Canola growers in North America and Europe fear warm, humid weather when their crop flowers because it’s ideal for developing sclerotinia stem rot.
But muggy weather is not a big deal for farmers in China, one of the world’s largest producers of the oilseed.
Varieties there have sclerotinia resistance, the result of natural evolution in the warm, humid climate and human selection to create commercial varieties.
Dwayne Hegedus, a research scientist with Agriculture Canada in Saskatoon, is studying Chinese rapeseed, looking for the genetic source of the resistance in a project funded by producers, industry and government.
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“The Chinese have been breeding for stem rot resistance for a long time, primarily because the growing conditions there are conducive almost annually for the development of stem rot,” Hegedus said.
In Canada and Europe, where those conditions are less frequent, varieties have no resistance and the only tools to battle the disease must be applied before the disease is confirmed.
“We are now identifying markers (in Chinese canola) for resistance genes so that we can easily move them into Canadian elite lines,” he said.
“The level of resistance is really quite astonishing.”
Hegedus’ work, which addresses a disease that costs the Canadian industry about $50 million a year, will be greatly assisted by an international effort to map the canola genome.
The genome is the complete sequence of the entire DNA in the oilseed. The initiative is also mapping the location of genes on the DNA and identifying their function.
Rapidly evolving technology is speeding the effort and slashing the cost to such an extent that it is encouraging researchers to think in new ways. In the early 2000s sequencing the human genome was a multibillion-dollar international effort likened to splitting the atom. However, sequencing will soon become a low cost, routine part of plant breeding and other fields of biology and medicine.
For canola growers like Rob Pettinger of Elgin, Man., genetic advances mean desired traits such as sclerotinia resistance will come faster.
“When the weather conditions are right for the fungus growth it can be very severe,” Pettinger said.
“Anytime you could develop a plant that is resistant, it is advantageous compared to spraying fungicide.”
The nature of the disease is such that farmers can’t wait for it to develop and then spray. They must use preventive fungicide applications if the weather conditions are right.
“With the spraying, you go ahead and spray whether or not it is there because once you see it, it is too late. Either you spray everything or take your chances without it.”
Hegedus said he has worked with Lone Buchwaldt of the Plant Gene Resources Centre, a huge seed library located at Agriculture Canada’s facility in Saskatoon. Buchwaldt has tested all the Brassica napus resources at the centre for stem rot and found resistance in types grown in Asia, including Pakistan and Korea.
“Now we are looking to determine whether or not the genes that contribute to stem rot resistance are the same in all the material or if they are different,” he said.
If they are different, then two sources of genetic resistance could be put into Canadian varieties.
“That would provide for much more robust, durable resistance.”
However, even with new technology, progress toward resistant commercial varieties is measured in years, Hegedus said.
“We already have some markers for (resistant genes) and in the next two to three years we should have a really good idea as to what markers are available for all the different sources of resistance that are available and then we can begin using those in breeding programs. We are probably four to five, six years out from having material in varieties that is resistant.”
