A virulent wheat fungus, previously found in East Africa and Yemen, has spread to Iran, and a UN food agency warned Wednesday that it could be heading across Central and the Indian subcontinent. The Rome-based Food and Agriculture Organization said that about 80 percent of all wheat varieties planted in Asia and Africa are susceptible to wheat stem rust - a fungus capable of destroying entire fields. Laboratory tests have confirmed the presence of the fungus in western Iran, a development which raises the alert for crops of major wheat producers like Afghanistan, India, Pakistan, Turkmenistan, Uzbekistan and Kazakhstan, the FAO said in a statement. "The detection of the wheat rust fungus in Iran is very worrisome," said Shivaji Pandey, director of the FAO's Plant Production and Protection Division. "The fungus is spreading rapidly and could seriously lower wheat production in countries at direct risk."