Scientists race to unlock secrets of the humble spud

Scientists around the world have teamed up to sequence the genome of the potato, hoping to crack the genetic code of one of the world's most important crops at a time of surging population growth and high food prices.

Solanum tuberosum, the scientific name of the humble white potato, looks simple. But it is chock full of mysteries hidden in its 12 chromosomes and 840 million DNA base pairs. Humans, by comparison, have 3 billion DNA base pairs.

The Potato Genome Sequencing Consortium includes scientists in 13 countries from New Zealand to India and Peru who are decoding different pieces of the genome.

It plans to have its work done in 2010 and will then make its findings public so plant breeders can create new seeds resistant to everything from droughts and diseases to extreme temperatures.

"We'll be able to design seeds more effectively and more efficiently after we know precisely which genes do what," said Gisella Orjeda, a biology professor at the Cayetano Heredia University in Lima who runs a lab that is sequencing one of the chromosomes.

Once the white potato genome is sequenced, researchers say it will become easier to identify genes in native and wild species of potatoes, which come in 5,000 varieties.

The potato, the world's third-most important food crop after wheat and rice, is being championed by food security experts who say it could cheaply feed an increasingly hungry world.

The United Nations named 2008 the International Year of the Potato to highlight its potential as an antidote to hunger.

Though the potato originated 8,000 years ago in Peru's Andes mountains, China is now the largest grower of the tuber. More farmers are planting it, especially in developing countries, as the world's population expands by 1 billion a decade.

Orjeda said the potato genome sequencing project, centered in the Netherlands, could usher in a new era for the potato, which its proponents call history's most important vegetable.

"The potato isn't just important now. It has always been important, it's what enabled the Industrial Revolution in Europe, by allowing for a population boom, but also what caused the potato famine in Ireland," she said.

History

The potato's story begins about 8,000 years ago near Lake Titicaca, which sits at 3,800 m above sea level in the Andes mountain range of South America, on the border between Bolivia and Peru. There, research indicates, communities of hunters and gatherers who had first entered the South American continent at least 7,000 years before began domesticating wild potato plants that grew around the lake in abundance.

Some 200 species of wild potatoes are found in the Americas. But it was in the Central Andes that farmers succeeded in selecting and improving the first of what was to become, over the following millennia, a staggering range of tuber crops. In fact, what we know as "the potato" (Solanum species tuberosum) contains just a fragment of the genetic diversity found in the seven recognized potato species and 5,000 potato varieties still grown in the Andes.

Although Andean farmers cultivated many food crops - including tomatoes, beans and maize, their potato varieties proved particularly suited to the quechua or "valley" zone, which extends at altitudes of from 3,100 to 3,500 m along the slopes of the Central Andes (among Andean peoples, the quechua was known as the "zone of civilization"). But farmers also developed a frost-resistant potato species that survives on the alpine tundra of the puna zone at 4,300 m.

The food security provided by maize and potato, consolidated by the development of irrigation and terracing, allowed the emergence around 500 AD of the Huari civilization in the highland Ayacucho basin. Around the same time, the city state of Tiahuanacu rose near Lake Titicaca, thanks largely to its sophisticated "raised field" technology, elevated soil beds lined with water canals, which produced potato yields estimated at 10 tons per hectare. At its height, around 800 AD, Tiahuanacu and neighboring valleys are believed to have sustained a population of 500,000 or more.

Agencies

(China Daily 09/15/2008 page7)