Soil microbes could help crops survive salty farmland by triggering a plant's roots to build more of a natural reinforcing compound called lignin, according to new research led by scientists at the University of East Anglia (UEA).
The discovery offers a possible bio-based tool for one of agriculture's fastest-growing problems: soil that has become too salty to farm productively. In greenhouse and field trials, plants treated with the beneficial bacteria grew stronger roots and produced higher yields under salty conditions than untreated plants.
A widespread problem: salt is choking farmland
Soil salinity is worsening around the world as a result of climate change, irrigation practices, and rising sea levels, and it's already a major threat to global food production. As salt builds up in soil, it stunts plant growth, damages roots, and can sharply cut crop yields.
"The build-up of salt in farmland is a major and worsening problem — driven by climate change, irrigation and rising sea levels," said Professor Jonathan Todd of UEA's School of Biological Sciences and the Quadram Institute on the Norwich Research Park. "Salt chokes plant growth, damages roots and severely impacts entire harvests — putting global food supplies at risk."
Scientists have long known that plants lean on communities of microbes living around their roots, known as the root microbiome, to help cope with environmental stress. But exactly how those partnerships work, and whether they hold up consistently across different crops and soils, had remained unclear until now.
How pseudomonad bacteria protect plant roots
The research team, led by Dr. Yanfen Zheng and including UEA scientists, examined root microbiomes across several crop species grown in different soil types. They found that a group of naturally occurring bacteria called pseudomonads consistently clustered around the roots of salt-stressed plants — a pattern that held true across maize, tomato, and rapeseed, suggesting a broad biological response rather than something specific to one crop.
Genetic analysis showed why these particular bacteria thrive in salty conditions. "Compared to other microbes, pseudomonads carry specialized genes that help them tolerate high salt levels, including sodium transport systems and other stress-resistance mechanisms," Todd explained.
When the researchers applied selected pseudomonad strains to soybean plants in both greenhouse studies and field trials, the bacteria successfully colonized the roots and meaningfully improved growth under saline conditions, producing stronger root systems and higher yields than untreated plants.
The lignin surprise: a new plant defense mechanism
The team expected the bacteria to help plants manage salinity by limiting how much sodium entered their tissues, the mechanism long assumed to underlie salt tolerance. Instead, they found no evidence that the bacteria affected sodium transport or ion balance at all.
"Instead of helping plants manage salt directly, the bacteria stimulated the plant to produce more of a substance called lignin," Todd said. "Roots of bacteria-treated plants showed a significant increase in lignin content, with some measurements rising by over 30 percent under salt stress." Lignin is a tough, woody compound found in plant cell walls that reinforces tissue and helps plants withstand physical and environmental stress.
The researchers went on to identify the specific genes responsible for boosting lignin production. When those genes were artificially overexpressed, plants performed markedly better in salty soil; conversely, plants genetically unable to produce lignin saw no benefit from the bacteria at all, confirming that lignin production is essential to this newly identified protective effect.
What this means for the future of farming
With large areas of farmland already affected by salinity, and more at risk as sea levels rise, the researchers see an opportunity to develop microbial treatments as an alternative to heavy chemical inputs. "By harnessing naturally occurring microbes like pseudomonads, bio-based treatments could be developed that help crops grow in saline soils without heavy chemical inputs," Todd said. "Microbial solutions could become an essential tool for maintaining crop yields and ensuring food security."
The findings, published in the journal Science Advances, add to a growing body of climate and agricultural science research exploring how natural biological processes can substitute for synthetic fertilizers and treatments. Readers can follow further developments in soil science and food security through ongoing science and environment coverage.
Frequently asked questions
Are these soil microbes already available for farmers to use?
Not yet. The pseudomonad strains were tested in greenhouse and field trials on soybean, and the researchers say further development is needed before a commercial bio-based treatment could reach farmers.
Which crops have shown a response to these bacteria?
The pseudomonad bacteria were found around the roots of salt-stressed maize, tomato, and rapeseed, and were directly tested on soybean plants in the study's trials.
