Contribution Of Arbuscular Mycorrhizal Fungi Research Articles

Grazing exclusion enriches arbuscular mycorrhizal fungal communities and improves soil organic carbon sequestration in the alpine steppe of northern Tibet

Fencing for grazing exclusion is regarded as a traditional and effective method for the natural restoration of degraded alpine steppe, and it effectively promotes plant growth and enhances soil carbon stocks. Arbuscular mycorrhizal fungi (AMF) are essential microorganisms in grassland that play a major role in plant-derived C translocation into the soil. However, the effects of fencing on AMF communities and their contributions to soil carbon sequestration are still unclear. In this study, alpine steppe areas with three different fencing durations (free grazing, medium-term fencing for 5-6 years and long-term fencing for more than 10 years) in the northern Tibetan Plateau were selected to explore the effects of grazing exclusion on AMF communities and their roles in soil carbon sequestration. The results showed that medium- and long-term fencing significantly increased both plant aboveground biomass and soil organic carbon (SOC) content. The AMF community composition varied significantly during different fencing durations, with a dramatic increase in the relative abundance of Glomus but a significant reduction in the relative abundance of Diversispora with longer fencing time. Medium-term fencing significantly increased AMF richness and the Shannon-Wiener index. Meanwhile, fencing significantly increased hyphal length density (HLD), glomalin-related soil protein (GRSP) and the proportion of macroaggregates (250-2,000 μm), all of which contribute positively to SOC. Structural equation modeling revealed that fencing time positively influenced HLD and the AMF community composition, subsequently affecting T-GRSP, which was tightly correlated with SOC. Our findings suggest the potentially important contribution of AMF to SOC sequestration, so more attention should be paid to AMF during alpine steppe fencing, particularly for enhancing the efficiency of degraded grassland restoration efforts.

Effects of Different Vesicular - arbuscular Mycorrhizal (VAM) Fungi on the Seedling Growth of Tecomella undulata

Tecomella undulata (Sm.) Seem. (family Bignoniaceae) is a tree found in desert parts of India, and Arabia. The cultivation of high-quality seedlings is vital for establishing a successful plantation and the contribution of arbuscular mycorrhizal fungi (AMF) in the soil plays a vital role in the nursery phase. A study conducted during the periods of 2021-22 and 2022-23 scrutinised the effect of four distinct species of Glomus spp. (G. mosseae, G. intraradices, G. fasciculatum and Glomus hoi) on Tecomella undulata seedlings in AMF-inoculated soil. The inoculation involved applying of 400-500 sporocarps/kg of soil during sowing and the evaluation encompassed growth and survival parameters. Results revealed that among the 4 Glomus species, soil inoculated with Glomus fasiculatum at 180 days after sowing, significantly increased the root colonization percentage with (50.69 and 46.71 %) in year (2021-22) and (2022-23) compared to the uninoculated control. Additionally, seedlings exhibited significantly higher no. of spores per 100g of soil, when treated with (Glomus fasiculatum) inoculated soil, which was statistically at par with soil inoculated with (Glomus intraradices) at (103.67 and 98.65). During both the experimental year, in terms of germination percentage, root length and root: shoot ratio were found non- significantly with (44.45 %), root length at 360 DAS, (26.67 and 25.74) respectively, root shoot ratio at 360 days after sowing. While, plant survival percentage (30.63 and 25.41%) at 90 DAS. Whereas, at 360 DAS, collar diameter (6.14 and 10.07 mm), shoot length (33.36 and 32.19 cm), plant biomass (8.31 and 8.05 g), leaf area (196.29 and 185.46 cm 2) was observed significantly higher in treatment T3 (Glomus fasiculatum) which was statistically at par with treatment T1 (G. intraradices). It is concluded from study that Glomus fasiculatum were found best for growth and survival of seedlings followed by Glomus intraradices as compare to control.

