Zinc solubilizing Pseudomonas spp. from vermicompost bestowed with multifaceted plant growth promoting properties and having prospective modulation of zinc biofortification in Abelmoschus esculentus L

Abstract

Zinc is an essential micronutrient necessary for the optimal development and yield of Okra (Abelmoschus esculentus L.). Plants absorb zinc in soluble form as Zn²⁺; a large amount of zinc in the soil are in insoluble forms. Zinc solubilizing microbes could be substitutes for zinc fertilizers and transform inorganic zinc into plant accessible forms. The study was aimed to isolate and screen a range of Zinc solubilizing bacteria (ZSB) from vermicompost for their plant growth-promoting properties with okra. Thirty bacterial isolates from vermicompost were examined for zinc solubilization with ZnO and ZnCO₃ using dilution plate method on Kings B medium. Two strains, i.e., VBZ4 and VBZ17, were found most prevalent Zn solubilizing isolates with 32 mm and 43 mm solubilization zone for ZnO supplemented media. Atomic absorption spectroscopy (AAS) was used for quantitative assessment of Zn solubilization, where VBZ4 displayed significantly higher solubility of ZnO (26.8 ppm) compared with VBZ17 (22.2 ppm). The quantitative results of plant growth promotion characters showed that VBZ4 and VBZ17 isolates to solubilize the maximum amount of phosphate with 316.72 μg/ml and 214.0 μg/ml, and indole acetic acid production, 10.2 μg/ml and 17.1 μg/ml respectively. Further, ZSB isolates were introduced with Okra seeds under pot experiment, where treatment P4 (seeds + VBZ4 + VBZ17) found significantly effective on plant growth and maximum zinc content in Okra fruit (2.85 mg/100g) compared to control. Application of these bacteria may help to provide sufficient amounts of Zn bioavailability, including improved plant growth in a sustainable manner.

Keywords:

• Okra
• PGP activity
• pseudomonas
• vermicompost
• zinc solubilization

Acknowledgment

The authors are very thankful to the Bhojia Institute of Life Sciences, Budh, Baddi, H.P., India, for technical support to complete this study and unlimited help in all steps.

Conflict of interest

The author declares that there is no conflict of interest.