Effect of Sargassum on the Behavior and Survival of the Earthworm Eisenia Fetida.

The massive influx of Sargassum natans and S. fluitans to the shores of the Mexican Caribbean has raised concerns regarding their potential impact on soil quality and health in coastal and agroecosystems. The effects of Sargassum accumulation remain largely unexplored. This study aimed to assess the impact of Sargassum on soil ecosystems by examining the behavior and survival of the epigean earthworm Eisenia fetida. The earthworm was exposed to varying concentrations of Sargassum (0, 25, 50, 75, and 100%) in two toxicological tests. Results from the avoidance test demonstrated that E. fetida exhibited strong aversion (> 80%) to a diet containing 100% Sargassum. Conversely, the acute test revealed minimal mortality, but growth decreased with increasing Sargassum concentrations. These findings can serve as early warning bioindicators for assessing the environmental risk posed by Sargassum in soil ecosystems.

Use of Phosphorus-Solubilizing Microorganisms as a Biotechnological Alternative: A Review.

Microorganisms with the ability to dissolve phosphorus have the potential to release this essential nutrient into the soil through natural solubilization processes, which allows for boosting plant growth and development. While literature reviews acknowledge their potential, unexplored territories concerning accessibility, application, and effective integration into sustainable agriculture necessitate further research. This manuscript employed distinct methodologies to execute a bibliometric analysis and a literature review. The combined application of both methodologies enables a holistic understanding of the domain landscape and its innovative facets. For the bibliometric analysis, the propositions of Donthu and Jia were utilized, supplemented by tools, such as Bibliometrix. The literature review adhered to a systematic methodology predicated on Petersen's guidelines to represent the domain accurately, pinpointing trends and gaps that could steer future, more detailed research. This investigation uncovers an escalating interest in studying these microorganisms since the 2000s, emphasizing their significance in sustainable agriculture and the context of phosphorus scarcity. It was also discerned that India and China, nations with notable agricultural sectors and a high demand for phosphorus fertilizers, spearheaded research output on this subject. This signifies their substantial contribution to the progression of this scientific field. Furthermore, according to the research consulted, phosphorus-solubilizing microorganisms play a pivotal role in the symbiotic interaction of soil with plant roots and represent an efficacious strategy to counteract the low availability of phosphorus in the soil and sustainably enhance agricultural systems. Finally, this review contributes to the relevant domain by examining existing empirical evidence with special emphasis on sustainable agriculture, improved understanding of phosphorus solubilization mechanisms, and recognition of various microbial entities.

Advances in the Development of Biofertilizers and Biostimulants from Microalgae.

Microalgae have commercial potential in different sectors of the industry. Specifically in modern agriculture, they can be used because they have the ability to supply nutrients to the soil and produce plant growth hormones, polysaccharides, antimicrobial compounds, and other metabolites that improve agricultural productivity. Therefore, products formulated from microalgae as biofertilizers and biostimulants turn out to be beneficial for agriculture and are positioned as a novel and environmentally friendly strategy. However, these bioproducts present challenges in preparation that affect their shelf life due to the rapid degradation of bioformulated products. Therefore, this work aimed to provide a comprehensive review of biofertilizers and biostimulants from microalgae, for which a bibliometric analysis was carried out to establish trends using scientometric indicators, technological advances were identified in terms of formulation methods, and the global market for these bioproducts was analyzed.

Microbeads as carriers for Bacillus pumilus: a biofertilizer focus on auxin production.

The study aimed to develop a solid biofertilizer using Bacillus pumilus, focusing on auxin production to enhance plant drought tolerance. Methods involved immobilising B. pumilus in alginate-starch beads, focusing on microbial concentration, biopolymer types, and environmental conditions. The optimal formulation showed a diameter of 3.58 mm ± 0.18, a uniform size distribution after 15 h of drying at 30 °C, a stable bacterial concentration (1.99 × 109 CFU g-1 ± 1.03 × 109 over 180 days at room temperature), a high auxin production (748.8 µg g-1 ± 10.3 of IAA in 7 days), and a water retention capacity of 37% ± 4.07. In conclusion, this new formulation of alginate + starch + L-tryptophan + B. pumilus has the potential for use in crops due to its compelling water retention, high viability in storage at room temperature, and high auxin production, which provides commercial advantages.

Identification and Characterization of Beneficial Soil Microbial Strains for the Formulation of Biofertilizers Based on Native Plant Growth-Promoting Microorganisms Isolated from Northern Mexico.

Plant growth-promoting microorganisms (PGPM) benefit plant health by enhancing plant nutrient-use efficiency and protecting plants against biotic and abiotic stresses. This study aimed to isolate and characterize autochthonous PGPM from important agri-food crops and nonagricultural plants to formulate biofertilizers. Native microorganisms were isolated and evaluated for PGP traits (K, P, and Zn solubilization, N2-fixation, NH3-, IAA and siderophore production, and antifungal activity against Fusarium oxysporum). Isolates were tested on radish and broccoli seedlings, evaluating 19 individual isolates and 12 microbial consortia. Potential bacteria were identified through DNA sequencing. In total, 798 bacteria and 209 fungi were isolated. Isolates showed higher mineral solubilization activity than other mechanisms; 399 bacteria and 156 fungi presented mineral solubilization. Bacteria were relevant for nitrogen fixation, siderophore, IAA (29-176 mg/L), and ammonia production, while fungi for Fusarium growth inhibition (40-69%). Twenty-four bacteria and eighteen fungi were selected for their PGP traits. Bacteria had significantly (ANOVA, p < 0.05) better effects on plants than fungi; treatments improved plant height (23.06-51.32%), leaf diameter (25.43-82.91%), and fresh weight (54.18-85.45%) in both crops. Most potential species belonged to Pseudomonas, Pantoea, Serratia, and Rahnella genera. This work validated a high-throughput approach to screening hundreds of rhizospheric microorganisms with PGP potential isolated from rhizospheric samples.

