Understanding the Molecular Mechanism of PGPR Strain Priestia megaterium from Tea Rhizosphere for Stress Alleviation and Crop Growth Enhancement

Abstract

The study aimed to assess the plant growth-promoting (PGP) capabilities and abiotic stress tolerance of strain IHB B 7164, with a focus on identifying associated genes through genomic analysis. Isolated from the tea rhizosphere, strain underwent screening for PGP traits and stress tolerance against various abiotic factors. Taxonogenomic analysis of the complete genome identified the bacterium as Priestia megaterium, exhibiting high similarity (97.04% ANI, 74.3% in silico DDH) to P. megaterium ATCC 14581. Functional annotations of the genome highlighted gene clusters associated with PGP traits and stress tolerance, substantiating the strain's potential in promoting plant growth under stress conditions. Under stressed culture conditions such as acidity/alkalinity, temperature fluctuations, desiccation, salinity, and exposure to calcium, aluminum, and iron salts, the strain demonstrated robust growth and PGP activities, affirming its status as a broad-spectrum rhizobacterium. Screening of PGP traits under acidic conditions revealed phosphate solubilization, ACC-deaminase activity and production of IAA-like auxins. Notably, gluconic and oxalic acids were consistently detected during solubilization of tri-calcium phosphate (TCP), aluminum phosphate (Al-P), and iron phosphate (Fe-P). Inoculation with the strain led to significant enhancements in tea nursery plants, including a 9% increase in plant height, 10% increase in leaf number, and substantial improvements in leaf fresh and dry weights. Similarly, pea and wheat yields recorded notable increases of 16.9% and 18.3%, respectively, under field conditions. These findings underscore the efficacy of P. megaterium strain IHB B 7164 as an abiotic stress-tolerant and broad-spectrum plant growth promoting rhizobacteria (PGPR) capable of enhancing plant growth and productivity across diverse agricultural settings.