Disentangling the contributions of arbuscular mycorrhizal fungi to soil multifunctionality

Soil multifunctionality represents a range of soil processes driven by the interactions between soil abiotic and biotic components. As a group of ubiquitous fungi that form mutualistic symbiotic associations with a vast array of terrestrial plants, arbuscular mycorrhizal (AM) fungi may play a critical role in maintaining soil multifunctionality, but the characteristics of their contributions remain to be unraveled. This mini-review aims to disentangle the contributions of AM fungi to soil multifunctionality. We provide a framework of concepts about AM fungi making crucial contributions to maintaining multiple soil functions, including primary productivity, nutrient cycling, water regulation and purification, carbon and climate regulation, habitat for biodiversity, disease and pest control, and pollutant degradation and detoxification, via a variety of pathways, particularly contributing to soil and plant health. This review contends that AM fungi, as a keystone component of soil microbiome, can govern soil multifunctionality, ultimately promoting ecosystem services.

Role of arbuscular mycorrhizal fungi in cadmium tolerance in rice (Oryza sativa L): a meta-analysis

Rice is an important agricultural product consumed globally. Rice polluted by cadmium (Cd) poses serious health risks. Numerous studies have shown that arbuscular mycorrhizal fungi (AMF) decrease Cd concentrations in the grain, shoots, and roots of rice. However, one study showed that AMF increased the root Cd concentration in rice. Therefore, a meta-analysis of the contribution of AMF to rice Cd tolerance became necessary. This meta-analysis was conducted to analyze the role of AMF in Cd tolerance in rice by searching the following databases: ProQuest, PubMed, Scopus, and ScienceDirect. A total of 571 studies were found, of which nine studies and 25 datasets were used in the meta-analysis. The period of inclusion of research reports was from January 1992 to April 2022. The results showed that with the addition of Rhizophagus irregularis, Cd concentration in the roots was higher than in the control group, although the overall Cd concentration in the plant was reduced. Four species of AMF reduced Cd concentration in rice shoots and grain tissues. These AMF species increased the biomass of rice root and shoot tissues; however, they did not affect grain biomass. AMF decreased the transfer factor (TF), and the TF of Glomus versiforme (12.99%) was significantly lower than the other three AMF types. We proposed that Cd could be enriched in rice roots, and the transfer of Cd to the grain could be inhibited. At the time of grain harvesting, rice roots are removed from the soil, thus removing Cd from the soil. This operation can efficiently improve both land-bearing capacity and soil without affecting rice yield. Thus, Cd was enriched in rice roots, and the poten-tial for Cd transfer to the grain was inhibited due to the decreased TF. The future research must focus on how R. irregularis could improve the HMA3 gene expression in rice root, and prevents the transportation of Cd from the roots to shoots.

Arbuscular Mycorrhizal Fungi Improve the Growth, Water Status, and Nutrient Uptake of Cinnamomum migao and the Soil Nutrient Stoichiometry under Drought Stress and Recovery.

Drought greatly influences the growth and ecological stoichiometry of plants in arid and semi-arid regions such as karst areas, where Cinnamomum migao (C. migao) is an endemic tree species that is used as a bioenergy resource. Arbuscular mycorrhizal fungi (AMF) play a key role in nutrient uptake in the soil-plant continuum, increasing plant tolerance to drought. However, few studies have examined the contribution of AMF in improving the growth of C. migao seedlings and the soil nutrient stoichiometry under drought-stress conditions. A pot experiment was conducted under natural light in a plastic greenhouse to investigate the effects of individual inoculation and Co-inoculation of AMF [Funneliformis mosseae (F. mosseae) and Claroideoglomus etunicatum (C. etunicatum)] on the growth, water status, and nutrient uptake of C. migao as well as the soil nutrient stoichiometry under well-watered (WW) and drought-stress (DS) conditions. The results showed that compared with non-AMF control (CK), AM symbiosis significantly stimulated plant growth and had higher dry mass. Mycorrhizal plants had better water status than corresponding CK plants. AMF colonization notably increased the total nitrogen and phosphorus content of C. migao seedlings compared with CK. Mycorrhizal plants had higher leaf and stem total carbon concentrations than CK. The results indicated that AM symbiosis protects C. migao seedlings against drought stress by improving growth, water status, and nutrient uptake. In general, the C. migao seedlings that formed with C. etunicatum showed the most beneficial effect on plant growth, water status, and nutrient uptake among all treatments. In the future, we should study more about the biological characteristics of each AMF in the field study to understand more ecological responses of AMF under drought stress, which can better provide meaningful guidance for afforestation projects in karst regions.

