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Inoculation with Bacillus subtilis is a promising approach to increase plant yield and nutrient acquisition. In this context, this study aimed to estimate the B. subtilis concentration that increases yield, gas exchange, and nutrition of lettuce plants in a hydroponic system. The research was carried out in a greenhouse in Ilha Solteira, Brazil. A randomized block design with five replications was adopted. The treatments consisted of B. subtilis concentrations in nutrient solution [0 mL "non-inoculated", 7.8 × 10 3 , 15.6 × 10 3 , 31.2 × 10 3 , and 62.4 × 10 3 colony forming units (CFU) mL -1 of nutrient solution]. There was an increase of 20% and 19% in number of leaves and 22% and 25% in shoot fresh mass with B. subtilis concentrations of 15.6 × 10 3 and 31.2 × 10 3 CFU mL -1 as compared to the non-inoculated plants, respectively. Also, B. subtilis concentration at 31.2 × 10 3 CFU mL -1 increased net photosynthesis rate by 95%, intercellular CO 2 concentration by 30%, and water use efficiency by 67% as compared to the non-inoculated treatments. The concentration of 7.8 × 10 3 CFU mL -1 improved shoot accumulation of Ca, Mg, and S by 109%, 74%, and 69%, when compared with non-inoculated plants, respectively. Inoculation with B. subtilis at 15.6 × 10 3 CFU mL -1 provided the highest fresh leaves yield while inoculation at 15.6 × 10 3 and 31.2 × 10 3 CFU mL -1 increased shoot fresh mass and number of leaves. Concentrations of 7.8 × 10 3 and 15.6 × 10 3 increased shoot K accumulation. The concentrations of 7.8 × 10 3 , 15.6 × 10 3 , and 31.2 × 10 3 CFU mL -1 increased shoot N accumulation in hydroponic lettuce plants., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Oliveira, Jalal, Aguilar, de Camargos, Zoz, Ghaley, Abdel-Maksoud, Alarjani, AbdElgawad and Teixeira Filho.)

Introduction and Aims: The 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., Methods: The treatments consisted of four PGPB inoculations (without inoculation, Azospirillum brasilense, Bacillus subtilis , and Pseudomonas 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)., Results: Inoculation of B. subtilis and P. fluorescens in combination with 1.5 kg ha -1 foliar 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 of P. fluorescens , which was statistically not different from the treatments with inoculation of B. subtilis as compared to control. The grain yield of wheat was increased with increasing nano-Zn foliar application up to 5 kg Zn ha -1 with the inoculation of A. brasilense in 2019, and foliar nano-Zn up to a dose of 1.5 kg ha -1 along with the inoculation of P. fluorescens in the 2020 cropping season. The zinc partitioning index was increased with increasing nano Zn application up to 3 kg ha -1 along with the inoculation of P. fluorescens . Zinc use efficiency and applied Zn recovery were improved at low doses of nano-Zn application in combination with the inoculation of A. brasilense, B. subtilis , and P. fluorescens , respectively, as compared to control., Discussion: Therefore, inoculation with B. subtilis and P. fluorescens along 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., Competing Interests: All the authors are aware of the manuscript publication and they have no financial, commercial, or other conflict of interest., (Copyright © 2023 Jalal, Oliveira, Fernandes, da Silva, da Costa, de Souza, Leite, Biagini, Galindo and Teixeira Filho.)

Introduction: Plant growth-promoting bacteria (PGPBs) could be developed as a sustainable strategy to promote plant growth and yield to feed the ever-growing global population with nutritious food. Foliar application of nano-zinc oxide (ZnO) is an environmentally safe strategy that alleviates zinc (Zn) malnutrition by improving biochemical attributes and storage proteins of grain., Methods: In this context, the current study aimed to investigate the combined effect of seed inoculation with PGPBs and foliar nano-ZnO application on the growth, biochemical attributes, nutrient metabolism, and yield of maize in the tropical savannah of Brazil. The treatments consisted of four PGPB inoculations [i.e., without inoculation , Azospirillum brasilense ( A. brasilense ) , Bacillus subtilis ( B. subtilis ) , Pseudomonas fluorescens ( P. fluorescens ), which was applied on the seeds] and two doses of Zn (i.e., 0 and 3 kg ha -1 , applied from nano-ZnO in two splits on the leaf)., Results: Inoculation of B. subtilis with foliar ZnO application increased shoot dry matter (7.3 and 9.8%) and grain yield (17.1 and 16.7%) in 2019-20 and 2020-2021 crop seasons respectively. Inoculation with A. brasilense increased 100-grains weight by 9.5% in both crop seasons. Shoot Zn accumulation was improved by 30 and 51% with inoculation of P. fluorescens in 2019-20 and 2020-2021 crop seasons. Whereas grain Zn accumulation was improved by 49 and 50.7% with inoculation of B. subtilis and P. fluorescens respectively. In addition, biochemical attributes (chlorophyll a, b and total, carotenoids, total soluble sugar and amino acids) were improved with inoculation of B. subtilis along with foliar nano ZnO application as compared to other treatments. Co-application of P. fluorescens with foliar ZnO improved concentration of grains albumin (20 and 13%) and globulin (39 and 30%). Also, co-application of B. subtilis and foliar ZnO improved concentration of grains glutelin (8.8 and 8.7%) and prolamin (15 and 21%) in first and second seasons., Discussion: Therefore, inoculation of B. subtilis and P. fluorescens with foliar nano-ZnO application is considered a sustainable and environmentally safe strategy for improving the biochemical, metabolic, nutritional, and productivity attributes of maize in tropical Savannah regions., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Jalal, Oliveira, Bastos, Fernandes, de Lima, Furlani Junior, de Carvalho, Galindo, Gato and Teixeira Filho.)