Common soil fungus protects corn crops from pests and boosts growth

A common soil fungus has the potential to protect corn from pests while helping the plants grow and develop. Researchers at Penn State found that promoting the soil fungus could be a beneficial strategy to help corn growers manage pests without the need for pesticides. 

In greenhouse and lab trials, the research team injected corn seeds with M. robertsii spores. The experts evaluated fungal colonization of leaves and roots, chlorophyll content, plant height and above-ground biomass, and the relative growth rate of the black cutworm.

“We saw that colonization of corn plants by the fungus M. robertsii promoted plant growth and boosted the expression of selected genes involved in plant defense in corn,” said study lead author Professor Mary Barbercheck. “The heightened defense response suppressed the growth rate of black cutworm larvae.”

Professor Barbercheck and her collaborators have been “casually following” the common soil fungus M. robertsii since 2003, when they began conducting organic plant studies. She was aware that M. robertsii was deadly to caterpillars and other insects, but became more interested in its potential when it was demonstrated that the fungus was absorbed by plant roots.

“I wondered if there is a lot of this fungus out there, how it is surviving in the field and what it is doing, so I expanded my work to focus more on it. I happen to work in organic systems, and so that’s where we’ve been studying it. But that doesn’t mean that it is not beneficial in conventional crop systems, too.”

The soil fungus was found to be present in 91 percent of the corn plants that developed from inoculated seeds, and was mostly detected in the plant roots instead of the leaves. 

Compared to control plants, colonized plants grew taller and had greater above-ground biomass. In addition, the relative growth rate of the black cutworm was lower on the leaves of fungus-infused plants.

Professor Barbercheck said the findings demonstrate that corn growers, specifically organic corn growers, can benefit from promoting the soil fungus across their corn fields. 

“Because this fungus appears to promote plant growth, to help control pests, and to alter the plant defense response to suppress at least some pest growth, we need to adjust our management practices to support it,”

“Next, we have to learn how much of the fungus is in plants and what the natural infection level is. And if we make a seed treatment out of it, how effective would it be?”

According to Professor Barbercheck, there is a shortage of organically produced feed grains in the United States. She said this may be due to hesitation among farmers to transition to organic fields because they don’t know how to manage pests without insecticides or weeds without herbicides. 

“We need to see what natural processes we can manage to make that transition less risky to help make organic farming more widespread. On a commercial level, there are opportunities for growers to take advantage of organic markets because there is a big demand that we currently are not meeting with domestic supplies.”

The study is published in the journal Biological Control.

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By Chrissy Sexton, Earth.com Staff Writer