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Inoculation with Pseudomonas fluorescens has been widely used due to its growth promotion and potential influence on plant nitrogen (N) metabolism. The objective of this study was to estimate the rate of P. fluorescens that provides the greatest growth, chlorophyll, foliar nitrate reductase (NR) enzyme activity and the reduction of nitrate (NO3−) accumulation in hydroponic lettuce plants. The treatments consisted of different rates of P. fluorescens inoculant via the nutrient solution, with rates ranging from 0, 8, 16, 32 and 64 mL 100 L−1 of solution. Inoculating with P. fluorescens at a dosage ranging from 23 and 34 mL 100 L−1 of solution resulted in significantly greater fresh and dry mass for both the shoots and roots of the plants. Notably, at rates of 32 and 37 mL 100 L−1 of P. fluorescens, there was a 39% increase in N accumulation and a remarkable 192% increase in ammonium (NH4+) accumulation in the shoots. Simultaneously, there was a significant 65% reduction in NO3− accumulation in the shoots, and at the highest rate of P. fluorescens, the NR activity increased. In addition, it was observed an increasing in the concentration of chlorophyll a, chlorophyll b, carotenoids, total carbohydrates and total amino acids in the leaves by 43, 74, 50, 98 and 165% at rates of 35, 36, 37, 38 and 50 mL 100 L−1 of P. fluorescens. Inoculation of P. fluorescens at a rate of 35 mL 100 L−1via nutrient solution in hydroponic lettuce cultivation provided increase of photosynthetic efficiency, N uptake, mass accumulation, shoot yield and a decrease in the accumulation of NO3− in the plant shoots. [ABSTRACT FROM AUTHOR]

The study of the application of biostimulants in agriculture aims to increase production and improve the efficient use of physical space and agricultural inputs, thus contributing to the sustainability of production systems. One of the new challenges is to verify the effects of joint application of these products to identify possible interactions during crop development. In this context, the present study aimed to evaluate the biostimulant potential of the isolated and combined use of nicotinamide and Azospirillum brasilense in developing cantaloupe melon plants and fruits. The treatments consisted of foliar application (combined and isolated) of nicotinamide (300 mg L−1) and A. brasilense (2 mL L−1). The results revealed that applying biostimulants positively influences gas exchange and vegetative growth of plants, especially in the root system. However, although the isolated application of each biostimulant resulted in greater effectiveness in terms of transpiration, stomatal conductance, and net CO2 assimilation, which provided an increase in the soluble solids content, the combined application of the two biostimulants resulted in significant gains in the growth of vegetative organs and fruits. Furthermore, combined applications of nicotinamide plus A. brasilense favored the development of biometric characteristics and fruit fresh weight, while isolated applications increased soluble solids content. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Brazil is the world's largest producer of common beans (Phaseolus vulgaris L.). Drought stress harms the morphological and agronomic traits of beans. This study evaluates the reaction to water deficit in five genotypes of black beans. The experiment was conducted in the IDR‐IAPAR‐EMATER in Londrina‐PR, Brazil. A split‐plot design was used, with three replications. The genotypes were included in the subplots and the treatments with or without water deficit in the plots. Water deficit was induced on the pre‐flowering stage and maintained for 20 days in the plots submitted to drought stress. For the growth analysis, plants were collected at 35, 54 and 70 days after emergence. At the stage of physiological ripeness, several morphological and yield traits were evaluated. The genotypes IPR Uirapuru and BRS Esplendor can be considered tolerant and used as a tolerant source to water deficit in common bean germplasm banks. The line LP 08‐90 has morphological and agronomic adaptations efficient to overcome water deficit's effects, presenting a higher grain yield in both crop conditions, which indicates the success of black beans breeding to deal with water deficit. [ABSTRACT FROM AUTHOR]

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.)