Damage inflicted by insects costs the Canadian agricultural industry billions of dollars a year. Efforts to control these destructive pests almost always involve the use of chemical insecticides which, used improperly, pose significant risk to human and environmental health. Canadian researchers are helping to show how, in many cases, genomics-based approaches can reduce and even eliminate the need for chemical control.
At the Agriculture and Agri-Food Canada (AAFC) Saskatoon Research and Development Centre, for example, researchers have recorded an important contribution to ongoing efforts to develop crop varieties that are resistant to the wheat midge—a major pest of wheat in western Canada—and the swede midge, a serious problem for canola growers in eastern Canada.
A complicated relationship
Healthy wheat kernels (top row) and kernels attacked by wheat midge larvae. Two of the orange-coloured larvae are visible on the middle kernel in the bottom row. (photo: AAFC)
In the case of the wheat midge, after its eggs hatch, the midge larvae feed on the developing wheat kernel inside the seed head, reducing yield and lowering the grade of the wheat. While that sounds straightforward, as AAFC Research Scientist Dr. Martin Erlandson explains, the interaction between the insect and its host plant is actually much more complex.
"For the wheat midge, for example, there are proteins in the saliva of the larvae that will trigger a defensive reaction in the plant, and destroy the larvae," says Dr. Erlandson. "But there are also proteins in its saliva that allow the larvae to escape notice by the plant."
Together, Dr. Erlandson and his colleagues in Saskatoon—Dr. Dwayne Hegedus, Dr. Boyd Mori and Dr. Tyler Wist—have, as well as identifying several proteins that warrant further study.
Resistance could be futile
The detailed information on the wheat and swede midge genomes compiled by the AAFC team—funded through the Government of Canada's Genomics Research and Development Initiative (GRDI)—marks an important step toward informing future efforts to breed varieties with built-in resistance to the midges.
There are midge-resistant wheat varieties available now—developed by researchers at AAFC—but how long those varieties remain resistant is a concern. "The resistance in these varieties is based on a single gene," says Dr. Hegedus. "Given insects' amazing ability to adapt and evolve, it's likely only a matter of time before the wheat midge is able to overcome that one resistance gene, which would leave chemicals as the only effective way to control the midge."
Next steps
Dr. Mori—now an assistant professor at the University of Alberta—says the hope is that the "effector proteins" identified during the research will enable the development of a screening process that could lead to the identification of additional genes that would counteract these proteins. Breeders could then select for these genes in order to develop crop varieties with broader resistance to these insect pests.
Bang for the buck
Dr. Erlandson readily admits that the results of the midge project may not strike anyone outside the scientific community as especially dramatic, but are nonetheless one of the keys to developing new ways to control these pests without at the same time putting the health of humans or the environment at risk. "In dollar terms, this was a relatively small project for the GRDI," says Dr. Erlandson, "But it's the kind of basic research that's essential to progress that might not happen without the GRDI."