Application of halotolerant Azotobacter chroococcum W4ii isolated from technosoils to mitigate salt stress in wheat plant

Abstract

Background: Technosoils are soils affected by human activities. One such soil, present in Inowrocław, central Poland, is characterized by increased salinity (ECe up to 70 dS/m) and has been influenced by a soda lime repository. Microorganisms retrieved from such environments that have naturally adapted to harsh environmental conditions, especially plant growth-promoting rhizospheric (PGPR) bacteria, can help degraded soils maintain their performance. This can contribute to increased plant biomass and protection against pathogens, resulting in a reduction of mineral fertilizers and pesticides used in agriculture. The goal of this research was to obtain PGPR from degraded soil and implement them into the soil under laboratory and field conditions to improve the growth of wheat seedlings. Methods: Azotobacter chroococcum W4ii was isolated from the rhizosphere of wheat (Triticum aestivum L.) for its plant growth properties on wheat plants under salt stress. Results: Wheat seeds co-inoculated with A. chroococcum W4ii under 200 mM salt stress showed significant improvement in various growth parameters such as plant height, shoot biomass, chlorophyll b content compared to un-inoculated ones. Bacterial inoculation decreased the level of malondialdehyde (MDA), whereas it elevated the antioxidative enzymatic activities of peroxidase (POD). The test isolate also enhanced the level of defense enzymes like β-1, 3-glucanase, which can protect plants from the infection of pathogens. The bacterium could also successfully colonize the wheat plants. Conclusions: These results indicate that A. chroococcum isolated from the technosoil has potential to promote wheat growth under salt stress and can be further used as bioinoculant in the salt affected agricultural fields.