Search Results (24)

Arbuscular mycorrhizal fungi (AMF) and phosphorus-solubilizing bacteria (PSB) play crucial roles in enhancing crop growth, increasing yields, and improving the soil microbial environment. The aim of this study was to investigate the effects of microbial inoculation and chlorothalonil on the AMF colonization rate in soybean roots, AMF spore density, nodule number, soybean biomass, and the composition of bacterial communities associated with soybean rhizosphere soil and AMF spores. The results indicated that the AMF colonization rate in soybean roots, AMF spore density, nodule number, and soybean biomass in the treatment inoculated with both Rhizophagus intraradices and Acinetobacter calcoaceticus were significantly greater than those in the other treatments. Inoculation with R. intraradices and A. calcoaceticus and spraying with chlorothalonil could influence the bacterial diversity in the rhizosphere soil of soybean. Compared with that in the control treatment, the relative abundance of Firmicutes in the rhizosphere soil of soybean plants inoculated with R. intraradices increased by 1.40%. In addition, both spraying with chlorothalonil and inoculation with A. calcoaceticus influenced the composition of AMF spore-associated bacterial communities. The relative abundance of Proteobacteria in AMF spore from soybean rhizosphere soil inoculated with R. intraradices and A. calcoaceticus increased by 12.42% compared to that in samples inoculated solely with A. calcoaceticus. This study provides a theoretical basis for microbial inoculation in improving the microenvironment of soybean rhizosphere soil and increasing soybean biomass. Full article

Soil health is typically evaluated using physical, chemical, and biological parameters. However, identifying cost-effective and interpretable metrics remains a challenge. The effectiveness of ecological outcome verification (EOV) in predicting soil health in grazing lands was assessed at 22 ranches. Sixty-four soil samples were analyzed using the Haney soil health test (HSHT) and phospholipid fatty acid (PLFA). Of 104 variables, 13 were retained following principal component analysis (PCA), including variables associated with plant community, carbon dynamics, and microbial community structure. Soils with enriched microbial and organic matter (SOM) characteristics supported a healthier ecological status, as corroborated by greater EOV scores. Water-extractable organic carbon (WEOC) was positively correlated to plant functional groups, whereas SOM was positively correlated with plant biodiversity and functional groups. Total bacteria were positively correlated with all EOV parameters. Microbial biomass (MB) was positively correlated with both water and energy cycle indexes, whereas arbuscular mycorrhizal fungi (AMF) was positively correlated with the water cycle. From the multiple regression analyses, water infiltration emerged as a key predictor of soil respiration and WEOC. Overall, the ecological outcomes measured by EOV have the potential to serve as a proxy for soil health, providing a practical tool for producers to make informed land management decisions. Full article

Agricultural systems are particularly impacted by global climate change (CC), responsible for the introduction of multiple environmental stressors negatively affecting plant growth. Soil microbial communities are crucial in agricultural practices, influencing crop performance and soil health. Human activities and CC threaten soil microbial biodiversity, leading to soil quality degradation and decreasing plant health and productivity. Among plant-beneficial microorganisms, mycorrhizal fungi are widespread in terrestrial ecosystems, including agroecosystems, and they play a key role by enhancing plants’ fitness and resilience to both abiotic and biotic stresses. Therefore, exploring the role of mycorrhizal symbiosis in sustainable agriculture has become increasingly critical. Moreover, the application of mycorrhizal bioinoculants could reduce dependence on inorganic fertilizers, enhance crop yield, and support plants in overcoming environmental stresses. This review, after briefly introducing taxonomy, morphology and mechanisms supporting the symbiosis establishment, reports the roles of mycorrhizal fungi and their associated bacteria in improving plant nutrition and mitigating CC-induced abiotic stresses such as drought and salinity, also giving specific examples. The focus is on arbuscular mycorrhizal fungi (AMF), but ericoid mycorrhizal (ErM) fungi are also considered as promising microorganisms for a sustainable agricultural model. New emerging concepts are illustrated, such as the role of AMF hyphosphere in acting as a preferential niche to host plant growth-promoting bacteria and the potential of ErM fungi to improve plant performance on Ericaceae plants but also on non-host plants, behaving as endophytes. Finally, the potential and limitations of mycorrhizal-based bioinoculants are discussed as possible alternatives to chemical-based products. To this aim, possible ways to overcome problems and limitations to their use are discussed such as proper formulations, the systematic check of AMF propagule viability and the application of suitable agronomical practices in the field. Full article

