Science is unlocking the riddle of how plants trigger disease resistance, opening the door to a new generation of 'designer' crops with powerful, built-in defense systems, says a pathologist at Agriculture and Agri-Food Canada's (AAFC) Lethbridge Research Centre.

Recent discoveries on the nature of disease resistance in plants at the molecular level have shed new light on the dynamics of pathogen virulence and host resistance, says Dr. Denis Gaudet, a specialist in molecular cereal pathology. At the same time, dramatic advances in plant genomics and other aspects of biology have given scientists new tools to apply this knowledge toward crop-protection strategies.

"A growing focus in crop development is to develop a molecular understanding of plant-defense responses and use this knowledge to design new disease resistant varieties," says Gaudet. "The potential benefits of this approach are stronger, longer-lasting crop protection, increased productivity and reduced need for pesticides."

Gaudet's perspective on the new era of crop disease resistance is the subject of a feature article in the October 2003 edition of Western Grains Research Magazine, available on the Western Grains Research Foundation (WGRF) Web site: www.westerngrains.com. Western Canadian wheat and barley growers are major investors in wheat and barley breeding research through the Wheat and Barley Check-off Funds, administered by WGRF. The Research Magazine offers "Ideas and issues for farmer research investors."

The key to the new potential in crop disease resistance lies in scientists' molecular understanding of how resistance works, says Gaudet. "For many common crop diseases, such as rusts, smuts and powdery mildew, plant resistance works by a two-step process: recognition of a threat, followed by activation of a defense response.

"Until recently, the focus in crop development has been on helping plants recognize threats, thereby activating the appropriate defense. This is currently done by inserting new resistance genes, 'R-genes,' that effectively permit the plant to recognize the pathogen. But now, with the knowledge we have today, we believe that the recognition system can be bypassed, so that the defense-response system switches on independently of a specific pathogen threat."

The result would be plants that are much less likely to become infected by a pathogen, he says. The approach would also reduce the risk of pathogen populations mutating to overcome the resistance.

"Genetic resistance is widely viewed as the most sustainable crop-protection tool, but if only one resistance source is used, even this is vulnerable to changes in the pathogen population," says Gaudet. "The new approach would allow us to trigger a battery of plant-defense responses, so pathogens are less likely to overcome any single defense."

Gaudet and colleagues are currently examining wheat genetics to identify and isolate genes involved in the plant's defense response to pathogens. "The profiles of the most efficient defense responses for individual diseases are like thumbprints. Once we understand and control the expression of the thumbprints, they can be used for disease-resistance breeding. In our pathology program, we are currently working with wheat, but the approach is directly transferable to other cereals, such as barley and corn."

Western Grains Research Foundation is funded and directed by Western crop producers, and allocates approximately $5 million annually to research through the Wheat and Barley Check-off Funds and a separate $9 million Endowment Fund.