Salinity-Resistant Bacteria: Revitalizing Salt-Damaged Soils & Boosting Crop Growth
- Soil salinization, a growing threat to global food security, is increasingly impacting agricultural lands worldwide.
- High salt concentrations create multiple challenges for plants.
- Conventional methods for reclaiming saline soils, such as scraping, flushing, leaching, or adding soil amendments like gypsum, often have limited success and can negatively impact the surrounding ecosystem.
Soil salinization, a growing threat to global food security, is increasingly impacting agricultural lands worldwide. The buildup of salt in soil inhibits plant growth, disrupts essential physiological processes, and reduces crop yields. Researchers are actively exploring strategies to mitigate these effects, with a focus on harnessing the power of plant growth-promoting bacteria (PGPB) to enhance crop resilience in saline environments.
The Impact of Soil Salinity
High salt concentrations create multiple challenges for plants. According to research published in , these include osmotic imbalance, ion stress, and oxidative damage, all of which can stunt growth and ultimately reduce productivity. The problem is particularly acute in regions like parts of China, Australia, the Middle East, and the southwestern United States, where soils are becoming increasingly saline.
Conventional methods for reclaiming saline soils, such as scraping, flushing, leaching, or adding soil amendments like gypsum, often have limited success and can negatively impact the surrounding ecosystem. This has spurred interest in more sustainable approaches that focus on enhancing plant tolerance to salt stress.
Harnessing the Power of Bacteria
A promising avenue of research involves utilizing salt-tolerant bacteria to promote plant growth in saline conditions. Scientists at Brigham Young University (BYU) have demonstrated success in inoculating alfalfa with bacteria capable of thriving in high-salt environments. As reported in , researchers led by Brent Nielsen, professor of microbiology and molecular biology at BYU, isolated over 40 different bacterial isolates, some of which can tolerate salt concentrations comparable to ocean water.
The BYU team found that specific bacterial isolates – Halomonas and Bacillus – significantly stimulated alfalfa growth even in the presence of 1 percent sodium chloride, a level that typically inhibits growth in uninoculated plants. This discovery suggests a potential pathway for reversing falling crop yields in salt-damaged farmlands.
Rhizobia and Legumes: A Symbiotic Relationship
Research at the Pontifical Catholic University of Valparaíso (PUCV) in Chile is focusing on the symbiotic relationship between legumes (beans, lentils, alfalfa, etc.) and soil bacteria called rhizobia. These bacteria are crucial for biological nitrogen fixation, a natural process that fertilizes the soil. However, soil salinization can disrupt this vital symbiosis.
Carolina Yáñez, a researcher at the Institute of Biology at PUCV, is leading a project investigating the use of extremophilic bacteria – microorganisms capable of surviving and thriving in extreme environments, including high salinity – to promote plant growth. The goal is to enable the successful association between rhizobia and legumes even in damaged soils, thereby revitalizing soil quality.
“Our bet is that if we use these Extremophilous bacteria, which have very particular characteristics, they will be able to live in salinized soils because they have all the information to do so and this will help this successful association between the rhizobium and the legume to happen, and the soils to be fertilized,” explained Yáñez.
Pioneer Plants and Soil Restoration
Legumes play an important ecological role as “pioneer plants” in degraded soils. They are often among the first plants to colonize barren areas, helping to nourish the soil and awaken dormant seed banks. Yáñez notes that legumes can help initiate the recovery of damaged ecosystems.
Ongoing Research and Future Directions
The PUCV research team is currently collecting extremophilic bacteria from various sources, including the Huasco salt flat and the Puquios area in Copiapó, Chile. They plan to evaluate approximately 50 bacterial strains for their salt tolerance and growth-promoting properties, with the aim of identifying candidates for association tests with rhizobia in bean plants.
Researchers are also investigating the role of gamma-aminobutyric acid (GABA), a non-protein amino acid found in bacteria, yeast, vertebrates, and plants, in mitigating damage caused by soil salinity. Studies suggest that certain Bacillus species can produce GABA, contributing to plant stress tolerance.
research indicates that Pseudomonas putida and Novosphingobium species can reduce salt-stress induced damage in citrus plants by lowering levels of abscisic acid (ABA). This highlights the diverse mechanisms by which PGPB can enhance plant resilience to salinity.
The research at PUCV, part of a Fondecyt project, is currently in its initial stages, involving controlled laboratory tests using beans as a model plant. Future plans include expanding to field trials in areas like Petorca, Chile, in the coming years. The long-term goal is to develop sustainable methods for improving the productivity of saline soils and safeguarding global food security.
“Soil is a priority for the recycling of nutrients and plays a fundamental role in ecosystem goods and services; it is a non-renewable resource because it takes thousands of years to form, despite which it suffers many abuses – pollution, garbage, burning – so if it is damaged we lose it,” Yáñez emphasized.