RESUMO
Inoculation of Azospirillum in maize has become a standard practice in Latin America. However, information on the behavior and population survival of the Azospirillum post-inoculation is scarce, making standardization difficult and generating variations in inoculation efficiency across assays. In this study, we tracked the colonization of three agriculturally relevant Azospirillum strains (Ab-V5, Az39, and the ammonium excreting HM053) after different inoculation methods in maize crops by qPCR. Besides, we assessed their ability to promote maize growth by measuring biometric parameters after conducting a greenhouse essay over 42 days. Inoculated plants exhibited Azospirillum population ranging from 103 to 107 cells plant-1 throughout the experiment. While all strains efficiently colonized roots, only A. argentinense Az39 demonstrated bidirectional translocation between roots and shoots, which characterizes a systemic behavior. Optimal inoculation methods for plant growth promotion varied among strains: soil inoculation promoted the best maize growth for the Ab-V5 and Az39 strains, while seed inoculation proved most effective for HM053. The findings of this study demonstrate that the inoculation method affects the behavior of Azospirillum strains and their effectiveness in promoting maize growth, thereby guiding practices to enhance crop yield.
Assuntos
Azospirillum , Zea mays , Zea mays/microbiologia , Zea mays/crescimento & desenvolvimento , Azospirillum/fisiologia , Raízes de Plantas/microbiologia , Raízes de Plantas/crescimento & desenvolvimento , Microbiologia do SoloRESUMO
This study aimed to isolate and characterize Pseudomonas native strains from the rhizospheric soil of Minthostachys verticillata plants to evaluate their potential as plant growth-promoting rhizobacteria (PGPR). A total of 22 bacterial isolates were obtained and subjected to various biochemical tests, as well as assessments of plant growth-promoting traits such as phosphate solubilization, hydrogen cyanide production, biocontrol properties through antibiosis, and indole acetic production. Genotypic analysis via 16S rRNA gene sequencing and phylogenetic tree construction identified the strains, with one particular strain named SM 33 showing significant growth-promoting effects on M. verticillata seedlings. This strain, SM 33, showed high similarity to Stutzerimonas stutzeri based on 16S rRNA gene sequencing and notably increased both shoot fresh weight and root dry weight of the plants. These findings underscore the potential application of native Pseudomonas strains in enhancing plant growth and health, offering promising avenues for sustainable agricultural practices.
RESUMO
Maize (Zea mays L.) is an essential commodity for global food security and the agricultural economy, particularly in regions such as San Martin, Peru. This study investigated the plant growth-promoting characteristics of native rhizobacteria isolated from maize crops in the San Martin region of Peru with the aim of identifying microorganisms with biotechnological potential. Soil and root samples were collected from maize plants in four productive zones in the region: Lamas, El Dorado, Picota, and Bellavista. The potential of twelve bacterial isolates was evaluated through traits, such as biological nitrogen fixation, indole acetic acid (IAA) production, phosphate solubilization, and siderophore production, and a completely randomized design was used for these assays. A completely randomized block design was employed to assess the effects of bacterial strains and nitrogen doses on maize seedlings. The B3, B5, and NSM3 strains, as well as maize seeds of the yellow hard 'Advanta 9139' variety, were used in this experiment. Two of these isolates, B5 and NSM3, exhibited outstanding characteristics as plant growth promoters; these strains were capable of nitrogen fixation, IAA production (35.65 and 26.94 µg mL-1, respectively), phosphate solubilization (233.91 and 193.31 µg mL-1, respectively), and siderophore production (34.05 and 89.19%, respectively). Furthermore, molecular sequencing identified the NSM3 isolate as belonging to Sporosarcina sp. NSM3 OP861656, while the B5 isolate was identified as Peribacillus sp. B5 OP861655. These strains show promising potential for future use as biofertilizers, which could promote more sustainable agricultural practices in the region.
RESUMO
The production of coconut tree seedlings is an important step in the production process, as it substantially affects the productive performance of the adult plant, and the way of obtaining seedlings directly reflects the added costs. To minimize costs, the introduction of biostimulants can be considered a viable and sustainable technology. This study aimed to evaluate the effects of applying Bacillus cereus in promoting growth and reducing the costs of producing Brazilgreen dwarf coconut seedlings. The study has two stages, the first was an experiment carried out in a commercial nursery in the state of Pará-Brazil. The design was completely randomized, with two treatments: control with water (100% mineral fertilization) and B. cereus inoculation (50% mineral fertilization), with 10 replicates each. Biometric parameters and the quality of seedlings were evaluated. In the second stage, the production of stimulated seedlings was compared to that of commercial seedlings, and the effective operating cost (COE) and the total operating cost (TOC) were determined. Biostimulation with B. cereus promotes the growth of coconut tree seedlings, increases seedling quality, and reduces nursery time. In addition, the cost of production is reduced by 10%. Thus, microbial technology is a positive strategy for the production of Brazilian green dwarf coconut seedlings. Using B. cereus can guarantee obtaining seedlings with high performance and at a lower cost. These results may favor obtaining adult plants with high productivity. Supplementary Information: The online version contains supplementary material available at 10.1007/s12088-023-01163-9.
