Application of Root Associated Zinc solubilizing Bacillus proteolyticus strain SH 25 on growth and augmentation of Zinc in Maize Plant

Zinc (Zn) stands out as a critical micronutrient crucial for the proper growth, development and functioning of plants. Recent studies indicate that zinc exists abundantly in soil, it predominantly persists in insoluble forms, hindering its uptake by plants. Zinc solubilizing bacteria (ZSB) emerge as pivotal agents in facilitating the transformation of insoluble zinc into soluble forms, thus aiding plant growth. To address this issue, the current study aimed at isolating, screening, identifying and characterizing efficient zinc solubilizing bacteria to enhance maize growth. Numerous bacteria were isolated from the maize rhizosphere in the Northern region of West Bengal by using the dilution plate technique. Screening involved the utilization of ZnO, zinc ores, with only four bacterial strains exhibiting notable zinc solubilizing capacity selected for further assessment. These strains underwent biochemical, morphological and plant growth-promoting (PGP) activity evaluations. The selected bacterial isolates, capable of solubilizing Zn, underwent further screening for their ability to promote plant growth under sterile conditions. The identified bacterium was classified as Bacillus proteolyticus (SH 25/OM584287) by molecular identification through MALDI-TOF-MS analysis and 16S rDNA sequencing. This ZSB isolate demonstrated various growth-promoting attributes including the production of organic acids, contributing to its effectiveness in enhancing maize growth. ZnSO4 served as the zinc source in this study. The impact of SH 25 on Zea mays (variety: SUPER DON-9533) was quantified using the Zinc Transformation Index (ZTI) measured via Atomic Absorption Spectroscopy (AAS).