Diffusion

Papa, patata, potato...

While the Incas called it papa (as do modern-day Latin Americans), Spaniards called the potato patata, apparently confusing it with another New World crop, the sweet potato (known as batata). In 1797, the English herbalist Gerard referred to the sweet potato as "common potatoes", and for many years S. tuberosum was known as the "Virginia potato" or "Irish potato" before finally displacing batata as the potato.

The diffusion of the potato from the Andes to the rest of the globe reads like an adventure story, but it began with a tragedy. The Spanish conquest of Peru between 1532 and 1572 destroyed the Inca civilization and caused the deaths - from war, disease and despair - of at least half the population.

The conquistadores came in search of gold, but the real treasure they took back to Europe was Solanum tuberosum. The first evidence of potato growing in Europe dates from 1565, on Spain's Canary Islands. By 1573, potato was cultivated on the Spanish mainland. Soon, tubers were being sent around Europe as exotic gifts - from the Spanish court to the Pope in Rome, from Rome to the papal ambassador in Mons, and from there to a botanist in Vienna. Potatoes were grown in London in 1597 and reached France and the Netherlands soon after.

But once the plant had been added to botanical gardens and herbalists' encyclopaedias, interest waned. European aristocracy admired its flowers, but the tubers were considered fit only for pigs and the destitute. Superstitious peasants believed the potato was poisonous. At the same time, however, Europe's "Age of Discovery" had begun, and among the first to appreciate potatoes as food were sailors who took tubers to consume on ocean voyages. That is how the potato reached India, China and Japan early in the 17th century.

The potato also received an unusually warm welcome in Ireland, where it proved suited to the cool air and moist soils. Irish immigrants took the tuber - and the name, "Irish potato" - to North America in the early 1700s.

Long summer days. The widespread adoption of the potato as a food crop in the northern hemisphere was delayed not only by entrenched eating habits, but by the challenge of adapting a plant grown for millennia in the Andes to the north's temperate climate. Only a drop of the rich potato gene pool had left South America, and it took 150 years before varieties suited to long summer days began to appear.

Those varieties arrived at a crucial time. In the 1770s, much of continental Europe was devastated by famines, and the potato's value as a food security crop was suddenly recognized. Prussia's Frederick the Great ordered his subjects to grow potatoes as insurance against cereal crop failure, while the French scientist Parmentier succeeded in having the potato declared "edible" (around the same time, on the other side of the Atlantic, US President Thomas Jefferson served french fries to White House guests).

After initial hesitation, European farmers - even those in Russia, where the potato was called the "devil's apple" - began growing potatoes on a large scale. Potato became Europe's food reserve during the Napoleonic wars, and by 1815 it had become a staple crop across northern Europe. By then, the Industrial Revolution was transforming agrarian society in the United Kingdom, displacing millions of rural people into crowded cities. In the new urban environment, the potato became the first modern "convenience food" - energy-rich, nutritious, easy to grow on small plots, cheap to purchase, and ready to cook without expensive processing.

Increased potato consumption during the 19th century is credited with helping to reduce the scourge of diseases such as scurvy and measles, contributing to higher birth rates and the population explosion in Europe, the US and the British Empire.

"Potato famine". But the potato's success proved a double-edged sword. For the tubers that were being cloned and cultivated across North America and Europe belonged to a few, genetically similar varieties. That meant they were highly vulnerable: a pest or disease that struck one plant could spread quickly to the rest.

The first sign of impending disaster came in 1844-45, when a mould disease, late blight, ravaged potato fields across continental Europe, from Belgium to Russia. But the worst came in Ireland, where potato supplied 80 percent of calorie intake. Between 1845 and 1848, late blight destroyed three potato crops, leading to famine that caused the deaths of one million people.

The Irish catastrophe led to concerted efforts to develop more productive and disease-resistant varieties. Breeders in Europe and North America, drawing on new potato germplasm from Chile, produced many of the modern varieties that laid the foundation for massive potato production in both regions for most of the 20th century.

Meanwhile, European colonialism and emigration were taking the potato to all corners of the globe. Colonial governors, missionaries and settlers introduced potato growing to the floodplains of Bengal and Egypt's Nile delta, the Atlas Mountains of Morocco, and the Jos plateau in Nigeria. Emigrant farmers took the potato to Australia and even to South America, establishing the potato in Argentina and Brazil.

In the Asian heartland, the tuber moved along more ancient routes, finding its way from the Caucasus to Turkey's Anatolian plateau, from Russia to western China, and from China to the Korean Peninsula. In the mountain valleys of Tajikistan, some potato types have been grown long enough to be considered "old local varieties".

The 20th century saw the potato finally emerge as a truly global food. The Soviet Union's annual potato harvest reached 100 million tonnes. In the years following the Second World War, huge areas of arable land in Germany and Britain were dedicated to potato, and countries like Belarus and Poland produced - and still do - more potatoes than cereals.

The potato came into its own as a snack food. The invention in the 1920s of the mechanical potato peeler helped make potato crisps America's top-selling snack. A restaurant chain founded by the McDonald brothers in the US in 1957 spent millions of dollars to "perfect the french fry". A Canadian firm, McCain, that began making frozen french fries in 1957, expanded to open 55 production facilities on six continents and now supplies one third of all french fried potatoes produced internationally.

Exploding demand. From the 1960s, cultivation potato of began expanding in the developing world. In India and China alone, total production rose from 16 million tonnes in 1960 to almost 100 million in 2006. In Bangladesh, potato has become a valuable winter cash crop, while potato farmers in southeast Asia have tapped into exploding demand from food industries. In sub-Saharan Africa, potato is a preferred food in many urban areas, and an important crop in the highlands of Cameroon, Kenya, Malawi and Rwanda.

The potato has an extraordinarily rich past, and a bright future. While production in Europe - the potato's "second home" for four centuries - is declining, the potato has ample room for expansion in the developing world, where its consumption is less than quarter that of developed countries.

Today in mountainous Lesotho, many farmers are shifting from maize to potato, assisted by an FAO project for production of virus-free seed tubers. In China, agriculture experts have proposed that potato become the major food crop on 60 percent of the country's arable land, and say a staggering 30 percent increase in potato yields is within reach.

And in Andes, where it all began, the Government of Peru created in July 2008 a national register of Peruvian native potato varieties, to help conserve the country's rich potato heritage. That genetic diversity, the building blocks of new varieties adapted to the world's evolving needs, will help write future chapters in the story of Solanum tuberosum.