RESUMO
Plant growth-promoting rhizobacteria (PGPR) play important roles in plant growth and defense under heavy metal (HM) stress. The direct integration of microbial and plant signals is key to the regulation of plant growth and HM stress defense, but the underlying mechanisms are still limited. Herein, we reveal a novel mechanism by which PGPR regulates plant growth-regulating substances in plant tissues and coordinates plant growth and defense in pak choi under cadmium (Cd) stress. This might be an efficient strategy and an extension of the mechanism by which plant-microbe interactions improve plant stress resistance. Azospirillum brasilense and heme synergistically reduced the shoot Cd content and promoted the growth of pak choi. The interaction between abscisic acid of microbial origin and heme improved Cd stress tolerance through enhancing Cd accumulation in the root cell wall. The interaction between A. brasilense and heme induced the growth-defense shift in plants under Cd stress. Plants sacrifice growth to enhance Cd stress defense, which then transforms into a dual promotion of both growth and defense. This study deepens our understanding of plant-microbe interactions and provides a novel strategy to improve plant growth and defense under HM stress, ensuring future food production and security.
Assuntos
Azospirillum brasilense , Cádmio , Heme , Poluentes do Solo , Azospirillum brasilense/fisiologia , Cádmio/toxicidade , Heme/metabolismo , Poluentes do Solo/toxicidade , Desenvolvimento Vegetal/efeitos dos fármacos , Raízes de Plantas/microbiologia , Raízes de Plantas/crescimento & desenvolvimento , Estresse FisiológicoRESUMO
Inoculation with rhizobacteria and feeding by herbivores, two types of abiotic stress, have been shown to increase the production of secondary metabolites in plants as part of the defense response. This study explored the simultaneous effects of inoculation with Bacillus amyloliquefaciens GB03 (a PGPR species) and herbivory by third-instar Spodoptera frugiperda larvae on essential oil (EO) yield and volatile organic compound (VOC) emissions in Ocimum basilicum plants. The density of glandular trichomes was also examined, given that they are linked to EO production and VOC emission. Herbivory increased EO content, but inoculation on its own did not. When combined, however, the two treatments led to a 10-fold rise in EO content with respect to non-inoculated plants. VOC emissions did not significantly differ between inoculated and non-inoculated plants, but they doubled in plants chewed by the larvae with respect to their undamaged counterparts. Interestingly, no changes were observed in VOC emissions when the treatments were tested together. In short, the two biotic stressors elicited differing plant defense responses, mainly when EO was concerned. PGPR did not stimulate EO production, while herbivory significantly enhanced it and increased VOC emissions. The combined treatment acted synergistically, and in this case, PGPR inoculation may have had a priming effect that amplified plant response to herbivory. Peltate trichome density was higher in inoculated plants, those damaged by larvae, and those subjected to the combination of both treatments. The findings highlight the intricate nature of plant defense mechanisms against various stressors and hint at a potential strategy to produce essential oil through the combined application of the two stressors tested here.
RESUMO
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.
Assuntos
Azospirillum brasilense , Cucumis sativus , Pisum sativum , Rhizobium leguminosarum , Plântula , Solanum lycopersicum , Solanum lycopersicum/microbiologia , Solanum lycopersicum/crescimento & desenvolvimento , Cucumis sativus/microbiologia , Cucumis sativus/crescimento & desenvolvimento , Plântula/crescimento & desenvolvimento , Plântula/microbiologia , Rhizobium leguminosarum/crescimento & desenvolvimento , Rhizobium leguminosarum/metabolismo , Azospirillum brasilense/crescimento & desenvolvimento , Azospirillum brasilense/metabolismo , Pisum sativum/microbiologia , Pisum sativum/crescimento & desenvolvimento , Raízes de Plantas/microbiologia , Raízes de Plantas/crescimento & desenvolvimento , Quimiotaxia , Exsudatos de Plantas/química , Exsudatos de Plantas/metabolismoRESUMO
The development of novel biotechnologies that promote a better use of N to optimize crop yield is a central goal for sustainable agriculture. Phytostimulation, biofertilization, and bioprotection through the use of bio-inputs are promising technologies for this purpose. In this study, the plant growth-promoting rhizobacteria Pseudomonas koreensis MME3 was genetically modified to express a nitric oxide synthase of Synechococcus SyNOS, an atypical enzyme with a globin domain that converts nitric oxide to nitrate. A cassette for constitutive expression of synos was introduced as a single insertion into the genome of P. koreensis MME3 using a miniTn7 system. The resulting recombinant strain MME3:SyNOS showed improved growth, motility, and biofilm formation. The impact of MME3:SyNOS inoculation on Brachypodium distachyon growth and N uptake and use efficiencies under different N availability situations was analyzed, in comparison to the control strain MME3:c. After 35 days of inoculation, plants treated with MME3:SyNOS had a higher root dry weight, both under semi-hydroponic and greenhouse conditions. At harvest, both MME3:SyNOS and MME3:c increased N uptake and use efficiency of plants grown under low N soil. Our results indicate that synos expression is a valid strategy to boost the phytostimulatory capacity of plant-associated bacteria and improve the adaptability of plants to N deficiency. KEY POINTS: ⢠synos expression improves P. koreensis MME3 traits important for rhizospheric colonization ⢠B. distachyon inoculated with MME3:SyNOS shows improved root growth ⢠MME3 inoculation improves plant N uptake and use efficiencies in N-deficient soil.
