Bacteria, fungi and other organisms living in the soil can actually end up having important effects on things like carbon sequestration and nutrient movement, said Maggie Wagner, associate professor of ecology and evolutionary biology at the University of Kansas.

Wagner said other researchers have been describing this type of ecological memory of soil microbes having some way to remember from their ancestors’ past. “It has a lot of important implications for how we can grow plants, including things like corn and wheat. Precipitation itself has a big influence on how plants grow, but also the memory of the microbes living in those soils could also play a role.”

While legacy effects previously have been reported, they aren’t well characterized. A better understanding could eventually benefit farmers and agricultural biotech firms, which could build on the research, she said.

The researchers wanted to better understand which microbes are involved at the genetic level, and which bacterial genes are being influenced?

By sampling soils from six sites across Kansas — from the state’s lower, rainier eastern half to its western High Plains, higher in altitude and drier because of the rain shadow of the Rocky Mountains — the researchers aimed to determine differences in legacy effects.

Wagner and her colleagues began testing the soils to better understand legacy effects of the samples’ microbes, using what she calls an “old-school technique, treating the microbes as a black box” by growing the plant in different microbial communities with different drought memories and then measured plants’ performance to understand what was beneficial and what was not.

The researchers challenged the microbial communities for five months, either with plenty of water or very little water.

“Even after many thousands of bacterial generations, the memory of drought was still detectable,” Wagner said. “One of the most interesting aspects we saw is that the microbial legacy effect was much stronger with plants that were native to those exact locales than plants that were from elsewhere and planted for agricultural reasons but weren’t native.”

While more plant species will need to be tested to confirm this hypothesis — the researchers tested one crop (corn) and one native plant (gamagrass) — the researchers said the findings could offer important context for farmers who want to use beneficial microbes to improve yields.

Additionally, the research team performed genetic analysis on both microbes and plants to better understand on the molecular level how legacy effects might function.

The KU researcher said gamagrass is being looked at as a possible source of genes to improve corn performance under challenging conditions.

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