Mycobiota of Mexican Maize Landraces with Auxin-Producing Yeasts That Improve Plant Growth and Root Development.

Compared to agrochemicals, bioinoculants based on plant microbiomes are a sustainable option for increasing crop yields and soil fertility. From the Mexican maize landrace "Raza cónico" (red and blue varieties), we identified yeasts and evaluated in vitro their ability to promote plant growth. Auxin production was detected from yeast isolates and confirmed using Arabidopsis thaliana plants. Inoculation tests were performed on maize, and morphological parameters were measured. Eighty-seven yeast strains were obtained (50 from blue corn and 37 from red corn). These were associated with three families of Ascomycota (Dothideaceae, Debaryomycetaceae, and Metschnikowiaceae) and five families of Basidiomycota (Sporidiobolaceae, Filobasidiaceae, Piskurozymaceae, Tremellaceae, and Rhynchogastremataceae), and, in turn, distributed in 10 genera (Clavispora, Rhodotorula, Papiliotrema, Candida, Suhomyces, Soliccocozyma, Saitozyma Holtermaniella, Naganishia, and Aeurobasidium). We identified strains that solubilized phosphate and produced siderophores, proteases, pectinases, and cellulases but did not produce amylases. Solicoccozyma sp. RY31, C. lusitaniae Y11, R. glutinis Y23, and Naganishia sp. Y52 produced auxins from L-Trp (11.9-52 µg/mL) and root exudates (1.3-22.5 µg/mL). Furthermore, they stimulated the root development of A. thaliana. Inoculation of auxin-producing yeasts caused a 1.5-fold increase in maize plant height, fresh weight, and root length compared to uninoculated controls. Overall, maize landraces harbor plant growth-promoting yeasts and have the potential for use as agricultural biofertilizers.

Contribution of Biofertilizers to Pulse Crops: From Single-Strain Inoculants to New Technologies Based on Microbiomes Strategies.

Pulses provide distinct health benefits due to their low fat content and high protein and fiber contents. Their grain production reaches approximately 93,210 × 103 tons per year. Pulses benefit from the symbiosis with atmospheric N2-fixing bacteria, which increases productivity and reduces the need for N fertilizers, thus contributing to mitigation of environmental impact mitigation. Additionally, the root region harbors a rich microbial community with multiple traits related to plant growth promotion, such as nutrient increase and tolerance enhancement to abiotic or biotic stresses. We reviewed the eight most common pulses accounting for almost 90% of world production: common beans, chickpeas, peas, cowpeas, mung beans, lentils, broad beans, and pigeon peas. We focused on updated information considering both single-rhizobial inoculation and co-inoculation with plant growth-promoting rhizobacteria. We found approximately 80 microbial taxa with PGPR traits, mainly Bacillus sp., B. subtilis, Pseudomonas sp., P. fluorescens, and arbuscular mycorrhizal fungi, and that contributed to improve plant growth and yield under different conditions. In addition, new data on root, nodule, rhizosphere, and seed microbiomes point to strategies that can be used to design new generations of biofertilizers, highlighting the importance of microorganisms for productive pulse systems.

Assessment of zinc solubilization potential of zinc-resistant Pseudomonas oleovorans strain ZSB13 isolated from contaminated soil / Avaliação do potencial de solubilização do zinco da cepa ZSB13 de Pseudomonas oleovorans resistente ao zinco isolada de solo contaminado

Zinc is an essential micronutrient that is required for optimum plant growth. It is present in soil in insoluble forms. Bacterial solubilization of soil unavailable form of Zn into available form, is an emerging approach to alleviate the Zn deficiency for plants and human beings. Zinc solubilizing bacteria (ZSB) could be a substitute for chemical Zn fertilizer. The present study aimed to isolate and characterize bacterial species from the contaminated soil and evaluate their Zn solubilizing potential. Zn resistant bacteria were isolated and evaluated for their MIC against Zn. Among the 13 isolated bacterial strains ZSB13 showed maximum MIC value upto 30mM/L. The bacterial strain with the highest resistance against Zn was selected for further analysis. Molecular characterization of ZSB13 was performed by 16S rRNA gene amplification which confirmed it as Pseudomonas oleovorans. Zn solubilization was determined through plate assay and broth medium. Four insoluble salts (zinc oxide (ZnO), zinc carbonate (ZnCO3), zinc sulphite (ZnS) and zinc phosphate (Zn3(PO4)2) were used for solubilization assay. Our results shows 11 mm clear halo zone on agar plates amended with ZnO. Likewise, ZSB13 showed significant release of Zn in broth amended with ZnCO3 (17 and 16.8 ppm) and ZnO (18.2 ppm). Furthermore, Zn resistance genes czcD was also enriched in ZSB13. In our study, bacterial strain comprising Zn solubilization potential has been isolated that could be further used for the growth enhancement of crops.(AU)

