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An international effort has yielded new wheat varieties resistant to a devastating fungus spreading from Africa towards Asia.

The research was presented at a meeting this week (17–20 March) in Ciudad Obregón, Mexico, which has attracted hundreds of crop specialists concerned with the rapid spread of Ug99 — a strain of stem rust fungus that first emerged in Uganda ten years ago.

Researchers have developed around 60 new wheat varieties containing several genes with a small resistance effect to Ug99. Although such genes might not provide as much protection as genes that cause a high level of resistance, the researchers believe they will be more efficient in the long term, as they will force the fungus to overcome a wider array of genetic barriers.

To obtain faster, more efficient results, the researchers continually exchanged breeding materials between the Mexico-based International Maize and Wheat Improvement Center (CIMMYT) and field stations in Njoro, Kenya, where Ug99 is well established.

"We sent a large number of plants to Kenya, where they were tested for their resistance in real world conditions," says Ravi Singh, a CIMMYT wheat expert and lead scientist of the study. Resistant varieties were sent back to Mexico, where other positive traits were added.

This 'shuttle breeding scheme', which took advantage of the two crop seasons per year in both Kenya and Mexico, halved the number of years required to generate and test varieties.

The resulting varieties of wheat also produce 5–10 per cent more grain than most popular varieties. "With high-yielding varieties, we expect a higher adoption rate, particularly in areas where Ug99 is not yet causing immediate problems," says Singh.

Ug99 has spread to Ethiopia, Iran, Kenya, Sudan and Yemen. Some scientists believe it is on the march toward South Asia, where farmers produce 19 per cent of the world's wheat.

Efforts are now being directed towards increasing seed stocks of the resistant varieties and to ensuring their adoption in nations at risk. The goal is to replace most wheat varieties under cultivation worldwide.

Although pleased with the information exchanged at the event, Thomas Lumpkin, director general of CIMMYT and one of the workshop's organisers, says more investment in research is needed to tackle such wheat diseases.

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