Image copyright Thinkstock Image caption Scientists have developed a variety of Desiree potatoes that are resistant to late blight

British scientists have developed genetically modified potatoes that are resistant to the vegetable's biggest threat - blight.

A three-year trial has shown that these potatoes can thrive despite being exposed to late onset blight.

That disease has plagued farmers for generations and it triggered the Irish potato famine in the 1840s.

EU approval is needed before commercial cultivation of this GM crop can take place.

The research is published in the journal Philosophical Transactions of the Royal Society B.

Media playback is unsupported on your device Media caption Lord Haskin: GM potatoes improve "cost and reliability"

Potatoes are particularly vulnerable to late blight, caused by a fungus-like organism that loves the damp and humid conditions that often occur during the growing season in Europe.

The speed with which this infection takes hold and the devastating impacts on the crop make it the number one threat to six million tonnes of potatoes produced in the UK each year.

Farmers have to be continuously on their guard and need to spray up to 15 times a season to protect against the disease.

As part of an EU-wide investigation into the potential for biotechnology to protect crops, scientists at the John Innes Centre and the Sainsbury Laboratory began a trial with blight-resistant potatoes in 2010.

Image copyright John Innes Centre Image caption The GM potato trials have been running for three years

The researchers added a gene to Desiree potatoes, from a wild South American relative, that helps the plant turn on its natural defences to fight off blight.

The scientists involved say that the use of techniques to add extra genes was crucial in developing a plant resistant to the blight.

"Breeding from wild relatives is laborious and slow, and by the time a gene is successfully introduced into a cultivated variety the late blight pathogen may already have evolved the ability to overcome it," said Prof Jonathan Jones, of the Sainsbury Laboratory, the lead author of the research paper.

"And I think it is better to control disease with genetics than with chemistry."

In 2012, the third year of the trial, all the non-GM potatoes became infected with late blight by August while the modified vegetables remained fully resistant to the end of the experiment.

Image copyright SPL Image caption Blight is a difficult and expensive pathogen to control

There was also a difference in yield, with the GM variety producing double the amount of tubers.

The scientists say that since the potatoes are grown from tubers rather than seeds, they are sterile and the issue of GM pollen escaping into the wild does not arise.

One area the scientists cannot comment on is the taste, as they were barred from eating the GM variety. However, they do not believe there is any mechanism by which the new genes can impact the flavour.

As late blight is a highly adaptive organism, the scientists at the Sainsbury Laboratory are eager to find more resistance genes and add them into the plant in a "stack".

This would make the chances of late blight overwhelming these potatoes very low. However, it might make the GM variety more expensive to plant.

"The balance will be in favour of the farmer," said Prof Jones.

"Yes, they may pay more for the seed but they will spend an awful lot less on fungicide."

GM spuds squashed GM giant Monsanto attained approval for a NewLeaf GM potato in 1995. This variety was designed to protect against the Colorado potato beetle. It was initially welcomed by growers, but the high costs and the development of more effective pesticides against the beetle brought the decline of the NewLeaf, and it was discontinued in 2001.

In 2010 BASF was given approval by the EU to grow a GM potato called Amflora. This was designed to produce large amounts of starch for industrial use. In 2012 BASF decided to stop growing these potatoes in Europe owing to widespread resistance to the technology.

The scientists believe the big challenge will be in getting regulatory approval for the new variety in Europe. The researchers have licensed the technology to an American company, Simplot, which wants to grow them in the US.

"I think it is unfortunate that American farmers are going to benefit from the fruits of European taxpayers' funded work way before Europeans," said Prof Jones.

"This kind of product will likely be on the US market within a couple of years and if we are lucky within eight to 10 years in Europe."

Critics of GM crops said that no matter how big the scale of the environmental benefits, they believe that consumers will not be interested.

"Is anyone really going to grow, sell or buy genetically modified potatoes?" said Liz O'Neil, director of GM Freeze.

"The law says that they will have to be labelled GM. Experience shows that the UK doesn't want GM in its shopping basket, and British farmers are far too smart to grow something they can't sell."

Regulatory hurdles

Other researchers welcomed the development but were equally negative about the chances of these new potatoes being grown in the UK.

"Late blight of potatoes is a difficult disease to control, and using genes from distant relatives is a valuable tool," said Prof Chris Pollock, of Aberystwyth University.

"Unfortunately, the problems in the current European regulatory process, which is expensive and extremely slow, means that this advance by UK scientists is far more likely to help farmers in other countries."

Only 600 of the GM potato plants have been grown, but the scientists have had to spend £40,000 to protect them over the three years of the trial.

Follow Matt on Twitter @mattmcgrathbbc.