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This study characterizes seedling exudates of peas, tomatoes, and cucumbers at the level of chemical composition and functionality. A plant experiment confirmed that Rhizobium leguminosarum bv. viciae 3841 enhanced growth of pea shoots, while Azospirillum brasilense Sp7 supported growth of pea, tomato, and cucumber roots. Chemical analysis of exudates after 1 day of seedling incubation in water yielded differences between the exudates of the three plants. Most remarkably, cucumber seedling exudate did not contain detectable sugars. All exudates contained amino acids, nucleobases/nucleosides, and organic acids, among other compounds. Cucumber seedling exudate contained reduced glutathione. Migration on semi solid agar plates containing individual exudate compounds as putative chemoattractants revealed that R. leguminosarum bv. viciae was more selective than A. brasilense, which migrated towards any of the compounds tested. Migration on semi solid agar plates containing 1:1 dilutions of seedling exudate was observed for each of the combinations of bacteria and exudates tested. Likewise, R. leguminosarum bv. viciae and A. brasilense grew on each of the three seedling exudates, though at varying growth rates. We conclude that the seedling exudates of peas, tomatoes, and cucumbers contain everything that is needed for their symbiotic bacteria to migrate and grow on. [ABSTRACT FROM AUTHOR]

Background: Water stress is a major danger to crop yield, hence new approaches to strengthen plant resilience must be developed. To lessen the negative effects of water stress on wheat plants, present study was arranged to investigate the role of synergistic effects of biochar, trans-zeatin riboside (t-ZR), and Azospirillum brasilense on soil improvement and enzymatic activity in water-stressed wheat. Results: In a three-replication experiment comprising of four treatments (T0: Control, T1: Drought stress (DS), T2: DS + t-ZR with biochar, T3: DS + A. brasilense with biochar), we observed notable improvements in soil quality and enzymatic activities in water-stressed wheat plants with the application of t-ZR and A. brasilense with biochar. In drought stress, Treatment having the application of A. brasilense with biochar performs best as compared to the other and significant increased the enzymatic activities such as peroxidase (7.36%), catalase (8.53%), superoxide dismutase (6.01%), polyphenol oxidase (14.14%), and amylase (16.36%) in wheat plants. Different enzymatic activities showed different trends of results. Soil organic C, dissolved organic C, dissolved organic N also enhanced 29.46%, 8.59%, 22.70% respectively with the application of A. brasilense with biochar under drought stress condition. Conclusions: The synergistic action of A. brasilense and biochar creates an effective microbiological environment that supports essential plant physiological processes during drought stress. This enhancement is attributed to improved soil fertility and increased organic matter content, highlighting the potential of these novel strategies in mitigating water stress effects and enhancing crop resilience. [ABSTRACT FROM AUTHOR]

The nitrogen (N) requirement for barley cultivation can vary from 90 to 130 kg ha−1 cycle−1, representing 30% of production costs. Furthermore, obtaining mineral N is difficult due to constant conflicts involving producing countries. Excess N will increase the cost of production and contaminate the soil and groundwater, unbalancing the fauna, flora, and microbiology of the environment. The objective of this research was to evaluate the management of inoculation and N fertilization with A. brasilense on the development and productivity of barley. Field experiment was carried out for two years. A randomized block design was used in a 5 (Factor A) × 2 (Factor D) factorial arrangement with four replications. In which the "factor A" included five doses of A. brasilense, whereas the "factor D" was evaluated N management (with or without N management). The inoculant used had approximately of 2.0 × 108 viable cells mL−1 (Ab-V5 and Ab-V6 strains). Innoculation was carried out on the seeds 1 hour before sowing, in order to homogenize the inoculant in the seeds, to guarantee homogeneity of the distribution of microorganisms on the seeds. The best dose of A. brasilense was 12.5 mL kg−1 of seed, which provided an increase in plant height, number of ears, mass and grain productivity. The use of A. brasilense showed significant improvements in management with or without the use of mineral N. However, better results are obtained when the association between N management and the use of inoculant is made. Thus, when using up to 22.5 kg of N, the best results were observed. [ABSTRACT FROM AUTHOR]

Background: Considering the challenges posed by nitrogen (N) pollution and its impact on food security and sustainability, it is crucial to develop management techniques that optimize N fertilization in croplands. Our research intended to explore the potential benefits of co-inoculation with Azospirillum brasilense and Bacillus subtilis combined with N application rates on corn plants. The study focused on evaluating corn photosynthesis-related parameters, oxidative stress assay, and physiological nutrient use parameters. Focus was placed on the eventual improved capacity of plants to recover N from applied fertilizers (AFR) and enhance N use efficiency (NUE) during photosynthesis. The two-year field trial involved four seed inoculation treatments (control, A. brasilense, B. subtilis, and A. brasilense + B. subtilis) and five N application rates (0 to 240 kg N ha−1, applied as side-dress). Results: Our results suggested that the combined effects of microbial consortia and adequate N-application rates played a crucial role in N-recovery; enhanced NUE; increased N accumulation, leaf chlorophyll index (LCI), and shoot and root growth; consequently improving corn grain yield. The integration of inoculation and adequate N rates upregulated CO2 uptake and assimilation, transpiration, and water use efficiency, while downregulated oxidative stress. Conclusions: The results indicated that the optimum N application rate could be reduced from 240 to 175 kg N ha−1 while increasing corn yield by 5.2%. Furthermore, our findings suggest that replacing 240 by 175 kg N ha−1 of N fertilizer (-65 kg N ha−1) with microbial consortia would reduce CO2 emission by 682.5 kg CO2−e ha−1. Excessive N application, mainly with the presence of beneficial bacteria, can disrupt N-balance in the plant, alter soil and bacteria levels, and ultimately affect plant growth and yield. Hence, highlighting the importance of adequate N management to maximize the benefits of inoculation in agriculture and to counteract N loss from agricultural systems intensification. [ABSTRACT FROM AUTHOR]

The evaluation of plant growth-promoting bacteria in order to increase corn productivity is a biotechnology of global interest. This study evaluated the efficiency of the consortium between P. fluorescens CNPSo 2719(=CCTB03) and A. brasilense Ab-V06 in corn. Four experiments were carried out in four different locations, with a randomized block design and four replications, with the treatments: (1) without inoculation and without application of N coverage; (2) without inoculation and application of 100% of the recommended dose of N in coverage (200 kg ha-1 of N); (3) Azospirillum brasilense + application of 75% of the recommended dose of N in coverage (150 kg ha-1 of N); (4) bacterial consortium of Azospirillum brasilense + Pseudomonas fluorescens + application of 75% of the recommended dose of N in coverage (150 kg ha-1 of N). In all locations, with the use of the bacterial consortium (A. brasilense + P. fluorescens) + 75% of the recommended dose of N in coverage, it was possible to reduce the dose of N in coverage by up to 25% without compromising the productivity of the crop. In this way, it is concluded that the use of the consortium of the two bacteria promotes savings of up to 25% of N fertilization in top dressing and the possibility of using two microorganisms with the capacity to stimulation plant growth with a single application. [ABSTRACT FROM AUTHOR]

Azospirillum brasilense Sp7 produces PHB, which is covered by granule-associated proteins (GAPs). Phasins are the main GAPs. Previous studies have shown phasins can regulate PHB synthesis. When A. brasilense grows under stress conditions, it uses sigma factors to transcribe genes for survival. One of these factors is the σ24 factor. This study determined the possible interaction between phasins and the σ24 factor or phasin-σ24 factor complex and DNA. Three-dimensional structures of phasins and σ24 factor structures were predicted using the I-TASSER and SWISS-Model servers, respectively. Subsequently, a molecular docking between phasins and the σ24 factor was performed using the ClusPro 2.0 server, followed by molecular docking between protein complexes and DNA using the HDOCK server. Evaluation of the types of ligand–receptor interactions was performed using the BIOVIA Discovery Visualizer for three-dimensional diagrams, as well as the LigPlot server to obtain bi-dimensional diagrams. The results showed the phasins (Pha4Abs7 or Pha5Abs7)-σ24 factor complex was bound near the −35 box of the promoter region of the phaC gene. However, in the individual interaction of PhaP5Abs7 and the σ24 factor, with DNA, both proteins were bound to the −35 box. This did not occur with PhaP4Abs7, which was bound to the −10 box. This change could affect the transcription level of the phaC gene and possibly affect PHB synthesis. [ABSTRACT FROM AUTHOR]

