Soil Warriors

Researchers Hone in on Disease-Fighting Microbes in the Soil

Emily Unglesbee
By  Emily Unglesbee , DTN Staff Reporter
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In just a few years, farmers may have access to soil tests that tell them if they have disease-fighting microbial populations and how to manage their soil to encourage them. (DTN photo by Chris Clayton)

ROCKVILLE, Md. (DTN) -- Have you ever wondered why one patch of soybeans dies from Sudden Death Syndrome (SDS), while 6 feet away, another patch thrives?

The answer may be smaller than you thought -- microscopic, even.

In a new study focused on SDS, Southern Illinois University plant pathologist Ahmad Fakhoury and a team of researchers took soil samples from 45 fields with patchy SDS symptoms in Illinois, Iowa and Minnesota. They combed through the millions of fungi, bacteria, nematodes and other microbial species in the soil, comparing the diseased areas to the healthy ones.

They found evidence that some soils possess "good guy" microbes that are likely helping suppress the activity of not just the SDS fungus, but many disease-causing pathogens, Fakhoury said.

"From past research, some of these organisms are known to play a bio-control role and have antifungal properties," he noted.

This growing field of research opens a door to a new world of disease management, where soil tests may soon tell a farmer how much disease risk he faces.

"We're starting to find these soil signatures that are going to tell us ultimately what healthy soil is," Fakhoury said. "If you have these organisms, then this is indicative of a healthy good soil -- that is, they're going to suppress disease versus being conducive to disease."

Fakhoury's SDS research uncovered an underground world teaming with life. From their 45 sampled fields, they identified hundreds of genetically distinct microbial species, such as fungi, bacteria, nematodes and more.

Some were significantly more abundant in the healthy soils versus the diseased ones.

Many of these good microbes had already been identified as disease-fighters from previous research, which drove home the importance of what Fakhoury's team found.

For example, a family of bacteria called the Actinomycetales, which were well represented in the healthy soils samples, have been shown to produce compounds with antibacterial, antifungal and nematicidal properties.

By exhaustively cataloguing the good microbes in the healthy soils, Fakhoury's research will help scientists create soil tests to identify disease-suppressing soil populations for farmers.

"Farmers already send soil samples to look for nitrogen, phosphorus or SCN," Fakhoury noted. "There's no reason we cannot do the same thing for these soil organisms."

As this field of research advances quickly, those tests may be here sooner than you think.

"At this point, we already have testing that can tell you about the presence of SDS-suppressing organisms," Fakhoury said. It will take time to standardize and fine-tune soil tests that cover a variety of diseases, but he estimates within a few years, such tests may be available to farmers.

Fakhoury and his team are already thinking further ahead.

They are finishing up a raft of research projects testing how common soil management practices like cover crops, fertilizers and tillage affect these disease-fighting microbial populations.

The work, funded by the United Soybean Board and the North Central Soybean Research Program, should help farmers make practical changes if they find their soils are lacking enough disease-fighting microbes.

"That way we can tell (farmers) if you have them, good, if not, here is what we can do," Fakhoury said.

See Fakhoury's SDS research here:…

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Emily Unglesbee