Midge Tolerant Wheat
New midge tolerant wheat varieties became commercially available in the spring of 2010. Midge tolerant varieties offer large savings for Prairie wheat growers since they will reduce downgrading and yield losses caused by wheat midge.
These varieties provide wheat growers with more flexibility in crop rotations and seeding dates, and also enable a significant drop in the use of insecticides, the traditional means of dealing with wheat midge.
The midge tolerance originates from a single gene – Sm1 – that was moved into spring wheat varieties using traditional plant breeding techniques. Several spring wheat varieties have been developed by Canadian wheat breeders at Agriculture & Agri-Food Canada (AAFC) in Winnipeg and Swift Current, and the Crop Development Centre at the University of Saskatchewan. Funding for these projects comes from the Western Grains Research Foundation check-off program, AAFC, CDC and variety distributors.
How it Works
When the insect begins to feed on the seed, the Sm1 gene causes the level of phenolic compounds (naturally occurring organic acids in wheat kernels) to elevate more rapidly than in wheat kernels without the Sm1 gene. The higher levels of phenolic acids cause the midge larvae to stop feeding and the larvae starve to death.
The mechanism that triggers the production of phenolic acids does not operate if midge larvae are not feeding on the seed, and in addition, these acids are reduced to normal levels by the time wheat reaches maturity – thus not affecting the quality or food value of the harvested grain.
Single Gene Resistance
It took more than 15 years and a huge financial investment for researchers to move this single gene, Sm1, into spring wheat varieties. It is the only known gene that confers tolerance to wheat midge.
Tolerance based on a single gene has a history of becoming ineffective over a relatively short period of time as insect populations change. An interspersed refuge system -planting a blend of a midge tolerant variety with a susceptible variety - is required in order to prevent the build-up of midge that are able to attack wheat carrying the Sm1 gene. Midge that are able to attack the Sm1 gene are called “virulent”. This can extend the life of midge tolerance from as little as 10 years to 90 years or longer.
Interspersed Refuge System