Exploring the uncharted: Zinc and phosphate solubilization in Zn-P isolates from wheat rhizosphere inceptisols

Abstract

This research delves into the untapped potential of phosphorous and zinc solubilizing rhizobacteria, known as Zn-P isolates, from wheat rhizosphere inceptisols. A total of thirty rhizosphere soil samples were collected, resulting in recovery of forty unique bacterial isolates. After initial screening, out of forty isolates, recovered on the basis of halozone formation on the nutrient agar medium. four were subjected to biochemical and further molecular identification. Four isolates, identified as Bacillus subtilis (Zn-P-1), Pseudomonas aureginosa (Zn-P-2), Staphylococcus aureus (Zn-P-3), and Methylobacterium organophyllum (Zn-P-4) through a set of 16S rRNA primers, forward (5́- GGATGAGCCCGCGGCCTA-3́) and reverse (5́- CGGTGTGTACAAGGCCCGG-3́), exhibited superior solubilization efficiency of phosphorous and zinc These strains were evaluated via in vitro and pot culture assays. The study found that Zn-P-1 demonstrated the highest zinc solubilization (134.87 mg/l) when ZnO was used as the zinc source as compared to ZnCO₃ and Zn-EDTA as also highest at 72.32 mg/l in CaH₂PO₄ and lowest at 14.44 mg/l with KH₂PO₄ using P sources, thus highlighting the role of Bacillus in zinc and phosphorous activity with substrate type. The inoculation of tri-calcium phosphate (TCP) and ZnCO₃, along with Bacillus and Methylobacterium, led to increased phosphorous and zinc solubilization, uptake, and use efficiency, marking these rhizobacteria as potentially beneficial for nutrient enhancement and PGPR activities in wheat crops grown in inceptisols.