Introduction and aimsThe intensive cropping system and imbalance use of chemical fertilizers to pursue high grain production and feed the fast-growing global population has disturbed agricultural sustainability and nutritional security. Understanding micronutrient fertilizer management especially zinc (Zn) through foliar application is a crucial agronomic approach that could improve agronomic biofortification of staple grain crops. The use of plant growth-promoting bacteria (PGPBs) is considered as one of the sustainable and safe strategies that could improve nutrient acquisition and uptake in edible tissues of wheat to combat Zn malnutrition and hidden hunger in humans. Therefore, the objective of this study was to evaluate the best-performing PGPB inoculants in combination with nano-Zn foliar application on the growth, grain yield, and concentration of Zn in shoots and grains, Zn use efficiencies, and estimated Zn intake under wheat cultivation in the tropical savannah of Brazil.MethodsThe treatments consisted of four PGPB inoculations (without inoculation,Azospirillum brasilense, Bacillus subtilis, andPseudomonas fluorescens, applied by seeds) and five Zn doses (0, 0.75, 1.5, 3, and 6 kg ha−1, applied from nano ZnO in two splits by leaf).ResultsInoculation ofB. subtilisandP. fluorescensin combination with 1.5 kg ha−1foliar nano-Zn fertilization increased the concentration of Zn, nitrogen, and phosphorus in the shoot and grain of wheat in the 2019 and 2020 cropping seasons. Shoot dry matter was increased by 5.3% and 5.4% with the inoculation ofP. fluorescens, which was statistically not different from the treatments with inoculation ofB. subtilisas compared to control. The grain yield of wheat was increased with increasing nano-Zn foliar application up to 5 kg Zn ha−1with the inoculation ofA. brasilensein 2019, and foliar nano-Zn up to a dose of 1.5 kg ha−1along with the inoculation ofP. fluorescensin the 2020 cropping season. The zinc partitioning index was increased with increasing nano Zn application up to 3 kg ha−1along with the inoculation ofP. fluorescens. Zinc use efficiency and applied Zn recovery were improved at low doses of nano-Zn application in combination with the inoculation ofA. brasilense, B. subtilis, andP. fluorescens, respectively, as compared to control.DiscussionTherefore, inoculation withB. subtilisandP. fluorescensalong with foliar nano-Zn application is considered a sustainable and environmentally safe strategy to increase nutrition, growth, productivity, and Zn biofortification of wheat in tropical savannah.