Cabbage serves as an important food and nutrition source for numerous communities in the world, yet its production requires substantial quantities of chemical fertilizers. In this study, we assessed the impact of both increasing nitrogen and phosphorus mineral (NP) fertilization, along with the application of plant growth-promoting bacteria (PGPB) on the N and P uptake, quality, and yield of cabbage. To this end, we conducted two consecutive field experiments following a randomized block design with four replicates and two factors: NP doses and PGPB inoculation. PGPB inoculation used a bacterial consortium comprising Azospirillum brasilense D7, Herbaspirillum sp. AP21, and Rhizobium leguminosarum T88. Our results showed a significant influence of both biofertilization and NP fertilization across both crop cycles; however, no interaction between these factors was observed. In the first crop cycle, 75% of NP mineral fertilization (equivalent to 93.6 kg ha−1 of N and 82.1 kg ha−1 of P) positively impacted yield and N uptake. Also, microbial inoculation significantly influenced crop yield, resulting in a 9-ton increase in crop yield per hectare due to biofertilization. In the second crop cycle, we observed a significant positive effect of mineral fertilization on cabbage yield and nutritional quality. The relative agronomic effectiveness (RAE) index showed that combining biological fertilization with 50% and 75% of the NP fertilization, respectively, increased yield by 66% and 48% compared to the commercial NP dosage without PGPB. Collectively, our results demonstrated that within our experimental setup, NP fertilization dosage can be reduced without any detrimental impact on yield. Moreover, biofertilization could enhance cabbage quality and yield in field conditions. [ABSTRACT FROM AUTHOR]

Herein we present the results of optimization of silver nanoparticles biosynthesis using a nonpathogenic soil bacterium Azospirillum brasilense. The conditions and parameters for synthesis of biogenic nanoparticles using A. brasilense vegetative cells, culture liquid, and homogeneous polyphenol oxidase preparations were analyzed. We have revealed the ranging effect of the incubation time, the concentration of silver ions, pH of the reaction mixture, and the concentration of metabolites, towards the production of colloidal silver nanoparticles with specified geometric parameters, high colloidal stability and relatively good monodispersity. The size, shape, and relative yield of electron-dense nanostructures were determined by transmission electron microscopy and dynamic light scattering; extinction spectra were recorded by UV-vis spectrophotometry. [ABSTRACT FROM AUTHOR]

Besides being a significant part of the Brazilian national economy, the common bean is a legume whose grains are part of the daily diet of the population of developing nations globally. Combining N-fixing bacteria and plant phytohormone producers through the use of inoculants is an alternative to improve plant growth and increase grain yield in the common bean production system. This study aimed to evaluate the effect of co-inoculation doses with Rhizobium tropici and Azospirillum brasilense, applied in the planting groove, on nodulation, growth and productivity parameters of the common bean. Five field experiments were conducted in a randomized block design with four replications. Restrictions were formulated, namely: absolute control, without fertilization and without co-inoculation (AC); nitrogen fertilization (NfT); single inoculation of R. tropici (Rt); R. tropici + one dose of A. brasiliense (Rt + Ab1f); R. tropici + two doses of A. brasiliense (Rt + Ab2f); R. tropici + three doses of A. brasiliense (Rt + Ab3f); R. tropici + four doses of A. brasiliense (Rt + Ab4f) and R. tropici + three doses of A. brasiliense (RP). The number of nodules (NN), nodule dry mass (NDM), aerial dry mass (ADM), root dry mass (RDM), pod number (NP), number of grains (NG), mass of 100 grain (100G) and grain yield (GY) were taken. The Rt + Ab4f co-inoculation provided a significant increase in NN, NDM, ADM and RDM values than the Rt and AC treatments. In addition, it also presented the highest GY stability, with an average production of 3499 kg ha− 1 from the five sites, which represents an increase of 15.4%, 14.8%, 11.0%, and 1.0% as compared to Rt, AC, RP, and NfT treatments, respectively. The results indicate the feasibility of the use of co-inoculation with R. tropici and A. brasilense in commercial production farms and for small producers in several countries of the world with similar edaphoclimatic conditions, reducing the use of nitrogen fertilizers, production costs and the prevention of negative environmental impacts. [ABSTRACT FROM AUTHOR]

The yield gain of soybean inoculated with Bradyrhizobium spp. or co-inoculated with Bradyrhizobium spp. and Azospirillum brasilense is variable. Inoculants can be applied in the sowing furrow or via seed treatment. There is a gap in our understanding of the efficacy of different inoculation methods. This study aimed to assess the agronomic efficiency of soybean inoculated and co-inoculated with Bradyrhizobium spp. and A. brasilense by different methods. The study was conducted in Paraná State, Brazil, in two seasons. Five treatments were tested: control; seed treatment with Bradyrhizobium spp. (SBr), seed treatment with Bradyrhizobium spp. + A. brasilense (SBr+Az), in-furrow treatment with Bradyrhizobium spp. (FBr), and in-furrow treatment with Bradyrhizobium spp. + A. brasilense (FBr+Az). Shoot dry weight, grain nitrogen content and grain yield were lower in 2018/19. In 2017/18, FBr+Az increased nodule number and dry weight compared with SBr. FBr+Az promoted a 47% increase in pods per plant compared with the control in both seasons. Regardless of season, grain nitrogen content was higher with FBr+Az (mean relative increase of 27%). FBr+Az was superior to SBr+Az in 2017/18, with a 12% increase in yield. Inoculation and co-inoculation improve morphological traits and soybean yield. In-furrow inoculation is more efficient than seed treatment. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate sorghum hybrids associated or not associated with Azospirillum brasilense and nitrogen fertilization (N) during planting on the yield, fermentative profile, and nutritional value of the respective silages. Five sorghum hybrids (Volumax, 201813B, 201814B, 201709B, BRS716) were evaluated with three nitrogen fertilization strategies using urea (100 kg ha-1 of N) and Azospirillum brasilense, and urea (100 kg ha-1 of N)/A. brasilense in association. A randomized block design was used in a 5 x 3 factorial scheme, with five hybrids, three fertilization strategies and three replications (blocks). The useful area of each experimental unit was 3 m x 3 m. The biomass sorghum hybrids showed a dry matter (DM) production (P = 0.01) 48.31% higher than the DM production of the Volumax forage (mean of 17.49 t ha-1 of dry matter). There was no difference between the sorghum hybrid silages in the pH values (mean of 4.11; P = 0.68), gas losses (mean of 3.74% of DM; P = 0.19). The sorghum hybrids biomass 201709B and BRS 716 showed better digestible and DM productivity. Azospirillum brasilense can be used as a nitrogen fertilization strategy in partial or total replacement of urea. [ABSTRACT FROM AUTHOR]

Plant growth-promoting bacteria and arbuscular mycorrhizal fungi improve plant tolerance to abiotic stress. Here, we evaluated the growth and nitrogen metabolism parameters of soybean (Glycine max (L.) Merril) plants subjected to waterlogging, followed by reoxygenation. Seeds were inoculated with Bradyrhizobium or co-inoculated with Bradyrhizobium and Azospirillum brasilense and/or Rhizophagus intraradices. Plants were subjected to waterlogging at the V8 stage for eight days, followed by reoxygenation for an additional four days. After both periods, plants were collected for growth analyses and quantification of amino acid and ureide content and glutamine synthetase (GS) and glutamate synthase (NADH-GOGAT) activity. Plants co-inoculated with A. brasilense and R. intraradices had increased levels of amino acids and ureides when exposed to waterlogging and reoxygenation. Similarly, co-inoculation increased GS and NADH-GOGAT activity during both conditions and mitigated the decreases in plant growth caused by waterlogging. Our results indicate that co-inoculation with Bradyrhizobium, A. brasilense, and R. intraradices alleviates the nitrogen deficit and improves the biomass accumulation of soybean plants exposed to waterlogging stress. However, A. brasilense showed the best performance in dealing with waterlogging conditions and recovering from them. [ABSTRACT FROM AUTHOR]

