High-throughput screening and genomic characterization of iron phosphate solubilizing bacteria for sustainable greenhouse production

Background and aims Phosphorus availability is often limited in greenhouse production due to the formation of insoluble metal complexes in soilless substrates. Phosphate solubilizing bacteria (PSB) can break down these insoluble metal cation complexes and increase plant available forms of phosphorus. This study aims to identify and characterize iron PSB that enhance phosphorus availability in soilless greenhouse systems. Methods A collection of 1044 rhizobacterial isolates was screened for iron phosphate solubilization using a malachite green colorimetric assay. Isolates demonstrating greater than 25 percent solubilization of supplied FePO 4 ·2H 2 O were selected, sequenced, and classified taxonomically. These candidate strains were assessed in greenhouse trials under phosphorus limited conditions to evaluate plant growth promotion. Whole genome sequencing and functional annotation were performed to identify genes involved in phosphate solubilization and rhizosphere adaptation. Results Malachite green assay screening identified 24 high performing strains with strong FePO 4 ·2H 2 O solubilization ability. Greenhouse evaluation showed that Pantoea communis C3A8 , Pantoea formicae C8D10, Pseudomonas sp. C6E7, Pseudomonas sp. C9D1 and Priestia megaterium C3F10 improved spectral indicators of plant quality in French marigolds, while three of the strains (C3A8, C8D10, and C6E7) also increased shoot digital biomass. Strain C3A8 significantly increased shoot tissue P content. These strains encode unique genes supporting multiple phosphorus solubilization mechanisms as well as traits for effective rhizosphere colonization. Conclusion These findings highlight the importance of targeted screening and genomic analysis for identifying effective iron PSB strains, supporting the development of strategies aimed at reducing fertilizer inputs and promoting sustainable nutrient management in greenhouse crop production.