ARS: Nursery is new tool in fight against Ug99 wheat stem rust

The first Winter Wheat Stem Rust Resistance Nursery, a key tool in the fight against the rust strain Ug99, has been established by the Agricultural Research Service (ARS) and international cooperators.

The nursery, established by ARS and the International Maize and Wheat Improvement Center (CIMMYT), is located in Ankara, Turkey, where CIMMYT coordinates its global winter wheat breeding program. It is the first of its kind for winter wheats, and is a joint effort to distribute 100 lines that have been identified by international scientists as having resistance to the deadly Ug99 stem rust and its descendants.

Thirty of the 100 lines in the nursery were developed by ARS scientists and contain resistance to stem rust races in Kenya and the United States. The lines developed by ARS focus on the use of four or five resistance genes that have been incorporated into various combinations in winter wheat lines.

According to David Marshall, research leader of the ARS Plant Science Research Unit in Raleigh, N.C., and coordinator of the wheat screening conducted in Kenya, multiple genes for resistance will slow the pathogens ability to readily overcome the new wheat varieties that breeders develop. The amount of time these genes can remain effective is key to maintaining resistance to stem rust in the United States.

Winter wheat lines in the nursery are being distributed by CIMMYT to wheat breeders and geneticists in 34 countries, including those that have been hit hardest by the disease.

Ug99, Puccinia graminis f. sp. tritici, is the most virulent race of stem rust fungus yet to emerge. First discovered in Uganda in 1999, the fungus has spread across Africa, Asia and the Middle East. Ug99 has been able to overcome most of the stem-rust-resistant wheat varieties developed during the past several decades. While other rusts only partially affect crop yields, Ug99 can wipe out entire wheat fields, resulting in 100-percent crop loss.