Assuntos
Óxido Nítrico Sintase , Pseudomonas , Pseudomonas/genética , Agricultura , SoloRESUMO
Corn head smut is a disease caused by the fungus Sporisorium reilianum. This phytosanitary problem has existed for several decades in the Mezquital Valley, an important corn-producing area in central Mexico. To combat the problem, a strain identified as Bacillus subtilis 160 was applied in the field, where it decreased disease incidence and increased crop productivity. In this study, the sequencing and analysis of the whole genome sequence of this strain were carried out to identify its genetic determinants for the production of antimicrobials. The B. subtilis 160 strain was found to be Bacillus velezensis. Its genome has a size of 4,297,348 bp, a GC content of 45.8%, and 4,174 coding sequences. Comparative analysis with the genomes of four other B. velezensis strains showed that they share 2,804 genes and clusters for the production of difficidin, bacillibactin, bacilysin, macrolantin, bacillaene, fengycin, butirosin A, locillomycin, and surfactin. For the latter metabolite, unlike the other strains that have only one cluster, B. velezensis 160 has three. A cluster for synthesizing laterocidine, an antimicrobial reported only in Brevibacillus laterosporus, was also identified. IMPORTANCE: In this study, we performed sequencing and analysis of the complete genome of the strain initially identified as Bacillus subtilis 160 as part of its characterization. This bacterium has shown its ability to control corn head smut in the field, a disease caused by the basidiomycete fungus Sporisorium reilianum. Analyzing the complete genome sequence not only provides a more precise taxonomic identification but also sheds light on the genetic potential of this bacterium, especially regarding mechanisms that allow it to exert biological control. Employing molecular and bioinformatics tools in studying the genomes of agriculturally significant microorganisms offers insights into the development of biofungicides and bioinoculants. These innovations aim to enhance plant growth and pave the way for strategies that boost crop productivity.
Assuntos
Anti-Infecciosos , Bacillus , Basidiomycota , Agentes de Controle Biológico/metabolismo , Zea mays/metabolismo , Genoma Bacteriano , Bacillus subtilis/genética , Bacillus subtilis/metabolismo , Basidiomycota/metabolismo , Fungos/genéticaRESUMO
The strain INPA03-11BT, isolated in the 1980s from nodules of Centrosema sp. collected in Manaus, Amazonas, Brazil, was approved by the Brazilian Ministry of Agriculture as a cowpea inoculant in 2004. Since then, several studies have been conducted regarding its phenotypic, genetic, and symbiotic characteristics under axenic and field conditions. Phenotypic features demonstrate its high adaptability to stressful soil conditions, such as tolerance to acidity, high temperatures, and 13 antibiotics, and, especially, its high symbiotic efficiency with cowpea and soybean, proven in the field. The nodC and nifH phylogenies placed the INPA strain in the same clade as the species B. macuxiense BR 10303T which was also isolated from the Amazon region. The sequencing of the 16S rRNA ribosomal gene and housekeeping genes, as well as BOX-PCR profiles, showed its potential as a new species, which was confirmed by a similarity percentage of 94.7% and 92.6% in Average Nucleotide Identity with the closest phylogenetically related species Bradyrhizobium tropiciagri CNPSo1112T and B. viridifuturi SEMIA690T, respectively. dDDH values between INPA03-11BT and both CNPSo 1112T and SEMIA690T were respectively 58.5% and 48.1%, which are much lower than the limit for species boundary (70%). Therefore, we propose the name Bradyrhizobium amazonense for INPA03-11BT (= BR3301 = SEMIA6463).