ROME — A multinational effort supported by the International Atomic Energy Agency (I.A.E.A.) and the United Nation’s Food and Agriculture Organization (F.A.O.) marked a key milestone recently when a Kenyan university debuted two new varieties of disease-resistant wheat to the nation's farmers, the F.A.O. said on Sept. 6.

Thousands of Kenyan farmers have visited Eldoret University in western Kenya for a two-day agriculture fair highlighting the latest farming technologies.

Supporting the development of the new varieties were the I.A.E.A.’s Technical Cooperation Department and the Joint F.A.O./I.A.E.A. Program of Nuclear Techniques in Food and Agriculture. The groups manage an interregional technical cooperation project to develop varieties of wheat that are resistant to a devastating type of fungus, causing a disease known as wheat stem rust.

Wheat stem rust was under control for over 30 years, but a resurgence of the disease was discovered in 1999 in Uganda that swiftly spread to neighboring Kenya.

The wheat stem rust, caused by the strain of the fungus known as Ug99 named after its place and year of origin, has since spread to Iran, Yemen and South Africa and threatens crops as far away as India as spores are carried by wind. Parasitic rusts threaten global wheat production, reducing plant growth and crop yields.

The disease may destroy up to 70% to 100% of the yield of wheat crop if not prevented.

“Improving food security in developing countries through the use of nuclear techniques is an important priority of the I.A.E.A.,” said Yukiya Amano, director-general of the I.A.E.A. “I am pleased that we have been able to make an important contribution to fighting wheat stem rust.”

Jose-Graziano da Silva, director-general of the F.A.O., added, “Wheat rusts, particularly the Ug99 strain, are a major threat to food security because rust epidemics can result in devastating yield losses. This international project involving affected countries, plant scientists and breeders and international organizations is a major breakthrough. It clearly shows the benefits of F.A.O./I.A.E.A. collaboration and that working together we can overcome the challenges we face.”

The rust-resistant wheat varieties were developed with the support of an I.A.E.A. technical cooperation project, Responding to the Transboundary Threat of Wheat Black Stem Rust (Ug99), which involved more than 20 nations and international organizations.

The varieties were developed using a nuclear technique for crop improvement known as mutation breeding. By exposing seeds, or plant tissue, to radiation, scientists accelerate the natural process of mutation, and then breeders are able to select and develop new varieties.

In 2009, Miriam Kinyua, a Kenyan plant breeder, sent 10 kilograms of five varieties of wheat seed to the F.A.O./I.A.E.A. laboratories in Seibersdorf, south of Vienna, where they were irradiated for mutation breeding.

The seeds were returned to Kenya where they were planted in a hot spot for the disease for screening and selection. Kinyua and her colleagues at the University of Eldoret’s Biotechnology Department identified eight lines resistant to Ug99. Four of the lines were submitted to Kenyan national performance trials, and two were officially approved as varieties by the national committee of the Ministry of Agriculture.

About 6 tonnes of seeds of the new varieties will be made available this month for the next planting season in Kenya.