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The objectives of this research were to: i) develop a mechanistic understanding of the synergy between microbial co-inoculation, nitrogen (N) fertilizer, and maize plants on biological 15 N fixation, and 15 N-recovery from applied fertilizers; and ii) explore the mechanist effects of microbial co-inoculation on N fractionations and derivation (fertilizer, atmosphere and soil), physiological responses on water use and carboxylation efficiencies and growth by using two different isotopic techniques under field conditions. Treatments included four seed inoculations (Control, B. subtilis, A. brasilense, and the combination of B. subtilis and A. brasilense), along with five levels of N application (0-240 kg N ha -1 ). Overall, the results indicate that maize co-inoculation with the above-mentioned bacteria enhanced photosynthetic efficiency leading to improved carboxylation efficiency and instantaneous water use efficiency in maize plants, likely due to an increase in net photosynthetic rate. This effect was more evident under low N availability. The findings also suggest that co-inoculation enhanced the ability of maize plants to absorb CO 2 , adjust to different soil N levels, and carry out photosynthesis, which resulted in higher carbon fixation and better maize growth. The N obtained from the atmosphere resulting from inoculation ranged from 25 to 50 kg N ha -1 . Nonetheless, N application rates exceeding 186 kg N ha -1 substantially diminished the ability of these bacteria to fix N 2 . The combination of inoculation with the application of 120-180 kg N ha -1 led to a synergistic effect resulting in the greatest N-use efficiency, -recovery and grain yield., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Introduction: Plant growth-promoting bacteria (PGPB) have been primarily studied for atmospheric nitrogen (N) fixation but they also have the capacity to improve nutrition and yield of crop plants., Methods: Therefore, the objective of this research was to investigate the effects of inoculation with PGPB in association with different N rates on N uptake, grain yield, and oil concentration of dwarf castor beans in succession to legumes and grasses in Ilha Solteira, Brazil. The treatments consisted of N rates (0 to 180 kg ha -1 of N) and inoculation with three plant growth-promoting bacteria ( Azospirillum brasiliense, Bacillus subtilis , and Pseudomonas fluorescens , applied by leaf) and a control with no-inoculation., Results: The grain and oil yields of castor beans were increased by 20 and 40% at a rate of 103 kg ha -1 of N in succession to grasses as compared to without N application. In addition, the grain yield of castor bean after legumes was increased by 28, 64, and 40% with estimated rates of 97, 113, and 92 kg ha -1 of N in combination with inoculations of A. brasilense , B. subtilis , and P. fluorescens as compared to without N application, respectively. Shoot, grain, and total N uptake were improved with foliar inoculation of A. brasilense , B. subtilis , and P. fluorescens at the N rates of 45, 90, and 135 kg ha -1 , respectively., Discussion and Conclusions: Topdressing of N at the rate of 103 kg ha -1 and foliar inoculation in succession to grasses and 180 kg ha -1 of N without the effect of foliar inoculation in succession to legumes are recommended for higher grain and oil yield of castor beans. Foliar inoculations with A. brasilense , B. subtilis , and P. fluorescens increased grain yield under reduced use of N fertilizer by 44, 37, and 49% in dwarf castor cultivation in succession to legumes, potentially contributing to sustainable agriculture., 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. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Gato, Oliveira, Jalal, Moreira, Hashem, de Lima, Leite, Al-Askar, Freitas, AbdElgawad, Ferreira, Santana, Bastos, Galindo, Zoz and Teixeira Filho.)

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.)

