Source: CIMMYT E-News, vol 3 no. 10, October 2006

Harvesting rust-resistant wheat at CIMMYT headquarters, El Batan, Mexico

CIMMYT puts stem rust resistant seeds into partners' hands for testing.

While the Global Rust Initiative (GRI) meeting in Alexandria focused on future strategy, preemptive work was well underway at CIMMYT as seeds of stem rust-resistant wheat lines were harvested and prepared for dispatch throughout the world. Ravi Singh, CIMMYT wheat scientist, explains, “This is a dynamic, ongoing process, as we constantly test and retest materials for resistance to stem rust while retaining desirable traits”.

On multiplication plots at CIMMYT’s El Batan headquarters in Mexico, workers have been harvesting wheat lines resistant to Ug99, the new, virulent strain of stem rust. These seeds are now ready to be sent to GRI partners across the area at risk. They will be grown at 30 experimental sites in countries as diverse as Ethiopia, Egypt, India and Afghanistan, and Mexico itself, to test for yield and adaptation to local conditions.

Researchers at CIMMYT and the International Center for Agricultural Research in the Dry Areas (ICARDA), together with national partners, will use these trials to decide which lines to send to countries in larger amounts. In Ethiopia, where stem rust infection is already prevalent, ten lines are currently being multiplied on a larger scale, and tests with farmers will begin next year.

The resistant lines have been selected from thousands grown and artificially infected with Ug99 at Njoro in Kenya since 2004. These have included cultivars planted across the world and advanced breeding lines from CIMMYT and many other partners. Some 8-10% showed resistance to Ug99, of which a small number with traits such as high yield potential and resistance to other diseases were selected for multiplication.

CIMMYT is not only distributing existing stem-rust-resistant wheats, but is part of efforts to breed materials that will lead to the release of new varieties. A range of sources, particularly lines that have shown Ug99 resistance in Kenya over two years’ testing, are being used to enhance the diversity of stem rust resistance in elite germplasm and valued cultivars. Singh and his team aim to create wheats with durable resistance to Ug99, by ‘pyramiding’ several minor resistance genes.

CIMMYT is also distributing the first stem rust resistance screening nursery, consisting of seeds of some 100 resistant lines. These will be tested for local performance and used in crosses by national breeding programs and other GRI partners. In response to the urgency of the stem rust threat, CIMMYT staff have worked hard to bring this release forward from 2007.

Singh’s goal is to provide farmers with cultivars that are not only resistant to Ug99, but also superior in other traits such as yield potential, grain quality and resistance to other diseases. As he says, “Except in East Africa, the advantage of stem rust resistance is not yet visible. By incorporating rust resistance into the advanced germplasm that we have available, we can provide farmers with tangible livelihood benefits, and we will see a better rate of adoption.”