O zinco é um micronutriente essencial necessário para o crescimento ideal das plantas. Ele está presente no solo em formas insolúveis. A solubilização bacteriana da forma indisponível de Zn no solo para a forma disponível é uma abordagem emergente para aliviar a deficiência de Zn em plantas e seres humanos. Bactérias solubilizadoras de zinco (ZSB) podem ser um substituto para fertilizantes químicos de Zn. O presente estudo teve como objetivo isolar e caracterizar espécies bacterianas de solo contaminado e avaliar seu potencial de solubilização de Zn. Bactérias resistentes ao Zn foram isoladas e avaliadas quanto ao seu MIC contra o Zn. Entre as 13 cepas bacterianas isoladas, ZSB13 apresentou valor máximo de MIC de até 30 mM/L. A cepa bacteriana com maior resistência ao Zn foi selecionada para análise posterior. A caracterização molecular de ZSB13 foi realizada por amplificação do gene 16S rRNA que o confirmou como Pseudomonas oleovorans. A solubilização do Zn foi determinada através de ensaio em placa e meio caldo. Quatro sais insolúveis (óxido de zinco (ZnO), carbonato de zinco (ZnCO3), sulfito de zinco (ZnS) e fosfato de zinco (Zn3 (PO4) 2) foram usados para o ensaio de solubilização. Nossos resultados mostram uma zona de halo clara de 11 mm em placas de ágar corrigidas com ZnO. Da mesma forma, ZSB13 mostrou liberação significativa de Zn em caldo alterado com ZnCO3 (17 e 16,8 ppm) e ZnO (18,2 ppm). Além disso, os genes de resistência ao Zn czcD também foram enriquecidos em ZSB13. Em nosso estudo, a cepa bacteriana compreendendo potencial de solubilização de Zn foi isolada e poderia ser usada posteriormente para o aumento do crescimento de safras.(AU)

Assessment of zinc solubilization potential of zinc-resistant Pseudomonas oleovorans strain ZSB13 isolated from contaminated soil / Avaliação do potencial de solubilização do zinco da cepa ZSB13 de Pseudomonas oleovorans resistente ao zinco isolada de solo contaminado

Zinc is an essential micronutrient that is required for optimum plant growth. It is present in soil in insoluble forms. Bacterial solubilization of soil unavailable form of Zn into available form, is an emerging approach to alleviate the Zn deficiency for plants and human beings. Zinc solubilizing bacteria (ZSB) could be a substitute for chemical Zn fertilizer. The present study aimed to isolate and characterize bacterial species from the contaminated soil and evaluate their Zn solubilizing potential. Zn resistant bacteria were isolated and evaluated for their MIC against Zn. Among the 13 isolated bacterial strains ZSB13 showed maximum MIC value upto 30mM/L. The bacterial strain with the highest resistance against Zn was selected for further analysis. Molecular characterization of ZSB13 was performed by 16S rRNA gene amplification which confirmed it as Pseudomonas oleovorans. Zn solubilization was determined through plate assay and broth medium. Four insoluble salts (zinc oxide (ZnO), zinc carbonate (ZnCO3), zinc sulphite (ZnS) and zinc phosphate (Zn3(PO4)2) were used for solubilization assay. Our results shows 11 mm clear halo zone on agar plates amended with ZnO. Likewise, ZSB13 showed significant release of Zn in broth amended with ZnCO3 (17 and 16.8 ppm) and ZnO (18.2 ppm). Furthermore, Zn resistance genes czcD was also enriched in ZSB13. In our study, bacterial strain comprising Zn solubilization potential has been isolated that could be further used for the growth enhancement of crops.

O zinco é um micronutriente essencial necessário para o crescimento ideal das plantas. Ele está presente no solo em formas insolúveis. A solubilização bacteriana da forma indisponível de Zn no solo para a forma disponível é uma abordagem emergente para aliviar a deficiência de Zn em plantas e seres humanos. Bactérias solubilizadoras de zinco (ZSB) podem ser um substituto para fertilizantes químicos de Zn. O presente estudo teve como objetivo isolar e caracterizar espécies bacterianas de solo contaminado e avaliar seu potencial de solubilização de Zn. Bactérias resistentes ao Zn foram isoladas e avaliadas quanto ao seu MIC contra o Zn. Entre as 13 cepas bacterianas isoladas, ZSB13 apresentou valor máximo de MIC de até 30 mM/L. A cepa bacteriana com maior resistência ao Zn foi selecionada para análise posterior. A caracterização molecular de ZSB13 foi realizada por amplificação do gene 16S rRNA que o confirmou como Pseudomonas oleovorans. A solubilização do Zn foi determinada através de ensaio em placa e meio caldo. Quatro sais insolúveis (óxido de zinco (ZnO), carbonato de zinco (ZnCO3), sulfito de zinco (ZnS) e fosfato de zinco (Zn3 (PO4) 2) foram usados para o ensaio de solubilização. Nossos resultados mostram uma zona de halo clara de 11 mm em placas de ágar corrigidas com ZnO. Da mesma forma, ZSB13 mostrou liberação significativa de Zn em caldo alterado com ZnCO3 (17 e 16,8 ppm) e ZnO (18,2 ppm). Além disso, os genes de resistência ao Zn czcD também foram enriquecidos em ZSB13. Em nosso estudo, a cepa bacteriana compreendendo potencial de solubilização de Zn foi isolada e poderia ser usada posteriormente para o aumento do crescimento de safras.

