Arbuscular mycorrhizal fungi enhance soybean phosphorus uptake and soil fertility under saline-alkaline stress.

The use of arbuscular mycorrhizal (AM) fungi is considered as an effective approach to enhance plants’ growth; nevertheless, its efficacy may vary with the type of inoculum and its application method. The present study, for the first time, investigates the effects of different mycorrhizal species applied through different methods on morpho-physiological growth, root system architecture, nutrient uptake, and root exudates of maize. Four AM fungi species viz., Claroideoglomus etunicatum (C.E), Rhizophagus intraradices (R.I), Funneliformis mosseae (F.M), and Diversispora versiformis (D.V) were applied to maize through seed coating, soil application, or seed coating+ soil application. A control without AM fungi was maintained for comparison. All the thirteen treatments were arranged in completely randomized design with three replications. Application of C.E, R.I, F.M, and D.V through different methods triggered the growth performance of maize by improving morpho-physiological characteristics and root morphology, modulating AM fungi colonization, enhancing the nutrient (N, P, K) uptake, and reducing the root exudates (oxalic, malonic, fumaric, malic, citric, and T-aconitic) compared with control. Among the different mycorrhizal species, F.M applied particularly through seed coating+ soil application was more effective in regulating maize growth as compared with C.E, R.I, or D.V species owing to better root system, higher root colonization, and greater nutrient uptake in this treatment. Interestingly, seed coating of F.M recorded statistically similar or higher shoot and root growth attributes compared with soil application particularly at 30 days after sowing. In crux, F.M applied through seed coating + soil application performed better than that of other mycorrhizal species. The obtained results also suggest that seed coating can be a cheap, viable, and efficient delivery system of AM fungi particularly for large scale application, as AM fungi seed coating had faster and greater effect on maize growth compared with soil application during early growth stages.

ABSTRACTA greenhouse experiment was conducted to evaluate the effectiveness of arbuscular mycorrhizal (AM) fungi in phytoremediation of lead (Pb)-contaminated soil by vetiver grass. Experiment was a factorial arranged in a completely randomized design. Factors included four Pb levels (50, 200, 400, and 800 mg kg−1) as Pb (NO3)2, AM fungi at three levels (non mycorrhizal (NM) control, Rhizophagus intraradices, Glomus versiforme). Shoot and root dry weights (SDW and RDW) decreased as Pb levels increased. Mycorrhizal inoculation increased SDW and RDW compared to NM control. With mycorrhizal inoculation and increasing Pb levels, Pb uptake of shoot and root increased compared to those of NM control. Root colonization increased with mycorrhizal inoculation but decreased as Pb levels increased. Phosphorus concentration and uptake in shoot of plants inoculated with AM fungi was significantly higher than NM control at 200 and 800 mg Pb kg−1. The Fe concentration, Fe and Mn uptake of shoot in plants inoculated with Rhizophagus intraradices in all levels of Pb were significantly higher than NM control. Mycorrhizal inoculation increased Pb extraction, uptake and translocation efficiencies. Lead translocation factor decreased as Pb levels increased; however inoculation with AM fungi increased Pb translocation.

