Prairie breeders explore heat-tolerance rating

Regionally specific canola varieties may eventually become reality, but breeding for specific traits may not be the answer

Many farmers, especially in Saskatchewan, are blaming hot and dry weather for disappointing canola yields.

Official numbers won’t be in for a while, but Saskatchewan Agriculture has pegged the provincial yield average at 35 bushels per acre. That’s much lower than average yields of 40 to 41 bu. per acre in recent years, based on Statistics Canada data.

Moose Jaw, for instance, recorded nearly 10 consecutive days above 30 C after the middle of August, which likely hindered pod fill and canola yields.

It’s almost impossible to predict summer weather, but given climate change and the frequency of extreme weather events, canola growers may need hybrids that are more tolerant of severe summer heat.

One option being explored is having a heat-tolerance rating on varieties, which could enable growers to choose hybrids suited for their regions.

“That is one way to manage it… having hybrids specific to certain (geographic) areas. That variety specific to a certain region is a lot more common in other crops, like corn and soybean,” said Rob Duncan, a University of Manitoba canola breeder.

There is variation for heat and drought tolerance within Brassica napus (canola), Duncan said, and major breeding programs are working on such traits.

Dale Burns, a canola breeder with Bayer CropScience Canada, said regionally specific hybrids could be a reality in the coming years.

“That’s something I think our canola industry should be trying to target … identifying some of those more regional products. If I think of our corn organization, they have a very fine-tuned system of identifying specific hybrids for specific parts of the U.S. Midwest.”

However, breeding for a single trait isn’t the best way to get there.

It’s difficult to develop crops that are heat or drought tolerant because weather is unpredictable. A company could set up test sites in a hot and arid region and then it rains for three weeks in the summer.

“The biggest issue with a lot of heat tolerance and drought tolerance (research) is consistency (in getting the conditions) that we’re trying to breed for,” Burns said. “Some years you might get it (the heat) in mid-July, the next year you might get it in the third week of August. Those would probably select for completely different hybrids, depending on the timing of that (heat) event.”

Instead, breeders should focus on an entire package of desirable traits. In other words, if you build a better canola, it will likely have more tolerance for heat and drought, Burns said.

Some of those improved traits, like more vigorous roots and additional biomass, will help canola plants tolerate periods of 30 C weather.

“Anytime you try to break plant breeding down into a single trait, it means you’re paying less attention to other traits and something will fall apart.”

That’s why breeders focus on yield stability. They want a hybrid that performs across a wide geography.

“That yield stability across a broad range of sites, that’s going to directly or indirectly select for a lot of traits all at once,” Burns said.

Canola yields might have been even lower in Saskatchewan this summer if farmers were growing varieties from a decade ago.

“What we’ve done in raising the average canola yields across the Prairies has more to do with raising the floor (yield)…. We’ve certainly raised the ceiling but we’ve raised the floor more,” Burns said.

While today’s hybrids are superior to canola from the past, growers will probably need hybrids with more heat and drought tolerance because blistering hot summers may now be the norm.

Part of the solution could be seeding more than one hybrid because certain canola varieties take longer to mature than others. That would reduce the likelihood of every acre on a farm getting heat at the wrong time.

“(Don’t) plant the whole farm to one (hybrid),” Duncan said.

“Maybe different hybrids with different maturities, to spread that risk out.”

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