3-Hydroxypropionic acid (3-HP) is a key building block for value-added chemicals. A biological route for synthesizing this molecule is two-step enzymatic reactions; dehydration of glycerol to 3-hydroxypropanal (3-HPA) by glycerol dehydratase and then oxidation of 3-HPA to 3-HP by aldehyde dehydrogenase. Here, we report an aldehyde dehydrogenase, an engineered α-ketoglutaric semialdehyde dehydrogenase (KGSADH) from Azospirillum brasilense. The variant, named 2C10, was obtained by applying a large KGSADH library to a selection method based on a 3-HP-responsive transcription factor and then a screening method for observing the activities of individual clones. 2C10 exhibited a 4.65-fold higher catalytic activity (kcat/Km: 100 ± 7.1 s−1mM−1) toward 3-HPA than the wild-type enzyme. The flask culture of Pseudomonas denitrificans with 2C10 resulted in an approximately 30% increase in 3-HP titer (43.2 mM) compared with that obtained using wild-type KGSADH (33.1 mM). Molecular dynamics simulations suggested that compared to the wild-type enzyme, 2C10 has a less flexible and smaller binding pocket for aldehyde substrates. [ABSTRACT FROM AUTHOR]

Background: Common bean has high production cost, mainly due to the use of inputs like nitrogen fertilizers. An alternative to replace the use of nitrogen fertilizers is the co-inoculation technique. This work aimed to evaluate the economic performance of the co-inoculation of Rhizobium tropici and different doses of Azospirillum brasilense applied at the V2–V3 stage of the common bean. Methods: The economic analysis was carried out based on data from five field experiments in five locations in the state of Goiás in Brazil. Treatments consisted of absolute control (AC), N-fertilizer treatment (NfT), single inoculation of R. tropici (Rt), R. tropici + one dose of A. brasilense (Rt + Ab1l), R. tropici + two doses of A. brasilense (Rt + Ab2l), R. tropici + three doses of A. brasilense (Rt + Ab3l) and R. tropici + four doses of A. brasilense (Rt + Ab4l). The economic analysis was carried out based on prices and market indexes, depending on the grain yield of the different treatments. Results: The best economic performance was obtained by the co-inoculation Rt + Ab3l, which provided the highest average values of gross revenue (2.471 US$ ha−1), net revenue (2.220 US$ ha−1), and benefit–cost ratio (1.4 US$ US$−1). Conclusions: Co-inoculation Rt + Ab3l also showed the lowest production costs (451 US$ ha−1), while the nitrogen treatment with 80 kg ha−1 of N resulted in the highest average production cost (499 US$ ha−1). [ABSTRACT FROM AUTHOR]

Background: Chromium (Cr) contamination in soil poses a serious hazard because it hinders plant growth, which eventually reduces crop yield and raises the possibility of a food shortage. Cr's harmful effects interfere with crucial plant functions like photosynthesis and respiration, reducing energy output, causing oxidative stress, and interfering with nutrient intake. In this study, the negative effects of Cr on mung beans are examined, as well as investigate the effectiveness of Azospirillum brasilense and salicylic acid in reducing Cr-induced stress. Results: We investigated how different Cr levels (200, 300, and 400 mg/kg soil) affected the growth of mung bean seedlings with the use of Azospirillum brasilense and salicylic acid. Experiment was conducted with randomized complete block design with 13 treatments having three replications. Significant growth retardation was caused by Cr, as were important factors like shoot and root length, plant height, dry weight, and chlorophyll content significantly reduced. 37.15% plant height, 71.85% root length, 57.09% chlorophyll contents, 82.34% crop growth rate was decreased when Cr toxicity was @ 50 µM but this decrease was remain 27.80%, 44.70%, 38.97% and 63.42%, respectively when applied A. brasilense and Salicylic acid in combine form. Use of Azospirillum brasilense and salicylic acid significantly increased mung bean seedling growth (49%) and contributed to reducing the toxic effect of Cr stress (34% and 14% in plant height, respectively) due to their beneficial properties in promoting plant growth. Conclusions: Mung bean seedlings are severely damaged by Cr contamination, which limits their growth and physiological characteristics. Using Azospirillum brasilense and salicylic acid together appears to be a viable way to combat stress brought on by Cr and promote general plant growth. Greater nutrient intake, increased antioxidant enzyme activity, and greater root growth are examples of synergistic effects. This strategy has the ability to reduce oxidative stress brought on by chromium, enhancing plant resistance to adverse circumstances. The study offers new perspectives on sustainable practices that hold potential for increasing agricultural output and guaranteeing food security. [ABSTRACT FROM AUTHOR]

Soilless crops have become an important alternative for large-scale vegetable production because of the quality of their products and optimization of resources. Brassinosteroids (Brs) and Plant Growth-Promoting Bacteria (PGPB), has been reported to promote growth and physiological parameters in soil crops, but there are few reports on the application of these compounds in soilless crops. The effects of Brs ((25R)-3β 5α-dihydroxy-spirostan-6-one) and three strains of PGPB (Bacillus velezensis, Pseudomona sp., and Azospirillum brasilense) on the growth and yield of lettuce under hydroponic conditions were evaluated. Two separate experiments were carried out: one using a substrate in pots under greenhouse conditions and the other using a deep-flow hydroponic system in a growth room with artificial LED lighting. Plant physiological parameters (yield, dry weight, root surface area, and leaf area) and PGPB attributes under in vitro tests (phosphate solubilization and indole-3-acetic acid (IAA) synthesis) were determined using in vitro tests. A completely randomized design was used in all experiments. The results showed that in in vitro tests Azospirillum brasilense and Pseudomonas sp. were the strains that synthesized the highest amounts of IAA (36 mg mL−1 and 34 mg mL−1, respectively). Phosphorus solubilization was significantly higher in the Pseudomonas sp. strain (110.35 µg mL−1). Regarding physiological and quality parameters, the application of Brs (0.5 ppm), Bacillus velezensis, and Azospirillum brasilense (1 × 106 CFU mL−1) caused an increase between 20% and 40% on variables such as plant yield, leaf area, root surface area, and colorimetry of lettuce for substrate or hydroponic conditions, respectively. [ABSTRACT FROM AUTHOR]

Guadua angustifolia produces phenolic compounds, and this production may be influenced by the application of chemical, organic, and biological fertilizers. Currently, the effect of such fertilizers on the synthesis dynamics of this group of metabolites in bamboo is unknown. In this study, the total phenolic content (TPC) and total flavonoid content (TFC) in the leaves of plants fertilized with diammonium phosphate (DAP) and humus in combination with the biofertilizers Promofort®, Azospirillum brasilense, Pseudomonas fluorescens, and Stenotrophomonas sp. were determined using colorimetric techniques across three sampling events (four, five, and seven months after planting). Additionally, an approximation of the bacterial profile of G. angustifolia roots was performed using the DGGE-PCR fingerprint technique. Through repeated measures ANOVA (rmANOVA), it was determined that there is no statistically significant three-way interaction between humus or DAP application, biological fertilizers, and time for either TPC or TFC. However, there were interactions between the sampling event and the application of biological fertilizers for both TPC and TFC, with the latter being promoted by the application of Promofort®. Finally, NMDS analyses and heatmaps with hierarchical clustering showed that the composition and abundance of OTUs in the bacterial profile varied with fertilization type and increased over time. [ABSTRACT FROM AUTHOR]

This study was developed to investigate the interactive effect of silicon (Si) application and the inoculation of plant growth promoting bacteria (PGPB) Azospirillum brasilense on wheat nutrient uptake and accumulation on biomass and grains when combined with nitrogen (N) application rates. The study was set up in a Rhodic Hapludox under no-till system, located in Selvíria, state of Mato Grosso do Sul, Brazil (tropical Savannah region). Treatments were tested in a randomized complete block design with four replicates, arranged in a full factorial design 2 × 2 × 5 and included: i) two soil amendment sources (Ca and Mg silicate as Si source and dolomitic limestone); ii) two seed inoculation (with and without A. brasilense) and iii) five N application rates applied as side-dress (0, 50, 100, 150 and 200 kg ha−1). Increasing N application rates positively influenced wheat nutrition with increased nutrient and Si uptake in shoot. Calcium and Mg silicate positively influenced wheat nutrition with greater shoot Si and grain N, P, K, B, Cu, Fe, Mn, Zn and Si uptake. In addition, Si was the third and sixth element most absorbed in wheat shoot and grain respectively. Inoculation with A. brasilense was found to increase nutrient uptake with greater shoot K and S and grain N, P, K, Mg, S, B, Cu, Mn, Zn and Si uptake. Azospirillum brasilense inoculation provided greater N uptake, with an increase of 5.8 and 8.9% on shoot and grain uptake. [ABSTRACT FROM AUTHOR]

