WGRF RESEARCH UPDATE Western Grains Research Foundation (WGRF) is a farmer-funded and -directed non-profit organization investing primarily in wheat and barley variety development to the benefit of western Canadian producers. Through investments of over $57 million, WGRF has assisted in the development and release of more than 100 new wheat and barley varieties over the past decade and a half, many of which are today seeded to large portions of the cropland in Western Canada. WGRF also invests in research on other western Canadian crops through the Endowment Fund. In fact, since 1981 the WGRF Endowment Fund has supported a wealth of innovation across Western Canada, providing over $26 million in funding for over 230 diverse research projects.
Building better blackleg resistance BY CLARE STANFIELD
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f you’ve been perusing the 2014 seed guides for a new canola variety to try out next year, chances are you’re not paying much attention to the “blackleg resistance” column. The fact is that just about every new canola variety released these days carries an R rating for blackleg resistance, and that’s working for us… for now. “Blackleg has been quite effectively controlled with resistant cultivars and crop rotations for many years,” says Gary Peng, research scientist with Agriculture and Agri-Food Canada in Saskatoon. “But now there’s a change; the pathogen is adapting and our rotational practice is being shortened.” The reality is that farmers and researchers alike have been seeing increased cases of blackleg resistance breaking down. In 2012, Peng says, many fields in Western Canada planted to R- or MR-rated canola varieties were found to have severe blackleg infestation. The question he’s trying to answer is: what’s happening? As Peng explains, the relationship between the blackleg pathogen, Leptosphaeria maculans, and the mechanisms of resistance are not well understood. “I think this is the key,” he says. “There is debate about which is the best strategy to use in Western Canada: specific resistance or quantitative resistance, and which one gives the strongest and most durable defence.” To unpack that a bit, specific resistance (SR), or majorgene resistance, is when a known blackleg resistance gene is matched to a specific race of the L. maculans pathogen. Quantitative resistance (QR), or adult plant resistance, is more of a scattergun approach where blackleg-resistant genes of unknown specificity are bred into a cultivar that tends to be effective against a wide range of pathogen races. “We know of 15 races so far, and there are 15 major SR genes to match them,” says Peng. Interestingly, most of the known SR genes have not been used in Canada. “It looks like we may have some quantitative resistance here, but we don’t really know how they work under varying pathogen race and environmental conditions.” It is a hugely complicated situation that even researchers are still grappling with. Here’s a quick snapshot (see if you can keep up): of the known SR genes, Rlm1 and LepR2 are unlikely to be effective anywhere on the Prairies based on the pathogen race composition, says Peng. Rlm2 and Rlm3 are not effective in southern Manitoba, which seems to be a blackleg hot spot in recent years, while Rlm4 does appear to be useful there. Rlm3 still has value in Saskatchewan and some parts of Alberta, while LepR3 seems to be moderately effective just about everywhere. Complicated? Yes. But that’s what Peng and his team are trying to figure out. “At a research level, we really need to understand how things work so we can provide the industry with specific information,” he says. “We want to get a picture of the dynamics at work here.” 22 CROPS GUIDE
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Sorting the puzzle pieces Peng, along with colleagues from private and public institutions across Western Canada, has launched a four-year research project, funded in part by the Western Grains Research Foundation (WGRF), to figure out what’s happening on the Prairies when it comes to blackleg incidence, pathogen adaptation and disease management. “The research has three objectives,” he says. “The first is to monitor the change in the pathogen population, the second is to understand why R-rated canola cultivars are losing resistance and aren’t working anymore in specific cases, and third is to develop some tools to understand the relationship between the host resistance and the pathogen population.” The research is timely: the 2012 spike in blackleg infection, especially in R-rated cultivars, suggests that virulent races of the pathogen are present and likely accumulating in fields, and our tight canola rotations are not helping. The goal is to provide information for better ways to breed more robust blackleg resistance into canola varieties, and to help farmers manage their own resistance strategies with more accuracy. The research focuses on gathering information about blackleg races and their populations across Western Canada. Peng began planting “trap fields” of Westar (which carries no resistance gene to blackleg) last year to understand the occurrence and distribution of specific races of blackleg. Isolates will be taken from these fields and tested for aggressiveness on canola lines carrying different R genes. Along with the trap fields, commercial canola fields that are seeded to R or MR cultivars and that experienced severe blackleg infestation, will also be sampled and tested to detect highly virulent races — if they are present, that is. “In the first year, we’ll have a benchmark of race populations, and then we’ll track them for several years, particularly in infested fields,” says Peng. He wants to know what the race composition is in those fields, and which races in particular are capable of overcoming the resistance genes in the cultivars, and how the crop rotation and residue management have influenced the disease situation. That knowledge, he says, could eventually help producers select appropriate canola varieties for specific field conditions and allow them to more proactively manage for the disease. It all sounds very good, but Peng urges caution. “We need to be really careful to not push too fast into this,” he says, explaining that there are many pieces to this puzzle and no one knows quite how they fit yet. “We need to learn from our successes in the past,” he says. “Learn why things have been working well in Western Canada and why other things have not.” Our short growing season, compared to Europe and Australia, does have a bearing, as does our short
NOVEMBER 2013
WGRF