Phosphate fertilization in highly weathered soils has been a major challenge for sugarcane production. The objective of this work was to evaluate the foliar levels of phosphorus (P) and nitrogen (N) and the technological quality and productivity of second ratoon cane as a function of inoculation with plant-growth-promoting bacteria (PGPBs) together with the residual effect of phosphate fertilization. The experiment was carried out at the research and extension farm of Ilha Solteira, state of São Paulo, Brazil. The experiment was designed in a randomized block with three replications in a 5 × 8 factorial scheme. The treatments consisted of five residual doses of phosphorus (0, 45, 90, 135 and 180 kg ha -1 of P 2 O 5 , 46% P) applied at planting from the source of triple superphosphate and eight inoculations from three species of PGPB ( Azospirillum brasilense , Bacillus subtilis and Pseudomonas fluorescens ), applied in single or co-inoculation at the base of stems of sugarcane variety RB92579. Inoculation with PGPBs influenced leaf N concentration, while inoculations with Pseudomonas fluorescens and combinations of bacteria together with the highest doses exerted a positive effect on leaf P concentration. Co-inoculation with A. brasilense + Pseudomonas fluorescens associated with a residual dose of 135 kg ha -1 of P 2 O 5 increased stem productivity by 42%. Thus, it was concluded that inoculations with Pseudomonas fluorescens and their combinations are beneficial for the sugarcane crop, reducing phosphate fertilization and increasing productivity.

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.)

The challenging alterations in climate in the last decades have had direct and indirect influences on biotic and abiotic stresses that have led to devastating implications on agricultural crop production and food security. Extreme environmental conditions, such as abiotic stresses, offer great opportunities to study the influence of different microorganisms in plant development and agricultural productivity. The focus of this review is to highlight the mechanisms of plant growth-promoting microorganisms (especially bacteria and fungi) adapted to environmental induced stresses such as drought, salinity, heavy metals, flooding, extreme temperatures, and intense light. The present state of knowledge focuses on the potential, prospective, and biotechnological approaches of plant growth-promoting bacteria and fungi to improve plant nutrition, physio-biochemical attributes, and the fitness of plants under environmental stresses. The current review focuses on the importance of the microbial community in improving sustainable crop production under changing climatic scenarios.

Wheat is one of the staple foods of the global population due to its adaptability to a wide range of environments. Nitrogen is one of the crucial limiting factors in wheat production and is considered a challenge to food security. Therefore, sustainable agricultural technologies such as seed inoculation with plant growth-promoting bacteria (PGPBs) can be adopted to promote biological nitrogen fixation (BNF) for higher crop productivity. In this context, the objective of the current study was to evaluate the effects of nitrogen fertilization and seed inoculations with Azospirillum brasilense, Bacillus subtilis and A. brasilense + B. subtilis on agronomic and yield attributes, grain yield, grain N accumulation, N use efficiency and applied N recovery in Brazilian Cerrado, which consists of gramineous woody savanna. The experiment was carried out in two cropping seasons in Rhodic Haplustox soil under a no-tillage system. The experiment was designed in a randomized complete block in a 4 × 5 factorial scheme, with four replications. The treatments consisted of four seed inoculations (control-without inoculation, inoculation with A. brasilense, B. subtilis and A. brasilense + B. subtilis ) under five N doses (0, 40, 80, 120 and 160 kg ha -1 , applied from urea) at the wheat tillering stage. Seed co-inoculation with A. brasilense + B. subtilis increased grain N accumulation, number of spikes m -1 , grains spike -1 and grain yield of wheat in an irrigated no-tillage system of tropical savannah, regardless of the applied N doses. Nitrogen fertilization at a dose of 80 kg ha -1 significantly increased grain N accumulation and number of grains spikes -1 and nitrogen use efficiency. Recovery of applied N was increased with inoculation of B. subtilis and co-inoculation of A. brasilense + B. subtilis at increasing N doses. Therefore, N fertilization can be reduced by the inclusion of co-inoculation with A. brasilense + B. subtilis in the cultivation of winter wheat under a no-tillage system of Brazilian Cerrado.

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.)

