New wheat varieties showing resistance to Ug99

In a study released at the Borlaug Global Rust Initiative 2009 Technical Workshop in Mexico, researchers have described a breakthrough in their efforts to develop varieties of wheat that are not only resistant to plant rust fungus Ug99, but also produce more grain than today’s most popular varieties.

The scientists, from Mexico's CIMMYT (International Maize and Wheat Improvement Center), Syria-based International Center for Agricultural Research in the Dry Areas (ICARDA), and the Kenya Agricultural Research Institute (KARI), have produced new types of high-yield wheat that contain 'multiple minor genes' that have resistance to Ug99.

Ravi Singh, a CIMMYT wheat geneticist and pathologist and lead author of the study, said high-yielding, Ug99-resistant spring wheat varieties are rapidly emerging through an intensive international shuttle breeding program. Breeding materials under development in CIMMYT’s test fields in Ciudad Obregón and Toluca — and at ICARDA fields in Aleppo, Syria — are sent to Kenya and Ethiopia, where they are exposed to Ug99 in real-world conditions.

They are then sent back to Mexico or Syria for further refinement and then back to Kenya and Ethiopia for more exposure.

Though the multiple minor genes may not provide the same level of protection as that provided by one or two major genes, it is high enough to be effective and the researchers believe that the larger array of genetic barriers could provide long-term protection against future stem rust mutations.

“We believe that this approach of endowing a plant with many minor resistance genes in combination can provide resistance comparable to the best single major resistance gene, giving us the potential to end this dangerous arms race against wheat stem rust,” Singh said.