Açaí (Euterpe oleracea Mart., Arecaceae), a palm tree native to the Amazon basin, faces problems associated with its initial development, such as uneven germination and slow growth. The objective of this study was to evaluate the initial biometric development of açaí palm seedlings as a function of inoculation, or co-inoculation, with plant growth-promoting microorganisms. The experiment was carried out in a nursery and the treatments consisted of inoculation, or co-inoculation, of seedlings with arbuscular mycorrhizal fungi (Glomus sp. and Gigaspora sp.), diazotrophic bacteria (Azospirillum brasilense) and beneficial microorganisms©, applied in the rhizosphere of the seedlings. At 90 days after sowing, there were no statistical differences between treatments for any of the individual variables. However, hierarchical cluster analysis revealed the existence of four clusters. Shoot height (25.0 cm), leaf insertion height (12.0 cm) and root length (12.1 cm) tended to be slightly lower in non-inoculated seedlings (cluster 1). Inoculation of mycorrhizal fungi tended to promote the best development of seedlings, especially verified through root length (18.3 cm), but forming a cluster with diazotrophic bacteria (cluster 4). On the other hand, co-inoculation of mycorrhizae and diazotrophic bacteria tended to result in the lowest means, especially for shoot dry mass (0.20 mg) (cluster 3). The mix of beneficial microorganisms©, alone or co-inoculated, always formed a single cluster (cluster 2). Inoculation of açaí palm seedlings affects their initial development, but does not promote significant growth and development in a period of 90 days. [ABSTRACT FROM AUTHOR]

Wheat production suffers greatly from drought stress, resulting in yield losses. Endophytes and rhizobacteria have been recognized as a valuable source in mitigating of drought stress by improving plant resistance and growth. In this review, we discuss how endophytes and rhizobacteria help wheat cope with drought stress. During drought stress, endophytes have been found to increase plant water usage efficiency and decrease water loss. Endophytes are harmless microorganisms that live inside plant tissues. Rhizobacteria establish colonies in the root system through various procedures, including phytohormones production, modification of root architecture, and activation of stress-inducible genes, thereby promoting plant growth and enhancing stress resistance. Numerous studies have shown how endophytes and rhizobacteria can improve the potential of wheat to withstand drought. For instance, inoculation with endophytes like Piriformospora indica and Bacillus spp. has been proven to enhance wheat plant yield and drought resistance. Similarly, it has been proven that rhizobacteria like Pseudomonas spp. and Azospirillum brasilense enhance drought tolerance through a variety of mechanisms. To minimize the consequence of wheat under drought conditions, the efficient method is the use of endophytes and rhizobacteria as biofertilizers, which could ultimately boost yields and sustainability. More research needs to be done so that it can be used most effectively in the field and so that we can better understand how they work. We explained current understanding of the role and mechanisms of endophytes and rhizobacteria in minimizing drought stress effects in wheat. Additionally, we highlighted areas of limited knowledge and suggested directions for future research. This review will provide the new suggestion on the role of endophytes and rhizobacteria in mitigating the drought stress in plants. [ABSTRACT FROM AUTHOR]

The soybean [Glycine max (L.) Merrill] relationship with the bacteria Bradyrhizobium japonicum is responsible for providing around 60% of the nitrogen (N) required for the crop and the remaining N comes from the soil or supplemental fertilization. To investigate if higher yields are possible, supplemental N studies and co-inoculation of Rhizobium with Azospirillum are necessary. This N rate (0, 30, 56, 112, 336 kg N ha−1) and inoculation study was conducted across eight environments in eastern North Dakota, USA, in 2021 and 2022. Also, the effect of supplemental N and co-inoculation on nodulation was evaluated. When N was applied at 112 kg N ha−1, nodulation was significantly inhibited. Co-inoculation increased the number of large nodules and the volume of nodules; however, the yield was not different from inoculation with B. japonicum. Nitrogen at 112 and 336 kg ha−1 increased grain yield, protein yield, and seed weight; however, the higher N rate decreased plant population. There were significant positive relationships between yield and protein content and seed weight, and negative relationships between oil and protein content, and yield and oil content. Based on a polynomial relationship, the highest yield (3711 kg ha−1) would be achieved at 273 kg N ha−1. The application of N resulted in a yield increase but using current prices may not be an economical choice. Additional research is necessary to verify if co-inoculation with efficient strains can improve biological N fixation. [ABSTRACT FROM AUTHOR]

Gram-negative Azospirillum brasilense accumulates approximately 80% of polyhydroxybutyrate (PHB) as dry cell weight. For this reason, this bacterium has been characterized as one of the main microorganisms that produce PHB. PHB is synthesized inside bacteria by the polymerization of 3-hydroxybutyrate monomers. In this review, we are focusing on the analysis of the PHB production by A. brasilense in order to understand the metabolism during PHB accumulation. First, the carbon and nitrogen sources used to improve PHB accumulation are discussed. A. brasilense accumulates more PHB when it is grown on a minimal medium containing a high C/N ratio, mainly from malate and ammonia chloride, respectively. The metabolic pathways to accumulate and mobilize PHB in A. brasilense are mentioned and compared with those of other microorganisms. Next, we summarize the available information to understand the role of the genes involved in the regulation of PHB metabolism as well as the role of PHB in the physiology of Azospirillum. Finally, we made a comparison between the properties of PHB and polypropylene, and we discussed some applications of PHB in biomedical and commercial areas. [ABSTRACT FROM AUTHOR]

The association of conventional fertilizers with fertilizers of organic origin is a well-known practice in agriculture for achieving high productivity and also with the adoption of inoculants, composed of bacteria for promoting better plant development of crops. Thus, the objective of the work was to investigate the growth and productivity of radish with organic fertilization and the influence of the use of nitrogen fixing bacteria of the genus Azospirillum spp. radish (Raphanus sativus L.) Hybrid Margaret Queen. The treatments were the use of different doses of organic fertilizer and the application of Azospirillum brasilense, besides the control. At the end of the cycle, plant height, tuber diameter, tuber fresh mass, tuber dry mass, and total tuber fresh mass were evaluated. With and without application of A. brasilense, increases of 16.5% and 6.40% in tuber diameter were obtained, respectively. Without application of A. brasilense, there was an increase of 0.37% in leaf dry mass when the maximum concentration of 8 kg m² of organic fertilizer was used. For root fresh mass and root dry mass, with foliar application of A. brasilense, there was an increase of 9.57% and 0.67%, while without A. brasilense there was an increase of 2.43% and 0.22%. There were increases of 12.83% for total fresh mass with the management of A. brasilense and 3.4% without A. brasilense, using the maximum concentration of 8 kg m² of organic fertilizer. For height, there was an increase of 5.12% without A. brasilense. It was concluded that organic fertilization alone or combined with A. brasilense is an alternative in radish production. [ABSTRACT FROM AUTHOR]

Natural biostimulants, such as microorganisms and seaweed extracts, are used in agriculture to improve crop yields with a sustainable approach. However, the interaction effects between different biostimulants have not been thoroughly investigated. The objective of this work was to evaluate the synergistic effects of microorganisms (Glomus intraradices and Azospirillum brasilense) and seaweed extract (Ascophyllum nodosum and Macrocytis pyrifera) on growth, yield and fruit quality of cucumber plants under soilless cultivation. Two doses of microorganisms (0 and 10 spores mL-1 + 106 CFU) and four concentrations of seaweed extract (0, 250, 500 and 2500 ppm) were evaluated. The experimental design used was a randomized complete block design with a factorial arrangement (2 x 4), with four replications per treatment. The results showed that the equatorial diameter of the fruit, yield and titratable acidity improve when applying microorganisms and seaweed extract in combination; however, when applying the two biostimulants the values of plant height, stem diameter, number of leaves, root length, biomass (fresh and dry), firmness, total soluble solids, vitamin C, chlorophyll (a and total) and indices of color (L* and b*) did not exceed those obtained when the biostimulants were applied individually. The combined application of microorganisms and seaweed extract improves cucumber yield, but not vegetative growth and, except for titratable acidity, fruit quality attributes. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the potential of the bacterium Bacillus arayabhattai strain CMAA 1363 in promoting maize growth and productivity, comparing it with a commercial formulation of an inoculant based on Azospirillum brasilense Ab-V5 Ab-V6. To this end, in each of four different edaphoclimatic regions, a trial was conducted consisting of six treatments as follows: four doses of B. aryabhattai, a standard dose of A. brasilense, and an absolute control, with four repetitions, totaling 24 experimental plots. The parameters evaluated were seed germination, phytotoxicity, plant height, stalk diameter, dry mass of the aerial parts and roots, and yield. The results showed that B. aryabhattai was not phytotoxic, promoted the growth of maize plants, and increased productivity at a dose of 4 mL kg-1 in a statistically similar way to the standard commercial product. Therefore, it may constitute a new inoculant for maize crop. [ABSTRACT FROM AUTHOR]

