Effects of the Combined Application of Arbuscular Mycorrhizal Fungi and Reconstructed Microbial Communities on Soil Functional Restoration

Background and aimsContinuous vegetable production under plastic tunnels faces challenges like soil degradation, increased soil-borne pathogens, and diminished eggplant yield. These factors collectively threaten the long-term sustainability of food security by diminishing the productivity and resilience of agricultural soils. This research examined the use of raw garlic stalk (RGS) waste and arbuscular mycorrhizal fungi (AMF) as a sustainable solution for these issues in eggplant monoculture. We hypothesized that the combined application of RGS waste and AMF would improve soil physicochemical properties compared to untreated soil in eggplant monoculture. The combined use of RGS and AMF was expected to suppress soil-borne pathogens, increase the abundance of soil beneficial microorganisms and alter fungal community structure. The combined application of RGS and AMF will significantly enhance eggplant yield compared to untreated plots. This study aimed to determine whether AMF and RGS, individually or in combination, can ameliorate the adverse effects of monoculture on eggplant soil. We also investigated whether these treatments could enhance eggplant yield.MethodsThe experiment was arranged in a completely randomized design with four treatments: AMF, RGS, and a combined treatment of AMF + RGS (ARGS), along with a control. Each treatment was replicated three times, Eggplant seedlings inoculated with AMF and treated with RGS amendments, both individually and combined. The effects on root traits, soil physicochemical properties, soil enzyme activity, and fungal community structure were investigated.ResultsRGS amendments and AMF inoculation improved root length, volume, and mycorrhizal colonization. The combined treatment showed the most significant improvement. RGS and AMF application increased soil nutrient availability (N, P, K) and organic matter content. Enzyme activities also increased with RGS and AMF treatments, with the combined application showing the highest activity. Soil electrical conductivity (EC) increased, while soil pH decreased with RGS and AMF amendments. Sequencing revealed a shift in the fungal community structure. Ascomycota abundance decreased, while Basidiomycota abundance increased with RGS and AMF application. The combined treatment reduced the abundance of pathogenic genera (Fusarium) and enriched beneficial taxa (Chaetomium, Coprinellus, Aspergillus). Pearson correlations supported the hypothesis that soil physicochemical properties influence fungal community composition.ConclusionsThis study demonstrates the potential of co-applying RGS and AMF in continuous cropping systems. It enhances soil physicochemical properties, reduces soil-borne pathogens, and promotes beneficial microbial communities and eggplant yield. This combined approach offers a sustainable strategy to address the challenges associated with eggplant monoculture under plastic tunnels.

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.

The excessive application of mineral fertilizers in maize cultivation leads to progressive soil contamination in the long term and increases the cost of production. An alternative to reduce over-fertilization is to perform a partial replacement with microbes that promote nutrition and growth, such as Arbuscular Mycorrhizal Fungi (AMF). A pot experiment which was followed by two field experiments was performed with and without the application of indigenous AMF in combination with five nitrogen–phosphorus–potassium (NPK) fertilization rates (100% NPK = N120P60K60; 75% NPK = N90P45K45; 50% NPK = N60P30K30; 25% NPK = N30P15K15; control = N0P0K0). The objective was to investigate whether the soil application of indigenous mycorrhizal fungi inoculum combined with NPK fertilization can provide higher maize yields and soil-available N, P, and K than chemical fertilization can alone. The greenhouse results showed that the application of AMF with a 50% NPK treatment significantly increased the plant’s growth, root colonization, leaf chlorophyll content, and N, P, and K tissue content. The results from the field conditions showed that there was a highly significant yield after the treatment with AMF + 50% NPK. The study also revealed that mycorrhizal fungi inoculation increased the available soil N and P concentrations when it was combined with a 50% NPK dose. This suggests that the inoculation of fields with AM fungi can reduce the chemical fertilizer application by half, while improving soil chemistry. The results suggested that AMF inoculation can be used in integrated soil fertility management strategies.

