Fungi help plants cope with stress

Plants have a microbiome community that helps them cope through stressful conditions, such as drought, wet conditions, cold or disease threats.

At Washington State University, scientists looked at the comparative roles of bacteria and fungi and they discovered that tiny fungi especially play a significant role in helping plants survive drought and other forms of extreme stress.

The researchers reviewed 288 experiments across 89 studies and compared the roles of bacterial versus fungal organisms living in and on plants.

“Plants’ abilities to tolerate stress are impacted by the bacteria and fungi that live on or inside them and make up the plant microbiome,” said Stephanie Porter, assistant professor in the School of Biological Sciences, in a university news release. “Just like how microbes in our digestive system help keep us healthy, microbes play an incredibly important role in plant health.”

Working with colleague Maren Friesen, assistant professor in the Department of Plant Pathology, Porter measured how beneficial microbes affect plants under normal and stressful conditions. They based their review on experiments ranging from common Pacific Northwest food crops to wild plant species.

In a wider collaboration, they worked with colleagues at Michigan State University and were able to compare five different classes of symbiotic bacteria and fungi that live on, in, and around plant roots and under stresses that included fungal diseases, grazing by animals and microscopic worms, heavy metal contamination, and drought, cold, and saline soils. They tallied the effect on plant growth, biomass and yield.

Results showed that, while beneficial bacteria are more helpful in normal conditions, symbiotic fungi, especially mycorrhizal fungi that colonize the plants’ root systems and enhance the plant’s uptake of nitrogen, phosphorus, and other micronutrients, provide added benefits during challenges. Those stresses included increased salinity, insect damage such as caterpillars eating leaves, and pathogen pressures.

“Stress makes these fungi even more important to plants, which we think is really interesting,” said Friesen in the news release.

The degree by which microbes eased stress was measured by how much the beneficial ones impacted plant performance in the stressful environment. In the plant experiments, the level of microbial stress relief was substantial, and the report stated that there are dramatic potential gains to be had from optimizing the beneficial microbe community, especially soil and root-dwelling fungi.

The value of beneficial fungi will become all the more critical as plants cope with increasing environmental stresses from climate change and could help mitigate the negative consequences of global warming in the future.

Friesen said that microbes offer a more sustainable tool for stress tolerance than the application of hormones and chemicals alone.

“Should growers want to foster the plant microbiome for stress resistance, our study suggests they should really focus on fungi,” Porter said. “These beneficial microbes could be the key to helping us grow more food in the coming decades.”

Productive land, water sources and plants performing at their fullest potential will be essential to meet the yields needed to feed the rapidly growing global population. But none of it is without challenges.

“Farmers are now having challenges with pathogens no longer responding to chemical treatments,” said Friesen. “There’s already a lot of interest in scientific and industry circles in identifying and harnessing microbial solutions to agricultural problems. This study gives us ideas about where to look.”

The research was published in the journal Functional Ecology.

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