The Agricultural Research Service of the US Department of Agriculture said it has identified a number of stem rust-resistant wheat varieties and was retesting them to verify their resistance.

USDA scientists at the ARS Small Grains and Potato Germplasm Research Unit in Aberdeen, Idaho, US, screened more than 3,000 wheat landraces from the National Small Grains Collection against new races of the stem rust pathogen found in Kenyan wheat fields. Landraces with confirmed resistance were crossed with susceptible wheat to determine the genetic basis of the resistance.

The researchers' goal was to find new genes for resistance to Ug99, a rust strain that has the capacity to overcome many of the resistant genes used in the past 50 years, the USDA said. The work will help African growers now and will help suppress disease and reduce damage in developing countries, as well as prepare for the potential arrival of Ug99 in the US.

Stem rust occurs wherever wheat is grown, the USDA said, destroying individual fields and resulting in losses from 50% to 70% over a large area.