Sandy soils are considered as a significant transition phase to desertification. The effective recovery of sandy soils is of great significance to mitigate the desertification process. Some studies have shown that arbuscular mycorrhizal (AM) fungi and biochar improved the sandy soil, but there have been very few studies regarding the combined effects of AM fungi and biochar amendments on sandy soil improvement. Additionally, the roles of the bacterial and fungal community during the process of sandy soil improvement remain unclear. A greenhouse pot experiment with four treatments, including a control (CK, no amendment), single AM fungi-assisted amendment (RI), single biochar amendment (BC), and combined amendment (BC_RI, biochar plus AM fungi), was set up. This study investigated the effects of different amendment methods on the Nitrariasi birica mycorrhizal colonization, biomass, nutrient (N, P, K, Ca, and Mg) content, soil organic carbon, soil nutrient (TN, TP, and TK) content, and soil water-stable aggregate composition. High throughput sequencing technology was used to investigate the roles of the bacterial and fungal communities during the process of sandy soil improvement. Combined with multiple analysis methods, the improvement mechanisms of different amendment methods were explored. The aim was to provide basic data and scientific basics for reasonably and effectively improving sandy soils. The results indicated that a significant mycorrhiza colonization was observed in the inoculation (RI and BC_RI) treatments, but there was no substantial difference in the mycorrhiza colonization with the RI and BC_RI. Compared with the CK, the shoot biomass and shoot element (N, K, Ca, and Mg) contents were significantly increased in the RI, and the shoot element (N, P, K, Ca, and Mg) contents were significantly increased in the BC and BC_RI; compared with the RI and BC, the root biomass and the root element (P, K, Ca, and Mg) contents were significantly increased in the BC_RI. Compared with the CK, the soil organic carbon contents were significantly increased in the BC and BC_RI, the soil TN contents were significantly increased by 152.54%, and the soil TP and TK contents were significantly decreased by 12.5% and 18.8%, respectively. The proportion of soil aggregates with particle sizes of 0.25-0.05 mm was the highest in each treatment, and the large particle size (>0.25 mm) soil aggregate was significantly increased in the BC_RI. Compared with the CK, the Sobs and Shannon indices of the bacterial/fungal community were significantly decreased in the RI and BC_RI. There was a difference in the microbial community compositions and abundance in the various treatments. The results of the RDA and network analysis were as follows:the effects of AM fungi, biochar, and combined amendment on the soil environment and microbial community structure were significant; in the different amendment treatments, the relationship of the microbial molecular ecological network was significantly changed, and the composition of the core species varied; compared with the RI, there was a higher network connection degree and a richer core species composition in the BC and BC_RI; moreover, the essential role of Rhizophagus intraradices was weaken and the core roles of the other microorganisms (especially bacterial species) were enhanced under the combined effects of biochar and AM fungi. The SEM results demonstrated that the application of AM fungi and biochar could directly affect the bacteria/fungi community structure, and further affect the plant growth and soil properties. The differences in the microbial community structure (especially the change in the microbial interaction) were the key driving factors that led to the difference in the soil improvement effectiveness. In summary, the effects of the different amendment methods on the improvement effectiveness of sandy soils varied. The microbial community played key roles in the process of sandy soil improvement, and there were potential advantages and applications in accelerating the ecological restoration of sandy soils under the combined AM fungi and biochar amendment.

Effects of arbuscular mycorrhizal (AM) fungi on plant growth and soil nutrient depletion are well known, but their roles as nutrient interceptor in riparian areas are less clear. The effects of AM fungi on growth, soil nutrient depletion and nutrient leaching were investigated in columns with two riparian grass species. Mycorrhizal and non mycorrhizal (NM) plants were grown in a mixture of riparian soil and sand (60% and 40%, w/w respectively) for 8 weeks under glasshouse conditions. Mycorrhizal colonization, AM external hyphae development, plant growth, nutrient uptake and NO 3 , NH 4 and available P in soil and leachate were measured. Mycorrhizal fungi highly colonized roots of exotic grass Phalaris aquatica and significantly increased plant growth and nutrient uptake. Columns containing of AM Phalaris aquatica had higher levels of AM external hyphae, lower levels of NO 3 , NH 4 and available P in soil and leachate than NM columns. Although roots of native grass Austrodanthonia caespitosa had moderately high levels of AM colonization and AM external hyphae in soil, AM inoculation had no significant effects on plant growth, soil and leachate concentration of NO 3 and NH 4 . But AM inoculation decreased available soil P concentration in deeper soil layer and had no effects on dissolved P in leachate. Although both grass species had nearly the same biomass, results showed that leachate collected from Austrodanthonia caespitosa columns significantly had lower levels of NO 3 , NH 4 and dissolve P than leachate from exotic Phalaris aquatica columns. Taken together, these data shows that native plant species intercept higher nutrient than exotic plant species and had no responsiveness to AM fungi related to nutrient leaching, but AM fungi play an important role in interception of nutrient in exotic plant species.

