Heat treatment kills fusarium

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Reading Time: 3 minutes

Published: November 14, 2002

Heat treating grain could soften the blow of fusarium head blight on

the Prairies.

Agriculture Canada research scientists have been testing the effects of

heat treatments for two years. The research shows the treatments can

virtually eliminate all fusarium pathogens from infected seed.

That could prove valuable to the eastern Prairies, which are struggling

with fusarium head blight and could lose critical markets for grain

unless more ways are found to cope with the cereal crop disease.

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The research could also benefit Alberta cattle feeders, who

traditionally import a lot of feed grain from the eastern Prairies.

As well, it could help organic farmers, who aren’t allowed to use

chemical fungicides.

Among the pathogens killed by the heat treatment are those caused by

Fusarium graminearum, the species of fusarium most devastating to

cereal crops in Manitoba and eastern Saskatchewan during the past

decade.

“The heat treatment can be quite effective,” said Jeannie Gilbert, a

research scientist and plant pathologist at Agriculture Canada’s Cereal

Research Centre in Winnipeg.

“We have certainly seen some effect there. Levels of fungal survival

were reduced to less than one percent in some treatments.”

The research centre applied heat treatments to wheat seed during both

years of the trials. Barley was included this year. The research

encompassed both healthy and infected seed.

A range of temperatures was used on infected seed for different lengths

of time. A treatment at 70 C over the course of five, 10 or 12 days

proved to be most effective.

At 90 C, the seed was essentially killed.

“It seemed to be too hot a treatment,” Gilbert said. “We got very low

emergence from that seed.”

While the findings are encouraging, there is a challenge that cannot be

overlooked. Because fusarium has already damaged the infected seed,

reduced germination and yields can still be expected, even after heat

treatment.

The seed industry and farmers wanting to use their own bin-run seed

would need to balance that limitation against the benefits of being

able to eliminate fusarium pathogens, which would alleviate the risk of

introducing fusarium into uninfected fields. However, higher planting

densities likely would be needed to compensate for reduced germination

and yield.

Research has not yet been done on higher-density seeding.

The Winnipeg trials also found that heat treatments slightly reduced

plant height. Time to maturity increased by about one-third of a day.

Kernel weight was not affected.

The Cereal Research Centre did the heat treatments in a special

incubator. Gilbert said an ordinary oven won’t work, because it does

not create the air movement needed to prevent seed from baking.

Economics will influence how the findings are used. The treatments

might prove too costly for bulk volumes of grain needed by commercial

farmers for planting, but they could be a godsend for plant breeders

and seed companies needing uninfected seed for the development and

multiplication of new crop varieties.

Heat treatments might also help keep Alberta’s borders open to imports

of higher-value seed stocks from the eastern Prairies. They may also

ease Alberta’s concerns about feed imports from Manitoba and

Saskatchewan.

Jim Calpas, a pest risk manager with Alberta Agriculture, is keeping

the heat treatments in mind as he looks at how pelleting affects

fusarium-infected feed.

Calpas visited a pelleting plant where temperatures reached between 77

and 88 C while feed was preconditioned to make it warm and moist before

it was pressed into pellets. The ground-up feed was treated with steam

for up to two minutes.

Calpas said he wants to duplicate that process on a smaller more

controlled basis for study that will lead to specific recommendations.

Pelleted feed is now viewed as a potential carrier of fusarium into

Alberta, but that might change if heat applied during pelleting can

consistently kill the pathogens.

“We’re trying to reduce the amount of Fusarium graminearum that gets in

contact with our fields,” Calpas said.

“Intuitively, it makes sense that the heat treatment process has an

effect.”

Agriculture Canada’s research on heat treatments is funded by the

Alberta Agricultural Research Institute.

In addition to work at the Cereal Research Centre, the treatments are

also being studied at Agriculture Canada’s research centres in Lacombe,

Alta., and Swift Current, Sask.

At Lacombe, researcher Kelly Turkington said the 2001 trials on

uninfected barley and oats seed found no reduction in germination or

yield when temperatures reached 70 C. The results for this year’s

trials at Lacombe had not been reviewed as of Nov. 4.

At the Cereal Research Centre, emergence was reduced following heat

treatments of 70 C on uninfected seed. There was no reduction in

emergence when uninfected seed was treated at 30 or 50 C, Gilbert said.

The research builds on work started by the Canadian Grain Commission,

which had shown the treatments could eradicate fusarium pathogens from

seed without much effect on germination.

About the author

Ian Bell

Brandon bureau

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