b'The 2019 data could help to shed some light on the cause oftreated with a fungicide to prevent any seed-borne issues with the hot spots.blackleg, he adds.Since a significant part of the province had lots and lots ofThe third key BMP is using blackleg-resistant varieties. precipitation and another pretty significant area had almost noIn Canada, all commercially available varieties are rated as rain, that will help us to sort out what the biggest driver is ofresistant or moderately resistant to blackleg. We are all doing these hot spots: is it the weather, or is it something else like thethis BMP already, says Cornelsen. The next level is stewarding crop rotation history or new blackleg races? After we do thisthe varieties better.analysis for a number of years in a row, we should be able to say with some certainty what is going on. Rotate Resistance Genes In addition to the big three BMPs, one of the secondary Three Key BMPs for Managing Blackleg practices on the CCCs blackleg BMP list is rotation of resistance Our top three best management practices for blackleggenetics. really come down to some of the basics for effective diseaseBlackleg resistance relies on two types of resistance: major management, says Cornelsen. gene resistance, which is very effective, but specific to particular Scouting is No.1. Monitoring is key to knowing if you have anblackleg races; and quantitative resistance, which involves issue with your resistant variety. multiple genes that each contribute a small amount to the plants She recommends rating the blackleg levels in your canolaoverall ability to resist the disease at stem cankering. fields each year, especially if you are using a short rotation andIn major gene resistance, the resistance gene in the plant if you think you may have a blackleg issue in some fields.has to match up with the corresponding avirulent gene in The best time for blackleg scouting to help make decisions forthe pathogen. For example, the resistance gene Rlm2 is only future years is at 60 per cent seed colour change, right aroundeffective against races with the avirulence gene Avrlm2.when you would typically swath the crop, says Cornelsen. Since the 1990s, resistant canola varieties with the same one You go into the field, pull up the plants, cut through the topor two major genes have been widely used on the Prairies. That of the root, and rate your plants on that 0 to 5 scale, with 0 beinghas put selection pressure on the pathogen to shift toward other a clean, healthy plant that has no sign of black tissue in theraces. Research by Gary Peng at Agriculture and Agri-Food cross section, and 5 is showing complete internal blackening.Canada in Saskatoon and others shows some Avrlm genes have Sampling instructions and the rating chart are available on thebecome less common and others have become more common CCC website. over the past couple of decades in Western Canada. You can use this severity rating to determine how much yieldEach year, as Hardings group assesses blackleg severity in you have potentially lost due to blackleg, if you were above orthe stems collected in the Alberta survey, whenever they see a below the provincial average [for the disease], and whether thestem with blackleg symptoms, they cut off a one-inch piece and disease level has been increasing over time in that field, she says.send it to Peng. Peng is currently monitoring the blackleg races That information helps you to make decisions the next timein Western Canada. His group isolates the blackleg fungus from you grow canola in that field. If the disease levels are rising,the samples and determines which avirulence genes are present. then maybe you need a varietal change, or maybe the disease isHarding also passes along the hot spot analysis from the Alberta so severe you need to think about extending your crop rotationsurvey in case that helps hone in on some areas that might be a on that particular field. concern for development of new blackleg races.Crop rotation is the second of the CCCs top three bestPengs research also suggests many canola cultivars probably management practices (BMPs).have both major gene and quantitative resistance. Even if Blackleg is very easily managed with an extended rotation,the pathogens population shifts to overcome a race-specific Cornelsen emphasizes. If you can move to growing canolamajor gene, most cultivars have non-race-specific quantitative once out of three years, you allow the old residue which housesresistance that slows the pathogens spread in the plant and the pathogen to die down in the field naturally. That willreduces the diseases impacts on yields.minimize the risk of the field having severe blackleg.Canada now has a voluntary labelling system that identifies When blackleg showed up as a real force to be reckoned withthe major resistance genes in canola cultivars. At present, in Alberta back in the 1970s and 1980s, it was managed withDeKalb, Canterra Seeds, Brett Young and Cargill are using this crop rotation. The one-in-four rotation with canola really camenew labelling system. about because of blacklegthe fungus does not survive veryThe old recommendation was just to switch your variety [if long in the soil unless it has host tissue, says Harding. Theyou noticed increasing problems with blackleg in a field]. You lower part of the canola stem persists the longest; it is kind of acould have unknowingly switched to a variety that would woody tissue that survives for two or three years. But once thatactually be worse for that field, explains Cornelsen. Now that breaks down, there is nothing left for the blackleg fungus toweve got more information, rotation of resistance genes has survive on, so it dies. become a new best management practice.The blackleg fungus can also be seed-borne, but close to 100Growers and agronomists can submit canola stubble samples per cent of the canola seed purchased has been cleaned andto a diagnostic lab to have blackleg races identified. The 24seed.ab.ca'