Normally, N-fixing Rhizobium exists in symbiosis. Even in isolation, they still can participate in N fixation by synthesizing nitrogenase and growing solely on N2 from the air.
Like Rhizobium, Frankia fixes atmospheric N by root nodulation. Its certain strains can live freely as well. The two N fixation bacteria species differ by hosts.
Frankia colonizes actinorhizal plants like alder, bayberry, sweetfern, Avens, etc. The N fixation symbiosis results in higher plant performance and improved soil conditions. This N-fixing genus is widely used in agroforestry. Associative symbiosis is typical for cereals and free-living N-fixing bacteria that may adhere to the host roots. They are closely associated with wheat, rice, corn, sugarcane, barley, sorghum, Setaria, biofuel crops like Pennisetum, and more.
Most N fixation bacteria reside on roots, but some aggressive types like Herbaspirillum may penetrate the entire plant. These microorganisms may enhance crop growth and boost yields , which is particularly important in poor soils. Besides N fixation, a significant peculiarity of plant growth-promoting rhizobacteria PGPR is phytohormone production , significant for yield increase. Free-living N-fixing bacteria are also a source of N for crops. For example, rice producers add aquatic Azolla ferns to their fields as green manure, and Azolla serves as a habitat to Anabaena Azolla cyanobacteria type , famous for N-fixing properties.
Cyanobacteria can live either symbiotically or freely and exist in moist soils and inland aquatic bodies. This type merges unique properties: it is classified as bacteria, though it resembles algae.
In fact, it contains chlorophyll, meaning cyanobacteria are phototrophs like plants. But unlike plants, they can fix N2. All vegetation indices in Crop Monitoring are directly or indirectly connected with chlorophyll content in crops. N immediately affects the amount and quality of the chlorophyll content so farmers can track it.
Apart from the aforementioned chlorophyll importance for the process of photosynthesis, its recognizable feature is providing green color to plants, which allows assessing the crop state.
Vibrant deep green is typical for healthy plants that contain chlorophyll in abundance. On the contrary, yellowing chlorosis and pale green signal chlorophyll deficiency and plant health deviations, possibly due to a lack of nitrogen fixation.
Besides, the pigment content in young crops is higher than in mature ones. ReCl is sensitive to chlorophyll content that directly corresponds to N fixation. Insufficient N fixation quantities result in slow crop development, small pale-green leaves, weak branching, premature yellowing, thin stems, etc.
Heavy rainfalls may also provoke N drops that a farmer can track on Crop Monitoring alongside ReCl index chart. Also, the platform provides weather forecasts for up to 14 days, which allows scheduling field activities and predicting the crop state.
ReCl is efficient at the state of active plant development and is not used at the harvesting time. Nitrogen fixation insufficiency results in reduced growth and smaller fruits, but excessive supply is no good either.
It affects root development and water saturation, delays fruit ripening, reduces storage life, and weakens cold resistance in crops. The optimal level of N is specific for each crop, so its lacking amount will also differ. Intensive agriculture heavily exploits synthetic fertilization for N fixation, harmful to the environment. Contrary, Biological N fixation proves to be friendly both to farmers and nature.
It is efficiently implemented through N-fixing crop species and certain microbial balance, contributing to organic farming. Thus, low maintenance nitrogen-fixing cover crop is a significant source of N itself, not to mention the other above-listed advantages. As for non-legumes, N-fixing bacteria inoculants are an efficient solution. They allow farmers to get the job done without artificial means. Symbiotic nitrogen fixation is reported to be more efficient than free-living ones since they release the nutrient to the host plant directly, sparing it the competition with other N-consumers.
In this regard, N fixation intracellular microorganisms e. Keeping the optimal N fixation balance with proper monitoring is the key to success. EOS Data Analytics partners up with Cambridge Technology to introduce precision agriculture and forestry technologies to growers of palm oil in Malaysia, modernizing production and decelerating climate change.
Views expressed in this publication are those of their authors and do not necessary reflect those of the authors' organization, the United Nations Environment Program, and the Global Environmental Facility.