Faced with the contrasting results of inoculation and co-inoculation in the bean crop, an experiment was carried out in pots, with the objective of evaluating the performance of the bean plant in treatments inoculated or co-inoculated with Rhizobium tropici and Azospirillum brasilense, via seeds, with or without chemical treatment with fungicide and insecticide, combined with 4 top-dressing nitrogen doses (0, 30, 60, and 120 kg ha-1), in a 'Latossolo Vermelho-Amarelo distrófico arenoso' soil collected from the surface layer from 0 to 0.20 m depth. The results of the Scott Knott test and regression showed that co-inoculation via seeds did not alter vegetative growth, components, and grain yield. However, without chemical treatment, co-inoculation increased plant root volume. Root dry matter production was higher when only A. brasilense was used and when combined with fungicide, or with insecticide and R. tropici. While the combination of fungicide, insecticide and A. brasilense increased the dry matter production of shoots and grains per plant. Even with inoculation or co-inoculation, there was a linear response of the common bean to topdressing fertilization up to 120 kg ha-1 of N in vegetative and root growth, pod production and grain per pod. [ABSTRACT FROM AUTHOR]

• Brasilense increases maize root attributes under water stress and high nitrogen. • Inoculation by A. brasilense with Az1 and Az2 is efficient in maize plants. • The use of inoculation by A. brasilense does not replace nitrogen fertilization in maize. • Inoculation with A. brasilense is an economically and ecologically viable technology. To determine whether Azospirillum brasilense mitigates water stress and lowers nitrogen fertilizer consumption in maize, physiology (pigments, nitrate reductase gas exchange, and water potential), macro/micronutrients, root shape, and biomass were studied. The experiment was carried out in a greenhouse and included seven treatments and four replications. Plants under water deficits were inoculated with Azospirillum strains (Az1 and Az2) under two nitrogen fertilization conditions (20 and 120 kg ha−1) and compared to control plants (with irrigation and fertilization of 120 kg ha−1 without inoculation). Inoculation with Az1 increased the pigment content under water stress, mainly in the 120 kg ha−1 nitrogen treatment. The maize root system showed the best response to inoculation with A. brasilense. The plants with inoculant Az1 at 120 kg ha−1 N responded similar to the control plants, which were under ideal growing conditions for length, surface area, root diameter and shoot and root dry mass. Inoculation with A. brasilense Az1 and 120 kg ha−1 nitrogen under water stress improved the physiology and root morphology of maize. However, the use of inoculation does not replace nitrogen fertilization in maize, and the possible reasons and consequences are discussed. Inoculation of plants with A. brasilense is an effective strategy that should be applied in maize production. [ABSTRACT FROM AUTHOR]

The microalga Chlorella sorokiniana and the microalgae growth-promoting bacteria (MGPB) Azospirillum brasilense have a mutualistic interaction that can begin within the first hours of co-incubation; however, the metabolites participating in this initial interaction are not yet identified. Nuclear magnetic resonance (NMR) was used in the present study to characterize the metabolites exuded by two strains of C. sorokiniana (UTEX 2714 and UTEX 2805) and A. brasilense Cd when grown together in an oligotrophic medium. Lactate and myo-inositol were identified as carbon metabolites exuded by the two strains of C. sorokiniana; however, only the UTEX 2714 strain exuded glycerol as the main carbon compound. In turn, A. brasilense exuded uracil when grown on the exudates of either microalga, and both microalga strains were able to utilize uracil as a nitrogen source. Interestingly, although the total carbohydrate content was higher in exudates from C. sorokiniana UTEX 2805 than from C. sorokiniana UTEX 2714, the growth of A. brasilense was greater in the exudates from the UTEX 2714 strain. These results highlight the fact that in the exuded carbon compounds differ between strains of the same species of microalgae and suggest that the type, rather than the quantity, of carbon source is more important for sustaining the growth of the partner bacteria. [ABSTRACT FROM AUTHOR]

Laccases highlight for xenobiotic bioremediation, as well as application in the fine chemical, textile, biofuel and food industries. In a previous work, we described the preliminary characterization of laccase LacMeta, a promising enzyme for the bioremediation of dyes, able to decolorization malachite green (MG), trypan blue, methylene blue. Here we demonstrate that LacMeta is indeed suitable for the complete degradation and detoxification of MG dye, not just for its discoloration, since some works show false positives due to the formation of colorless intermediates such as leucomalachite. The optimal pH and temperature parameters of LacMeta were 5.0 and 50 °C, respectively (MG as substrate). LacMeta was tolerant of up to 10 mmol L− 1 EDTA (82%) and up to 5% (V/V) acetone (91%) and methanol (71%), while SDS promoted severe inhibition. For ions, a high tolerance to cobalt, zinc, manganese, and calcium (10 mmol L− 1) was also observed (> 90%). Even under high-salinity conditions (1 mol L− 1 NaCl), the residual bleaching activity of the dye remained at 61%. Furthermore, the bleaching product of MG did not inhibit the germination of sorghum and tomato seeds and was inert to the vegetative structures of the germinated seedlings. Additionally, this treatment effectively reduced the cytotoxic effect of the dye on microorganisms (Escherichia coli and Azospirillum brasilense), which can be explained by H-NMR spectral analysis results since LacMeta completely degraded the peak signals corresponding to the aromatic rings in the dye, demonstrating extreme efficiency in the bioremediation of the xenobiotic at high concentrations (50 mg L− 1). [ABSTRACT FROM AUTHOR]

Sustainable agriculture is a concept developed in the late 20th century to promote the production of crops using the biological capabilities of cultivated organisms while minimizing the human impact on agrocenoses. In recent years, the discovery of new types of bacteria that positively impact plant growth has opened up opportunities for the development of effective microbiological preparations and they offer promising prospects for adaptive crop production, enabling farmers to adjust to changing environmental conditions while reducing reliance on anthropogenic inputs. Corn, as the third most important grain crop after wheat and rice, is sensitive to a lack of moisture. Therefore, understanding the mechanisms of adaptation and resistance of this plant to drought remains an urgent task. The aim of the work was to determine the effect of bacterization of Zea mays("Early gourmet 121") seeds by strains of rhizobacteria on the development of corn under conditions of artificial drought in a vegetation experiment. Strains of bacteria with known properties useful for plant growth and development were used – Bacillus cereus, Pseudomonas putida, Azospirillum brasilense and Azotobacter chroococcum. The study investigated the indicators of seedlings and the content of mono-, oligo-, and soluble sugars in the leaves and the activity of polyphenol oxidase in the roots. The results showed that bacterization of seeds with suspensions of P. putida led to an increase in the length of roots in plants grown under moisture deficit conditions and significantly affected the above-ground parts. Positive effects on the mass of the above-ground parts were observed when seeds were bacterized with suspensions of P. putida, A. chroococcum and a mixture of bacterial suspensions and grown under sufficient irrigation. A similar positive effect occurred when seeds were bacterized only with a mixture of suspensions of the tested bacteria under drought conditions. Bacterization of corn seeds with P. putida or A. brasilense resulted in increased root mass and sugar accumulation in leaves when growing seedlings under conditions of moisture deficit. Additionally, inoculation of P. putida or A. chroococcum seeds increased the activity of polyphenol oxidase enzyme in seedling roots. While the bacteria showed a positive impact on corn development under some conditions, this effect was not observed when there was sufficient moisture. Therefore, we believe that a more promising approach for developing biological preparations based on beneficial microorganisms is to explore combinations of multiple soil bacteria strains. By identifying a mix of bacteria that can effectively stimulate plant growth in both stressed and favourable conditions, we can maximize the potential benefits for crop production. Such combinations of bacteria may enhance plant growth and yield not only during drought stress but also under optimal conditions, providing a more robust and reliable solution for crop management. [ABSTRACT FROM AUTHOR]