Water deficiency has been recognized as a major abiotic stress that causes losses in maize crops around the world. The maize crop is very important due to the range of products that are derived from this plant. A potential way to reduce the damages caused by water deficiency in maize crops is through the association with plant growth-promoting bacteria (PGPB) and arbuscular mycorrhizal fungi (AMF). To define the mechanisms developed by associative PGPB and AMF in maize that are involved in protection against moderate drought (MD), this study evaluated the biometrical, anatomical, biochemical, and physiological parameters of maize grown under MD and inoculated with different PGPB (Azospirillum brasilense strain Ab-V5 and Bacillus sp. strain ZK) and with AMF. The relative water content did not change in the treatments. The association with ZK increased the shoot:total ratio, total dry weight, maximum quantum yield of photosystem II, vascular cylinder thickness, and vascular cylinder area. The Ab-V5 inoculation led to an increment in root dry weight, the area of metaxylem vessel elements, and nitrate reductase activity. The AMF association did not lead to changes in the measured parameters. The results indicate that the association with PGPB is a relevant alternative to contribute to reducing losses in maize crops under drought. However, AMF is not indicated for this crop under drought. Full article

Bioremediation technology, another strategy known for restoring degraded environments, utilizes beneficial microorganisms, including arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (NFB). Despite its potential, the biological processes of these microorganisms in contaminated sites remain poorly understood, hindering effective pollutant toxicity reduction. Establishing a connection between plant root systems and these microorganisms is crucial for enabling plant survival in heavy metal-contaminated soils. Narra (Pterocarpus indicus Willd.), a leguminous plant, typically associates with symbiotic nitrogen-fixing bacteria, forming nodules in the roots. Additionally, Narra forms a symbiotic relationship with AMF, phosphorus-fixing microbes, making it an ideal tree species for rehabilitating mined-out areas. In this study, five microbial biofertilizers, namely: MYKORICH^®, MYKOVAM^®, newMYC, newNFB, and combined newMYC+newNFB, plus a control were used to test their root colonization potential on Narra seedlings grown in nickel (Ni) and gold (Au) mined-out soils collected from Taganito Mining Corporation (TMC) and Manila Mining Corporation (MMC) in Claver and Placer, Surigao del Norte, Philippines, respectively. The results showed that newMYC had the highest root colonization in Ni mined-out soil, while MYKORICH^® excelled in Au mined-out soil. The AMF spore count was highest in MYKORICH^® for Ni mined-out soil and newMYC in Au mined-out soil. NFB colonization was highest in newMYC-treated seedlings for Ni mined-out soil and combined newMYC+newNFB for Au mined-out soil. The microbial biofertilizers utilized in this research, such as MY-KORICH^®, MYKOVAM, newMYC, newNFB, and combined newNFB and newMYC, naturally occur in the environment and can be easily extracted. This cost-effective characteristic provides an advantage for mining companies seeking treatments for soil amelioration to rehabilitate mined-out areas. Full article

Stress factors typical in urban environments adversely affect the productivity and vigor of trees and may limit the development of tree roots with associated soil fungi and bacteria. Studies on mycorrhizal symbiosis and the activity of soil microorganisms are important in monitoring the adaptation of trees to urban conditions. We compared the symbiotic activity of arbuscular mycorrhizal fungi (AMF) living in the rhizosphere of mature white chestnut trees (Aesculus hippocastanum L.) in an urban ecosystem at sites with varying degrees of anthropopressure and in a rural area. We used two methods: (1) direct analysis of the root samples, (2) assessment of the colonization of trap plants grown in the soil taken from under selected white horse chestnut trees. The seasonality of mycorrhizal colonization and soil microbial respiration based on the enzyme activity of nonspecific dehydrogenase (DHA) was studied over several growing seasons. The concentrations of macronutrients in the soil from all study sites were in the ranges accepted as normal for the upper soil layer. However, the C/N ratio indicated carbon limitation in the soil at urban and rural study sites. The results showed that arbuscular mycorrhizal fungi indigenous in the rhizosphere of A. hippocastanum developed a functioning mycorrhizal symbiosis at all research sites, including at highly disturbed urban locations, and that the mycorrhizal colonization varied between the study sites and the research term. The trap culture method confirmed the high biological potential of the soil microbial community, including AMF in urban ecosystems, which was comparable to that at the reference site in the rural environment. Soil moisture strongly affected the overall soil microbial vitality. This research showed that the mycorrhizal status of A. hippocastanum is more strongly influenced by climatic conditions and seasonal rhythms of trees than by urban/non-urban locations. Full article

