Understanding plant-soil interaction could lead to new ways to combat weeds

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Using high-powered DNA-based tools, a recent study at the University of Illinois identified soil microbes that negatively affect ragweed and provided a new understanding of the complex relationships going on beneath the soil surface between plants and microorganisms.”Plant scientists have been studying plant-soil feedback for decades,” said U of I microbial ecologist Tony Yannarell. “Some microbes are famous for their ability to change the soil, such as the microbes that are associated with legumes — we knew about those bacteria. But now we have the ability to use high-power DNA fingerprinting tools to look at all of the microbes in the soil, beyond just the ones we’ve known about. We were able to look at an entire microbial community and identify those microbes that both preferred ragweed and affected its growth.”Although it would seem that the logical conclusion would be to simply add anti-ragweed microbes to soil, Yannarell said that adding microbes to soil hasn’t been successful in the past. An effective strategy, however, to suppress weeds might be to use plants that are known to attract the microbes that are bad for ragweed, and in so doing, encourage the growth of a microbial community that will kill it.The study used Manhattan, Kan. (sunflower) and Urbana, Ill. (ragweed) and conducted trials independently at agricultural research facilities in Michigan, Illinois, Kansas, South Dakota, and Oregon, using local soils gathered on site. These particular weeds were selected because ragweed is a more common weed east of the Mississippi and sunflower is more common in the West.The experiment allowed Yannarell and his colleagues to observe how three generations of ragweed and sunflower interacted with the microbial community in the soil. The plants interact with each other indirectly due to the differing effects they each have on the microbes in the soil.”We used the same soil continuously so it had a chance to be changed,” Yannarell said. “We let the plants do the manipulation.”Interestingly, they did not find the same ragweed-preferring microbe across all five states. …


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