A successful microbial inoculant can increase root colonization and establish a positive interaction with native microorganisms to promote growth and productivity of cereal crops. Zinc (Zn) is an intensively reported deficient nutrient for maize and wheat production in Brazilian Cerrado. It can be sustainably managed by inoculation with plant growth-promoting bacteria and their symbiotic association with other microorganisms such as arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE). The objective of this study was to evaluate the effect of Azospirillum brasilense inoculation and residual Zn rates on root colonization and grain yield of maize and wheat in succession under the tropical conditions of Brazil. These experiments were conducted in a randomized block design with four replications and arranged in a 5 × 2 factorial scheme. The treatments consisted of five Zn rates (0, 2, 4, 6 and 8 kg ha -1 ) applied from zinc sulfate in maize and residual on wheat and without and with seed inoculation of A. brasilense . The results indicated that root colonization by AMF and DSE in maize-wheat cropping system were significantly increased with interaction of Zn rates and inoculation treatments. Inoculation with A. brasilense at residual Zn rates of 4 kg ha -1 increased root colonization by AMF under maize cultivation. Similarly, inoculation with A. brasilense at residual Zn rates of 2 and 4 kg ha -1 reduced root colonization by DSE under wheat in succession. The leaf chlorophyll index and leaf Zn concentration were increased with inoculation of the A. brasilense and residual Zn rates. The inoculation did not influence AMF spore production and CO 2 -C in both crops. The grain yield and yield components of maize-wheat were increased with the inoculation of A. brasilense under residual Zn rates of 3 to 4 kg ha -1 in tropical savannah conditions. Inoculation with A. brasilense under residual Zn rates up to 4 kg ha -1 promoted root colonization by AMF and DSE in the maize cropping season. While the inoculation with A. brasilense under 2 and 4 kg ha -1 residual Zn rates reduced root colonization by AMF and DSE in the wheat cropping season. Therefore, inoculation with A. brasilense in combination with Zn fertilization could consider a sustainable approach to increase the yield and performance of the maize-wheat cropping system in the tropical savannah conditions of Brazil.

Even though it is a forest native plant, there are already several studies evaluating the small genome of Jatropha curcas L., which belongs to the Euphorbiaceae family, and may be an excellent representative model for the other plants from the same family. Jatropha curcas L. plant has fast growth, precocity, and great adaptability, facilitating silvicultural studies, allowing important information to be obtained quickly, and reducing labor costs. This information justifies the use of the species as a model plant in studies involving the reproduction of native plants. This study aimed to evaluate the possibility of using Jatropha curcas L. as a model plant for studies involving native forest plants and establish possible recommendations for the vegetative propagation of the species using hardwood cuttings. The information collected can be helpful to other native forest plant species, similar to Jatropha curcas L. To this end, the effects of hardwood cutting length (10, 20, and 30 cm) and the part of the hardwood cuttings (basal, middle, and apex) were evaluated. Moreover, the influence of immersing the hardwood cuttings in solutions containing micronutrients (boron or zinc) or plant regulators (2,4-D, GA3) and a biostimulant composed of kinetin (0.09 g L -1 ), gibberellic acid (0.05 g L -1 ), and 4-indole-3-butyric acid (0.05 g L -1 ). The experiments were carried out in duplicates. In one duplicate, sand was used as the substrate, and rooting evaluations were made 77 days after planting. In another duplicate, a substrate composed of 50% soil, 40% poultry litter, and 10% sand was used, and the evaluations of the saplings were performed 120 days after planting. The GA3 solutions inhibited the roots' and sprouts' emissions, while immersion in 2,4-D solution increased the number of primary roots at 77 days after planting. The hardwood cuttings from the basal part of the branch had the best results for producing saplings.