Assessment of zinc solubilization potential of zinc-resistant Pseudomonas oleovorans strain ZSB13 isolated from contaminated soil

Abstract Zinc is an essential micronutrient that is required for optimum plant growth. It is present in soil in insoluble forms. Bacterial solubilization of soil unavailable form of Zn into available form, is an emerging approach to alleviate the Zn deficiency for plants and human beings. Zinc solubilizing bacteria (ZSB) could be a substitute for chemical Zn fertilizer. The present study aimed to isolate and characterize bacterial species from the contaminated soil and evaluate their Zn solubilizing potential. Zn resistant bacteria were isolated and evaluated for their MIC against Zn. Among the 13 isolated bacterial strains ZSB13 showed maximum MIC value upto 30mM/L. The bacterial strain with the highest resistance against Zn was selected for further analysis. Molecular characterization of ZSB13 was performed by 16S rRNA gene amplification which confirmed it as Pseudomonas oleovorans. Zn solubilization was determined through plate assay and broth medium. Four insoluble salts (zinc oxide (ZnO), zinc carbonate (ZnCO3), zinc sulphite (ZnS) and zinc phosphate (Zn3(PO4)2) were used for solubilization assay. Our results shows 11 mm clear halo zone on agar plates amended with ZnO. Likewise, ZSB13 showed significant release of Zn in broth amended with ZnCO3 (17 and 16.8 ppm) and ZnO (18.2 ppm). Furthermore, Zn resistance genes czcD was also enriched in ZSB13. In our study, bacterial strain comprising Zn solubilization potential has been isolated that could be further used for the growth enhancement of crops.

Resumo O zinco é um micronutriente essencial necessário para o crescimento ideal das plantas. Ele está presente no solo em formas insolúveis. A solubilização bacteriana da forma indisponível de Zn no solo para a forma disponível é uma abordagem emergente para aliviar a deficiência de Zn em plantas e seres humanos. Bactérias solubilizadoras de zinco (ZSB) podem ser um substituto para fertilizantes químicos de Zn. O presente estudo teve como objetivo isolar e caracterizar espécies bacterianas de solo contaminado e avaliar seu potencial de solubilização de Zn. Bactérias resistentes ao Zn foram isoladas e avaliadas quanto ao seu MIC contra o Zn. Entre as 13 cepas bacterianas isoladas, ZSB13 apresentou valor máximo de MIC de até 30 mM/L. A cepa bacteriana com maior resistência ao Zn foi selecionada para análise posterior. A caracterização molecular de ZSB13 foi realizada por amplificação do gene 16S rRNA que o confirmou como Pseudomonas oleovorans. A solubilização do Zn foi determinada através de ensaio em placa e meio caldo. Quatro sais insolúveis (óxido de zinco (ZnO), carbonato de zinco (ZnCO3), sulfito de zinco (ZnS) e fosfato de zinco (Zn3 (PO4) 2) foram usados para o ensaio de solubilização. Nossos resultados mostram uma zona de halo clara de 11 mm em placas de ágar corrigidas com ZnO. Da mesma forma, ZSB13 mostrou liberação significativa de Zn em caldo alterado com ZnCO3 (17 e 16,8 ppm) e ZnO (18,2 ppm). Além disso, os genes de resistência ao Zn czcD também foram enriquecidos em ZSB13. Em nosso estudo, a cepa bacteriana compreendendo potencial de solubilização de Zn foi isolada e poderia ser usada posteriormente para o aumento do crescimento de safras.

Assessment of zinc solubilization potential of zinc-resistant Pseudomonas oleovorans strain ZSB13 isolated from contaminated soil / Avaliação do potencial de solubilização do zinco da cepa ZSB13 de Pseudomonas oleovorans resistente ao zinco isolada de solo contaminado

Abstract Zinc is an essential micronutrient that is required for optimum plant growth. It is present in soil in insoluble forms. Bacterial solubilization of soil unavailable form of Zn into available form, is an emerging approach to alleviate the Zn deficiency for plants and human beings. Zinc solubilizing bacteria (ZSB) could be a substitute for chemical Zn fertilizer. The present study aimed to isolate and characterize bacterial species from the contaminated soil and evaluate their Zn solubilizing potential. Zn resistant bacteria were isolated and evaluated for their MIC against Zn. Among the 13 isolated bacterial strains ZSB13 showed maximum MIC value upto 30mM/L. The bacterial strain with the highest resistance against Zn was selected for further analysis. Molecular characterization of ZSB13 was performed by 16S rRNA gene amplification which confirmed it as Pseudomonas oleovorans. Zn solubilization was determined through plate assay and broth medium. Four insoluble salts (zinc oxide (ZnO), zinc carbonate (ZnCO3), zinc sulphite (ZnS) and zinc phosphate (Zn3(PO4)2) were used for solubilization assay. Our results shows 11 mm clear halo zone on agar plates amended with ZnO. Likewise, ZSB13 showed significant release of Zn in broth amended with ZnCO3 (17 and 16.8 ppm) and ZnO (18.2 ppm). Furthermore, Zn resistance genes czcD was also enriched in ZSB13. In our study, bacterial strain comprising Zn solubilization potential has been isolated that could be further used for the growth enhancement of crops.

