Microbial Biofortification of Iron in Solanum tuberosum L. through Siderophore-Producing Rhizobacteria along with L-Tryptophan and Iron Sulphate Supply

Food security necessitates not only increasing crop yields but also enhancing food quality while simultaneously mitigating the detrimental effects of agricultural practices on natural resources and the environment. Iron (Fe) deficiency is a prevalent nutritional concern that affects a significant portion of the global population, particularly children and pregnant women. One potential solution to address these deficiencies is microbial biofortification, which involves the intentional augmentation of beneficial nutrients within agricultural plants. Plant growth–promoting rhizobacteria (PGPR) can enhance the Fe content in the edible parts of plants through various direct and indirect methods. This study aimed to assess the combined impact of two bacterial isolates, both individually and in conjunction with L-tryptophan and iron sulphate, on the growth, physiology, tuber characteristics, and Fe content of potatoes (Solanum tuberosum L.). The findings indicated that the application of PGPR and plant growth regulators (PGR) significantly enhanced plant height, haulm yield, and the number of tubers per plant. Fe content was notably increased by the sole application of L-tryptophan (24.58%) and bacterial strains (Z-20 increased by 17.54% and Z-37 by 31.05%). Furthermore, the introduction of the microbial consortia and L-tryptophan resulted in a remarkable enhancement, with up to a two-fold increase in the Fe concentration of potatoes compared to the control. Additionally, nitrogen (N) and phosphorus (P) concentrations also increased significantly. The results indicate that the presence of rhizobacteria can facilitate nutrient absorption by plants from the soil. This study demonstrates that the combined use of microbial-assisted biofortification and PGR is a promising, economically viable strategy for addressing micronutrient deficiencies, especially in resource-limited countries.