接种AM菌对西部黄土区采煤沉陷地柠条生长和土壤的修复效应

Societal Impact StatementSorghum is an important cereal crop that provides calories and nutrients for much of the world's population, and it is often grown with low fertiliser input. Optimising the yield, nutritive content and bioavailability of sorghum grain with minimal input is of importance for human nutrition, and arbuscular mycorrhizal (AM) fungi have previously shown potential to assist in this. Across sorghum genetic diversity, AM fungi improved the yield, nutrition and zinc and iron bioavailability of grain in a low phosphorus soil. Thus, food production systems that effectively manage AM fungi may improve consumer outcomes.Summary Sorghum is a C4 cereal crop that is an important source of calories and nutrition across the world, predominantly cultivated and consumed in low‐ and middle‐income countries. Sorghum can be highly colonised by arbuscular mycorrhizal (AM) fungi, and the plant‐fungal association can lead to improvements in biomass and nutrient uptake. High‐throughput phenotyping allows us to non‐destructively interrogate the ‘hidden’ effects of AM fungi on sorghum growth and phenology. Eight genetically diverse sorghum genotypes were grown in a soil amended with 2 or 20 mg P kg−1 and inoculated with an AM fungal culture of Rhizophagus irregularis. High‐throughput phenotyping uncovered the ‘hidden’ effects of AM fungi on growth and phenology, while grain biomass, nutrition, Zn and Fe bioavailability and root AM colonisation was determined after destructive harvest. Sorghum plants colonised by AM fungi generally performed better than non‐AM control plants, with greater yield, harvest indices, and grain P, Zn and Fe contents. During the early growth stages, AM colonisation led to temporary growth depressions. There were also AM fungal and P fertilisation effects on sorghum time‐of‐flowering. The sorghum genotype with the highest AM colonisation could barely produce grain when non‐inoculated. The two genotypes that failed to mature had very low AM colonisation. Generally, the genetically diverse sorghum genotypes were highly responsive to AM colonisation and produced more grain of greater nutritive quality when colonised, without adverse consequences for micronutrient bioavailability.

A greenhouse pot experiment was conducted to assess the effects of biochar (BC) and arbuscular mycorrhizal fungus (AMF)−Funneliformis mosseae (Fm), Glomus versiforme (Gv) and Rhizophagus intraradices (Ri) on the plant growth and Cd/Pb accumulation by corn grown in the soils artificially contaminated with 5 mg Cd and 300 mg Pb kg−1 soil. The single AMF inoculation and combined usage of AMF and BC evidently improved the P contents of maize. Furthermore, the combined use of AMF and BC produced pronounced positive effect on corn growth, and the shoot biomass in Gv + BC group was 9.85-fold higher than that of the control. Meanwhile, the single BC addition and combined utilization of AMF and BC significantly reduced Cd and Pb concentrations in maize, and the greater reduces were found in the combined utilization, and the lowest Cd concentration of shoot was appeared in Gv + BC group. The single BC addition and combined application of AMF and BC significantly increased soil pH, and reduced soil diethylenetriaminepentaacetic acid (DTPA)-extractable Cd/Pb. This study demonstrated a synergistic effect between AMF (Gv, Fm, Ri) and BC on improving maize growth and decreasing Cd/Pb accumulation in maize, and the combined use of Gv and BC brought the most pronounced effect, which could provide a feasible strategy for safe production of maize from Cd/Pb-polluted soils.

Vermicompost and/or compost and arbuscular mycorrhizal fungi are conducive to improving the growth of pistachio seedlings to drought stress

This study evaluated the effects of arbuscular mycorrhizal fungi (AMF) on plant growth, nutrient uptake, and heavy metal accumulation on polluted land using a meta-analysis approach. Data from 33 relevant studies were selected based on inclusion criteria, specifically articles in English, observational research, and investigating the role of AMF in plant growth and productivity on polluted land. The results showed that plants inoculated with AMF experienced significant accumulation of heavy metals in roots, such as Pb (p<0.01), Ni (p<0.01), Cr (p<0.01), Mn (p<0.05), Fe (p<0.05), and As (p<0.05). The AMF significantly reduced the accumulation of heavy metals such as Cr, Ni, Fe, and Cu on the upper part of fodder forage (p<0.01). Forage growth was also enhanced due to AMF. The AMF greatly increased the fresh weight, length, and phosphorus (P) content of fodder forage roots (p<0.01). It also increased the plant's biomass, fresh weight, dry weight, height, nitrogen (N), phosphorus (P), and potassium (K) contents (p<0.01). In conclusion, AMF is important in increasing plant growth, nutrient uptake and reducing heavy metal accumulation in forage on polluted land.

