These tiny soil microbes could rescue crops from salty farmland

A team including scientists from the University of East Anglia (UEA), led by Chinese researcher Dr. Yanfen Zheng, found that naturally occurring soil bacteria can significantly improve plants’ ability to survive in saline conditions.

The study also uncovered a previously unknown way these microbes protect crops such as maize, tomato, and rapeseed from salt stress. The discovery could eventually help farmers grow food on land that has become too salty for conventional agriculture.

Soil salinity threatens global agriculture

Salt buildup in farmland is becoming an increasingly serious problem because of climate change, irrigation practices, and rising sea levels. As salt accumulates in soil, it stunts plant growth, damages roots, and can sharply reduce crop yields.

Prof Jonathan Todd, from UEA’s School of Biological Sciences and the Quadram Institute on the Norwich Research Park, said: “The build-up of salt in farmland is a major and worsening problem — driven by climate change, irrigation and rising sea levels.

“Salt chokes plant growth, damages roots and severely impact entire harvests — putting global food supplies at risk.

“We know that plants rely on communities of microbes around their roots, called the root microbiome, to help them cope with environmental stress. But exactly how these relationships work, and whether they are consistent across crops and soils, has remained largely unclear.

“We found that plants appear to recruit beneficial bacteria in salty soil conditions, which in turn trigger internal changes that strengthen their physical structure and resilience.

“If scientists can harness this natural process, it could mark the beginning of a new era in climate-resilient agriculture.”

Root microbes drawn to salt stressed plants

To better understand these plant and microbe partnerships, the researchers examined root microbiomes from multiple crop species grown in different soil types.

They discovered that a group of naturally occurring bacteria known as pseudomonads consistently gathered around plant roots exposed to salt stress. The same pattern appeared across several crops, including maize, tomato, and rapeseed, suggesting this is a widespread biological response rather than something unique to a single plant.

Genetic analyses also explained why these bacteria perform so well in salty environments.

Prof Todd said: “Compared to other microbes, pseudomonads carry specialized genes that help them tolerate high salt levels, including sodium transport systems and other stress-resistance mechanisms.”

Stronger roots and higher yields

The team then introduced selected pseudomonad strains to soybean plants. In both greenhouse studies and field trials, the bacteria successfully colonized the roots and substantially improved plant growth under salty conditions.

“We found that plants treated with the microbes showed stronger root systems, better development and higher yields compared to untreated plants grown in salty soils,” said Prof Todd.

An unexpected plant defense

The researchers were surprised to discover that the bacteria were not helping plants by reducing salt levels inside their tissues.

“The most surprising thing was finding out how the bacteria helped plants cope.

“For decades, it was thought that plants survive salinity by controlling sodium levels -essentially keeping harmful salt out. But we found no evidence that bacteria influenced sodium transport or ion balance.

“Instead of helping plants manage salt directly, the bacteria stimulated the plant to produce more of a substance called lignin.

“Roots of bacteria-treated plants showed a significant increase in lignin content, with some measurements rising by over 30 percent under salt stress.”

Lignin strengthens plants naturally

Lignin is a strong, woody material that forms part of plant cell walls. It acts like a built in support system, reinforcing plant tissues and helping them withstand environmental stress.

The researchers identified the key genes responsible for increasing lignin production. When those genes were artificially overexpressed, plants performed much better in salty soil.

By contrast, plants that were unable to produce lignin did not benefit from the bacteria, showing that lignin production is essential to the newly discovered protective effect.

Prof Todd said: “We hope this discovery opens up new possibilities for agriculture.

“By harnessing naturally occurring microbes like pseudomonads, bio-based treatments could be developed that help crops grow in saline soils without heavy chemical inputs.

“With vast areas of farmland already affected by salinity and more under threat, microbial solutions could become an essential tool for maintaining crop yields and ensuring food security.”

The findings were published in the journal Science Advances in the paper, “Pseudomonads associated to salt-stressed plants facilitate stress adaption of soybean through enhanced lignin biosynthesis.”