Arbuscular mycorrhizal fungi (AMF) form a vital symbiotic relationship with plants. Through their extensive hyphal networks, AMF extend the absorptive capacity of plant roots, thereby allowing plants to reach otherwise inaccessible micronutrient sources. Iron, a critical micronutrient involved in photosynthesis and other metabolic processes, often becomes inaccessible owing to its tendency to form insoluble complexes in soil. AMF symbiosis significantly ameliorates this challenge by enhancing iron uptake and homeostasis in plants, altering root architecture, and producing root exudates that improve iron solubility. Moreover, the interaction with diverse soil bacteria, particularly plant growth-promoting rhizobacteria, can potentiate the benefits of AMF symbiosis. Siderophores are low-molecular-weight chelators with iron-binding capacities produced by various microorganisms and plant roots. They play pivotal roles in regulating intracellular iron and have been identified in different mycorrhizal associations, including AMF. While molecular mechanisms behind AMF-mediated iron uptake have been partially explored, the intricate networks involving AMF, plants, siderophores, and other soil microbiota are largely unknown. This review focuses on the multifaceted roles of AMF in plant–iron homeostasis, interactions with soil bacteria, and the potential of siderophores in these processes, emphasizing the possibilities for harnessing these relationships for sustainable agriculture and enhancing plant productivity. Full article

This study of a legume’s rhizosphere in tripartite symbiosis focused on the relationships between the symbionts and less on the overall rhizosphere microbiome. We used an experimental model with different garden pea genotypes inoculated with AM fungi (Rhizophagus irregularis and with a mix of AM species) to study their influence on the population levels of main trophic groups of soil microorganisms as well as their structure and functional relationships in the rhizosphere microbial community. The experiments were carried out at two phenological cycles of the plants. Analyzes were performed according to classical methods: microbial population density defined as CUF/g a.d.s. and root colonization rate with AMF (%). We found a proven dominant effect of AMF on the densities of micromycetes and actinomycetes in the direction of reduction, suggesting antagonism, and on ammonifying, phosphate-solubilizing and free-living diazotrophic Azotobacter bacteria in the direction of stimulation, an indicator of mutualistic relationships. We determined that the genotype was decisive for the formation of populations of bacteria immobilizing mineral NH₄⁺-N and bacteria Rhizobium. We reported significant two-way relationships between trophic groups related associated with soil nitrogen and phosphorus ions availability. The preserved proportions between trophic groups in the microbial communities were indicative of structural and functional stability. Full article

Invasive weeds of the Asteraceae family are widespread in the world. Arbuscular mycorrhiza (AM) is one of the main factors contributing to the successful distribution of these species that is most clearly manifested in the subfamily Asteroideae. The benefits of plant-AMF symbiosis are most significant under unfavorable biotic and abiotic conditions. The specificity of the relationship between arbuscular mycorrhizal fungi (AMF) communities and plants and is determined at the presymbiotic stage. The AMF colonization level is higher in invasive species than in native ones, but AMF communities associated with Asteraceae invasive species are less diverse. AMF communities of Asteraceae invaders often include fewer common species (e.g., species belonging to Diversisporales). Invaders also reduce native AMF species richness in new areas. Arbuscular mycorrhizal fungi can form mycorrhizal networks that allow the redistribution of nutrients in plant communities. The most significant influence of AMF associated with invasive Asteraceae plants is seen in the formation of soil and rhizosphere microbiota, including the suppression of beneficial soil bacteria and fungi. This review could be useful in the development of practical recommendations for the use of AMF-based fertilizers. Full article