The use of beneficial fungi and bacteria stimulate plant growth and serve to improve yield and food quality in a sustainable manner. The electrical conductivity of nutrients solution is closely linked to better nutrition of vegetable plants in a hydroponic system. Therefore, objectives of current study were to evaluate the effect of isolated and combined inoculation with Azospirillum brasilense and Trichoderma harzianum under two electrical conductivities on growth, nutrition, and yield of lettuce in hydroponic cultivation. The experiment was designed in a strip-plot block with five replications in a 4 × 2 factorial scheme. The treatments were consisted of four microbial inoculations (without, A. brasilense, T. harzianum and co-inoculation) and electrical conductivities (1.2 and 1.4 dS m -1 ). Inoculation with A. brasilense and T. harzianum increased lettuce root growth by 47% and 20%, respectively. The single inoculation of T. harzianum provided higher fresh leaves yield (24%) at electrical conductivity of 1.2 dS m -1 , while single inoculation with A. brasilense increased fresh leaves yield by 17% at electrical conductivity 1.4 dS m -1 . The lowest shoot NO 3 - accumulation (40%) was observed with inoculation of A. brasilense and highest (28%) with inoculation T. harzianum in both electrical conductivities. Inoculation with A. brasilense increased leaf accumulation of K, P, Ca, Mg, Fe, Mn, Cu, and Zn, which are essential for human nutrition and being recommended to improve yield of lettuce plants in hydroponics. It is recommended to use EC 1.4 dS m -1 of the nutrients solution to improve accumulation of K, Mn, Cu, and Zn, regardless of inoculations for biofortification of lettuce with application of fertilizers., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Biofortification of cereal crops with zinc and diazotrophic bacteria is a sustainable solution to nutrient deficiency and hidden hunger. The inoculation of staple grain crops such as maize is increased with reducing productivity losses while improving nutrition and use efficiency under climatic extremes and weathered soils of tropical savannah. Therefore, objectives of our study were to evaluate the influence of seed inoculation with diazotrophic bacteria (No inoculation-Control, Azospirillum brasilense , Bacillus subtilis , and Pseudomonas fluorescens ) together with residual effect of soil Zn (absence and presence) on growth, yield, Zn nutrition, Zn use efficiencies, and intake of maize in 2019 and 2020 cropping seasons. The inoculation of B. subtilis increased hundred grain mass and yield (14.5 and 17%), while P. fluorescens under residual Zn fertilization has improved shoot and grain Zn concentration in shoot (29.5 and 30.5%). and grain (25.5 and 26.2%), while improving Zn accumulation in shoot (33.8 and 35%) and grain (37.2 and 42%) of maize. The estimated Zn intake in maize was also increased with A. brasilense inoculation and residual Zn application. The Zn use efficiencies including Zn use efficiency, agro-physiological, and utilization efficiency was increased with B. subtilis , while applied Zn recovery was increased with A. brasilense inoculations under residual Zn fertilization. Zinc use efficiency was increased by 93.3 and 397% with inoculation of B. subtilis regardless of Zn application. Therefore, inoculation with B. subtilis and P. fluorescens along residual Zn fertilization is considered the most effective and sustainable strategy for agronomic biofortification of maize under harsh tropical conditions of Brazil.

Phosphorus (P) is a critical nutrient for high sugarcane yields throughout its cultivation cycles, however, a higher amount of P becomes rapidly unavailable to plants due to its adsorption to soil colloids. Some plant growth-promoting bacteria (PGPBs) may be able to enhance P availability to plants and produce phytohormones that contribute to crop development, quality, and yield. Thus, this study aimed to evaluate leaf concentrations of nitrogen (N) and P, yield, and technological quality of sugarcane as a function of different levels of phosphate fertilization associated with inoculation of PGPBs. The experiment was carried out at Ilha Solteira, São Paulo-Brazil. The experimental design was randomized blocks with three replications, consisting of five phosphorus rates (0, 25, 50, 75, and 100% of the recommended P 2 O 5 rate) and eight inoculations, involving three species of PGPBs ( Azospirillum brasilense , Bacillus subtilis, and Pseudomonas fluorescens ) which were applied combined or in a single application into the planting furrow of RB92579 sugarcane variety. The inoculation of B. subtilis and P. fluorescens provided a higher concentration of leaf P in sugarcane. The P 2 O 5 rates combined with inoculation of bacteria alter technological variables and stalk yield of sugarcane. The excess and lack of phosphate fertilizer is harmful to sugarcane cultivation, regardless of the use of growth-promoting bacteria. We recommend the inoculation with A. brasilense + B. subtilis associated with 45 kg ha -1 of P 2 O 5 aiming at greater stalk yield. This treatment also increases sugar yield, resulting in a savings of 75% of the recommended P 2 O 5 rate, thus being a more efficient and sustainable alternative for reducing sugarcane crop production costs.