Screening of Drought-Tolerant, Silicate-Solubilizing Bacteria and Their Efficacy in Enhancing the Growth and Yield of Rice under Water Stress

The beneficial impacts of silicate-solubilizing bacteria (SSB) on rice growth and yield under water stress remain poorly understood. Thus, this study was conducted to screen, identify, and evaluate the efficacy of drought-tolerant silicate bacteria in improving rice growth and yield under water deficit conditions.

Ten isolates were screened for their silicate-solubilizing capacity and their drought tolerance. A two-factor pot experiment was subsequently conducted in a glasshouse to evaluate the effects of SSB on rice growth and yield under both flooded and water deficit conditions. The water deficit condition was imposed using an alternate wetting and drying technique with water applied every 10 days from 35 to 105 days after sowing. The experiment was carried out in a randomized complete block design with four replications. The pot experiment included four bacterial inoculations and two soil conditions.

In vitro assays identified Pseudomonas aeruginosa and Enterobacter sichuanensis as the most effective strains, exhibiting the highest levels of silicate solubilization and drought tolerance. In the pot experiment, the water deficit condition effectively induced physiological stress in rice, as evidenced by a reduction in relative water content (RWC) compared with the flooded condition. Treatments with E. sichuanensis and co-inoculation significantly increased plant height, relative water content, root length, SPAD value, and Si and lignin content in rice. Across both flooded and water-deficit conditions, the E. sichuanensis and co-inoculation treatments improved total grain yield by 9.25% and 12.88%, respectively, compared with the control.

Notably, the E. sichuanensis and co-inoculation treatments enhanced Si uptake in rice regardless of water conditions, resulting in improved physiological attributes and yield components compared to the control.

These findings underscore the potential of E. sichuanensis and co-inoculation strategies to serve as biofertilizers to mitigate the impacts of water stress in rice and contribute to sustainable rice production. Further research is needed to validate their efficacy at the field scale and to optimize their formulation as biofertilizers.