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Disease resistance key to new variety development

Insects, heat, hail and wind were only part of the problem. Diseases such as sclerotinia did significant damage to canola crops this growing season.

Statistics Canada’s experimental Crop Condition Assessment Program initially estimated the Western Canadian canola harvest at over 16 million metric tonnes, averaging 34.2 bushels per acre. But Stats Can’s October 4 estimate dropped the estimated canola harvest to 13.4 million metric tonnes, with an average yield of 28.2 bushels per acre.

Developing new varieties that are more disease resistant is becoming more and more important.

Sclerotinia resistance

Chris Anderson, the canola breeding lead with Monsanto Canada, says that as canola acres grow, Monsanto’s plant breeders are looking for new resistance sources and focusing on building durable resistance into plants. Anderson explains that by not relying on a single gene to give a new variety resistance, plant breeders hope to cut the risk of diseases overcoming that resistance.

Pioneer Hi-Bred released two new sclerotinia tolerant canola varieties in introductory volumes this year: D3154S and 45S54. DuPont retailers will sell D3154S, and Pioneer’s sales reps will market 45S54 in commercial volumes in 2013.

The two new varieties have had similar performance and disease resistance levels in the trials leading up to this year, says Dave Harwood, senior research manager at Pioneer Hi-Bred. Pioneer is awaiting this year’s results, but Harwood expects both varieties to shine with the high sclerotinia levels. He adds that Pioneer characterizes its sclerotinia tolerant varieties as having moderate resistance.

“It means that under moderate to low (disease) pressures a producer could not use a fungicide and (still) have protection from the disease. It means under high levels of pressure, such as the Red River Valley where they can have sclerotinia virtually every year, the combination of the trait with a crop protection product, a fungicide, is a good two-pronged approach to minimizing yield loss from sclerotinia.”

Pioneer isn’t the only company turning its attention to sclerotinia. Bayer Crop Science plans to roll out a sclerotinia tolerant InVigor hybrid in 2014.

Blaine Woycheshin, manager of Bayer’s oilseed crops, describes the new variety as “the first line of defence for growers in areas where disease pressure is not always present and the decision to spray is difficult.”

“However, under extreme sclerotinia pressures, I believe growers may still have to use integrated management systems,” which he says would include a fungicide such as Proline.

Agronomic practices still key

Yield is still Canterra Seeds’ number one priority when selecting varieties from breeding partners. Brian Cummings, sales director, says that Canterra combines yield with other desirable traits such as standability, early or late maturity, and high oil content. Clubroot and blackleg resistance are included in disease packages. But sclerotinia tolerance isn’t a priority right now.

“We would still encourage proper rotations and fungicides, particularly fungicides sprayed at the appropriate time. People are monitoring and being aware of the fact that disease is out there. And this year it was out there probably more than we’ve ever seen,” says Brian Cummings, director of sales for Canterra Seeds. He adds that while some varieties are more susceptible than others, there isn’t a shared rating for sclerotinia at this time.

None of the agricultural company representatives contacted for this interview suggested thatfarmers can avoid spraying when fields are heavily infected, even with the sclerotinia tolerant varieties currently available or set for release in the near future.

Chris Anderson of Monsanto explains there are few genetic sources of true sclerotinia resistance for plant breeders to draw on, making it challenging to develop sclerotinia tolerant varieties. Monsanto is looking at sclerotinia tolerant varieties, but Anderson is hesitant to make any claims about tolerance levels before they’ve been evaluated.

Blackleg and clubroot

Resistance to blackleg and clubroot is becoming more important as canola acres grow.

“We don’t have a product that isn’t an R (rated as resistant) to blackleg. Again, that being said, that blackleg strain continues to evolve in western Canada. As we push our rotations… that blackleg R value is going to become even more important to customers,” says Brian Cummings of Canterra.

Woycheshin says all of Bayer’s canola varieties are rated resistant to blackleg. Clubroot resistance is also a priority, and in 2012 Bayer released a new clubroot resistant variety, InVigor L135C. InVigor L135C yielded at 138 per cent of the checks in the 2010 WCC/RCC Co-op Trials.

“It’s an excellent combination of early maturity and high yield potential,” says Woycheshin.

Monsanto is looking for new sources of clubroot resistance and plans to combine multiple sources of resistance in each hybrid, to prolong resistance. Monsanto’s plant breeders also plan to stack resistance traits, such as blackleg and clubroot, in one plant, Anderson adds.

Pioneer’s Harwood calls any variety lacking blackleg resistance a deal-breaker. He thinks clubroot and sclerotinia resistant traits will become more in demand, and Pioneer plans to release more hybrids with moderate sclerotinia resistance in the near future.

Pioneer’s long-term goals go beyond moderate resistance. Harwood adds that “…somewhere around 2015 we’ll be introducing materials that both stack sclerotinia and clubroot resistance, but as well elevate that level of sclerotinia resistance to something close to fungicide replacement where even in the high pressure zones, we’ll have a level of protection that will eliminate the need for fungicides.” †

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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