Effectiveness of the Plant Growth-Promoting Rhizobacterium Pantoea sp. BRM17 in Enhancing Brassica napus Growth in Phosphogypsum-Amended Soil

Abstract Phosphogypsum (PG) is a by-product of the phosphate fertilizer industry that represents an environmental concern. BRM17, a newly isolated strain from Tunisian PG BRM17 with the ability to solubilize inorganic phosphate, was identified as Pantoea sp. based on the analysis of 16S rDNA sequencing. The plant growth-promoting traits of BRM17 were analyzed by investigating the production of siderophores, indolic compounds (IAA), exopolysaccharides (EPS), ammonia (NH 3 ), and 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity. Observation of Arabidopsis thaliana roots inoculated with BRM17 tagged with a far-red fluorescent protein (mkate2) revealed that Pantoea sp. colonized the surface and inner part of the roots. A pot experiment was conducted to investigate the ability of BRM17 to promote the growth of canola ( Brassica napus ) in PG-amended soil in both sterilized and non-sterilized conditions. An increase in shoot and root biomass was observed in plants that were inoculated with BRM17 and cultivated in 2% PG amended soil. This effect was more significant in the sterilized condition. Furthermore, canola inoculated with BRM17 was able to grow in 100% PG, unlike non-inoculated plants. This study provides a strong basis for the further development of Pantoea sp. BRM17 inoculum to solubilize inorganic phosphate, due to its ability to overcome difficulties related to plant growth in PG dump sites or in PG-amended soils.