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New wheat midge-tolerant varieties are top performers

Four wheat varieties (three Canada Western Red Spring and one Canada Western Extra Strong) with tolerance to wheat midge damage were supported for registration in 2007, with Certified seed quantities of AC Unity VB and AC Goodeve VB (CWRS varieties) now available for the spring 2010 planting season. But who should grow them?


February 24, 2010
By Bruce Barker

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Four wheat varieties (three Canada Western Red Spring and one Canada Western Extra Strong) with tolerance to wheat midge damage were supported for registration in 2007, with Certified seed quantities of AC Unity VB and AC Goodeve VB (CWRS varieties) now available for the spring 2010 planting season. But who should grow them?

WTCM-10-12--Unity-wheat
The new wheat midge-tolerant varieties have a good agronomic package. (Photo courtesy of SeCan Association.)


“Choosing a wheat midge-tolerant variety becomes a matter of matching expectations versus reality,” explains Alliance Seed Corporation’s general manager Dale Alderson. “It is better to set up the right expectations in the first place than have farmers choosing the varieties for reasons that are not part of the genetic offer from the variety.”

Alderson’s concern comes from the high yield performance the wheat midge varieties displayed in performance testing. The three CWRS wheat midge-tolerant varieties had yield performance at the top of their wheat class, creating the concern that farmers might choose the varieties even if they are not in an area where wheat midge is a concern. His company has marketing rights to AC Goodeve VB, and plans to focus marketing of AC Goodeve VB in areas that have, or potentially have, wheat midge issues.

Ron DePauw, the plant breeder at Agriculture and Agri-Food Canada at Swift Current, Saskatchewan, who developed AC Goodeve VB, shares those concerns, and says that the yield performance of the variety has as much to do with widespread midge activity as it does with yield genetics. However, he says there is no obvious yield penalty to the Sm1 gene that confers tolerance to midge. “I think we underestimate the amount of wheat midge damage occurring on the Prairies, at least as far as where the Co-op trials are. In my mind, I think that the yield advantage from the tolerance is typical of what is going on in many areas,” says DePauw. 

DePauw explains that when midge damage is observed in harvested samples of non-tolerant varieties, that is only the tip of the iceberg, because many midge-damaged kernels are blown out the back of the combine. As a result, it is difficult to get a realistic picture of how high yielding the tolerant varieties are without wheat midge. On the other hand, widespread wheat midge infestations, even at low levels, might justify the use of the tolerant varieties.

Having said that, the decision to use one of the wheat midge-tolerant varieties becomes a balance between other agronomic factors, and whether wheat midge might be a problem
in the area.

Good overall performance
Both AC Unity VB and AC Goodeve VB demonstrated good agronomics and yield in the Co-op trials. 

AC Goodeve VB has very high yield, protein content similar to the check, and very good lodging resistance. It is rated good for stem and leaf rust resistance, and is two days earlier maturing than AC Barrie. 

AC Unity VB is an awned variety with very high grain yield, improved leaf rust resistance and maturity equal to AC Barrie, along with very good sprouting resistance. It yielded 116 percent of AC Barrie and 106 percent of Superb across all sites in 2004 to 2006 Co-op registration trials. Similar performance is being observed in regional variety trails, especially in Saskatchewan. AC Unity VB is available through SeCan retailers.

Stephen Fox is the AAFC plant breeder who developed AC Unity VB, as well as two other wheat midge-tolerant varieties, AC Fieldstar VB and AC Shaw VB (both CWRS). Gavin Humphreys developed AC Glencross (CWES). Fox has a slightly different take on the yield performance of the tolerant varieties. “The last two years have had pretty low wheat midge levels, and with the regional variety testing, from what I’ve seen, the varieties seem to do just fine even when the midge are not around,” says Fox.

Whether the tolerant varieties might have an advantage under low midge pressure is debatable, as research is only now being conducted in this area. Given that, Fox would not hesitate to recommend the tolerant varieties wherever midge has been a concern in the past. “I’ve watched the varieties pretty closely in the trials, and there doesn’t seem to be a yield drag with the tolerance. They have pretty good yield genetics, regardless of the presence of wheat midge tolerance.”

Alderson believes that the wheat midge lines will be acceptable performing CWRS lines in non-wheat midge pressure areas, and in wheat midge pressure areas, they will perform better than most farmers’ expectations.

So how to choose?
Since 2010 will be the first time that wheat midge-tolerant varieties are commercially available, there is not a lot of history to go on when it comes to performance of the varieties.  

DePauw says a good starting point is to assess the risk of wheat midge in a particular area. He suggests speaking to the elevator manager to find out what damage was like during the last few years. Some areas have had wheat midge damage to as many as 50 percent of the grain samples being downgraded due to midge, and the tolerant varieties would be highly desirable in these areas. In areas with lower damage, the varieties still might have a good fit, because of the year-to-year fluctuations in wheat midge infestations.

Wheat midge forecast maps are also published in Alberta and Saskatchewan, and can be found on-line on their respective provincial ministry websites. These are based on fall surveys of cocoons found in the soil, and projections made based on the number of cocoons. 

DePauw advises growers in traditional wheat midge areas, like north-central Saskatchewan, into central Alberta and down to southwest Manitoba, to consider the varieties. Wheat midge cocoons can survive in the soil for three or four years, so just because the midge pressure has been lower in the last few years, does not mean the problem will not be back next year. “If you look at the Lethbridge area, where there hasn’t been any wheat midge damage, the varieties may or may not have something to offer. It depends on the total agronomic package that a grower is after. The probability of benefit from the tolerance is much lower than in an area like the Parkland and central Saskatchewan that has had historic infestations,” explains DePauw.
 
Local seed growers who have had production experience with the varieties would also be good sources of comparative information for the performance of the varieties.

Although the decision to grow a tolerant variety will ultimately revolve around a combination of agronomic and economic factors, one thing is for certain: the new tolerant varieties have pretty good all-around performance for the first ones out of the gate. Farmers in traditional wheat midge areas should consider growing the new varieties on a portion of their wheat acres to get a sense of how they perform on their own farm.