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New midge-tolerant wheat varieties

Western Canadian farmers have had access to midge-tolerant wheat varieties since 2010, and more are slated for release in 2013

In 2006, Prairie wheat farmers lost about $40 million to wheat midge damage that dropped grades and yields. But since 2010, midge-tolerant varieties have been on the market in Western Canada.

Midge-tolerant wheat varieties were developed by wheat breeders with Agriculture and Agri-Food Canada and the Crop Development Centre. Each variety contains the SM1 gene, a naturally occurring gene that triggers the plant to produce phenolic acid when attacked.

“So as soon as the midge bite the kernels that have SM1 gene, they’re kind of turned off by it. And they start looking elsewhere. And they’re not very mobile, so then they end up starving to death,” says Mike Espeseth, communications manager with the Western Grains Research Foundation.

New midge-tolerant varieties for 2013

AC Vesper VB is a midge-tolerant Canadian Western Red Spring slated for commercial release in spring 2013. It’s a good fit for anyone who has been growing other wheat midge-tolerant varieties, says Todd Hyra, Western Canadian business manager with SeCan.

“It offers a yield bump over Unity, and that’s one of its biggest strengths. It probably has a little bit stronger straw than Unity.”

However, AC Unity VB is a unique variety because it’s tolerant to wheat midge and has a partially solid straw.

“And so if any individuals are faced with the combination of pests, being sawfly and midge, then Unity is really the only product that offers protection to both of those.”

Hyra says he tells farmers that spraying for midge defeats the purpose of using a midge-tolerant variety.

“Under extreme, extreme pressure, because the midge have to take a bite of the kernel, there will be some downgrading. So you’ll see some damage in the sample. But it won’t be near the level that you would expect to see in a sample that has no tolerance.”

Canterra Seeds released AC Conquer VB in limited quantities in 2012. Canterra is releasing AC Conquer VB in larger quantities for 2013. Brent Derkatch, Canterra’s director of operations and business development, says he expects supplies will be tight soon.

“Wherever farmers have historically grown CPS wheat varieties, I think this variety is a very good fit. And I think that it would also expand beyond where midge is present as well,” says Derkatch.

AC Conquer VB is the only midge-tolerant Canadian Prairie Spring wheat. Derkatch says it’s a great choice for farmers purchasing certified seed of a new variety. It offers a 25 to 30 per cent yield bump over a standard CWRS variety, he says.

But farmers in areas with high fusarium head blight levels may want to be cautious about growing AC Conquer VB.

“This variety does have an improved fusarium tolerance, relative to some other CPS wheat varieties. But the CPS class as a whole doesn’t have as strong a fusarium tolerance relative to some of the CWRS varieties that have been developed more recently.”

Derkatch says there is a renewed interest in CPS wheat from all parts of the value chain, and AC Conquer VB will be a good fit.

“We are looking to do some more work to understand the more quality attributes of the variety to see what other markets the variety may fit into.”

There are currently several other midge-tolerant varietal blends, including AC Unity, AC Goodeve, AC Glencross, AC Fieldstar, AC Shaw and CDC Utmost. For more information, visit

Stewardship agreements to protect technology

Because wheat midge tolerance is based on just one gene, wheat midge populations can develop resistance, rendering the technology ineffective.

Virulent midge can survive on midge-tolerant wheat. Very low levels of virulent midge already exist. But virulence is a recessive trait, so offspring of virulent and non-virulent midge can’t eat the midge-tolerant wheat.

To prevent virulent wheat midge populations from building up, each midge-tolerant wheat variety is sold as a varietal blend. The blends are comprised of 90 per cent midge-tolerant wheat and 10 per cent susceptible wheat. This refuge system gives the non-virulent midge something to eat, keeping a lid on virulent midge numbers. Without a refuge system, midge tolerance could break down within 10 years.

Farmers who purchase a midge-tolerant blend must sign a stewardship agreement. The agreement only allows farmers to save seed for one generation past certified so that the blend retains the right ratio of susceptible and non-susceptible varieties.

If the susceptible variety level declines, it would drive the midge population to convert to virulence on the SM1 gene and build up, eventually breaking down the technology, says Espeseth.

“If there’s more refuge — so say if the refuge was 20 or 30 per cent — then that means there’s more of the susceptible variety in there. And if heavy midge damage came, farmers would be disappointed with the level of midge (tolerance) relative to the 90-10 varietal blend,” says Espeseth.

All midge-tolerant wheat purchases are recorded in a database. Farmers may be audited to make sure they are following the stewardship agreement.

“We use the database to find anomalies in purchase patterns. If somebody’s coming back and buying midge-tolerant wheat every two years, there may be some random audits there, but they’re probably compliant. Maybe some have exited farming, or the variety didn’t work for them, and that’s fine, but that will be the follow up discussion that we’ll have,” says Hyra.

Midge-tolerant varieties are the culmination of years of research, supported by funding from check-off dollars, variety distributors, Agriculture and Agri-Food Canada and the Crop Development Centre. Espeseth says researchers haven’t yet identified another midge tolerance source.

“It took them 15 years to get this single gene into the wheat varieties, so it’s really important to (have) stewardship and seed management to protect this technology,” says Espeseth.

Hyra says the stewardship agreements and audits are for the industry’s long-term benefit.

“This is a technology that was developed by public breeders and released for the overall good of wheat growers in western Canada. And we get one shot at making sure it lasts for as long as we can make it last.” †

About the author

Field Editor

Lisa Guenther

Lisa Guenther is field editor for Grainews based at Livelong, Sask. You can follow her on Twitter @LtoG.



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