Microbes offer hope against rising soil salinity

Researchers have identified naturally occurring soil bacteria that could help farmers protect crops from increasing soil salinity caused by climate change and rising sea levels.

Scientists at the University of East Anglia (UEA) and the Quadram Institute have found that plants under salt stress appear to send out a microbial “cry for help”, attracting beneficial bacteria that improve resilience and maintain growth.

Prof Jonathan Todd, from UEA’s School of Biological Sciences and the Quadram Institute, said salinisation represented a growing challenge for agriculture. 

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“As sea water encroaches on farmland, it causes major problems for soil fertility, for biodiversity in the soils and most prominently on crop yield,” he told Farmers Weekly.

Plants adapted to naturally salty environments have mechanisms that protect them from losing water, but most crops do not, he explained.

“They don’t grow well, and they’re subjected to nasty oxidative stress, their yields go down, and they just look really poorly and sick.

“If our crop regions are subjected to salinity, we need strategies to be able to allow those plants to live in those conditions.”

The study, led by Chinese researcher Dr Yanfen Zheng, found that crops exposed to saline conditions consistently recruited strains of naturally occurring bacteria known as pseudomonads.

These microbes were identified in maize, tomato, rapeseed and sorghum across both acidic and alkaline soils.

Plant survival

“In most of [the crop plants] this cry for help was recruiting specific strains of pseudomonads, which had a specific benefit to the plants in allowing them to survive much better and be more productive in saline conditions,” said Prof Todd.

The bacteria, which are drawn to plant roots under salt stress, were found to stimulate production of lignin – a compound that strengthens cell walls and improves tolerance to environmental stress.

Trials in soybean showed plants treated with the microbes developed stronger roots, improved growth and delivered higher yields in saline conditions, both in greenhouse experiments and field trials.

The response was not seen in wheat and rice, suggesting different microbes may play a similar role in those crops.

Essential tool

Researchers also identified genes involved in the process. Plants engineered to increase lignin production thrived under salt stress, while plants unable to produce lignin lost the benefits of the bacteria altogether.

Prof Todd said the findings could pave the way for biological seed or soil treatments.

“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 are published in Science Advances in a paper titled “Pseudomonads associated to salt-stressed plants facilitate stress adaption of soybean through enhanced lignin biosynthesis”.