Reductions in pore space caused by soil compaction considerably impact soil permeability to air and water by crop roots. The inoculation of arbuscular mycorrhizal (AM) fungi to alleviate this problem has been explored around the world. A pot experiment was conducted to assess the effects of AM fungi inoculation on the growth of two crops, tomato (Solanum lycopersicum L.) and maize (Zea mays L.), and the soil structure in a clay soil (lime concretion black soil). The results showed that AM fungi inoculation increased shoot nitrogen (N) and phosphorus (P) concentrations of maize by 32.4% and 17.0%, respectively. Soil alkali-hydrolyzable N and Olsen-P were 30.1% and 29.9% higher, respectively, in inoculated maize plants than in the corresponding uninoculated treatments for 30 days. No effect of AM fungi on nutrient uptake and soil-available nutrients was found for tomato plants. The NMWD (normalized mean weight diameter, an index to evaluate soil aggregates) values for tomato and maize plants inoculated with AM fungi were 46.2% and 17.7% higher, respectively, than uninoculated plants and the same trends were detected for soil organic carbon (SOC) content. A significant positive relationship was found between SOC and NMWD, indicating that increasing SOC might be one mechanism by which AM fungi improved soil structure. Our results suggested that AM fungi might not always benefit plant growth and nutrient absorption after inoculating for 30 days, but contributed to soil structure improvement even with low colonization.

Although positive effects of arbuscular mycorrhizal (AM) fungi on plant performance under drought have been well documented, how AM fungi regulate soil functions and multifunctionality requires further investigation. In this study, we first performed a meta-analysis to test the potential role of AM fungi in maintaining soil functions under drought. Then, we conducted a greenhouse experiment, using a pair of hyphal ingrowth cores to spatially separate the growth of AM fungal hyphae and plant roots, to further investigate the effects of AM fungi on soil multifunctionality and its resistance against drought. Our meta-analysis showed that AM fungi promote multiple soil functions, including soil aggregation, microbial biomass and activities of soil enzymes related to nutrient cycling. The greenhouse experiment further demonstrated that AM fungi attenuate the negative impact of drought on these soil functions and thus multifunctionality, therefore, increasing their resistance against drought. Moreover, this buffering effect of AM fungi persists across different frequencies of water supply and plant species. These findings highlight the unique role of AM fungi in maintaining multiple soil functions by mitigating the negative impact of drought. Our study highlights the importance of AM fungi as a nature-based solution to sustaining multiple soil functions in a world where drought events are intensifying.

Effects of arbuscular mycorrhizal fungi on growth and Na+ accumulation of Suaeda glauca (Bunge) grown in salinized wetland soils