Argenta, G. Plant parameters as indicators of nitrogen status in maize. Ausubel, F. Current Protocols in Molecular Biology. Chagas Junior, A. Phenotypic characterization of rhizobia strains isolated from Amazonian soils and symbiotic efficiency in cowpea.
Acta Scientiarum Agronomy Ferreira, D. Sisvar: a computer statistical analysis system. Fred, E. Laboratory Manual of General Microbiology. Genetic and symbiotic diversity of nitrogen-fixing bacteria isolated from agricultural soils in the western Amazon by using cowpea as the trap plant.
Applied and Environmental Microbiology Gyaneshwar, P. Legume-nodulating betaproteobacteria: diversity, host range and future prospects. Molecular Plant-Microbe Interactions Hoagland, D. The water culture method for growing plants without soil. AES Circular, Igual, J. Phosphate-solubilizing bacteria as inoculants for agriculture: use of updates molecular techniques in their study.
Agronomie Krasova-Wade, T. Diversity of indigenous bradyrhizobia associated with three cowpea cultivars Vigna unguiculata L. African Journal of Biotechnology 2: Lane, D. In: Stackebrandt E.
Nucleic acid techniques in bacterial systematics. Lima, A. Nitrogen-fixing bacteria communities occurring in soils under different uses in the western Amazon Region as indicated by nodulation of siratro Macroptilium atropurpureum. Plant and Soil Martins, L. Contribution of biological nitrogen fixation to cowpea: a strategy for improving grain yield in the semi-arid region of Brazil.
Biology and Fertility of Soils Moreira, F. Science of the Total Environment Nitrogen-fixing Leguminosae nodulating bacteria, p. In: Moreira, F. Soil biodiversity in Amazonian and other Brazilian ecosystems. Characterization of rhizobia isolated from different divergence groups of tropical leguminosae by comparative polyacrylamide gel electrophoresis of their total proteins.
Systematic and Applied Microbiology Biodiversity of rhizobia isolated form a wide range of forest legumes in Brazil. Molecular Ecology 7: Pan, B. Preincubation of B. Poustini, K. Preincubation of Rhizobium leguminosarum bv. Journal of Agricultural Science and Technology 9: Pule-Meulenberg, F.
Symbiotic functioning and bradyrhizobial biodiversity of cowpea Vigna unguiculata L. BMC Microbiology Rademaker, J. In: Akkemans, A.
In this context, Bosea spp. In addition, despite that our analysis with BLASTx suggested the presence of the nitrogenase enzyme in genomes of our isolates; the neighbor-joining tree analysis did not show a high similarity when our predicted nitrogenase-like enzymes were compared with representative nitrogenases taken from GenBank.
This result also might explain the low specificity of universal primer sets found in the literature and used in this study Supplementary Table 1 , which could not adequately cover the nitrogenases harbored by native bacteria living in Chilean Andisols.
Accordingly, and as discussed by Gaby and Buckley , while several universal primers have been designed and empirically tested for nitrogenase, some of them can generate false positive reactions; and therefore, primers must be used with caution and validated with genomic DNA from phylogenetically diverse N 2 -fixing strains from different environments.
Likewise, members of the genus Roseomonas have been recognized as a PGPB found in a wide variety of environments, including the in rhizospheres of rice Ramaprasad et al.
In this study, we noted that there were large differences in microbiota present in rhizosphere and root endosphere samples. Similarly, Robinson et al. Bouffaud et al. These differences in the composition and structure of bacterial communities between rhizosphere and root endosphere were also confirmed by DGGE.
Our results suggest a compartmentalization between rhizosphere and root endosphere for both studied communities 16s rRNA and nif H. Such separation has been described as being common in plants Mahaffee and Kloepper, and we propose that these differences might also be influenced by a combination of different factors, including soil composition pH, organic matter, and nutrients , soil management fertilization, rotation, and tillage and plant genotype, phonological stages, and defense mechanisms and the presence of other microbial communities fungi, nematode, and protozoa.