Arbuscular Mycorrhizal Fungi Shift Soil Bacterial Community Composition and Reduce Soil Ammonia Volatilization and Nitrous Oxide Emissions.

Arbuscular mycorrhizal fungi (AMF) establish mutualistic relationships with the majority of terrestrial plants, increasing plant uptake of soil nitrogen (N) in exchange for photosynthates. And may influence soil ammonia (NH3) volatilization and nitrous oxide (N2O) emissions directly by improving plant N uptake, and/or indirectly by modifying soil bacterial community composition for the soil C availability increasing. However, the effects of AMF on soil NH3 volatilization and N2O emissions and their underlying mechanisms remain unclear. We carried out two independent experiments using contrasting methods, one with a compartmental box device (in 2016) and the other with growth pot experiment (in 2020) to examine functional relationships between AMF and soil NH3 volatilization and N2O emissions under varying N input. The presence of AMF significantly reduced soil NH3 volatilization and N2O emissions while enhancing plant biomass and plant N acquisition, and reducing soil NH4+ and NO3-, even with high N input. The presence of AMF also significantly reduced the relative abundance within the bacterial orders Sphingomonadales and Rhizobiales. Sphingomonadales correlated significantly and positively with soil NH3 volatilization in 2016 and N2O emissions, whereas Rhizobiales correlated positively with soil N2O emissions. High N input significantly increased soil NH3 volatilization and N2O emissions with increasing relative abundance of Sphingomonadales and Rhizobiales. These findings demonstrate the contribution of AMF in regulating NH3 and N2O emission by improving plant N uptake and altering soil bacterial communities. They also suggest that altering the rhizosphere microbiome might offer additional potential for restoration of N-enriched agroecosystems.

Arbuscular mycorrhizal fungi enhanced rice proline metabolism under low temperature with nitric oxide involvement.

Arbuscular mycorrhizal fungi (AMF) are known to improve plant stress tolerance by regulating proline accumulation, and nitric oxide (NO) plays an important signaling role in proline metabolism. Environmental nitrogen (N) affects AMF colonization and its contribution to host plants resistance to stress conditions. However, the relationship between proline metabolism and NO in mycorrhizal rice and the effect of N application on symbiont proline metabolism under low temperature have not been established. Pot culture experiments with different temperature, N and exogenous NO donor treatments were conducted with non-mycorrhizal and mycorrhizal rice. The results showed that AMF enhanced rice proline accumulation under low-temperature stress and decreased glutamate (Glu) and ornithine (Orn) concentrations significantly. In comparison with non-mycorrhizal rice, AMF colonization significantly decreased the Glu concentration, but had little effect on the Orn concentration under low-temperature stress, accompanied by increasing expression of OsP5CS2, OsOAT and OsProDH1. Exogenous application of NO increased proline concentration both under normal and low temperature, which exhibited a higher increase in mycorrhizal rice. NO also triggered the expression of key genes in the Glu and Orn pathways of proline synthesis as well as proline degradation. Higher N application decreased the AMF colonization, and AMF showed greater promotion of proline metabolism at low N levels under low temperature stress by regulating the Glu synthetic pathway. Meanwhile, AMF increased rice nitrate reductase (NR) and nitric oxide synthase (NOS) activities and then enhanced NO accumulation under low N levels. Consequently, it could be hypothesized that one of the mechanisms by which AMF improves plant resistance to low-temperature stress is the accumulation of proline via enhancement of the Glu and Orn synthetic pathways, with the involvement of the signaling molecule NO. However, the contribution of AMF to rice proline accumulation under low-temperature stress was attenuated by high N application.

