People tend to become creatures of habit, but what happens when the same old same old stops working? 

This is what University of Wisconsin-Madison researcher Dr. Damon Smith discovered during his work on the Phytophthora Management Project. 

“The project came about because we had some consultants and farmers telling us that they were planting varieties which had previously been known to be resistant (to Phytophthora) and the soybean plant appeared to be susceptible to the pathogen,” Smith said. 

This is one project the Wisconsin Soybean Marketing Board (WSMB) has invested in. Every year, WSMB utilizes checkoff funds to support research projects in various areas from pests, disease or weed management, breeding to improve resistance, solving the soybean quality conundrum and more areas. 

“As leaders in the soybean industry, investing checkoff funds in research is one way we can help our fellow soybean growers,” WSMB President Jonathan Gibbs said. “Through checkoff research, we’re able to provide unbiased information for the growers that they asked for. We’re soybean farmers working for soybean farmers.” 

Smith said the support of WSMB is appreciated and that they wouldn’t have made it this far without checkoff funding. 

The project: Let’s break it down 

Phytophthora is a soilborne disease found in soybeans. A well-known tool to fight this pathogen was a single gene of resistance, Rps1K, in the soybean variety. The downside of a single gene resistance is if used repeatedly the pathogen will adapt.  

This is where necessary change must happen.  

Smith started his research in a familiar place, one already funded by the Wisconsin Soybean checkoff.  

The Soybean Cyst Nematode Testing Project is a free tool that farmers around Wisconsin can utilize by sending in a soil sample that is tested for the disease.  

Leveraging this program, Smith said they use the same soil samples after the initial testing to then test for the presence or absence of both Phytophthora and the related group Phythium. As a group these are called water molds because they usually favor excessively wet soils, standing water or soils that are not well drained. 

“It’s a good way for us to get a wide swath of soil samples from across the state and be able to look at what’s actually out there,” Smith said. “We did this over 2022 and 2023, with 378 soil samples from 39 counties in the state. That’s pretty good coverage of the soybean production area.” 

The Phytophthora Management Project also collected plant samples from farmers and researchers. 

Using isolates from both the soil samples and the soybean plants, Smith conducted an assay, which is a test of the sample to determine the type of pathogen. Smith then used genetic markers through a pathotyping assay, a specific test to determine the single genes at work in the isolates.  

Out of all the samples collected, 33 different species of water mold were found. 

Most were pathogens of the Pythium group, and some were related to Phytophthora. Smith said Pythium pathogens are under attributed to damage in soybean fields.  

“What’s interesting is the last time anybody had pathotyped the Phytophthora groups was about 20 years ago,” Smith said. “At that time, they said, this particular gene should be a good gene to use in fields because the way the population was at that time was pretty sensitive to that gene.” 

The results collected through this project showed Phytophthora can easily overcome the Rps1k gene, which was a concern already, and some other RPS genes deployed in common commercial soybean varieties.  

According to Smith, the new gene, Rps3a, should probably be deployed in varieties now.  

The project: Let’s talk recommendations 

• Choose the right soybean variety that probably has the Rps3a gene or multi-gene resistance 

• Use fungicide seed treatments that are effective against these water mold pathogens or cultural management practice 

• Improve field drainage 

The project: Let’s see the future 

“What we would like to do is wait now a few years before we collect more soil samples to see if there was a shift,” Smith said. “We’re going to continue trying to characterize that population to see if we can learn anything more about the actual species. Then we’ve started, not only in Wisconsin, but across the North Central Region, doing some uniform seed treatment trials specifically to address the Pythium problem.”  

‘Useful resource’ 

The soybean cyst nematode project utilized for this research is another Wisconsin soybean checkoff-funded project.  

With the ability to use the soil samples in other projects – along with soybean cyst nematode research – this program stretches past its intensions to assist with further research.  

Smith and University of Wisconsin-Madison researcher Dr. Shawn Conley used this program for a sudden death syndrome project several years ago as well.  

“I think that’s the other key piece, is that it’s a critical program, and something that’s a really useful resource for the soybean farmers here in the state,” Smith said.