Researchers at the University of East Anglia have helped uncover a hidden ally in the fight against one of agriculture's greatest threats - salty soil.
Led by Chinese collaborator Dr Yanfen Zheng, a new study shows how naturally occurring soil bacteria can dramatically boost plants' ability to survive in salty conditions.
The findings reveal a previously unknown mechanism by which microbes help plants – including maize, tomato and rapeseed - survive in harsh environments.
It is hoped that the breakthrough could have major implications for agriculture worldwide by helping crops survive in soil that would otherwise be unusable.
A new era of climate-resilient agriculture
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."
How the research happened
Researchers analysed plant root microbiomes across multiple crop species and soil types. They found that a type of naturally occurring soil bacteria called pseudomonads are consistently drawn to plant roots under salt stress.
This pattern held true across many different crops including maize, tomato and rapeseed - suggesting a broadly conserved biological response rather than a coincidence.
Genetic analysis revealed why these bacteria thrive in harsh conditions.
Prof Todd said: "Compared to other microbes, pseudomonads carry specialised genes that help them tolerate high salt levels, including sodium transport systems and other stress‑resistance mechanisms."
A powerful boost for crops
The researchers introduced pseudomonad strains into soybean plants and found that they successfully colonised plant roots and significantly improved plant growth under salt stress - both in greenhouse experiments and real‑world field trials.
"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.
A surprising mechanism
"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 per cent under salt stress."
Nature's built‑in defence system
Lignin is a tough, woody substance found in plant cell walls. It acts like a natural shield, strengthening tissues and helping plants withstand environmental stress.
The researchers went on to identify key genes involved in this process. And when these genes were artificially overexpressed, plants thrived in salty conditions.
Conversely, plants that couldn't produce lignin lost the benefit entirely, even when the helpful bacteria were present.
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."
'Pseudomonads associated to salt-stressed plants facilitate stress adaption of soybean through enhanced lignin biosynthesis' is published in the journal Sciences Advances.