Contribution of arbuscular mycorrhizal fungi to nitrogen and phosphorus uptake efficiency and productivity of faba bean crop on contrasting cropping systems

The present study was focused on evaluating the effect of AMF (Arbuscular Mycorrhizal Fungi) inoculation on nitrogen and phosphorus uptake efficiency and productivity of faba bean (Vicia faba L.) crop, under different fertilization levels on organic or conventional cropping systems. The 2-year field experiment was conducted in central Greece and laid out in a split-plot design, with three replications, two main plots (AMF inoculation treatments) and five sub-plots (fertilization treatments). The results demonstrated that plants of AMF inoculated plots exhibited greater plant height, leaf area index (LAI), leading to higher biomass, and consequently higher final seed yields. Regarding the quality parameters, including nutrients (nitrogen and phosphorus) uptake and their utilization indices, similar results to those of the productivity results were found with the AMF inoculated plants presented the higher values. Finally, all the parameters of the root system, including AMF root colonization and weighted mycorrhizal dependency (WMD), were negatively affected by fertilization level, particularly in an inorganic form. As a conclusion, the current study confirmed that replacement of inorganic inputs by organic in combination with AMF inoculation, should be seriously considered as a sustainable practice of faba bean crop cultivation under Mediterranean conditions.

The pivotal role of cultivar affinity to arbuscular mycorrhizal fungi in determining mycorrhizal responsiveness to water deficit

Arbuscular mycorrhizal fungi (AMF) have gained remarkable importance, having been proved to alleviate drought stress-induced damage in wheat due to their ability to ameliorate plant water use efficiency and antioxidant enzyme activity. However, despite the current relevance of the topic, the molecular and physiological processes at the base of this symbiosis never consider the single cultivar affinity to mycorrhization as an influencing factor for the metabolic response in the AMF-colonized plant. In the present study, the mycorrhizal affinity of two durum wheat species (T. turgidum subsp. durum (Desf.)) varieties, Iride and Ramirez, were investigated. Successively, an untargeted metabolomics approach has been used to study the fungal contribution to mitigating water deficit in both varieties. Iride and Ramirez exhibited a high and low level of mycorrhizal symbiosis, respectively; resulting in a more remarkable alteration of metabolic pathways in the most colonised variety under water deficit conditions. However, the analysis highlighted the contribution of AMF to mitigating water deficiency in both varieties, resulting in the up- and down-regulation of many amino acids, alkaloids, phenylpropanoids, lipids, and hormones.

Suppression of AMF accelerates N2O emission by altering soil bacterial community and genes abundance under varied precipitation conditions in a semiarid grassland.

Nitrous oxide (N2O) is one of the most important greenhouse gases contributing to global climate warming. Recently, studies have shown that arbuscular mycorrhizal fungi (AMF) could reduce N2O emissions in terrestrial ecosystems; however, the microbial mechanisms of how AMF reduces N2O emissions under climate change are still not well understood. We tested the influence of AMF on N2O emissions by setting up a gradient of precipitation intensity (+50%, +30%, ambient (0%), −30%, −50%, and −70%) and manipulating the presence or exclusion of AMF hyphae in a semiarid grassland located in northeast China. Our results showed that N2O fluxes dramatically declined with the decrease in precipitation gradient during the peak growing season (June–August) in both 2019 and 2020. There was a significantly positive correlation between soil water content and N2O fluxes. Interestingly, N2O fluxes significantly decreased when AMF were present compared to when they were absent under all precipitation conditions. The contribution of AMF to mitigate N2O emission increased gradually with decreasing precipitation magnitudes, but no contribution in the severe drought (−70%). AMF significantly reduced the soil’s available nitrogen concentration and altered the composition of the soil bacteria community including those associated with N2O production. Hyphal length density was negatively correlated with the copy numbers of key genes for N2O production (nirK and nirS) and positively correlated with the copy numbers of key genes for N2O consumption (nosZ). Our results highlight that AMF would reduce the soil N2O emission under precipitation variability in a temperate grassland except for extreme drought.

Arbuscular mycorrhizal fungi improve the growth and drought tolerance of Cinnamomum migao by enhancing physio-biochemical responses.

