Refuge sought for West’s midge-tolerant SWS wheats

Soft white spring wheat. (

Refuge seed and other stewardship measures will be needed for the “majority” of soft white spring (SWS) wheat varieties grown on the Prairies, to protect the midge-tolerant trait many of them have now been found to have.

That’s the assessment of seed marketing agency SeCan, which sells at least three SWS varieties now found to have the midge-tolerant Sm1 trait.

According to SeCan, the research to find genetic markers linked to Sm1 since the launch of Midge Tolerant Wheats (MTWs) has now led to the discovery of Sm1 in SWS wheats.

Sm1, a naturally occurring trait first seen in U.S. soft red winter wheat, was crossed into red spring wheats for the benefit of Prairie producers, starting with MTW varieties such as AC Unity and AC Goodeve released in 2010.

Seven official MTW varieties are expected to be released this year alone, bringing the number available in the West to 19.

The Sm1 trait, SeCan said, “was not intentionally crossed” into SWS wheats, but was “part of the background” of many SWS varieties.

The finding, made during genetic marker research at the University of Saskatchewan’s Crop Development Centre, means the affected SWS varieties “will require stewardship,” SeCan said Wednesday.

Affected SeCan SWS wheats include AAC Indus and AC Sadash and the Canada Western Special Purpose (CWSP) variety AAC Awesome. The new genetic marker has also turned up Sm1 in another SeCan variety, AAC Paramount, which awaits field confirmation, the company said.

SeCan said Wednesday it now plans to add refuge seed to all future seed stocks released to SeCan members of AAC Awesome, AAC Indus, AC Sadash and, pending confirmation, AAC Paramount.

“Refuge” seed is a percentage — in this case, 10 per cent — of a susceptible seed variety interspersed into varietal seed with a desired tolerance trait. Allowing target pests to feed on refuge prevents the pests from developing resistance to the desired trait and helps extend the trait’s useful life.

Remediation is expected to be difficult for AC Sadash, which today makes up over half of total SWS acres, SeCan said.

Rather than move to deregister Sadash, SeCan said it plans to work with its members and the industry to add refuge to all seed stocks available “as soon as realistically possible.”

It’s “in the best interests of the industry that AC Sadash remain available,” SeCan said, hoping growers will do “what is right” to protect the Sm1 trait.

The fact that Prairie producers for years have been growing SWS wheats without a refuge already puts the Sm1 trait at risk, SeCan said.

Traditionally, SWS wheat acres on the Prairies have been seeded under irrigation in southern Alberta, an area that “typically has little to no midge pressure.”

SWS wheats, with their high-starch, low-protein profile, have also traditionally been destined for milling, for end-users in the pastry sector.

However, SeCan said, in the past seven or eight years, “we have seen growth in soft white acres into non-traditional areas — to supply the feed and ethanol market.”

Harpinder Randhawa, a wheat breeder with Agriculture and Agri-Food Canada, recently noted in a Country Guide article that 10-20 per cent of SWS wheat now goes to traditional milling, while the rest goes to industrial uses such as ethanol, silage and malt.

Thus, according to Statistics Canada, Saskatchewan last year outseeded Alberta in SWS area for the first time ever, putting in 420,000 acres compared to Alberta’s 210,000.

With that expanded area in mind, “we need to act as quickly as possible to put a stewardship plan in place for the benefit of all wheat producers,” not just SWS growers, SeCan said Wednesday.

When midge larvae feed on wheat seed with the Sm1 trait, the gene causes the level of phenolic compounds — naturally-occurring organic acids in wheat kernels — to elevate more rapidly than in wheats without Sm1, in turn causing the larvae to stop feeding and starve to death.

Sm1, however, is a single-gene resistance trait, which according to the MTW Stewardship Team “has a history of becoming ineffective over time as insect populations change.” — Network

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