Synergistic effects of Bacillus pumilus strain JSR1 and gold nanoparticles on growth enhancement in Trigonella foenum-graecum L. 

The growing demand for sustainable agriculture has led to the exploration of eco-friendly alternatives to chemical fertilisers. The co-application of Plant Growth-Promoting Rhizobacteria (PGPR) in combination with nanoparticles is a potential strategy. In this study, a potent rhizobacterium from the rhizosphere of Trigonella foenum-graecum L. (fenugreek) was isolated, and its synergistic effect with chemically synthesised gold nanoparticles (AuNPs) on plant growth and development was evaluated. A total of 100 bacterial isolates with different morphologies were isolated from ten rhizospheric soil samples from the Saurashtra region of Gujarat and assessed for plant growth-promoting characteristics. Bacillus pumilus (J3) was the most promising isolate, exhibiting all the PGP traits. The chemically synthesised gold nanoparticles were characterised using a UV-visible spectrophotometer and Transmission Electron Microscopy (TEM). A pot experiment was conducted in the Biotechnology Research Laboratory, Atmiya University, Rajkot, Gujarat, from November 2024 to March 2025 to evaluate individual and synergistic effects of J3 and AuNPs (10–50 ppm) on fenugreek growth. A significant improvement in germination rate and various growth factors was observed with J3 combined with 10 and 20 ppm AuNPs. The synergistic effects of AuNPs and the PGPR strain suggest potential for the enhancement of fenugreek production and may be employed for sustainable crop improvement methods on other economically significant crops.