Resumo O zinco é um micronutriente essencial necessário para o crescimento ideal das plantas. Ele está presente no solo em formas insolúveis. A solubilização bacteriana da forma indisponível de Zn no solo para a forma disponível é uma abordagem emergente para aliviar a deficiência de Zn em plantas e seres humanos. Bactérias solubilizadoras de zinco (ZSB) podem ser um substituto para fertilizantes químicos de Zn. O presente estudo teve como objetivo isolar e caracterizar espécies bacterianas de solo contaminado e avaliar seu potencial de solubilização de Zn. Bactérias resistentes ao Zn foram isoladas e avaliadas quanto ao seu MIC contra o Zn. Entre as 13 cepas bacterianas isoladas, ZSB13 apresentou valor máximo de MIC de até 30 mM/L. A cepa bacteriana com maior resistência ao Zn foi selecionada para análise posterior. A caracterização molecular de ZSB13 foi realizada por amplificação do gene 16S rRNA que o confirmou como Pseudomonas oleovorans. A solubilização do Zn foi determinada através de ensaio em placa e meio caldo. Quatro sais insolúveis (óxido de zinco (ZnO), carbonato de zinco (ZnCO3), sulfito de zinco (ZnS) e fosfato de zinco (Zn3 (PO4) 2) foram usados ​​para o ensaio de solubilização. Nossos resultados mostram uma zona de halo clara de 11 mm em placas de ágar corrigidas com ZnO. Da mesma forma, ZSB13 mostrou liberação significativa de Zn em caldo alterado com ZnCO3 (17 e 16,8 ppm) e ZnO (18,2 ppm). Além disso, os genes de resistência ao Zn czcD também foram enriquecidos em ZSB13. Em nosso estudo, a cepa bacteriana compreendendo potencial de solubilização de Zn foi isolada e poderia ser usada posteriormente para o aumento do crescimento de safras.

Taxonomical and functional bacterial community profiling in disease-resistant and disease-susceptible soybean cultivars.

Highly varied bacterial communities inhabiting the soybean rhizosphere perform important roles in its growth and production; nevertheless, little is known about the changes that occur in these communities under disease-stress conditions. The present study investigated the bacterial diversity and their metabolic profile in the rhizosphere of disease-resistant (JS-20-34) and disease-susceptible (JS-335) soybean (Glycine max (L.) Merr.) cultivars using 16S rRNA amplicon sequencing and community-level physiological profiling (CLPP). In disease-resistant soybean (AKADR) samples, the most dominating phyla were Actinobacteria (40%) followed by Chloroflexi (24%), Proteobacteria (20%), and Firmicutes (12%), while in the disease-susceptible (AKADS) sample, the most dominating phyla were Proteobacteria (35%) followed by Actinobacteria (27%) and Bacteroidetes (17%). Functional profiling of bacterial communities was done using the METAGENassist, and PICRUSt2 software, which shows that AKADR samples have more ammonifying, chitin degrading, nitrogen-fixing, and nitrite reducing bacteria compared to AKADS rhizosphere samples. The bacterial communities present in disease-resistant samples were significantly enriched with genes involved in nitrogen fixation, carbon fixation, ammonification, denitrification, and antibiotic production. Furthermore, the CLPP results show that carbohydrates and carboxylic acids were the most frequently utilized nutrients by the microbes. The principal component analysis (PCA) revealed that the AKADR soils had higher functional activity (strong association with the Shannon-Wiener index, richness index, and hydrocarbon consumption) than AKADS rhizospheric soils. Overall, our findings suggested that the rhizosphere of resistant varieties of soybean comprises of beneficial bacterial population over susceptible varieties.

Rhizobacteria from Brazilian semiarid biome as growth promoters of soybean (Glycine max L.) under low water availability.

Caatinga is the predominant biome in the Brazilian semiarid region. Its vegetation is composed by plants and microorganisms with high tolerance to drought. Microorganisms associated with plants in this biome can develop mechanisms to protect cells from water stress and desiccation. The aim of this study was to identify plant growth-promoting rhizobacteria associated with the drought-tolerant legume Mimosa artemisiana and to examine their effect on the growth of soybean (Glycine max L.) under drought condition (irrigation with 30% of field capacity). Rhizospheric soil was collected along the Caatinga (In the States of Bahia and Pernambuco) at 4 collection points, totaling sixty subsamples. Xerotolerant bacteria with plant growth-promotion characteristics were isolated in a selective culture medium for diazotrophic bacteria. Two strains of the genera Bacillus and one Paenibacillus were promising in in vitro and in vivo tests. Both were able to grow in a medium with low water availability (0.919 Aw) and could produce exopolysaccharides and indole acetic acid (up to 130 µg mL-1). In addition, they produced 1-aminocyclopropane-1-carboxylate (ACC) deaminase and formed biofilms under drought conditions. The inoculation with the isolated strains in the seedling root system mitigated the adverse effects of drought, increasing roots and shoots dry weights of soybean seedlings compared with non-inoculated.

