Taking the guesswork out of breeding disease-resistant wheat

For plant breeders trying to develop a variety of wheat that can resist the growing threat posed by fusarium head blight, it is something of a race against time.

The disease makes wheat unfit for consumption by humans or animals and the infection is spreading to ever-larger areas of major wheat-growing countries around the world, including Canada. Fusarium head blight — FHB — is now considered the number-one problem facing Canadian wheat producers, and a serious risk to an industry that generates close to $5.4 billion in export revenues for Canada every year.

The search for immunity

Dr. Thérèse Ouellet, a research scientist at Agriculture and Agri-Food Canada (AAFC), says that since the 1980s, scientists have been able to identify a handful of varieties of wheat that shows resistance to the fungus. "Unfortunately," says Dr. Ouellet, "None of these varieties is suitable for food production — they can only be used as breeding stock, in the hope that one day, we will be able to develop a high-quality variety of wheat that is also resistant to fusarium head blight."

The difficulty is that breeding new varieties of wheat is a slow process that involves a lot of trial-and-error. Basically, a breeder cross-pollinates a variety of wheat that is resistant to the fungus with a more desirable variety, and hopes for the best. Including the field trials and other tests, it can be as long as 15 years before the breeder is able to determine whether they have succeeded in developing a variety with potential as a commercial crop, or even if the best performing plants have any value as part of further breeding efforts.

Genomics investment opens new possibilities

Since 1999, with the support of the Government of Canada's Genomics Research and Development Initiative (GRDI), researchers at AAFC have been applying the relatively new science of genomics in an effort to take some of the guesswork out of wheat breeding. In doing so, the time needed to develop and test a new variety of FHB-resistant wheat could be reduced to as little as five years. Initially led by Dr. Daryl Somers at the AAFC Cereal and Research Centre in Winnipeg, the research has expanded and is now headed up by Dr. Curt McCartney at the Winnipeg labs and by Dr. Ouellet at the Eastern Cereal and Oilseed Research Centre in Ottawa.

From the beginning, the research has focussed on identifying the 'genetic markers' of resistance to FHB — indicators pointing to specific parts of the genetic make-up of FHB-resistant varieties that enable them to fight off the disease.

It is not an easy task. The wheat genome is exceptionally complex — five times more complicated than the human genome — and it has not yet been fully sequenced. Still, Dr. Somers and his team were able to identify four specific elements of the wheat genome that appear to play a role in FHB resistance.

Better targeting of research

"What this means," says Dr. Somers, now Research Director for Applied Genomics at the Vineland Research and Innovation Centre , "Is that breeders can take a more logical approach. After two varieties have been crossed, they can look for these markers in the genetic make-up of succeeding generations of plants. If they are not there, they will know there is no point doing any further testing with those particular plants."

"With traditional breeding techniques, you end up wasting a lot of time growing and studying plants that will be susceptible to the disease," says Dr. McCartney. "With marker-assisted breeding techniques developed through research such as that led by Dr. Somers — the work on which Dr. Ouellet and I are building — you can, at an early stage, identify and discard the plants that are not likely to work, and spend more time studying the plants you are likely to want."

Dr. Ouellet's research is focused on understanding how the specific parts of the genetic make-up associated with FHB resistance works. "Knowing which genetic elements contribute to FHB resistance in the plant is a critical step," says Dr. Ouellet. "But if we can understand how those elements function — which combination of elements in the plant provides the best resistance, for example — we can bring an additional level of strategy to breeding efforts."

Attracting interest - and funding

It is a mark of their success that the research being carried by Drs. McCartney and Ouellet is no longer being funded through GRDI — because support from GRDI is no longer needed. Recognizing the potential benefits of their teams' work, several other organizations have come forward to provide funding to continue the projects. Their work will become part of a major research program aimed at developing new and better varieties of wheat led by the National Research Council of Canada, in partnership with AAFC, the province of Saskatchewan, and the University of Saskatchewan.

Dr. Ouellet and Dr. McCartney are quick to share the credit for their achievements with the many other researchers who have contributed to their projects for a number of years, as well as their collaborators in Germany, France, the U.S. and other countries. "This is one of the benefits of GRDI that is sometimes overlooked," says Dr. Ouellet. "GRDI has given Canada the capacity to contribute to advances in genomics around the world — and since we can contribute, we can also share in the advances made by others."

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