In the ongoing hunt for seed grain contaminated with fusarium graminearum, it is essential to have a sensitive and reliable test. The lab work must be impeccable if producers hope to find the culprit seeds before they go into the ground.
The fusarium graminearum DNA test recently introduced by the Alberta Research Council is sensitive enough to detect a single infected seed in a 10-gram batch of 800 to 1,000 clean seeds.
“It’s basically the same sort of CSI crime lab work you see on TV, although searching for fusarium isn’t quite as glamorous,” said Ralph Lange, the research council scientist in Vegreville, Alta., who developed the test.
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“We use the same scientific process, the same kind of DNA work used by top forensic labs around the globe. By comparison, the traditional plate method can only detect one contaminated seed in a batch of 200 seeds.”
Although Europe began using fusarium DNA tests five years ago, Lange said they had many shortcomings.
“Their tests were not relevant to western Canadian farming conditions. We knew we could do better.”
European DNA labs extract test material from green plant material rather than from the seed.
“Here in Canada, our direct concern is fusarium in the grain, in the actual seed, so that’s the kind of test we need,” he said.
“If farmers want to slow or stop the spread of fusarium, they need to know about the seed itself, not the green plant material.”
He also said western Canadian isolates, which are a specific sample of fungus taken from an individual seed and then isolated from other samples, may be genetically different from those in Europe.
“Any tests developed in Europe would be relevant to European isolates. It would be European seeds and diseases. They may not relate to our situation at all.”
Lange said there were also problems with the conventional plate testing process, which begins by sterilizing the outside surface of the seed.
“What we are searching for in any type of fusarium test is living organisms. By sterilizing the outside surface of the seed, you kill anything on that surface, which would include fusarium graminearum. So the plating test is faulty before it even begins. This often gives you a false negative reading before the test even starts, because you’ve already destroyed the very thing you are searching for.”
Lange said a DNA test is more reliable because it can tell if seed has ever been exposed to fusarium graminearum and can handle 800 or more seeds from each sample.
“If there is one contaminated seed in that sample lot, we can find it.”
Before the council could commercialize, it had to be sure the test repeatedly gave the same correct results.
“It’s a bit of a leap, going from a research paper developed on a lab bench to a reliable test that farmers can trust,” Lange said.
“We did lots of testing and we worked closely with our project partners at 20/20 Seed Labs. We had grain samples from farmers all across Western Canada.”
Although not at liberty to describe the development of the new process in detail, Lange said the council ran its tests against grain kernels that had known, quantified levels of fusarium.
“We start with a documented level of contamination in a particular kernel, and we run our new test against that kernel to see if our results are the same as what is already documented. If our new test is a good one, the results will match up every time. If our new test is faulty, we get results that differ from the known facts.”
At 20/20 Seed Labs in Nisku, Alta., Kim Kenwood said checks on the new DNA process repeatedly gave a perfect match.
“We went through about a thousand seed samples from farmers when we did our pilot testing last year,” he said. “In the early stages, we got perfect agreement between the DNA test and the traditional plate test.”
Initially the results were nearly all negative, which Kenwood said was because the lab wasn’t getting enough contaminated grain samples.
“So I started sneaking some known positive seeds into the samples. I renumbered them so the technicians had no idea I was slipping positives into the system.”
He said the test detected all of the known positive seeds.
“The estimates of the level of contamination varied slightly, but the yes-no accuracy was 100 percent. In Alberta, the legal requirement is a simple yes-no. The level isn’t relevant. If the seed tests positive for fusarium graminearum, you cannot use it.”
