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Innovative science brightens outlook for Fusarium resistance

While Prairie wheat farmers continue their uphill battle with Fusarium Head Blight (FHB) in the field, Agriculture and Agri-Food Canada (AAFC) researchers are targeting resistance at the cellular level that may represent a key long-term solution to this costly cereal disease.

Dr. François Eudes, a cereal biotechnologist, leads an innovative study at AAFC's Lethbridge Research Centre to identify sources of resistance to deoxynivalenol (DON) and other mycotoxins that are produced by Fusarium graminearum, the fungal pathogen that causes FHB.

"The mycotoxins produced by Fusarium make contaminated grain unacceptable for feed or food," explains Eudes. "By targeting resistance to these mycotoxins, we hope to select material that has a lower risk of mycotoxin accumulation. That could mean reduced susceptibility to Fusarium spread."

In wheat, breeding programs in North America have focused mainly on one source of FHB-resistant germplasm -- Sumai 3 from China. But because this resistance is controlled by several genes and the resistance mechanism is not well understood, researchers have had difficulty transferring it into wheat lines that meet the agronomic and market standards of Canadian wheat. Only one resistant cultivar derived from Sumai 3, Alsen, has recently been registered in Canada and the U.S. Eudes' study -- currently halfway through its three-year workplan -- takes a different path toward selecting new sources of resistance.

The process involves working with microspores -- the male sexual cells of dust-like plant pollen -- in a simple petri dish. Using tissue culture techniques, researchers trigger the development of these cells into plant embryos. During this "embryogenesis" stage, they add a mix of FHB mycotoxins to the culture medium.

"The microspores that successfully develop into embryos and regenerate into plants will be those that are the most resistant progeny to the mycotoxins," says Eudes. "Therefore we will have selected genetics that either detoxify the mycotoxins or have an ability to tolerate them. We can then breed these genetics into future wheat varieties."

The two types of mycotoxin resistance Eudes is targeting are known, respectively, as type III and type IV FHB resistance. It is believed that Sumai 3 features a combination of two different types of resistance, related not to the mycotoxins but to the fungal pathogen itself -- protection against both initial infection (type I) and spread (type II). However, there is great uncertainty surrounding the overall nature of FHB resistance in wheat germplasm. If the method used by Eudes and colleagues is proven effective, it may provide a tool to help researchers get a clearer idea of the FHB resistance in other types of wheat.

"One of our theories, supported by recent work by ourselves and U.S. colleagues, is that a level of type II resistance may be present in most common wheat, while a large variability exists for types I, III, and IV," says Eudes. "It's also possible that what many believe is type II resistance is actually a combination of resistance that includes types III and IV. The problem has been finding good methods for identifying and selecting resistance sources."

As resistant genetics are identified, researchers will use another innovative technique, double haploidy regeneration, to quickly advance these genetics toward new varieties. This technique allows researchers to develop true breeding lines in just one generation rather than the roughly eight needed with traditional breeding methods. It also greatly simplifies evaluation.

"In the case of early screening for mycotoxin resistance, the double haploidy technique allows us to identify and discard the most susceptible lines at the earliest time," says Eudes. "This saves years of testing, and significantly reduces research and development costs."

The Lethbridge Research Centre's breeding programs for winter wheat, soft white spring wheat and hard white winter wheat will be the first to benefit from the project, which will also feed into Agriculture and Agri-Food Canada's wheat development efforts for prairie spring and hard red spring wheat. The project may also prove valuable as a model for similar efforts in barley and corn, two other major Canadian crops affected by Fusarium.

The study is supported in part by the Alberta Agricultural Research Institute. FHB research at Agriculture and Agri-Food Canada's Lethbridge Research Centre illustrates the government's commitment to promote innovation for growth, maintain the security of the food system and protect the health of the environment, as proposed in the new Agricultural Policy Framework. The framework aims to increase profitability for producers by giving them the tools and capabilities to respond to constantly changing consumer demands for safe food produced in an environmentally responsible way.

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