Drought is the main limiting factor for plant growth in karst areas with a fragile ecological environment. Cinnamomum migao H.W. Li is an endemic medicinal woody plant present in the karst areas of southwestern China, and it is endangered due to poor drought tolerance. Arbuscular mycorrhizal fungi (AMF) are known to enhance the drought tolerance of plants. However, few studies have examined the contribution of AMF in improving the drought tolerance of C. migao seedlings. Therefore, we conducted a series of experiments to determine whether a single inoculation and coinoculation of AMF (Claroideoglomus lamellosum and Claroideoglomus etunicatum) enhanced the drought tolerance of C. migao. Furthermore, we compared the effects of single inoculation and coinoculation with different inoculum sizes (20, 40, 60, and 100 g; four replicates per treatment) on mycorrhizal colonization rate, plant growth, photosynthetic parameters, antioxidant enzyme activity, and malondialdehyde (MDA) and osmoregulatory substance contents. The results showed that compared with nonmycorrhizal plants, AMF colonization significantly improved plant growing status; net photosynthetic rate; superoxide dismutase, catalase, and peroxidase activities; and soluble sugar, soluble protein, and proline contents. Furthermore, AMF colonization increased relative water content and reduced MDA content in cells. These combined cumulative effects of AMF symbiosis ultimately enhanced the drought tolerance of seedlings and were closely related to the inoculum size. With an increase in inoculum size, the growth rate and drought tolerance of plants first increased and then decreased. The damage caused by drought stress could be reduced by inoculating 40–60 g of AMF, and the effect of coinoculation was significantly better than that of single inoculation at 60 g of AMF, while the effect was opposite at 40 g of AMF. Additionally, the interaction between AMF and inoculum sizes had a significant effect on drought tolerance. In conclusion, the inoculation of the AMF (Cl. lamellosum and Cl. etunicatum) improved photosynthesis, activated antioxidant enzymes, regulated cell osmotic state, and enhanced the drought tolerance of C. migao, enabling its growth in fragile ecological environments.

Higher diversity and contribution of soil arbuscular mycorrhizal fungi at an optimal P-input level

As not only an indicator but also key determinants of soil health, the performance of arbuscular mycorrhizal (AM) fungi under intensive cropping systems remains incompletely understood, particularly with regard to quantitative contributions to crop phosphorus (P) acquisition and scientific managements of P-input levels. Here, we firstly investigated the diversity and vitality of AM fungi along with decreasing P-input levels from P100 (local regular rate) to P50 (50 % off) in a greenhouse experiment to explore the optimal P-input level, and further determined the apparent contribution of AM fungi to maize (Zea mays L.) P acquisition at optimal level in a field microplot experiment with root mycorrhization inhibition by benomyl application and in another pot experiment upon AM fungal inoculation in a sterilized soil. Decreasing P input decreased the amount but increased the efficiency of plant P acquisition, and increased the diversity and colonization of AM fungi, in addition to shaping the community composition. Notably, P80 (20 % off) appeared to be an optimal level that balanced mycorrhizal vitality, maize growth and P-acquisition efficiency. The apparent contribution of AM fungi to maize P acquisition determined in both field and pot experiments were approximately 36 % and 21 % at P80 and P100, respectively, while grain yields at P80 with mycorrhizae reached the level equivalent to that of P100 without mycorrhizae, indicating a replacement of 20 % of P fertilizers by adequate mycorrhizal management. It highlights that stronger AM associations by optimizing P input allow for relatively high crop P-acquisition efficiency upon high mycorrhizal benefits, favoring agricultural production in a sustainable manner with reduced dependence on inputs.

Contribution of arbuscular mycorrhizal fungi and soil amendments to remediation of a heavy metal-contaminated soil using sweet sorghum