Influence of Trichoderma harzianum and Bacillus thuringiensis with reducing rates of NPK on growth, physiology, and fruit quality of Citrus aurantifolia / Influência de Trichoderma harzianum e Bacillus thuringiensis na redução das taxas de NPK no crescimento, fisiologia e qualidade de frutos de Citrus aurantifolia

Continuous use of chemical fertilizers gradually shrinks the crop yield and quality, and these adverse effects can be reduced by adopting new sustainable practices such as the use of manure, biofertilizers, and nano fertilizers. Limited information is existed on the application of Trichoderma harzianum and Bacillus thuringiensis microbes to improve lemon seedlings growth, physiology, and fruit formation. Therefore, the current study is aimed to evaluate the effects of T. harzianum and B. thuringiensis microbes mixing with low levels of inorganic fertilizer (NPK) on the plant growth, development, and quality of limau nipis (key lemon) fruits. The lemon seedlings growing media were inoculated during transplanting with T. harzianum and B. thuringiensis at various NPK fertilizers under polybagged conditions. The seedlings were grown around eighteen (18) months after inoculation with biofertilizers followed by Randomized Complete Block Design (RCBD) with five (5) replications. The results showed that T. harzianum with 50 g of NPK treatment (T2) increased the seedling's height, branch number, leaf height, ground area, and absolute growth rate (AGR) plant height by 50.12%, 107.84%, 17.91%, 17.91%, 116.93%, and 56.02%, respectively, over the control treatment. The number of leaves (60.82%), leaf area (42.75%), stem diameter (27.34%), specific leaf area (SLA) (39.07%), leaf area index (LAI) (54.40%), and absolute growth rate for leaf number (73.86%), leaf area (306.85%) and stem diameter (46.8%) of lemon seedlings increased significantly with B. thuringiensis plus 50 g NPK treatment (T3). The applications of B. thuringiensis with 25 g NPK fertilizer treatment (T5) increased leaf fresh weight (LFW), leaf dry weight (LDW), leaf moisture content (LMC), specific leaf weight (SLW), leaf relative growth rate (RGR), and chlorophyll content by 96.45%, 56.78%, 13.60%, 24.76%, 45.45%, and 16.22%, respectively, over the control group. In addition, T5 treatment increased the fruits number, individual fruit weight, fruit diameter, fruit dimension, leaf total soluble solids (TSS), and fruit TSS content of lemon tress by 81.81%, 55.52%, 43.54%, 25.69%, 89.47%, and 70.78% compared to the control treatment. Furthermore, soil inoculation of B. thuringiensis significantly increased the pulp to peel ratio and juice content of lemon fruits. From this study, it can be concluded that soil inoculation of both T. harzianum and B. thuringiensis with 25-50% NPK during transplanting improved plant growth, physiology, and fruit quality of limau nipis trees.

O uso contínuo de fertilizantes químicos diminui gradualmente o rendimento e a qualidade das culturas, e esses efeitos adversos podem ser reduzidos com a adoção de novas práticas sustentáveis, como o uso de esterco, biofertilizantes e nanofertilizantes. A informação limitada existe sobre a aplicação de micróbios Trichoderma harzianum e Bacillus thuringiensis para melhorar o crescimento de mudas de limão, fisiologia e formação de frutos. Portanto, o presente estudo tem como objetivo avaliar os efeitos da mistura de micróbios T. harzianum e B. thuringiensis com baixo nível de fertilizante inorgânico (NPK) no crescimento, desenvolvimento e qualidade de frutos de limau nipis (limão-chave). Os meios de cultivo de mudas de limão foram inoculados durante o transplante com T. harzianum e B. thuringiensis em vários fertilizantes NPK sob condições de polybag. As mudas foram cultivadas em torno de 10 meses após a inoculação com biofertilizantes seguidas de delineamento em blocos completos randomizados (RCBD) com 5 repetições. Os resultados mostraram que T. harzianum com 50 g de tratamento NPK (T2) aumentou a altura de plântulas, número de ramos, altura de folha, área do solo e taxa de crescimento absoluto (AGR) em 50,12%, 107,84%, 17,91%, 17,91%, 116,93% e 56,02%, respectivamente, em relação ao tratamento controle. O número de folhas (60,82%), área foliar (42,75%), diâmetro do caule (27,34%), área foliar específica (SLA) (39,07%), índice de área foliar (IAF) (54,40%) e taxa absoluta de crescimento para número de folhas (73,86%), área foliar (306,85%) e diâmetro do caule (46,8%) das mudas de limão aumentaram significativamente com B. thuringiensis mais 50 g de tratamento NPK (T3). As aplicações de B. thuringiensis com 25 g de tratamento com fertilizante NPK (T5) aumentaram a massa fresca da folha (LFW), massa seca da folha (LDW), teor de umidade da folha (LMC), peso específico da folha (SLW), taxa de crescimento relativo da folha (RGR) e teor de clorofila em 96,45%, 56,78%, 13,60%, 24,76%, 45,45% e 16,22%, respectivamente, em relação ao grupo controle. Além disso, o tratamento T5 aumentou o número de frutos, peso individual do fruto, diâmetro do fruto, dimensão do fruto, sólidos solúveis totais foliares (SST) e teor de SST do fruto do limão em 81,81%, 55,52%, 43,54%, 25,69%, 89,47% e 70,78% em relação ao tratamento controle. Além disso, a inoculação no solo de B. thuringiensis aumentou significativamente a relação polpa/casca e o teor de suco de frutos de limão. A partir deste estudo, pode-se concluir que a inoculação no solo de T. harzianum e B. thuringiensis com 25-50% de NPK durante o transplante melhorou o crescimento das plantas, a fisiologia e a qualidade dos frutos de limau nipis.

