A new screening tool that will tell producers the risk of a root rot infection in their pulse crops could be available as early as next year.
“At the moment, if producers are concerned about whether they have root rot in their field, they can take their soil to a commercial testing lab to determine if they have presence or absence of aphanomyces root rot,” said federal research scientist Syama Chatterton.
“But really, all that tells them is yes or no — it doesn’t tell them what the quantity of inoculum is in their soil and what their risk is of actually getting the disease if they were to plant susceptible hosts like pea or lentil.”
Chatterton’s team is developing a “quantitative risk analysis tool” that will allow producers to submit soil samples to a seed-testing lab to categorize inoculum levels in the soil as low, medium, or high risk of developing root rot. The first phase of the research is determining how much inoculum is needed in the soil to trigger the disease.
“We’re trying to link the amount of inoculum in the soil to disease severity,” said Chatterton.
With aphanomyces root rot — a devastating disease that has been spreading through pea and lentil fields across Alberta — the inoculum starts out as oospores, or long-lived resting spores.
“We’ve determined that it takes about 100 oospores per gram of soil to give you a moderate disease risk,” said Chatterton.
“We have a pretty clear idea of how much inoculum is needed in the soil to produce disease.”
Chatterton is now working on the second phase of the research — developing a molecular tool that quantifies the DNA of the oospores in the soil.
So far, that molecular tool is able to quantify oospores at higher levels (anything above 100 oospores per gram of soil), but the challenge now is detecting oospores at levels lower than that.
“We’d be able to go in and for sure determine what a high-risk field is,” said Chatterton. “It takes about 100 oospores per gram of soil to develop disease, but unfortunately, with the molecular tools that we have, we get a lot of false negatives at about that 100-oospore level.”
And because inoculum builds up in the soil over time, it could almost be too late by the time that level of disease risk is identified.
“It’s very important for us to be able to detect the lower levels of inoculum so that producers would have a heads-up that the inoculum is starting to build in that field and they should maybe pull back on the pea and lentil rotation to try and keep it under that threshold level of 100 oospores per gram of soil,” said Chatterton.
Chatterton’s team has developed a new mechanism to see if they can “reduce that false negative rate,” as well as different soil extraction protocols.
“We don’t want to release a test or a risk assessment tool until we’re confident that we have reduced that false negative level,” she said, adding that the test likely won’t cost “much more than, say, a clubroot test.”
“Most optimistic, we’d be maybe six more months, but it might take another year or two before we can bring those two different aspects together — an improved extraction protocol from the soil and improved detection methods.”
Once it comes online, this test will offer pulse producers a little more certainty as to the level of root rot in their field, and the risk of planting a susceptible crop on any given year.
“When we’re dealing with these root rot issues, we really have few management recommendations that we can provide to producers,” said Chatterton.
“The most standard recommendation is that a producer should avoid planting peas or lentils in a highly infested field for at least six to eight years, but we can’t really tell a producer when it’s safe for them to plant peas or lentils again.
“They need to have some sort of tool that helps them make those important management decisions for their farm.”