Owing to their potential advantages such as waste reduction, recycling, and economic attributes, fast-growing bioenergy crops have the capacity to effectively phytoremediate heavy metal-contaminated soils. However, little is known about the role of microbial and chemical amendments in phytoremediation using bioenergy crops. Here, we studied the contributions of inoculation with the arbuscular mycorrhizal fungus (AMF) Acaulospora mellea and three soil amendments, i.e., hydroxyapatite (HAP), manure, and biochar, at doses of 0.1% and 1% (weight:weight) to heavy metal phytoremediation using sweet sorghum grown on an abandoned agricultural soil, with environmentally realistic contamination (2.6 mg kg−1 Cd, 1796 mg kg−1 Pb, and 1603 mg kg−1 Zn), in a plant growth chamber. Mycorrhizal colonization, plant biomass and metal accumulation, metal availability, and soil pH were determined in harvested seedlings 12 weeks after sowing. The results showed that root colonization by indigenous AMF decreased by 28%-46% with HAP, but increased after manure and biochar applications as compared to the no amendment control (CK). The AMF inoculation increased root colonization rates by 16%-128% and in particular, alleviated the inhibition of HAP. The remediation effects were highly dependent on the amendment type and dose. Among the three soil amendments, HAP was the most effective in promoting plant growth and phytostabilization of Cd, Pb, and Zn and phytoextraction of Cd, particularly at a dose of 1%. Compared to CK, 1% HAP decreased DTPA-extractable Cd, Pb, and Zn concentrations in soil by 31%-43%, 30%-38%, and 22%-23%, respectively. Manure and biochar also exerted positive effects on heavy metal immobilization, as indicated by lower DTPA extractability, but only the 1% manure treatment showed plant growth-promoting effect. The AMF inoculation did not affect plant growth, but increased soil pH and induced synergistic interactions with amendments on the immobilization of Cd and Pb. In conclusion, soil amendments, particularly HAP, produced positive impacts and synergistic interactions with AMF on the phytostabilization of heavy metals using sweet sorghum. Accordingly, sweet sorghum combined with soil amendments and AMF may be an effective strategy for heavy metal phytoremediation.

Response to Inoculation with Arbuscular Mycorrhizal Fungi of Two Tomato (<i>Solanum lycopersicum</i> L.) Varieties Subjected to Water Stress under Semi-Controlled Conditions

In arid and semi-arid regions, the growth and development of cultivated plants, especially tomato (Solanum lycopersicum L.), are severely limited by water deficit. Thus, to cope with this constraint, the plant establishes symbiotic relationships with arbuscular mycorrhizal fungi (AMF) in the soil whose extension of the hyphae allows a better and deeper exploration; this notably improves the hydromineral nutrition of the plant. Therefore, the choice of fungal partner becomes crucial for the establishment of a crop in water-deficient soil. In this context, the contribution of AMF to the water stress tolerance of two varieties of tomato plants was assessed under semi-controlled conditions. Parameters, such as the mycorrhizal frequency, intensity of mycorrhization, relative mycorrhizal dependency, growth, and biochemical parameters (carbon, nitrogen, phosphorus, and proline contents) of plants subjected to three levels of water stress (T100, T70, and T30), were evaluated. The highest frequencies and intensities of mycorrhization and relative mycorrhizal dependencies were obtained with plants of the Xewel variety inoculated with Rhizophagus fasciculatus (F: 95.24%, 88.35%, and 13.64%; M: 40.52%, 37.52%, and 11.22%; D: 23.7%, 54.4%, and 78.82%) and in those of the Lady Nema variety inoculated with Claroideoglomus etunicatum (F: 95.12%, 87.01%, and 15.25%; M: 40.66%, 37.99%, and 11.42%; D: 19.27%, 57.01%, and 70.98%), respectively at water regimes of T100, T70 and T30. These same symbiotic couples recorded, at T30, the best survival rates (+ 40%) and the higher aerial (77% and 74%) and root dry weights (80% and 59%). Plants of the Xewel variety inoculated with R. fasciculatus recorded the highest contents of carbon (T70: 30.59% and T30: 21.55%) and phosphorus (T70: 0.18% and T30: 0.17%). Plants of the Lady Nema variety recorded the highest nitrogen contents with 3.51% and 3.20%, respectively at T70 and T30. Plants of the Lady Nema variety, inoculated with C. etunicatum, also recorded the highest proline contents (572.25, 739.44, and 1165 nmoles•g−1 of fresh material), followed by those of the Xewel variety inoculated with R. fasciculatus (580.36, 763.65, and 1112.11 nmoles•g−1 of fresh matter), respectively at T100, T70, and T30. For the Lady Nema variety, the best fungal partner is C. etunicatum, followed by R. fasciculatus and, finally, Funneliformis mosseae. However, for the plants of the Xewel variety, R. fasciculatus is the most efficient, followed by F. mosseae and C. etunicatum. This suggests that, in tomatoes, the efficiency of mycorrhizal symbiosis under water stress conditions is not only dependent on the host plant but on both associated symbiotic partners. Hence, it is a need for screening to identify the best symbiotic couples in a stressful environment.

