Isolation of potential Zn solubilizing bacteria from corn rhizosphere

Abstract

Deficiency of micronutrients is a limiting factor in crop productivity. In terms of micronutrient deficiencies, zinc (Zn) deficiency is considered the most common. Obstacles to the availability of Zn in plants are not caused by the low total concentration of Zn, but by the low solubility of Zn in the soil. Therefore, a feasible approach is to exploit the capacity of soil microorganisms, especially bacteria, to convert the insoluble form of Zn to the soluble form of Zn, thereby increasing its availability and ability of plants to absorb it. This study aims to isolate various bacteria with the potential to dissolve Zn. Bacterial isolates obtained from the rhizosphere of corn plants were tested on insoluble zinc compounds, such as ZnCO3, ZnO, and Zn3(PO4)2 separately. Dissolving potential was assessed qualitatively by observing the formation of transparent zones. Of the 56 types of bacteria tested, only 6 isolates formed transparent zones. The results showed variations in the efficiency of dissolving insoluble Zn compounds between bacteria and the Zn sources used. Isolate Btg.2.3 showed the widest transparent zone in Zn media (ZnO, ZnCO3, and Zn3(PO4)2) with sizes of 20.0 mm, 24.0 mm and 15.7 mm, while isolate Bn.1.7 showed the smallest transparent zone with sizes 14.0 mm, 14.3 mm and 8.7 mm. The area of the transparent zone indicates the level of solubility and can be related to the dissolution of soluble Zn compounds produced by bacterial isolates. Of the Zn sources used, ZnCO3 showed the highest formation of transparent zones, followed by ZnO and Zn3(PO4)2.