The cultivation of Echinacea purpurea for commerce and obtaining high-quality plant material on a large scale remain a challenge for growers. Another challenge for the following decades is to create sustainable agriculture that meets society’s needs, has no environmental impact, and reduces the use of fertilizers and pesticides. The aims of this overview were: (1) to present the importance of the chemical compounds reported in E. purpurea; (1) to synthesize results about cultivation of the E. purpurea with arbuscular mycorrhizal fungi (AMF) and associated microorganisms; (2) to exemplify similar research with plants from the Asteraceae family, due to the limited number of published Echinacea studies; (3) to collect recent findings about how the inoculation with AMF affects gene expressions in the host plants; (4) to propose perspective research directions in the cultivation of E. purpurea, in order to increase biomass and economic importance of secondary metabolite production in plants. The AMF inocula used in the Echinacea experiments was mainly Rhizophagus irregularis. The studies found in the selected period (2012–2022), reported the effects of 21 AMFs used as single inocula or as a mixture on growth and secondary metabolites of 17 plant taxa from the Asteraceae family. Secondary metabolite production and growth of the economic plants were affected by mutualistic, symbiotic or parasitic microorganisms via upregulation of the genes involved in hormonal synthesis, glandular hair formation, and in the mevalonate (MVA), methyl erythritol phosphate (MEP) and phenylpropanoid pathways. However, these studies have mostly been carried out under controlled conditions, in greenhouses or in vitro in sterile environments. Since the effect of AMF depends on the variety of field conditions, more research on the application of different AMF (single and in various combinations with bacteria) to plants growing in the field would be necessary. For the identification of the most effective synergistic combinations of AMF and related bacterial populations, transcriptomic and metabolomic investigations might also be useful. Full article

A successful microbial inoculant can increase root colonization and establish a positive interaction with native microorganisms to promote growth and productivity of cereal crops. Zinc (Zn) is an intensively reported deficient nutrient for maize and wheat production in Brazilian Cerrado. It can be sustainably managed by inoculation with plant growth-promoting bacteria and their symbiotic association with other microorganisms such as arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE). The objective of this study was to evaluate the effect of Azospirillum brasilense inoculation and residual Zn rates on root colonization and grain yield of maize and wheat in succession under the tropical conditions of Brazil. These experiments were conducted in a randomized block design with four replications and arranged in a 5 × 2 factorial scheme. The treatments consisted of five Zn rates (0, 2, 4, 6 and 8 kg ha⁻¹) applied from zinc sulfate in maize and residual on wheat and without and with seed inoculation of A. brasilense. The results indicated that root colonization by AMF and DSE in maize–wheat cropping system were significantly increased with interaction of Zn rates and inoculation treatments. Inoculation with A. brasilense at residual Zn rates of 4 kg ha⁻¹ increased root colonization by AMF under maize cultivation. Similarly, inoculation with A. brasilense at residual Zn rates of 2 and 4 kg ha⁻¹ reduced root colonization by DSE under wheat in succession. The leaf chlorophyll index and leaf Zn concentration were increased with inoculation of the A. brasilense and residual Zn rates. The inoculation did not influence AMF spore production and CO₂-C in both crops. The grain yield and yield components of maize–wheat were increased with the inoculation of A. brasilense under residual Zn rates of 3 to 4 kg ha⁻¹ in tropical savannah conditions. Inoculation with A. brasilense under residual Zn rates up to 4 kg ha⁻¹ promoted root colonization by AMF and DSE in the maize cropping season. While the inoculation with A. brasilense under 2 and 4 kg ha⁻¹ residual Zn rates reduced root colonization by AMF and DSE in the wheat cropping season. Therefore, inoculation with A. brasilense in combination with Zn fertilization could consider a sustainable approach to increase the yield and performance of the maize–wheat cropping system in the tropical savannah conditions of Brazil. Full article

Researchers have used both soil nematode data and soil quality index (SQI) data as indicators of soil quality. However, the relationship between soil nematodes and soil quality index is poorly understood. This study explored the relationship between soil nematode properties and soil quality in different land-use types in a subtropical karst region of Southwest China. We selected the following five typical land-use types that differ in the degree of soil disturbance: cropland (maize and soybean), sugarcane, mulberry, forage grass, and forest. SQI was calculated on the basis of bulk density (BD), soil pH, the ratio of soil organic carbon to total nitrogen (C:N), the contents of soil water (SWC), soil total nitrogen (TN), soil organic carbon content (SOC), calcium (Ca), magnesium (Mg), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), ammonium nitrogen (AN), nitrate nitrogen (NN), bacteria, fungi, actinomycetes (ACT), and arbuscular mycorrhizal fungi (AMF). We found that the abundance, Simpson dominance index, and metabolic footprint of soil nematodes were highest in the forest, followed by sugarcane, cropland (maize and soybean), forage grass, and mulberry. The SQI was highest in the forest and lowest in the cropland. There was no significant difference observed among the other three regions. In addition, the SQI was positively correlated with the total nematode biomass and abundances of total nematodes, fungivores, and herbivores, the abundances of total nematodes biomass and total nematode abundance, fungivores, and herbivores. A random forest model revealed that the dominant nematode genera (i.e., Coomansus and Acrobeloides) and the rare genera (i.e., Heterocephalobus) were closely associated with soil quality. Our results suggest that the soil nematodes (especially keystone genera) may mediate the effects of ecosystem disturbance on soil quality. These findings increase our understanding of the relationships between soil organisms and soil quality. Full article

