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Brandon Researchers On The Hunt For Root Rot Pathogens

Studies at the Brandon Research Centre have not yet turned up fusarium graminearum in root rot pathogens affecting local peas and dry beans.

Last year, researchers began looking at the possibility that the fungus responsible for fusarium head blight in wheat could infect those crops after a recent report from North Dakota discovered that the graminearum strain was infecting peas and beans at low percentages.

“We’re seeing lots of fusarium species and rhizoctonia, and we’re just trying to take a look at what might be the most predominant one,” said Debra McLaren, a researcher at BRC.

“Fusarium species are most common root rot pathogens in beans, but so far we haven’t seen any graminearum.”

In peas, fusarium solani has been more frequently isolated in recent years as the most common cause of root rot, but determining whether there has been a shift in fungal populations is important.

Recent findings indicate a greater presence of fusarium avenaceum in both Manitoba and North Dakota.

Greenhouse and lab pathogenicity testing is currently underway to determine whether the isolates found are in fact causing the root rot lesions observed in field crops, she added.

It appears that the pathogen population may be changing. Identification of the root rot pathogens affecting field peas is critical to screen for host resistance and design effective control measures.

Root rot is a major disease of field peas and beans in Manitoba, causing significant yield reductions by reducing plant stands and compromising root systems. Short rotations can exacerbate the problem.

Samples are being collected and sent to Bob Connor at the AAFC Morden in order to screen for host resistance and designing effective control measures. The new information will be used in breeding programs aimed at developing better resistance in new cultivars.

“If you’re screening for resistance, you want to make sure that you’ve got the correct and most predominant pathogens so that you can get some lines of peas and beans that are more resistant to what we’re looking at out in the field,” said McLaren.

In the first year of the three-year study supported by the Manitoba Pulse Growers Association, it has been shown that fusarium graminearum has the potential to infect bean cultivars in Manitoba.

If the graminearum strain starts showing up in local fields, farmers may be faced with more rotation headaches, because inoculum on crop residues in the field could be passed on from legumes to wheat from year to year.

However, even if it is found on peas and beans in Manitoba, it might not be highly pathogenic to wheat.

“We need to know what’s out there,” she said. “If some of the pathogens are changing a bit over time, or if there is some synergy developing between some of them, that’s important to know as far as for screening lines for resistance to root rot.”

McLaren is also working with other scientists to expand the registered use of Bartlett Superior 70 Oil in integrated pest management programs to reduce damage to potatoes from Potato Virus Y.

Bartlett Superior 70 Oil, a light mineral oil that is sprayed weekly onto crops to interfere with the mouthparts of the aphids that transmit the virus, is already registered for use in other crops and serves as an environmentally friendly control option.

Data from replicated studies is being submitted to the Pest Management Regulatory Authority (PMRA) and a new expanded label use approval may be forthcoming this spring, she said. [email protected]

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