All modern potato varieties can be traced back to a type of potato grown in Peru more than 7,000 years ago, according to US research.

The DNA from around 360 types of potatoes, both wild and cultivated, was analysed by scientists from the University of Wisconsin-Madison and found to stem from a broad area of southern Peru, reported BBC News Online.

"In contrast to all prior hypotheses of multiple origins of the cultivated potato, we have identified a single origin from a broad area of southern Peru," lead scientist Dr David Spooner was quoted by the BBC as saying.

Previously, modern varieties of potatoes were believed to have originated from a much larger area of South America.