In Chilean Andisols, as wells as other agroecosystems, our knowledge on N 2 -fixing bacterial populations associated with plants is very limited. In this sense, based on the relevance of plant microbiome upon fitness and production of crops, an exhaustive study on the abundance, diversity and activity of N 2 -fixing bacterial populations could be essential to the develop of novel fertilizers and management agronomic strategies to improve the efficiency of N fertilization in the field with the consequent low cost for the farmers and environmental benefits.
JR performed experiments and developed the manuscript. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Indole acetic acid and phytase activity produced by rhizosphere bacilli as affected by pH and metals.
Soil Sci. Plant Nutr. Ahmad, F. Plant growth promoting potential of free-living diazotrophs and other rhizobacteria isolated from Northern Indian soil.
Baldani, J. The art of isolating nitrogen-fixing bacteria from non-leguminous plants using N-free semi-solid media: a practical guide for microbiologists. Plant Soil , — Beckers, B. Performance of 16s rDNA primer pairs in the study of rhizosphere and endosphere bacterial microbiomes in metabarcoding studies. Beneduzi, A. Diversity and plant growth promoting evaluation abilities of bacteria isolated from sugarcane cultivated in the South of Brazil.
Soil Ecol. Berg, G. Unraveling the plant microbiome: looking back and future perspectives. Bertsch, P. Google Scholar. Bhattacharyya, P. Plant growth-promoting rhizobacteria PGPR : emergence in agriculture. World J. Bouffaud, M. Is plant evolutionary history impacting recruitment of diazotrophs and nif H expression in the rhizosphere? Breidenbach, B. The effect of crop rotation between wetland rice and upland maize on the microbial communities associated with roots.
Campos, D. Microencapsulation by spray drying of nitrogen-fixing bacteria associated with lupin nodules. Chen, Q. Roseomonas rhizosphaerae sp. Clarke, K. Non-parametric multivariate analyses of changes in community structure. Testing of null hypotheses in exploratory community analyses: similarity profiles and biota-environment linkage. Biological Nitrogen Fixation.
Hoboken, NJ: Wiley Blackwell. De Meyer, S. Multilocus sequence analysis of Bosea species and description of Bosea lupini sp. Biotic interactions in the rhizosphere: a diverse cooperative enterprise for plant productivity. Plant Physiol. Ding, Y. Isolation and identification of nitrogen-fixing bacilli from plant rhizospheres in Beijing region.
Endophytic bacteria from selenium-supplemented wheat plants could be useful for plant-growth promotion, biofortification and Gaeumannomyces graminis biocontrol in wheat production. Soils 50, — Elkoca, E. Influence of nitrogen fixing and phosphorus solubilizing bacteria on the nodulation, plant growth, and yield of chickpea.
Gaby, J. A comprehensive evaluation of PCR primers to amplify the nif H gene of nitrogenase. Han, J. Culturable bacterial community analysis in the root domains of two varieties of tree peony Paeonia ostii. FEMS Microbiol. Hartmann, A. Hashimoto, T. Janssen, P. Improved culturability of soil bacteria and isolation in pure culture of novel members of the divisions Acidobacteria, Actinobacteria, Proteobacteria , and Verrucomicrobia.
Jia, X. Elevated temperature altered photosynthetic products in wheat seedlings and organic compounds and biological activity in rhizosphere soil under cadmium stress. Jorquera, M. Bacterial community structure and detection of putative plant growth-promoting rhizobacteria associated with plants grown in Chilean agro-ecosystems and undisturbed ecosystems. Effect of nitrogen and phosphorus fertilization on the composition of rhizobacterial communities of two Chilean Andisol pastures. Plant growth-promoting rhizobacteria associated with ancient clones of creosote bush Larrea tridentata.
Kearse, M. Geneious Basic: an integrated and extendable desktop software platform for the organization and analysis of sequence data.
Bioinformatics 28, — Kembel, S. Incorporating 16S gene copy number information improves estimates of microbial diversity and abundance. PLoS Comput. Kim, D. Roseomonas soli sp. Lagos, L. Bacterial community structures in rhizosphere microsites of ryegrass Lolium perenne var. Nui as revealed by pyrosequencing. Lane, D.
Stackebrandt and M.
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