Rare microorganisms help corn grow in saline soils.

Research conducted by Embrapa, in partnership with Brandeis University in the United States, has identified extremophilic archaea (a group of microorganisms distinct from bacteria and adapted to extreme conditions) as capable of increasing corn's tolerance to excess salt in the soil and allowing plants to grow vigorously even under saline stress conditions. The researchers demonstrated that these archaea colonize the rhizosphere, the region of the soil near the roots, characterized by intense chemical and biological exchanges. The work was published in the journal [Journal Name - missing from original text]. Environmental Microbiome.

The microorganisms were isolated from the roots of saltwort (Atriplex nummularia), a plant naturally adapted to salinity and used in the phytoremediation of saline soils. After cultivation in the laboratory, they were evaluated in corn plants. The crop is strategic for food production and highly sensitive to the accumulation of salts in the soil, which compromises plant growth and reduces productivity.

In experiments conducted in a controlled environment, researchers observed that, under saline stress, archaea reduced the toxic effects of salt, allowing corn to maintain more vigorous growth and greater physiological tolerance compared to plants not treated with archaea.

Analysis by qPCR, a molecular technique used to detect the quantity of microorganisms present in a sample, of the 16S rRNA gene specific for archaea confirmed successful colonization. The abundance of these microorganisms in the rhizosphere of the corn increased proportionally to the increase in soil salinity.

Whole genome sequencing identified genes associated with the production of phytohormones (plant hormones), such as auxins, and osmoprotectants, substances that help maintain cellular water balance in saline environments. This finding highlights the potential of archaea to interact with the plant and mitigate osmotic stress caused by salt. In the assays, the presence of these microorganisms increased biomass and preserved chlorophyll levels even under high salt concentrations.

The result reinforces the technology's potential to strengthen the stability of food production in areas affected by salinization. Unlike bacteria, which are better known organisms, archaea belong to their own domain of living beings and stand out for their high resistance to harsh chemical conditions.

Biotechnological potential

According to Itamar Melo, a researcher at Embrapa Meio Ambiente who coordinated the study, salinized soils end up being excluded from agricultural production and become a significant environmental liability, since there are few effective technologies for their recovery. The researcher points out that the main commercial crops are sensitive to excess salt, which further limits the use of these areas.

According to him, the application of microorganisms adapted to saline environments, which co-evolved with halophytic plants—those naturally tolerant to salt—is emerging as an alternative to reduce the damage caused by salinity and enable cultivation in soils previously considered unproductive. “The problem is not limited to the semi-arid region, where about 30% of irrigated areas suffer from salinization. It is present in various regions of Brazil and the world.”

Melo points out that the situation worsens in areas with high evaporation and inadequate management, such as irrigation with brackish water. "In this context, microbial inoculants based on archaea emerge as a promising innovation in the field of bio-inputs and can open a new front for agriculture in degraded areas."

Researcher João Paulo Ventura, scientifically affiliated with Embrapa Meio Ambiente, where he developed his doctoral thesis, led the research, conducting the experiments and analyzing the study's data. According to him, the results change the way science views these microorganisms.

According to Ventura, the study demonstrates that archaea are not only organisms capable of surviving in extreme environments, but can also act as strategic allies for sustainable agriculture. Until now, the interactions between plants and archaea were poorly understood and rarely explored, mainly due to the difficulties of cultivating these microorganisms in the laboratory.

The researcher states that experiments have proven that, when inoculated, archaea establish successful competitive colonization in corn roots. "The abundance of these microorganisms increases as soil salt levels rise, indicating adaptation to adverse conditions and potential application in areas affected by salinity."

According to him, the findings reposition the role of these organisms. "From microbiological curiosities associated with extreme environments, archaea are now seen as concrete biotechnological tools, with the potential to sustain agricultural productivity and contribute to food security in areas affected by salinization and climate change," he states.

Impact and challenge of salinization

This research addresses a structural problem in agriculture. In the semi-arid region, especially the Caatinga, salinization compromises production and income in rural areas. Surveys by Embrapa indicate that Brazil has approximately 16 million hectares of soil affected by salts, with more than half concentrated in the semi-arid Northeast. Between 20% and 25% of the irrigated areas in the region already present salinity or drainage problems, impacting crops such as corn, beans, cotton, and sorghum.

Globally, reports from the Food and Agriculture Organization of the United Nations (FAO) indicate that 1,38 billion hectares have some degree of salinity and another 1 billion are at risk. Between 20% and 50% of the world's irrigated areas suffer losses in fertility and productivity.

More conservative estimates indicate that approximately 833 million hectares are already moderately to severely affected. The impact is particularly critical in irrigated areas, which are responsible for a large part of food production in dry and semi-arid regions. Between 20% and 50% of these lands have salt levels capable of reducing soil fertility and crop productivity.

The effects go beyond agricultural production. The United Nations (UN) associates soil salinization with direct impacts on food security, estimating that around 1,5 billion people live in regions where salinization threatens the stability of food production.

Practical applications in the field

In the short term, the results indicate potential for testing under real production conditions. Bioinoculants based on archaea isolated from naturally saline environments, or microbial consortia adapted to this stress, could be evaluated for application to seeds or directly to the soil before planting.

The hypothesis is that this strategy will help crops such as corn, beans, and vegetables maintain productive performance in areas irrigated with brackish water, a common situation in the semi-arid Northeast of Brazil. Integrated with already established management practices, such as crop rotation with halophytic plants (species adapted to environments with high salinity), minimum tillage, and balanced fertilization, microbial inoculation can reduce the effects of salinization on crops, increase the resilience of agricultural systems, and contribute to food security and income in rural areas.

What is soil salinization?

It is a process of excessive accumulation of soluble salts (such as sodium and chloride) in the upper layers of the soil, reducing its fertility and agricultural productivity. This phenomenon can occur naturally—especially in arid and semi-arid regions—but is intensified by human activities such as inadequate irrigation, poor water management, and excessive use of fertilizers.

As it happens

• Dry climates and high evaporation: water evaporates and salts remain on the surface.
• Poorly drained irrigation: excess water without adequate drainage causes the water table to rise, accumulating salts.
• Use of water with high salinity: irrigating with brackish water also tends to concentrate salts.

More information at doi.org/10.1186/s40793-025-00698-2