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This study investigated the possibility of using phosphate-solubilizing bacteria (PSB) with plant-growth-promoting (PGP) capabilities to improve the growth properties of rice plants under ferruginous ultisol (FU) conditions through bio-priming. The following PSB with PGP properties were used in this study: Bacillus cereus strain GGBSU-1, Proteus mirabilis strain TL14-1, and Klebsiella variicola strain AUH-KAM-9, which were previously isolated and characterized based on 16S rRNA gene sequencing. Biosafety analysis of the PSB isolates was conducted using blood agar. The rice seeds were then bio primed with the PSB for 3, 12, and 24 h and then sown in a composite FU soil sample. Differences in germinat ion bioassay were investigated 15 weeks after bio-priming using scanning electron microscopy (SEM), morphology, physiology, and biomass parameters. The composite FU soil used in this study had high pH, low bioavailable phosphorus, low water-holding capacity, and high iron levels, which resulted in low growth properties of rice seeds without bio-priming in the FU soil. Germination parameters were improved in seeds bio primed with the PSB, especially after 12 h of priming, compared with seeds without priming. SEM showed higher bacterial colonization in bio primed seeds. Bio-priming of rice seeds with the studied PSB under FU soil conditions significantly improved seed microbiome, rhizocolonization, and soil nutrient properties, thereby enhancing the growth properties of rice. This indicated the ability of PSB to solubilize and mineralize soil phosphate and improve phosphorus availability and soil properties for optimum plant usage in phosphate-stressed and iron toxic soils. [ABSTRACT FROM AUTHOR]

Phosphorus (p) is a chemical component that has a concentration in the world’s land mass of around one gram for each kilogram. 85% to 95% of cellular phosphorus is available in the vacuole, 31p-nmr examinations uncovers the inadequacy of inorganic phosphorus (pi) efflux from the vacuole to make-up for a fast reduction of the cytosolic pi focus during phosphorus starvation. Activities of phosphorus use involve biogeochemical mechanisms of phosphorus in soil, the phosphorus cycle, chelation of iron (Fe), manganese (Mn) and aluminium (Al) and their subsequent removal from forming insoluble phosphorus compounds, transformation of phosphorus in the soil, and fixation of phosphorus in the soil. Phosphorus utilisation occur through solubilization by microbes which could be bacteria, fungi or bio-fertilizers that produce phytohormone, siderophores and antibiotics. However, factors affecting phosphorus solubilization are pH and temperature which are key predominant players for phosphorus adsorption dynamics from the soil and rhizosphere by plants, soil phosphorus transformation, spatial availability and acquisition of soil phosphorus, root architecture, bioavailability and acquisition of soil phosphorus, phosphorus cycling and bioavailability in soil-plant systems, its chemistry as well as its final uptake and utilization by plants. Overall, the phosphorus nutrition of plants is majorly monitored by phosphorus dynamics in the soil/rhizosphere-plant continuum. Given the usefulness of phosphorus to plants and its importance as a strategic resource, a better understanding of phosphorus dynamics in the soil/rhizosphere-plant continuum is necessary to lead the establishment of integrated phosphorus-management strategies involving manipulation of soil and rhizosphere activities, development of phosphorus-efficient crops, and improving phosphorus-recycling efficiency in the future. [ABSTRACT FROM AUTHOR]