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Plant Science Today (PST)

Research Articles

Vol. 13 No. sp5 (2026): Recent Advances in Agriculture

Isolation, characterisation and evaluation of native zinc-solubilising bacteria from the sorghum rhizosphere

DOI
https://doi.org/10.14719/pst.15912
Submitted
7 June 2026
Published
01-09-2026

Abstract

Zinc is an important micronutrient required for plant growth and development. However, a large proportion of soil zinc occurs in insoluble forms that are poorly available to plants, leading to zinc deficiency. To alleviate the zinc deficiency, zinc-solubilising bacteria (ZSB) are employed. This study aimed to isolate, characterise and assess the zinc solubilisation potential of different genera from the rhizosphere soil of sorghum. A total of 10 ZSB isolates were obtained using Bunt and Rovira medium amended with 0.1 % zinc oxide (ZnO). The isolates were screened for their ability to solubilise insoluble 0.1 % ZnO using a plate assay. Among the 10 isolates, ZNS2 exhibited the highest zinc solubilisation efficiency (224.99 %), followed by ZNS7 (212.49 %) in zinc oxide. In the quantitative assay, ZNS2 released the highest available zinc (299.79 mg L-1) in ZnO-amended medium. Zinc solubilisation was associated with a significant reduction in pH of the medium, suggesting organic acid-mediated solubilisation. The isolates ZNS1, ZNS2, ZNS7, ZNS8 and ZNS9 were non-haemolytic (γ-haemolysis) on blood agar, indicating non-pathogenicity. Based on the 16S rRNA sequencing, isolates ZNS1, ZNS2, ZNS7, ZNS8 and ZNS9 were identified as Niallia nealsonii, Pseudomonas fluorescens, Micrococcus luteus, Klebsiella pneumoniae and Paenibacillus lautus, respectively. To the best of our knowledge, N. nealsonii, M. luteus and P. lautus are reported here for the first time as zinc solubilising bacteria. These isolates demonstrated considerable potent for improving zinc availability and may contribute to reducing dependence on chemical zinc fertilisers. These findings suggest that native rhizobacterial isolates could serve as sustainable, low-cost bioinoculants for improving zinc bioavailability and addressing zinc-related malnutrition. Further studies are required to evaluate their zinc-solubilising efficiency under soil conditions and their effects on crop growth and zinc uptake.

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