Iran informed FAO that it had discovered Ug99 -- a virulent fungus strain first detected in Uganda in 1999 -- in the west of the country. The fungus spores can be carried by the wind over large distances.

"Countries east of Iran, like Afghanistan, India, Pakistan, Turkmenistan, Uzbekistan and Kazakhstan, all major wheat producers, are most threatened by the fungus and should be on high alert," FAO said.

Shivaji Pandey, director of FAO’s Plant Production and Protection Division, called the arrival of Ug99, which can destroy wheat fields, as "very worrisome".

"The fungus is spreading rapidly and could seriously lower wheat production in countries at direct risk," he said.

"Affected countries and the international community have to ensure that the spread of the disease gets under control in order to reduce the risk to countries that are already hit by high food prices."

The spread of the wheat disease comes as world wheat stocks are already at 30-year lows and prices are soaring to record highs. A researcher at Oregon State University said the US wheat crop could be hit by the fungus within the next four to five years.