Experts have been aware of the threat since a major epidemic swept across North America’s wheat belt in the 1950s, destroying up to 40 per cent of the crop. Since then, tens of millions of pounds have been invested in developing rust-resistant varieties of the grain. However, an outbreak in Uganda in 1999 was discovered to have been caused by a virulent mutation of the fungus. There has been alarm at the speed at which further mutations have subsequently developed and spread across continents.
Plant scientists in Britain estimate the latest developments mean that 90 per cent of all current African wheat varieties are now vulnerable to the disease.