Synergistic effect of Zinc Solubilizing Bacteria and Consortia on the zinc marker enzymes and gaseous exchange parameters in Rice (Oryza sativa L.) for zinc biofortification

Abstract

This study investigates the impact of Zinc Solubilizing Bacteria (ZSB) and their consortia on key physiological and biochemical in two rice varieties, PD 26 and NDR 359, over two consecutive growing seasons (2022 and 2023). Unlike individual bacterial strains, microbial consortia harness the synergistic interactions between multiple species, leading to enhanced zinc solubilization efficiency and improved plant responses. The application of consortia significantly boosted the activities of zinc-dependent enzymes, including carbonic anhydrase (CA) and superoxide dismutase (SOD). It also significantly improved gaseous exchange parameters, including stomatal conductance, internal CO₂ concentration, photosynthetic rate, and transpiration rate. Maximum CA activity in both the varieties was recorded with Consortium1 (T4) and Consortium2 (T5), resulting in an increase of up to 44.60 % and 29.88 % in PD 26 and NDR 359 respectively. Similarly, SOD activity increased by up to 65.11 % in PD 26 and 39.99 % in NDR 359. ZSB consortia treatments also enhanced stomatal conductance by up to 61.92 %, with a significant increase in internal CO₂ concentration, photosynthetic rate, and transpiration rate. Additionally, ZSB positively influenced leaf zinc content and grain yield, with the maximum yield observed with Consortium2 (T5). Regression analysis showed a significant positive correlation between leaf zinc content and CA, SOD activities as well as with photosynthetic rate (R² = 0.64 to 0.95). Principal component analysis (PCA) highlighted the superior performance of consortia treatments in modulating physiological traits, underscoring their potential as sustainable biofortification agents. These findings demonstrate that ZSB consortia outperform individual strains by leveraging multi-strain synergies, leading to enhanced zinc bioavailability and crop productivity.