Recent advancements for microorganisms and their natural compounds useful in agriculture.

During the past years, microorganisms have been the cause of many problems for human's health. However, today with the development of many techniques of microbiology, the researchers have studied several roles of microorganisms which may help the society. Microbial-based products are expected to play important role in agriculture-enhancing plant production and therefore increasing crop's yieldeswani et al. . Microorganisms can act by several action mechanisms including antibiosis or mechanisms in plant-microbe interactions underlining the dual function of microbial strains toward plant nutrition and protection. The market has increased with the development of microbial-based products. Currently, it is normal to think that microorganisms help us in agriculture by applying them as biological control. In this mini review, we collect the last findings about this topic including very recent literature. KEY POINTS: • Microorganisms play a beneficial role in agriculture by different mechanisms. • One of these mechanisms is the secretion of chemical compounds with different activities.

Current trends in plant growth-promoting microorganisms research for sustainable food security.

The use of intensive non-sustainable agricultural practices for satisfying global food demand is degrading the agro-ecosystems, leading to their inability to produce efficient and equitable sources of calories. Microbial communities play an important role in the improvement of soil fertility and plant development; thus, the genetic and metabolic diversity of microbiota in agro-ecosystems is a promising alternative for designing microbial inoculants to not only produce enough food but also mitigates the economic, health, social, and environmental issues caused by conventional agriculture. This Special Issue has been launched to compile and inspire high-impact recent advancements on bioprospecting beneficial microorganisms as a sustainable strategy to warranty global food security.

Desarrollo de marcadores moleculares del tipo SCAR para la identificación de Azospirillum brasilense Az39 / Development of sequence characterized amplified región markers for identification of Azospirillum brasilense Az39

Resumen Azospirillum brasilense Az39 es utilizada por empresas productoras de inoculantespara la formulación de bioinsumos en América del Sur desde hace más de 30 a˜nos. Esta cepapuede promover el crecimiento, desarrollo, así como la capacidad de tolerar diferentes tiposde estrés en las plantas inoculadas, lo que determina un aumento de la productividad de culti-vos de interés agronómico. En la actualidad, no existen protocolos en Argentina que permitanconfirmar la identidad de Az39 en productos comerciales a nivel de laboratorios de control decalidad de inoculantes. Por ello, el objetivo de este trabajo fue desarrollar una metodología enbase molecular que permita la identificación certera de A. brasilense Az39. Con la secuenciacompleta del genoma y mediante herramientas bioinformáticas, se pudieron reconocer frag-mentos de ADN presentes únicamente en el genoma de Az39. Se dise˜naron cebadores dirigidosa amplificar por PCR dichas secuencias. Como resultado se observaron los productos específicosúnicamente en la presencia de la cepa de interés. La reacción pudo detectar un título mínimode 105UFC/ml (4,5 ng/l ADN) o de 102UFC/ml (0,88 ng/l ADN) o una concentración mínimade 0,098 ng/l ADN, dependiendo del método de extracción utilizado. Los cebadores fueronevaluados en el análisis de productos comerciales obtenidos del mercado nacional, arrojandoresultados positivos, tanto en muestras directas como así también en pruebas confirmatoriasa partir de colonias aisladas de tales productos. La metodología desarrollada en este trabajo,permite la detección certera de A. brasilense Az39 en cultivos puros o mezclas complejas demicroorganismos.

Abstract Azospirillum brasilense Az39 has been used since more than 30 years by several companies in South America for biofertilizers production. This strain may promote plants growth and development, as well as the ability of inoculated plants to tolerate environmental stresses, which determines an increase in the productivity under field conditions. At present, there are no protocols in Argentina to confirm the identity of Az39 in commercial products; however, such biofertilizers are formulated almost exclusively with this strain. Therefore, the objective of this paper was to develop a molecular methodology that allows the accurate identification of A. brasilense Az39. Using the complete genome sequence and several bioinformatics tools, fragments of DNA present only in the Az39 genome were recognized. A set of PCR primers to amplify these sequences were designed, and the specific products were observed only in the strain of our interest. The sensitivity of the methodology was evaluated, where the strain could be detected up to a titer of 105 CFU/ml (4.5 ng/pl ADN) or 102 CFU/ml (0.88 ng/pl DNA) or in a minimal concentration of 0.098 ng/pl DNA, depending on the DNA extraction methodology used. Primers were tested against direct samples of commercial inoculants and cultures, in both cases there were specifics products, both in direct samples and in confirmatory tests from isolated colonies from those products. The procedure presented in this paper allows the accurate identification of A. brasilense Az39 in pure cultures, mixtures of microorganisms, and commercial biofertilizers.

