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Robust soil kills fungi


Beneficial organisms create natural antibiotics to fight fungus


By MATTHEW WEAVER


Capital Press


USDA researchers say naturally occurring antibiotics can help farmers combat soil diseases.


Linda Thomashow, USDA Agricultural Research Service research geneticist in Pullman, Wash., said beneficial microorganisms in the soil create natural, simple compounds that work against fungal pathogens that attack crops like wheat and canola.


Establishing a good population of beneficial organisms in the soil offers natural protection from the diseases, she said.


The researchers are working to identify ways to make the best use of natural suppression through cropping or fertilizer practices.


They want to understand which cultivars make the best use of natural biocontrol organisms, said David M. Weller, research leader for the USDA ARS in Pullman, Wash.


"Anything we can do to utilize those natural organisms to lessen the need for pesticides is beneficial," he said. "We're making use of resources right on the farm and don't cost anything to the grower."


Some crop rotations are more favorable than others, Thomashow said. Planting potatoes or oats into wheat rotations will interrupt the organisms' ability to suppress diseases.


Soilborne pathogens are everywhere, Weller said. He believes addressing plant activity underground is the key to the next green revolution.


In most cases, breeding is done to produce greater yield, quality and for resistance to above-ground diseases. In many cases, there aren't resistant varieties for soil-borne illnesses and breeders rarely think about breeding wheats to support naturally occurring, beneficial organisms, he said.


"The plant has to depend on those naturally occurring microorganisms to provide the first line of defense against attack by these soilborne pathogens," he said.


Take-all is a soilborne disease in wheat that is most serious in high rainfall zones or areas under irrigation.


According to Washington State University, it causes more than $1 billion per year in damage by rotting roots and depriving plants of water and nutrients.


It's long been known that the disease will be severe when growing wheat continuously for four to five years, Weller said, but natural resistance builds up and the disease tapers off and declines.


"Eventually (the microorganisms) overcome the pathogen and suppress the disease," he said.


It takes perseverance for several years to get through poor yields until the beneficial organisms build up and kick in, Weller said.


"Sometimes, the economics of farming just don't allow you to take several years of yield losses before you reach that benefit," he said.


Yields return to about 90-95 percent of normal when using the natural suppression after a Take-all problem occurs, Weller said. That's comparable to the results a farmer might see using chemicals or seed treatments for soil-borne pathogens, he said.


The researchers are eying possibilities to develop commercial uses for the beneficial organisms. Weller said they would be used in concert with conventional farming practices.


"It's utilized in its current form, but I think we can make better use of it in order to increase food production we're going to need as we move through this century," Weller said.






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