Well, maybe not a whole lot more resistant, but definitely partially resistant, thanks to a new discovery here at CCDM.
Why is partial resistance so good? Because it’s an enormous step up from the current resistance levels in canola varieties – which pretty much have no resistance.
CCDM researchers Toby Newman, Mark Derbyshire and Lars Kamphuis recently screened a collection of 218 varieties for sclerotinia resistance.
They narrowed this down to 14 of the best varieties, and then from 14, they discovered two varieties with strong partial resistance to sclerotinia stem rot pathogens.
“We’re at the point where we can highly recommend breeders start incorporating these lines into their breeding programs as they have great potential to enhance sclerotinia stem rot resistance in commercial canola varieties,” Mark said.
“We’re hopeful that once they start incorporating this material into their programs, that in the future more resistant varieties will become available, and we’re working closely with two commercial programmes now to try and make that happen.”
Listen to the crop disease podcast where Mark and Lars talk about the discovery, along with a breeding update from AGT CEO Haydn Kuchel and management advice from DPIRD Research Scientist Ciara Beard:
Managing sclerotinia stem rot this season
DPIRD Research Scientist Ciara Beard, based in Geraldton WA and also on the Crop Disease Podcast, said sclerotinia is a very challenging disease to manage and fungicides are highly relied upon to manage the disease.
“The big problem with sclerotinia is that once it infects a crop, that paddock will have sclerotia (disease inoculant) left behind that can infect the next lot of canola or pulse crop, and so, just over time, the WA wheatbelt is becoming higher risk for sclerotinia because of the build up of the sclerotia in the soil.”
Ciara said sclerotinia was a very challenging disease to manage because a grower needs to protect their crop before the symptoms appear, and because it’s heavily reliant on weather, it’s very hard to know whether it’s going to be a season that will favour it.
She said the main management strategy was rotation and to know the risk from when a previously infected pulse or canola crop was last in the paddock.
She said the other management strategy was to know when to apply foliar fungicide.
“So the Sclerotinia CM app, which was produced by the GRDC-funded National Canola Pathology project, is a really good tool to help you make a decision on whether to apply a fungicide or not in a given season in your particular paddock,” she said.
“We recommend that every season, but particularly this season where yield potentials are down a little bit and the weather is particularly unpredictable, it’s good to have a play with that and try different scenarios before applying a fungicide that may not be needed.”
Ciara said if growers had a resistant variety available to them, there would be less need for fungicides, reducing the risk of fungicide resistance and improving overall profitability for growers too.
“I think most growers would say – yes please – to a resistant variety, that would be a great idea” she said.
Resistant varieties are really the best hope we’ve got
In the Crop Disease Podcast, CCDM’s Lars Kamphuis talks about the challenges of working with a disease that is so environmentally dependent, meaning there needs to be a similar environment for all potential varieties to be tested.
“So our team is working on trying to look at what temperature and humidity are important for the disease to express in different canola varieties, to help breeders breed sclerotinia resistance into them,” he said.
“You can imagine that also becomes a challenge for growers – when do they decide to apply a fungicide application and get that timing right?
“Because if you miss that timing of when the spores are likely to be released and land on the canola, and you still apply your fungicide, then not only have you wasted money on applying a fungicide, but you still get the crop damage and economic loss from sclerotinia.
“Sclerotinia resistant varieties are really just what’s needed by industry, and I’m glad to be part a team helping to make that happen with a great step forward with this partially resistant germplasm discovery.”
We’re all glad too, Lars.
The paper, title Association Mapping Combined with Whole Genome Sequencing Data Reveals Candidate Causal Variants for Sclerotinia Stem Rot Resistance in Brassica napus can be found here.
Or watch the video on this research!