitude region of southern Chile, especially on Chiloé Archipelago where it is thought to have originated.

Genetic testing done in 2005 showed that both subspecies derive from a common ancestor from the area of southern Peru.

There are about five-thousand potato varieties worldwide.

Three thousand of them are found in the Andes alone, mainly in Peru, Bolivia, Ecuador, Chile, and Colombia.

They belong to eight or nine species, depending on the taxonomic school.

Apart from the five-thousand cultivated varieties, there are about 200 wild species and subspecies, many of which can be cross-bred with cultivated varieties, which has been done repeatedly to transfer resistances to certain pests and diseases from the gene pool of wild species to the gene pool of cultivated potato species.

Genetically modified varieties have met public resistance in the United States and in the European Union.

Most modern potatoes grown in North America arrived through European settlement and not independently from the South American sources.

However, at least one wild potato species, Solanum fendleri, is found as far north as Texas and used in breeding for resistance to a nematode species that attacks cultivated potatoes.

A secondary center of genetic variability of the potato is Mexico, where important wild species that have been used extensively in modern breeding are found, such as the hexaploid Solanum demissum, as a source of resistance to the devastating late blight disease.

Another relative native to this region, Solanum bulbocastanum, has been used to genetically engineer the potato to resist potato blight, see Sarpo Mira right.

The International Potato Center, based in Lima, Peru, holds an ISO-accredited collection of potato germ-plasm.