This study evaluated the combined effect of foliar spray inoculation with plant growth-promoting bacteria (PGPB) and nitrogen doses on the yield, development, and nutritive value of Megathyrsus maximus cv. BRS Zuri. The experimental design was randomized blocks with four replications, with repeated measures in time. Foliar inoculation of two bacteria (Azospirillum brasilense Ab-V5 (CNPSo 2083) and Ab-V6 (CNPSo 2084) and Pseudomonas fluorescens (CNPSo 2799)) and 40 and 80 kg ha−1 N (urea) rates, in addition to the control (without inoculation and N fertilization), were applied. In the rainy season, at the level of 40 kg ha−1 of N, inoculation of both A. brasilense and P. fluorescens increased, respectively, the tiller number by 33% and 25% (22 February), and the N accumulated in tissues by 42% and 25% (22 January), while in the previous year (21 February) the beneficial effects of both bacteria were observed in the percentage of leaf blade and in the true digestibility in vitro. When the foliar spray was inoculated with A. brasilense Ab-V5 and Ab-V6 and P. fluorescens CNPSo 2799, with 80 kg N ha−1, the root system of Zuri grass increased by 61% and 30%, respectively. [ABSTRACT FROM AUTHOR]

The intercropped of cultures and biological organisms are sustainable ways to produce due to the benefits for the environment, soil, and plant, in addition to reducing costs in cultivation. The objective was to evaluate the influence of doses of Azospirillum brasilense in two soil classes in the cultivation of single maize and in intercropping with Brachiaria ruziziensis. The experimental design was in randomized block, in a 2 × 2 × 3 factorial scheme, with six replications. First factor being two soils: Latossolo Vermelho Eutrófico (clayish) and Latossolo Vermelho Distrófico (sandy); the second factor two types of cultivation: single maize and intercropped with B. ruziziensis; the third inoculation factor: without inoculant, with one dose (120 mL per 50 kg of seed), and with two doses of A. brasilense. The potential of clayey soils had high values in relation to sandy soil for the trait hundred grain weight, and, also when associated in intercrop of maize with brachiaria for plant height, number of grains per ear had higher values than in sandy soils. One or two doses of A. brasilense in clayey soil and intercropped of maize with brachiaria resulted in higher maize grain yield. [ABSTRACT FROM AUTHOR]

There has been an investigation using the association between three soil tillage systems (conventional, minimum, and no-tillage) with different previous crops (Pearl millet, Sun hemp, pigeon pea, and cowpea) and combination of nitrogen fertilization with Azospirillum brasilense in order to assess the technical efficiency of growing green corn under different soil tillage systems associated with crops before the planting of green corn under the combined presence of nitrogen fertilization and A. brasilense. The experiment was carried out on the Experimental Farm of the Universidade Federal de Sergipe, municipality of São Cristóvão, state of Sergipe, Northeast region, Brazil, from February to October, 2020. The chosen design was conducted in experimental strips with divided subplots, where the strips were made of by the systems. The subplots where the crops were randomized within each strip in three replications. This experiment evaluated green corn regarding: a) plant height; b) total leaf chlorophyll content; c) dry biomass yield; d) dry matter; e) mineral matter; f) crude protein; g) neutral and acid detergent fiber; h) total digestible nutrients. The CT/Guandu/N treatment promoted a greater increase in corn plant height and chlorophyll content; MT/Pearl millet/I obtained higher dry biomass yield; GO NT/Cowpea/N had the highest dry matter content; MT/Guandu/I promoted higher crude protein. Neutral and acid detergent fiber, total digestible nutrients were better in NT/Guandu/I, NT/Cowpea, and MT/Cowpea, respectively. The objective of the study was to evaluate the technical efficiency of forage production from green corn residues. [ABSTRACT FROM AUTHOR]

The objective was to evaluate the effect of inoculation with Azospirillum brasilense and levels of nitrogen fertilization on the productive aspects of the spineless cactus (Nopalea cochenillifera). The experiment was carried in Ribeirão do Largo, Southwest region of the state of Bahia, from April 2019 to April 2020. The experiment was carried out in a 2x4 factorial, in a randomized block design with eight treatments and four replications. The treatments consisted of the absence or inoculation with Azospirillum brasilense and nitrogen fertilization levels 0, 50, 100 and 150 kg-1 of N ha-1. There was a positive effect for the use of the bacteria on cladode area index, height, number of secondary, tertiary and total cladodes, total weight for cladodes of all orders and also for final weight per ha-1. There was a significant effect of the use of the inoculant for the levels of total soluble sugars and starch, where there was a decrease in the values for the treatments submitted to the use of the bacteria. There was a quadratic effect for the weight of the tertiary cladodes, number of tertiary cladodes and total of spineless cactus when submitted to nitrogen fertilization levels. There was a linear test for cladodes area index when nitrogen fertilization was used. The use of Azospirillum brasilense is positive for the cultivation of spineless cactus, improving development and increasing crop productivity. [ABSTRACT FROM AUTHOR]

The coinoculation of plant growth-promoting bacteria (BPCP) and rhizobium can have a beneficial effect on the nodulation and growth of leguminous plants, being an alternative to enhance biological nitrogen fixation (BNF) and crop productivity. The study aimed to evaluate the efficiency of the inoculation of Bradyrhizobium japonicum and Azospirillum brasilense in an isolated and combined way on the nodulation and growth of two peanut cultivars (Arachis hypogaea L.) cultivated in a sandy soil of the Cerrado. The treatments were arranged in a randomized block design (DBC) in a 2 × 4 factorial scheme: two peanut cultivars [IAC Tatu ST (upright height) and Runner IAC 886 (creeping height)] and four seed inoculation treatments [control (without inoculation), inoculation with Bradyrhizobium japonicum, inoculation with Azospirillum brasilense and coinoculation with B. japonicum and A. brasilense], with four replications. At 60 days after sowing, root nodulation, plant growth and dry matter partitioning were evaluated. The results showed that the inoculation of peanut seeds with B. japonicum and A. brasilense in isolation and/or in combination can provide sustainability for the peanut production system in the Cerrado region by improving root nodulation and plant growth. [ABSTRACT FROM AUTHOR]

Brazil is an important peanut producer, but despite its high production, there still needs to be an inoculant for the peanut crop. In addition, the use of microorganisms that promote plant growth (PGPM) is not common, and this crop is highly dependent on chemical fertilizers. An excellent alternative to reduce the use of fertilizers and chemical inputs in peanut crops while reducing the production cost and environmental impact is the use of PGPM. The objective of this study was to evaluate the effects of Azospirillum brasilense, Bacillus subtilis, Bradyrhizobium japonicum, and Trichoderma harzianum as single inoculants and co-inoculants on the growth promotion and productivity of peanuts in greenhouse and field conditions. In the greenhouse, the experiment was conducted with 12 treatments with six repetitions. In the field conditions, the experiment was conducted with five treatments with four repetitions. Both experiments were conducted in randomized blocks. In general, all the microorganisms evaluated in the present study promoted increases in root dry mass, shoot dry mass, phosphorus concentrations, and plant height in the greenhouse and under field conditions compared with the control. Interestingly, the mixtures of microorganisms inoculated in peanut plants did not promote greater plant growth and development compared with inoculations of the microorganisms separately. Specifically, in the field, the highest productivity was found for the inoculation of B. japonicum alone. The PGPM evaluated in the present study for peanut crops generally promoted some increases in productivity in greenhouse and field conditions. [ABSTRACT FROM AUTHOR]

One of the worst environmental conditions limiting crop plant productivity is salinity. As a result, ecologically friendly methods are urgently needed to boost the development and yield of wheat growing on saltine soils. Two-year field studies to examine the effects of applying compost tea (CT) and effective microorganisms (EMs; Azospirillum brasilense, Pseudomonas koreensis, and Bacillus circulans) on the growth and yield of two wheat cultivars, namely Sids 12 as a salinity susceptible cultivar and Misr 1 as a salinity resistant cultivar, under salt-affected soils. The findings corroborated our hypothesis that, in comparison to the control and the individual applications of EM or CT, the combined application (EM + CT) significantly improved growth, yield, uptake of nutrients, and photosynthetic characteristics. Furthermore, the combined application markedly (p ≤ 0.05) boosted the antioxidant enzymes. Our research showed that the combination treatment could increase soil microbial activity and activate critical soil enzymes, primarily dehydrogenase and urease. In general, the combination treatment has demonstrated a good effect in terms of stimulating plant development and raising element concentrations in wheat under salt stress. [ABSTRACT FROM AUTHOR]

The application of biological products in agricultural crops has become increasingly prominent. The growth-promoting bacterium Azospirillum brasilense has been used as an alternative to promote greater yield in maize crops. In the context of precision agriculture, interpreting geospatial data has allowed for monitoring the effect of the application of products that increase the yield of corn crops. The objective of this work was to evaluate the potential of Kriging techniques and spectral models through images in estimating the gain in yield of maize crop after applying A. brasilense. Analyses were carried out in two commercial areas treated with A. brasilense. The results revealed that models of yield prediction by Kriging with a high volume of training data estimated the yield gain with a root-mean-square error deviation (RMSE%), mean absolute percentage error (MAPE%), and R2 to be 6.67, 5.42, and 0.88, respectively. For spectral models with a low volume of training data, yield gain was estimated with RMSE%, MAPE%, and R2 to be 9.3, 7.71, and 0.80, respectively. The results demonstrate the potential to map the spatial distribution of productivity gains in corn crops following the application of A. brasilense. [ABSTRACT FROM AUTHOR]

