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Researchers winning battle with tan spot in wheat

With help from farmers, researchers at the University of Manitoba are winning the long battle with tan spot in wheat, says wheat breeder Dr. Anita Brûlè-Babel.

The university researchers are transferring new sources of genetic tan spot resistance into wheat germplasm adapted to the Prairies – a crucial stepping stone toward new wheat varieties with tan spot resistance. This research is supported by producers through the Wheat Check-off Fund, administered by Western Grains Research Foundation.

Tan spot is a worldwide, residue-borne leaf-spotting disease that attacks wheat, causing typical yield losses of 3-15 percent. Under the right conditions, yield losses can reach as high as 50 percent. “The incidence of tan spot and other leaf-spotting diseases has increased with the shift to zero and minimal tillage, where crop residue on the soil acts as a medium for disease growth,” says Brûlè-Babel.

A team of University of Manitoba researchers, including Brûlè-Babel, Dr. Lakhdar Lamari and Dr. Murray Balance, have been investigating tan spot for over 15 years. Brûlè-Babel has transferred tan spot resistance genes into three Canada Western Red Spring backgrounds and hopes to have germplasm for wide release to breeding programs in one or two years. The University of Manitoba previously developed the tan spot-resistant extra strong variety, Amazon, registered in 1999.

“We have essentially laid the foundation for developing tan spot-resistant cultivars for Western Canada,” says Brûlè-Babel. This work continues as new sources of resistance and new races of the pathogen are identified.

Ongoing germplasm development work plays a vital supporting role to breeding programs, she explains. “Germplasm development work essentially makes the breeder’s job easier – if a source of resistance is not in a background adapted to the right conditions, far more effort is required to bundle it into an acceptable variety along with all the other necessary traits.”

Since the university’s breeding program focuses on winter wheat, Brûlè-Babel has also established a back-cross program where resistance genes are moved into winter wheat backgrounds. “The genes work in both spring and winter wheat. It just so happens that most of the sources of resistance have been found in spring wheat.”

Delving further into how the resistance genes are inherited and how they interact with other resistance genes, she hopes to develop molecular markers for the genes. “Having markers will allow us to track and actually pyramid multiple resistance genes into the same genetic background, strengthening the plant’s resistance.”

While Brûlè-Babel’s work continues, her colleagues continue to explore the variability of the pathogen and the molecular and biochemical interface between the host and the pathogen.

“In the meantime, farmers can control tan spot by using suitable crop rotations and fungicides. But both tactics have their economic and practical limitations,” she says. “We believe the most economical method of reducing losses to this disease is to incorporate genetic resistance into commercial cultivars of wheat.”

This effort is helping keep researchers one step ahead of the pathogen. “We want to ensure we have the materials that are ready and can be moved quickly into the Prairie farmer’s hands,” she adds.

The Wheat Check-off Fund allocates approximately $3 million annually toward wheat variety development research.

WGRF information at www.westerngrains.com

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