World's cultivated potatoes all have a single origin in southern Peru, scientists from the US Department of Agriculture (USDA) reported on Monday.

The new findings, appearing in the Proceedings of the National Academies of Sciences, are expected to conclude the debate around potatos' origin.

Humans have cultivated potatoes for thousands of years, but there has been great controversy about the ubiquitous vegetable's origins.

The scientists analyzed DNA markers in 261 wild and 98 cultivated potato varieties to assess whether the domestic potato arose from a single wild progenitor, or whether it arose multiple times.

The results clearly show that the first domesticated potato is genetically closest to a species now found only in southern Peru, according to David Spooner, the USDA scientist who led the study.

"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," said Spooner.

The multiple-origins theory was based in part on the broad distribution of potatoes from north to south across many different habitats, through morphological resemblance of different wild species to cultivated species, and through other data.

But the DNA data shows that in fact all cultivated potatoes can be traced back to a single origin in southern Peru, he said.

The earliest archaeological evidence suggests that potatoes were domesticated from wild relatives by indigenous agriculturalists more than 7,000 years ago, Spooner said. Today, the potato is a major crop in many countries around the world.

The new study focusing on how the potato has evolved into different species during thousands of years may help control potato disease, Spooner said.

"When researchers discover an important trait -- for example, that a certain species is resistant to disease -- then everything related to that species becomes potentially useful," he said.

"We can screen samples to see if related germ plasm has similar resistance, in which case we may be able to guide plant breeders to germ plasm to use in breeding programs," he added.

Beyond the agricultural benefits, Spooner's study also indicated single origins of other crops. The researchers said that they "help rewrite a small but important chapter of evolutionary history."

"The single origin of potato parallels results suggesting single origins of other crops including barley, cassava, maize, einkorn wheat, and emmer wheat," they wrote in the paper.