A greenhouse pot experiment was conducted to investigate the effects of arbuscular mycorrhizal (AM) fungi Claroideoglomus etunicatum (CE) and Rhizophagus intraradices (RI) on AM colonization rate, biomass, nutrient uptake, C:N:P stoichiometry, and the uptake and transport of lanthanum (La) and lead (Pb) by maize (Zea mays L.) grown in La-and Pb-contaminated soils (combined La-Pb concentrations of 50, 200, and 800 mg·kg-1). The aim was to provide a scientific basis for the remediation of soils contaminated by rare earth elements and heavy metals. The results indicated that symbiotic associations were successfully established between the two isolates and maize, and the average AM colonization rate ranged from 26.7% to 95.8%. The increasing concentrations of La and Pb in soils significantly decreased the mycorrhizal colonization rate, biomass, and mineral nutrition concentrations of the maize, and significantly increased C:P and N:P ratios and the concentrations of La and Pb in shoots and roots of maize. The shoot and root dry weights of maize were significantly increased by 17.8%-158.9% with two AM fungi inoculations, while the P concentration of shoots and roots of the maize were significantly increased by 24.5%-153.8%. Inoculation with two AM fungi decreased the C:P and N:P ratios, consistent with the growth rate hypothesis. With AM fungi inoculation in three types of La-Pb co-contaminated soils, root Pb concentrations of the maize significantly increased by 51.3%-67.7%; shoot Pb concentrations of the maize significantly decreased by 16.0%-67.7%; and the transport rate of Pb from root to shoot of the maize decreased by 31.5%-54.7%. Meanwhile, inoculation with AM fungi significantly increased the shoot La concentrations in the maize grown in soils mildly contaminated with La-Pb, while it significantly decreased shoot La concentrations, increased root La concentrations of maize, and inhibited the transport of La from root to shoot of the maize grown in soils moderately contaminated with La-Pb, but had no significant effect in severely contaminated soils. The results showed that AM fungi had the potential to promote phytoremediation of soils contaminated with rare earth elements and heavy metals, with potential applications to revegetate such contaminated soil ecosystems.

Root rot is a serious soil-borne disease, with negative consequences on crop yield and quality. Arbuscular mycorrhizal (AM) fungi are a group of soil microorganisms, which play important physiological and ecological functions by establishing symbionts with plant roots. AM fungi could induce plant resistance against root rot by regulating physiological and biochemical processes. As a biological agent, AM fungi are used to antagonize soil-borne diseases such as root rot, which is a hotspot in the field of plant-microorganism interaction. We comprehensively reviewed the suppression effect of AM fungi on plant root rot, and the effect of AM fungi on root morphology of host plant, plant nutrition levels, as well as their role in competing with pathogens for ecological sites, activating plant defense systems, and regulating root exudates. Finally, we discussed the potential mechanism of AM fungi inhibiting root rot, as well as the practical problems in the efficient utilization of AM fungi were discussed, in order to provide the theoretical basis for the biological control protocol to antagonize root rot with AM fungi.

Societal Impact StatementThe inoculation with arbuscular mycorrhizal (AM) fungi shows great potential to increase the tolerance of host plants toward toxic arsenic. In many Asian countries and elsewhere, crops are increasingly being irrigated with arsenic‐contaminated groundwater, which causes loss of yield and the risk that arsenic enters the food chain. Greenhouse cultivation experiments demonstrated that AM fungi are able to increase the arsenic tolerance in crop plants, but the results are highly variable. This meta‐analysis demonstrates that AM fungi significantly reduce the arsenic concentration, and at the same time, positively modify the nutrient supply and the biomass in host crops that are grown under arsenic stress. Thus, the inoculation with AM fungi represents a promising approach to alleviate the negative effects of arsenic on crop growth, which deserves to be developed in future studies.SummaryRecent greenhouse experiments showed that the inoculation of crop plants with arbuscular mycorrhizal (AM) fungi does not only improve plant nutrition but also shows great potential to increase the host plants’ tolerance toward the toxic metalloid arsenic (As). This approach could alleviate negative effects of crop plants grown under As stress, which causes substantial loss of yield and the risk of As entering the food chain. This is especially relevant in Asian countries and elsewhere where As subsequently accumulates in soil due to irrigation with As‐polluted groundwater. Overall effects of AM fungi symbiosis on seven crop plants grown under As stress were assessed by a meta‐analysis that included 299 studies obtained from 27 independent publications. Biomass, concentrations of As and phosphorus (P), and P/As ratios in plant tissue were used to evaluate the effects of AM fungi in host crops. Inoculation with AM fungi reduced As concentrations in tissue of host plants by 19% on average, while it increased the P/As ratio and biomass at the same time by 64% and 53%, respectively. With the exception of Helianthus annuus, AM effects were highly significant in all crop plants. The meta‐analysis results illustrate that AM fungi are able to significantly reduce As concentration, and at the same time, positively modify the nutrient supply and the biomass in host crops. These promising results strongly encourage the implementation of field trials as a next step toward the development of AM fungi‐based approaches to alleviate the negative effects of As stress on crop growth.