Bioprospecting phosphate solubilising bacteria for agriculture application

Phosphorus plays a crucial role in plant growth, influencing vital processes such as photosynthesis, respiration and the synthesis of nucleic acids. However, plants can only utilise phosphorus in the form of orthophosphate. Most of the phosphorus in the soil is in forms that are difficult to assimilate. Farmers often use chemical fertilisers to provide soluble phosphorus. This continuous behaviour will lead to the depletion of natural phosphate reserves and higher prices, increasing costs for the farmer and subsequently the consumer. In addition, the continued accumulation of phosphorus compounds in the soil contributes to soil and water pollution. The problem is exacerbated by the formation of phosphorus complexes in alkaline soils, in the form of calcium phosphate, and in acidic soils, in the form of aluminium/iron phosphate. A sustainable alternative to increase phosphorus availability for plants is the use of phosphorus solubilising bacteria (PSB) as biostimulants and biofertilisers. The aim of this study was to assess the ability of various bacterial strains from different areas (mainland Portugal, Sal Island (Cape Verde), Huíla (Angola) and the Namib Desert (Angola)) to solubilise phosphorus. After initial characterisation, some strains were selected for greenhouse tests and applying them individually to soils with pH 7 and 8. Subsequently, the most promising strains were tested in a consortium in field trials, using maize (Zea mays L.) as a model crop, given its contribution as a key cereal for global food security. In addition, the antioxidant response (superoxide dismutase and catalase activity), metabolic activity (electron transport system and soluble proteins) and how these bacteria influence the absorption of nutrients by plants were investigated. The results of this study are relevant in a context of growing environmental pressure and climate change and could contribute to the development of more productive and ecological agricultural methods, reducing the use of chemical fertilisers and protecting the environment.