Medicinal and aromatic plants (MAPs) have been used worldwide for thousands of years and play a critical role in traditional medicines, cosmetics, and food industries. In recent years, the cultivation of MAPs has become of great interest worldwide due to the increased demand for natural products, in particular essential oils (EOs). Climate change has exacerbated the effects of abiotic stresses on the growth, productivity, and quality of MAPs. Hence, there is a need for eco-friendly agricultural strategies to enhance plant growth and productivity. Among the adaptive strategies used by MAPs to cope with the adverse effects of abiotic stresses including water stress, salinity, pollution, etc., their association with beneficial microorganisms such as arbuscular mycorrhizal fungi (AMF) can improve MAPs’ tolerance to these stresses. The current review (1) summarizes the effect of major abiotic stresses on MAPs’ growth and yield, and the composition of EOs distilled from MAP species; (2) reports the mechanisms through which AMF root colonization can trigger the response of MAPs to abiotic stresses at morphological, physiological, and molecular levels; (3) discusses the contribution and synergistic effects of AMF and other amendments (e.g., plant growth-promoting bacteria, organic or inorganic amendments) on MAPs’ growth and yield, and the composition of distilled EOs in stressed environments. In conclusion, several perspectives are suggested to promote future investigations. Full article

Estimates are that land area occupied by grass pasture far exceeds that of other crops; at least half are at some stage of degradation. The use of elite plant-growth-promoting microorganisms (PGPM) as inoculants represents an important strategy to achieve qualitative and quantitative improvements in forage biomass, increasing the productivity and sustainability of livestock production. Several studies have reported the benefits of PGPM in grass pastures, with an emphasis on bacteria of the genera Azospirillum, Pseudomonas, Bacillus, rhizobia, and on arbuscular mycorrhiza fungi (AMF). The main grasses studied are Urocholoa (syn. Brachiaria), Megathyrsus (syn. Panicum), Paspalum, Cynodon, and Agropyron. Several microbial processes associated with improvements in root and shoot growth, nutrient content in biomass, and other benefits have been described. Promotion of plant growth has been associated with the synthesis of phytohormones and enzymes regulating several steps of plant development, nutrient mineralization by release of microbial molecules, biological nitrogen fixation, nutrient uptake facilitation by means of molecules such as exopolysaccharides, amongst others. Outstanding benefits of increased root growth, resulting in higher uptake of water and nutrients, either by phytohormones released by bacteria or by expanding root surface by AMF, have been reported. Biocontrol is another important property of PGPM, by a variety of mechanisms, including the synthesis of antimicrobial molecules, lytic enzymes, siderophores, and the release of specific inhibitory compounds such as hydrogen cyanide. Although improvements in forage management can enhance microbial performance, as shown for AMF, in general, inoculation with elite strains positively impacts growth parameters. Globally, the use of microbial inoculants has significantly increased in the past few years, but their application is still modest on grass pastures, which are generally degraded and would need special use of microbial inoculants for reclamation. Efforts towards increasing the use of PGPM in pastures can have deep positive environmental, economic, and social impacts worldwide. Full article

A crucial challenge to face in the treatment of biofilm-associated infection is the ability of bacteria to develop resistance to traditional antimicrobial therapies based on the administration of antibiotics alone. This study aims to apply magnetic hyperthermia together with controlled antibiotic delivery from a unique magnetic-responsive nanocarrier for a combination therapy against biofilm. The design of the nanosystem is based on antibiotic-loaded mesoporous silica nanoparticles (MSNs) externally functionalized with a thermo-responsive polymer capping layer, and decorated in the outermost surface with superparamagnetic iron oxide nanoparticles (SPIONs). The SPIONs are able to generate heat upon application of an alternating magnetic field (AMF), reaching the temperature needed to induce a change in the polymer conformation from linear to globular, therefore triggering pore uncapping and the antibiotic cargo release. The microbiological assays indicated that exposure of E. coli biofilms to 200 µg/mL of the nanosystem and the application of an AMF (202 kHz, 30 mT) decreased the number of viable bacteria by 4 log₁₀ units compared with the control. The results of the present study show that combined hyperthermia and antibiotic treatment is a promising approach for the effective management of biofilm-associated infections. Full article