Hormonomic Changes Driving the Negative Impact of Broomrape on Plant Host Interactions with Arbuscular Mycorrhizal Fungi.

Belowground interactions of plants with other organisms in the rhizosphere rely on extensive small-molecule communication. Chemical signals released from host plant roots ensure the development of beneficial arbuscular mycorrhizal (AM) fungi which in turn modulate host plant growth and stress tolerance. However, parasitic plants have adopted the capacity to sense the same signaling molecules and to trigger their own seed germination in the immediate vicinity of host roots. The contribution of AM fungi and parasitic plants to the regulation of phytohormone levels in host plant roots and root exudates remains largely obscure. Here, we studied the hormonome in the model system comprising tobacco as a host plant, Phelipanche spp. as a holoparasitic plant, and the AM fungus Rhizophagus irregularis. Co-cultivation of tobacco with broomrape and AM fungi alone or in combination led to characteristic changes in the levels of endogenous and exuded abscisic acid, indole-3-acetic acid, cytokinins, salicylic acid, and orobanchol-type strigolactones. The hormonal content in exudates of broomrape-infested mycorrhizal roots resembled that in exudates of infested non-mycorrhizal roots and differed from that observed in exudates of non-infested mycorrhizal roots. Moreover, we observed a significant reduction in AM colonization of infested tobacco plants, pointing to a dominant role of the holoparasite within the tripartite system.

Contribution of Arbuscular Mycorrhizal Fungi, Phosphate-Solubilizing Bacteria, and Silicon to P Uptake by Plant.

Phosphorus (P) availability is usually low in soils around the globe. Most soils have a deficiency of available P; if they are not fertilized, they will not be able to satisfy the P requirement of plants. P fertilization is generally recommended to manage soil P deficiency; however, the low efficacy of P fertilizers in acidic and in calcareous soils restricts P availability. Moreover, the overuse of P fertilizers is a cause of significant environmental concerns. However, the use of arbuscular mycorrhizal fungi (AMF), phosphate–solubilizing bacteria (PSB), and the addition of silicon (Si) are effective and economical ways to improve the availability and efficacy of P. In this review the contributions of Si, PSB, and AMF in improving the P availability is discussed. Based on what is known about them, the combined strategy of using Si along with AMF and PSB may be highly useful in improving the P availability and as a result, its uptake by plants compared to using either of them alone. A better understanding how the two microorganism groups and Si interact is crucial to preserving soil fertility and improving the economic and environmental sustainability of crop production in P deficient soils. This review summarizes and discusses the current knowledge concerning the interactions among AMF, PSB, and Si in enhancing P availability and its uptake by plants in sustainable agriculture.

English

Studies have shown arbuscular mycorrhizal fungi (AMF) enhance phosphorus (P) uptake and drought tolerance in maize (Zea mays L.) grown in semiarid soils. However, little is known regarding the contribution of AMF to maize treated with different levels of phosphorus and grown in different soil moisture levels. This study was conducted to determine the effects of AMF (Glomus fasciculatum) inoculation on growth and P uptake of maize treated with different levels of soil P and soil moisture. Different P levels (0, 50, and 100 kg P ha-1) were applied on maize grown in soils with and without mycorrhizal fungi, and at different moisture levels producing -0.05, -0.4, -0.8, and -1.5 MPa of drought stress. Increasing P rates significantly (p < 0.05) reduced mycorrhizal colonization. Mycorrhizal colonization was higher under moderate than under lower soil moisture levels. Drought stress × soil P content × AMF inoculation interaction had significant (p < 0.05) effect on maize shoot and root dry weight and tissue P concentration. Overall, results of this study suggest that mycorrhizal inoculation enhances P uptake and maximizes maize biomass under low, moderate, and high soil moisture conditions without P applications. Except for the lowest soil moisture level (-1.5 MPa), mycorrhizal plants produced higher biomass, with greater tissue P content than nonmycorrhizal plants at all soil P and soil moisture levels. These results indicate that establishing efficacious AMF with maize could be an efficient alternative for growers than relying on P fertilizer application and its associated costs and environmental concerns. Keywords: Arbuscular Mycorrhiza Fungi, Drought Tolerance, Phosphorus Levels, Maize Plants.