Brazil is the second-largest producer and the first exporter of beef, with herds mainly raised in extensive pastures, where Megathyrsus maximus occupies over 30 Mha. About 70% of the pastures are under degradation, and using plant growth-promoting bacteria (PGPB) may contribute to reversing this scenario. We investigated the effects of PGPB on the growth of six cultivars of M. maximus—Tanzania-1, Massai, BRS Zuri, Mombaça, BRS Tamani, and BRS Quênia—under greenhouse conditions. Plants were inoculated, or not, with the elite strains of Azospirillum brasilense CNPSo 2083 + CNPSo 2084, Bacillus subtilis CNPSo 2657, Pseudomonas fluorescens CNPSo 2719, or Rhizobium tropici CNPSo 103. At 35 days after emergence, plants were evaluated for ten root growth traits, shoot dry weight, and the levels of macro and micronutrients accumulated in shoots. Several root traits were increased due to inoculation in all genotypes, impacting plant growth and nutrient uptake. Despite the differences in effectiveness, all genotypes benefited from PGPB to some degree, but Mombaça and BRS Zuri were more responsive. Scanning electron microscopy indicated that bacterial species differed in their capacity to colonize seeds and rootlets. The results show that inoculation with elite PGPB strains may represent an important strategy for the sustainability of M. maximus pastures. [ABSTRACT FROM AUTHOR]

This study evaluated the ability of the bacterium Azospirillum brasilense to establish a synergic association with the microalgae Chlorella sp. and Scenedesmus sp. co-cultured in suspension and supplied with biogas (75% CH4–25% CO2). The results demonstrated that under the stressful composition of biogas, signal molecule production, such as indole-3-acetic acid (IAA) and tryptophan (Trp) production by the bacterium and microalgae, respectively, allowed the maintenance of their affinity and mutualistic association. Chlorella sp. and Scenedesmus sp. co-cultured in suspension with the bacterium showed higher CO2 fixation rates, 0.29 ± 0.05 and 0.31 ± 0.06 g·L−1·day−1, respectively, than cultured alone, 0.17 ± 0.04 and 0.22 ± 0.03 g·L−1·day−1. Similarly, biomass production of Chlorella sp. (1.4 ± 0.4 g·L−1) and Scenedesmus sp. (1.6 ± 0.5 g·L−1) and their cell composition—mainly carbohydrates and proteins—also enhanced in both microalgae interacting with the bacterium. Overall, these results indicate that, co-cultured in suspension, this consortium microalga–A. brasilense did not change its mutualistic interaction during the specific conditions of CO2 capture from biogas. [ABSTRACT FROM AUTHOR]

There is little information about the production of agave plants in the nursery, so this research assessed the growth in the nursery of Agave angustifolia plants originating from inflorescence bulbils, subjected to different substrates, fertigation doses, and inoculation with Azospirillum brasilense. The bulbils were established for two months in a 50% peat-50% perlite substrate. One hundred and eighty plants were individually transferred to 3.8 dm3 pots for evaluation in an experiment with three factors: 1) type of irrigation: 1.1) water, or 1.2) fertigation with Steiner’s nutrient solution (NS), NS-50%, or 1.3) NS-100%; 2) inoculation with Azospirillum brasilense, 2.1) inoculated plants, 2.2) noninoculated plants; 3) substrate, mixtures of bovine manure (BM) + sand (S) in different proportions, Mix1: 75% BM + 25% S; Mix2: 25% BM + 75% S; Mix3: 50% BM + 50% S. Morphological characteristics were quantified for one year. The largest plants were those that were in substrates with 50% BM, and were fertirrigated with NS-100% and inoculated with Azospirillum brasiliense. The smallest plants were those established a in a substrate with the lowest manure content, irrigated with only water and without inoculation, which was respectively 71.6 and 54.10 cm high, 21 and 15.6 leaves, 76.6 and 62.2 mm in stem diameter, 84.4 and 59.8 cm in rosette diameter. [ABSTRACT FROM AUTHOR]

Rice production in the Central Plains of Thailand plays a key role in the country's food security. However, the overuse of inputs coupled with the rising production costs are making it increasingly difficult for smallholder rice farming to remain economically and environmentally sustainable. Replicated production-scale field trials of Cost Reduction Operating Principles (CROP)—Thailand's national package of best management practices for rice production—were established in tandem with laser land leveling (LLL), mechanical drum seeder, and the application of two biofertilizer products (i.e., PGPR II, that contains Azospirillum brasilense Sp. TS29 and Burkholderia vietnamiensis S45; and LDD #12, that contains Azotobacter tropicalis, Burkholderia unamae and Bacillus subtilis) and compared with farmer's practices (FP). Performance indicators (PI) promoted by the Sustainable Rice Platform (SRP) were used to assess economic and environmental indicators. CROP + PGPR had significantly higher net income (79%) and nitrogen-use efficiency (57%) compared with FP. Pesticide use (28%), seed (60%), inorganic fertilizer N (41%) and total production costs (19%) were reduced in all CROP treatments compared with FP. These results demonstrate that the application of CROP, LLL, mechanical drum seeder, and biofertilizers can substantially improve the economic and environmental sustainability of rice production in the Central Plains of Thailand. [ABSTRACT FROM AUTHOR]

Salicylic acid and Azospirillum brasilense stimulate plant growth and productivity. In some environments, plant physiology similarly responds to both bioactive products. Considering this, a field experiment was conducted to study the physiological effect of Salicilic acid and A. brasilense on growth and grain yield of maize plants. The experiment involved three treatments consisting of imbibed seeds in an aqueous solution of SA (0.01 mM), inoculated seeds with A. brasilense and a control treatment. Seed imbibition in SA and inoculation with A. brasilense improved vegetative growth in the early stages of crop ontogeny, increasing leaf growth, plant height, stem diameter and biomass accumulation. Spikelet length and weight were greater in plants first inoculated with A. brasilense and then treated with SA. Results indicated that SA stimulated biomass partitioning towards leaves, root and stem, while A. brasilense mainly affected leaf growth, plant height, ear dimensions and grain yield. Such results turn crucial for biological fertilization strategies aimed at reducing pollutant loads that accompany chemical fertilizers. Both products can be part of maize management practices given competitive economic advantages and sustainability. [ABSTRACT FROM AUTHOR]

Microbial biome of soil biocenosis determine the main functional role in the circulation of substances and energy and represent key components of the transformation of organic residues, both their mineralization and immobilization of nutrients. Therefore, the studying of the biome of soil microorganisms (especially dominant strains) is the scientific basis for the development of measures aimed at enhanced reproduction of chernozem fertility. Two dominant endophytic bacterial isolates were recovered from native Hordeum vulgare rhizosphere varieties at central Ukraine area. New isolates were evaluated for their morphological and biochemical characteristics. So, the aim of the work was to investigate and identify these important dominant strains of bacteria with help of the innovative colorimetric identification system for carbohydrate utilization - KB009 TM HiCarbo Kit. The results of researches based on the study of morphological, biochemical and physiological state of bacteria in regard to sources of carbon and metabolic similarity with standard strain Azospirillum brasilense. Methods of research - physiological features were studied by one of the most accurate methodological approaches in determining the physiological diversity of the association of soil microorganisms - the testing system KB009 TM HiCarbo Kit for carbon sources. Thanks to previous investigation, it was learned number of dominant groups of microorganisms, microbiological processes orientation and ecological indexes of biodiversity. And in result of the researches, it was possible to classify allocated dominant strains to the genus Phyllobacterium and Bacillus. [ABSTRACT FROM AUTHOR]