Bacteria-Plant interactions: an added value of microbial inoculation / Interacciones bacteria-planta: un valor añadido de la inoculación microbiana

Abstract High world population and the increase in global food demands results in an indiscriminate use of chemical fertilizers by farmers, causing soil deterioration and other environmental problems. In recent years there has been a collective concern to preserve the environment through sustainable and environmentally friendly techniques. Plant growth-promoting bacteria (PGPB) are widely known to benefit plants in a sustainable manner, reducing chemical fertilizers application. Many studies have shown that these bacteria not only improve crop yields but also its quality, increasing certain nutrients and molecules that are important for human health such as aminoacids, proteins, vitamins, flavonoids, antioxidants, essential oils, among others. This work compiles recent information of PGPB as an alternative of chemical fertilizer for improving crop yields and plant metabolites production.

El incremento acelerado de la población mundial que conlleva al aumento en la demanda de alimentos; ha ocasionado el uso indiscriminado de fertilizantes químicos por parte de los agricultores, provocando así el deterioro del suelo y con ello los subsecuentes problemas ambientales. En los últimos años ha surgido la preocupación colectiva de preservar el medioambiente a través del uso de técnicas sostenibles y ambientalmente amigables. Las bacterias promotoras de crecimiento vegetal (PGPB) son ampliamente conocidas por incrementar el crecimiento y desarrollo de las plantas de manera sostenible permitiendo así la reducción de la aplicación de fertilizantes químicos. Muchos estudios han demostrado que estas bacterias no solo mejoran el rendimiento de los cultivos sino también la calidad de estos, aumentando ciertos nutrientes y moléculas que son importantes para la salud del ser humano que los consume como aminoácidos, proteínas, vitaminas, flavonoides, antioxidantes, aceites esenciales, entre otros. Este trabajo recopila información reciente de las PGPB como alternativa a los fertilizantes químicos para la mejora en el rendimiento de los cultivos y la producción de metabolitos en las plantas.

[Development of sequence characterized amplified region markers for identification of Azospirillum brasilense Az39]. / Desarrollo de marcadores moleculares del tipo SCAR para la identificación de Azospirillum brasilense Az39.

Azospirillum brasilense Az39 has been used since more than 30 years by several companies in South America for biofertilizers production. This strain may promote plants growth and development, as well as the ability of inoculated plants to tolerate environmental stresses, which determines an increase in the productivity under field conditions. At present, there are no protocols in Argentina to confirm the identity of Az39 in commercial products; however, such biofertilizers are formulated almost exclusively with this strain. Therefore, the objective of this paper was to develop a molecular methodology that allows the accurate identification of A. brasilense Az39. Using the complete genome sequence and several bioinformatics tools, fragments of DNA present only in the Az39 genome were recognized. A set of PCR primers to amplify these sequences were designed, and the specific products were observed only in the strain of our interest. The sensitivity of the methodology was evaluated, where the strain could be detected up to a titer of 105 CFU/ml (4.5 ng/µl ADN) or 102 CFU/ml (0.88 ng/µl DNA) or in a minimal concentration of 0.098 ng/µl DNA, depending on the DNA extraction methodology used. Primers were tested against direct samples of commercial inoculants and cultures, in both cases there were specifics products, both in direct samples and in confirmatory tests from isolated colonies from those products. The procedure presented in this paper allows the accurate identification of A. brasilense Az39 in pure cultures, mixtures of microorganisms, and commercial biofertilizers.

Analysis of the denitrification pathway and greenhouse gases emissions in Bradyrhizobium sp. strains used as biofertilizers in South America.

AIMS: Greenhouse gases are considered as potential atmospheric pollutants, with agriculture being one of the main emission sources. The practice of inoculating soybean seeds with Bradyrhizobium sp. might contribute to nitrous oxide (N2 O) emissions. We analysed this capacity in five of the most used strains of Bradyrhizobium sp. in South America. METHODS AND RESULTS: We analysed the denitrification pathway and N2 O production by Bradyrhizobium japonicum E109 and CPAC15, Bradyrhizobium diazoefficiens CPAC7 and B. elkanii SEMIA 587 and SEMIA 5019, both in free-living conditions and in symbiosis with soybean. The in silico analysis indicated the absence of nosZ genes in B. japonicum and the presence of all denitrification genes in B. diazoefficiens strains, as well as the absence of nirK, norC and nosZ genes in B. elkanii. The in planta analysis confirmed N2 O production under saprophytic conditions or symbiosis with soybean root nodules. In the case of symbiosis, up to 26.1 and 18.4 times higher in plants inoculated with SEMIA5019 and E109, respectively, than in those inoculated with USDA110. CONCLUSIONS: The strains E109, SEMIA 5019, CPAC15 and SEMIA 587 showed the highest N2 O production both as free-living cells and in symbiotic conditions in comparison with USDA110 and CPAC7, which do have the nosZ gene. Although norC and nosZ could not be identified in silico or in vitro in SEMIA 587 and SEMIA 5019, these strains showed the capacity to produce N2 O in our experimental conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report to analyse and confirm the incomplete denitrification capacity and N2 O production in four of the five most used strains of Bradyrhizobium sp. for soybean inoculation in South America.