The race is on to find wheat varieties resistant to the deadly wheat rust fungus Puccinia graminis as it continues its march from Africa towards the major wheat-growing regions of Asia.
Scientists thought they had beaten P. graminis in the 1950s, when they developed resistant wheat varieties.
But in 1999 a new strain emerged in Uganda capable of destroying previously resistant crops.
In late 2006 the strain — dubbed Ug99 — developed a new mutation allowing it to attack even more varieties of wheat. And in January it was found to have spread to Yemen (see Deadly wheat disease 'a threat to world food security').
So far, 90 per cent of wheat varieties tested are susceptible to Ug99, including all the major types in the Middle East and West Asia, reports Erik Stokstad.
The main objective for plant breeders now is to identify resistant varieties of wheat in the regions already affected and, perhaps more crucially, those in Ug99's path.
Breeders will have to scale up seed production of resistant varieties. But it is a race against time ― Ug99 could be in Egypt before the year is out.