Stevia (Stevia rebaudiana Bertoni) is an important industrial crop, and its leaves contain steviol glycosides (SGs), which are valuable compounds because they are characterized by a high sweetness and low caloric content. SGs yield depends on nitrogen (N) nutrition; however, the role of N uptake in SGs synthesis needs clarification, especially in organic farming systems that depend on organic and biofertilizers. Plant growth-promoting bacteria (PGPB; i.e., Azospirillum brasilense and Bacillus circulans) and compost were used to study the effect of N nutrition on SGs yield. The experiment consisted of five N treatments with or without PGPB inoculation. The fertilization treatments were: C = without N, T 1 = urea, T 2 = compost, T 3 = urea and compost (75% of N from urea and the rest from compost) and T 4 = urea and compost (50% of N from urea and the rest 50% from compost). Compost and PGPB increased the soil quality indicators and enhanced the synthesis of chlorophyll and nutrient uptake by stevia plants. Mixtures of compost and urea under inoculation with PGPB enhanced soil microbes and enzymatic activity. The highest significant value of nitrogen use efficiency (NUE) resulted from urea alone, while the maximum phosphorus (P) and potassium (K) uptake came from compost. Although urea led to an increase in stevia N uptake, it led to a clear decrease in SGs yield. Urea decreased the total soluble sugar and leaf C/N ratio by 29% and 31%, respectively, compared to those of C. T 4 increased the SGs concentration by 74% and 46%, respectively, compared to that of urea alone in the presence and absence of PGPB. PGPB enhanced the soil quality and promoted nutrient uptake, resulting in significant increases in SGs yield. Regulating N uptake enhanced synthesis of soluble sugars and increased the C/N ratio, which caused an increase in SGs production. The use of compost and plant growth-promoting bacteria is a suitable strategy to produce stevia plants with low rates of inorganic nitrogen without any yield loss. [Display omitted] • Compost and plant growth-promoting bacteria (PGPB) enhances stevia growth. • Compost and PGPB reregulate N-uptake in stevia plants. • Urea decreased the total soluble sugar and leaf C/N ratio. • Regulating N-uptake increased the synthesis steviol glycosides (SGs). • The findings might be an aid for sustainable N management in stevia production. [ABSTRACT FROM AUTHOR]

Polyethylene glycol (PEG 6000) was used to establish osmotic stress conditions during growth of the type strain Azospirillum brasilense Sp7 and its spontaneous variants Sp7.4 and Sp7.8, because it causes a stable decrease in the water potential and thus makes it possible to simulate the effect of drought on the bacterial population. While PEG suppressed the motility of azospirilla, it had no effect on the ability of strains Sp7 and Sp7.8 to form biofilms, as well as on the metabolic activity of the biofilms formed in the absence of stress. PEG 6000-caused osmotic stress promoted biofilm formation in Sp7.8. While the biofilms of the Sp7.4 variant were those most sensitive to the negative effect of the water stress, the growth variables of the planktonic culture of this variant under stress conditions exceeded the values for both Sp7 and Sp7.8. In biofilms, strains Sp7, Sp7.4, and Sp7.8 produced polysaccharides and the plant hormone IAA; desiccation-resistant cell forms emerged. The variants Sp7.4 and Sp7.8, similarly to Sp7, formed biofilms during plant root colonization and affected the morphology of the root system of wheat seedlings. Our results show that spontaneous variants of strain Sp7 may be of interest for further research directed at selection of promising Azospirillum strains to enhance the drought resistance of plants. [ABSTRACT FROM AUTHOR]

Bacterial-fungal interactions are important in the functioning of natural ecosystems. We examined possible synergistic or antagonistic effects during the degradation of polycyclic aromatic hydrocarbons (PAHs) by a fungal–bacterial co-culture. Bacteria and fungi were grown in a liquid nutrient medium supplemented with PAH substrates. The degradation of PAHs and the identification of metabolites were checked by HPLC. Enzyme activities were spectrophotometrically measured with test substrates. Compared to monocultures, the co-culture yielded higher mycelium dry weights and higher numbers of bacterial colony-forming units (CFUs). Both organisms and their co-culture transformed three- and four-ring PAHs into the corresponding quinones. The degradation of PAHs was accompanied by the production of fungal extracellular laccase and versatile peroxidase, whose activities were higher in the co-culture than they were in the monocultures. The presence of exogenous indole-3-acetic acid (IAA) boosted PAH degradation and enzyme production. The xylotrophic basidiomycete Pleurotus ostreatus Florida and the plant-growth-promoting rhizobacterium Azospirillum brasilense exerted a positive mutual effect, including increases in mycelium dry weight, number of CFUs, degradation of PAHs, and production of fungal extracellular enzymes. IAA may be a factor in the interactions of P. ostreatus Florida with A. brasilense. [ABSTRACT FROM AUTHOR]

Bacteria of the genus Azospirillum include several plant associated bacteria which often promote the growth of their host plants. Although the host range of Azospirillum brasilense Sp7 is much wider than its close relative Azospirillum lipoferum 4B, it lacks the ability to efficiently utilize D-glucose for its growth. By comparing the genomes of both the species, the genes of A. lipoferum 4B responsible for conferring D-glucose utilization ability in A. brasilese Sp7 were identified by cloning individual or a combination of genes in a broad host range expression vector, mobilizing them in A. brasilense Sp7 and examining the ability of exconjugants to use D-glucose as sole carbon source for growth. These genes also included the homologs of genes involved in N-acetyl glucosamine utilization in Pseudomonas aeruginosa PAO1. A transcriptional fusion of the 5 genes encoding glucose-6-phosphate dehydrogenase and 4 components of glucose phosphotransferase system were able to improve D-glucose utilization ability in A. brasilense Sp7. The A. brasilense Sp7 strain engineered with D-glucose utilization ability showed significantly improved root colonization of rice seedling. The improvement in the ability of A. brasilense Sp7 to colonize rice roots is expected to bring benefits to rice by promoting its growth. Key points: • Genes required for glucose utilization in Azospirillum lipoferum were identified. • A gene cassette encoding glucose utilization was constructed. • Transfer of gene cassette in A. brasilense improves glucose utilization and rice root colonization.. [ABSTRACT FROM AUTHOR]

The rational use of nitrogen fertilization is fundamental, not only to increase recovery efficiency, but also to increase crop productivity and reduce the production costs and risks of environmental impacts. In the State of Rio Grande do Sul in Brazil, irrigated rice productivity can surpass 8 tonne·ha−1 as a result of the technification of the crop and favorable environmental conditions, yet there is great variability in the agronomic efficiency of chemical nitrogen fertilizers, which rarely exceed 50% of the applied dose. Biological nitrogen fixation is one of the technological alternatives for reducing the use of nitrogen in this crop. In this study, the agronomic efficiency of Azospirillum brasilense strains Ab-V5 and Ab-V6 in terms of biological nitrogen fixation in flood-irrigated rice cultivars in a lowland agroecosystem was evaluated through five field experiments. A. brasilense combined with reduced nitrogen fertilization (reduction of 30 kg N·ha−1) increased the dry mass of the aerial part of rice plants by 3.2%, and promoted an increase in N concentration in stems and leaves and in the N content exported by grains by 43% and 27.5%, respectively, in relation to the absence of N and inoculant, and promoted an average increase of 30% in rice production. [ABSTRACT FROM AUTHOR]

Increased soil salinity is one of the main concerns in agriculture and food production, and it negatively affects plant growth and crop productivity. In order to mitigate the adverse effects of salinity stress, plant biostimulants (PBs) have been indicated as a promising approach. Indeed, these products have a beneficial effect on plants by acting on primary and secondary metabolism and by inducing the accumulation of protective molecules against oxidative stress. In this context, the present work is aimed at comparatively investigating the effects of microbial (i.e., Azospirillum brasilense) and plant-derived biostimulants in alleviating salt stress in tomato plants by adopting a multidisciplinary approach. To do so, the morphological and biochemical effects were assessed by analyzing the biomass accumulation and root characteristics, the activity of antioxidant enzymes and osmotic stress protection. Furthermore, modifications in the metabolomic profiles of both leaves and root exudates were also investigated by ultra-high performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/QTOF-MS). According to the results, biomass accumulation decreased under high salinity. However, the treatment with A. brasilense considerably improved root architecture and increased root biomass by 156% and 118% in non-saline and saline conditions, respectively. The antioxidant enzymes and proline production were enhanced in salinity stress at different levels according to the biostimulant applied. Moreover, the metabolomic analyses pointed out a wide set of processes being affected by salinity and biostimulant interactions. Crucial compounds belonging to secondary metabolism (phenylpropanoids, alkaloids and other N-containing metabolites, and membrane lipids) and phytohormones (brassinosteroids, cytokinins and methylsalicylate) showed the most pronounced modulation. Overall, our results suggest a better performance of A. brasilense in alleviating high salinity than the vegetal-derived protein hydrolysates herein evaluated. [ABSTRACT FROM AUTHOR]