Late blight, caused by the organism Phytophthora infestans, remains a great worry for the modern day potato farmer.Annually UK farmers spend around £60m keeping the infection at bay with pesticides. In a bad year, losses and control measures combined can account for half the total cost of growing potatoes.In the latest of a series of field trials, conducted in 2012, the fungus was unable to break down the defences of any of the GM potatoes.Non-modified plants grown at the trial site were all infected after being denied protection from chemicals.However, no-one can say at this stage how long the GM strain will hold out against blight as it is notorious for its ability to overcome resistance.Scientists are now conducting further research aimed at identifying multiple resistance genes that will thwart future blight attacks.Lead scientist Professor Jonathan Jones, from The Sainsbury Laboratory, said: "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."With new insights into both the pathogen and its potato host, we can use GM technology to tip the evolutionary balance in favour of potatoes and against late blight."The Irish potato famine first hit in 1845 and continued in the years that followed. It is estimated that one million people died and over one million emigrated, reducing the population by a quarter. Because of late blight, potatoes are one of the crops most affected by chemical pesticides. In northern Europe, farmers typically spray a potato crop 10 to 15 times - even as many as 25 times in a bad year.CHAR(13) + CHAR(10) CHAR(13) + CHAR(10)The new research, which focused on Desiree potatoes, addressed the problem of reinforcing blight resistance while maintaining crop characteristics pleasing to producers and consumers.The aim was to produce a crop that could fight off blight without the aid of chemicals.During three years of trials, the scientists grew potatoes containing a gene from a super-resistant wild strain from South America.Normal cultivated potatoes naturally possess around 750 resistance genes, but in most varieties late blight is able to evade them.The trials, managed by The Sainsbury Laboratory, took place at the John Innes Centre plant research institute in Norwich.In 2012, the researchers took advantage of a year with ideal conditions for late blight. Instead of inoculating the plants, the scientists waited for them to be infected naturally by spores blowing on the wind.By early August, 100% of the non-GM potatoes in the study were infected. CHAR(13) + CHAR(10)In contrast, all the GM plants maintained full resistance against the pest until the end of the experiment.The GM plants also produced a much greater potato yield. Results from the trials, funded by the Biotechnology and Biological Sciences Research Council and The Gatsby Foundation, appear In the journal Philosophical Transactions of the Royal Society B.