The Inhibitory Effect of Endophyte-Infected Tall Fescue on White Clover Can Be Alleviated by Glomus mosseae Instead of Rhizobia.

In artificial ecosystems, mixed planting of gramineous and leguminous plants can have obvious advantages and is very common. Due to their improved growth performances and stress tolerance, endophyte-infected grasses are considered to be ideal plant species for grasslands. However, endophytic fungi can inhibit the growth of neighboring nonhost leguminous plants. In this study, we chose endophyte-infected and endophyte-free tall fescue (Lolium arundinaceum Darbyshire ex. Schreb.) and clover (Trifolium repens) as the experimental materials to explore whether arbuscular mycorrhizal fungi and rhizobium can alleviate the inhibitory effect of endophyte infection on clover. The results showed that endophytic fungi significantly reduced clover biomass. Arbuscular mycorrhizal fungi inoculation significantly increased the biomass of clover in both endophyte-infected tall fescue/clover and endophyte-free tall fescue/clover systems but the beneficial contribution of arbuscular mycorrhizal fungi was more obvious in the endophyte-infected tall fescue/clover system. Rhizobia inoculation could alleviate the detrimental effect of tall fescue on the growth of clover but did not alleviate the detrimental effect of endophyte infection on the growth of clover.

The contribution of arbuscular mycorrhizal fungi to ecosystem respiration and methane flux in an ephemeral plants‐dominated desert

AbstractArbuscular mycorrhizal fungi (AMF) can significantly influence the soil carbon cycle, however, their impacts on desert soils are still unclear. Here, a field control experiment, using in‐growth mesocosms, was conducted to quantitatively assess the contribution of AMF and ephemeral plants to ecosystem respiration (Re) and methane (CH4) flux in the Gurbantunggut Desert in China, from April to May 2017. Ephemeral plant biomass was significantly increased by AMF infection. Re was significantly positively correlated with AMF infection rate, whereas CH4 flux was significantly negatively correlated. The contribution of AMF to Re was up to 24%, comparable to the contribution of non‐AMF microbial respiration, which accounted for up to 36%, whereas the respiration of ephemeral plants accounted for 40%. Variation in Re was most strongly associated with soil organic carbon and soil available potassium concentrations and soil temperature. Non‐AMF microorganisms accounted for most of the CH4 flux (up to 85%). In contrast, AMF only accounted for 15% of total CH4 flux. The CH4 flux was significantly influenced by soil NO3−‐N content, soil moisture, soil temperature and soil NH4+‐N content. Overall, AMF significantly influenced Re and CH4 flux, and also enhanced the growth of ephemeral plants, which have an important role in the carbon cycle in desert ecosystems.

Roles of Arbuscular Mycorrhizal Fungi on Plant Growth and Performance: Importance in Biotic and Abiotic Stressed Regulation

Arbuscular mycorrhizal fungi (AMF) establish symbiotic associations with most terrestrial plants. These soil microorganisms enhance the plant’s nutrient uptake by extending the root absorbing area. In return, the symbiont receives plant carbohydrates for the completion of its life cycle. AMF also helps plants to cope with biotic and abiotic stresses such as salinity, drought, extreme temperature, heavy metal, diseases, and pathogens. For abiotic stresses, the mechanisms of adaptation of AMF to these stresses are generally linked to increased hydromineral nutrition, ion selectivity, gene regulation, production of osmolytes, and the synthesis of phytohormones and antioxidants. Regarding the biotic stresses, AMF are involved in pathogen resistance including competition for colonization sites and improvement of the plant’s defense system. Furthermore, AMF have a positive impact on ecosystems. They improve the quality of soil aggregation, drive the structure of plant and bacteria communities, and enhance ecosystem stability. Thus, a plant colonized by AMF will use more of these adaptation mechanisms compared to a plant without mycorrhizae. In this review, we present the contribution of AMF on plant growth and performance in stressed environments.