Pseudomonas spp., a zinc-solubilizing vermicompost bacteria with plant growth-promoting activity moderates zinc biofortification in tomato.

Zinc is an essential micronutrient necessary for optimal development of tomato (Solanum lycopersicum L.). Zinc-solubilizing microbes could be substitutes for zinc supplementation and transform inorganic zinc into accessible forms. The objective of the study was to culture and screen a variety of zinc-solubilizing bacteria (ZSB) from vermicompost for various plant growth-promoting (PGP) characteristics in tomato. Thirty-isolates from vermicompost were screened for Zn-solubilization and PGP activity. A quantitative assessment of Zn solubilization indicated maximum Zn solubilization was achieved with isolate VBZ4 (26.8 mg∙L⁻¹) followed by isolate VBZ17 (22.2 mg∙L⁻¹) on ZnO and 18.3 mg∙L⁻¹ (isolate VBZ4), 15.6 mg∙mL⁻¹ (isolate VBZ17) on ZnCO₃ enriched media. The isolates were examined in association with tomato plants for growth, where isolate VBZ4 improved plant growth and maximum zinc content in tomato fruit (2.87 mg/100 g) followed by isolates VBZ4+ VBZ17 and isolate VBZ17 with 2.17 mg/100 g and 2.06 mg/100 g Zn content, respectively. Isolates VBZ4 and VBZ17 were identified as Pseudomonas sp. VBZ4 and P. stutzeri VBZ17. Application of these bacteria may help provide sufficient Zn bioavailability which could lead to improved plant growth in a sustainable manner. [ABSTRACT FROM AUTHOR]