Medicinal products of plant origin have been extensively used in complementary medication for health promotion, disease prevention, and treatments. The demand for medicines of plant origin has increased in recent decades. Attempts to artificially cultivate medicinal plants have become more important due to high demand, low productivity, and difficulties in synthesizing some important active compounds extracted from medicinal plants. Inoculation with arbuscular mycorrhizal (AM) fungi may enhance the growth of medicinal plants and the production of medicinal metabolites. However, the diversity, function, and applications of AM fungi to medicinal plants have received little attention until recently. Advances in studying AM fungi in association with medicinal plants provide better understanding of AM fungi on the improvement of plant growth and active constituent accumulation. The effectiveness of AM fungi in inducing medicinal value of plants provides benchmark information that can be used in development and prioritization of future exploration. This chapter reviews the diversity of AM fungi in the rhizosphere of some valuable medicinal plants and the impact of AM inoculation on the growth and medicinal properties of medicinal plants.

Contribution of biochar and arbuscular mycorrhizal fungi to sustainable cultivation of sunflower under semi-arid environment

The date palm is a commercially important woody crop and is a good target plant for improving agricultural yields in extreme environments. However, salinity has been the primary abiotic stress complicating its cultivation and damaging its production worldwide. This study investigated the effect of alleviating salt stress on date palm growth and development by using arbuscular mycorrhizal fungi (AMF) and/or compost. The experiment was arranged in a completely randomized design with eight treatments. The treatments comprised control without inoculation or amendment and application of compost (made from green waste) and AMF (an autochthonous consortium) individually or in combination under non-saline (0 mM NaCl) or saline (240 mM NaCl) conditions. Growth, physiological characteristics, nutrient uptake, chlorophyll content, oxidative stress markers, and antioxidant enzyme activities were assessed. Salt stress increased sodium (Na+) and chlorine (Cl-) content, lipid peroxidation and proline, soluble sugar, and H2O2 content. However, it reduced growth parameters, AMF colonization, leaf water potential, nitrogen (N), phosphorus (P), potassium (K+), calcium (Ca2+), and chlorophyll content. The application of AMF and compost separately or in combination mitigated the deleterious effects induced by salinity. AMF inoculation contributed to plant salt tolerance through strategies such as increased nutrient uptake (particularly P and Ca2+), chlorophyll content, relative water content, stomatal conductance, antioxidant enzymatic activities (superoxide dismutase, ascorbate peroxidase, catalase) and by decreasing lipid peroxidation and H2O2 content. Plants grown in soil amended with compost under salt stress showed an improvement particularly in K+ and proline content and a decrease in H2O2 concentration compared to controls under the saline condition. In the presence of NaCl stress, the dual application of the compost and AMF consortium maximized plant growth, stomatal conductance, leaf water potential, all antioxidant enzyme activities and P, K+, N, and Ca2+ uptake as well as proline and soluble sugar content. However, it reduced Na+ and Cl- uptake and oxidative stress marker content. In conclusion, our study suggests that the application of AMF with compost has the potential to improve the tolerance of date palm seedlings to salt stress more than AMF or compost applied separately.

Biochar and arbuscular mycorrhizal fungi stimulate rice root growth strategy and soil nutrient availability

Arbuscular mycorrhizal (AM) fungi reside in the rhizosphere and form mutualistic associations with plant roots. They promote photosynthesis, improve stress resistance, and induce secondary metabolite biosynthesis in host medicinal plants. The AM fungi that are symbiotic with medicinal plants comprise a wide array of species and have abundant germplasm resources. Though research on the AM fungi in medicinal plants began relatively recently, it has nonetheless become an investigative hot spot. Several scholars have explored the diversity and the growth-promoting effects of mycorrhizal fungi in hundreds of medicinal plants. Current research on symbiotic AM fungi in medicinal plants has focused mainly on the effects of inoculating host plants with symbiotic mycorrhizal fungi. However, research on the symbiotic AM fungi in medicinal plants continues to expand, and further study is required to determine the mechanisms by which AM fungi interact with host plants. This paper introduces the diversity of symbiotic AM fungi of medicinal plants and the effects of AM fungi on rhizosphere soil of medicinal plants, including soil structure, microbiota, enzyme activities, etc. This review focuses on the effects of AM fungi on medicinal plants, including antioxidant enzyme systems, drought resistance, nutrient absorption profiles of macro- and micronutrients, accumulation of secondary metabolites such as terpenes, phenolic compounds, and nitrogenous compounds, and prevention of diseases. This review is expected to provide a reference for the application of AM fungi in medicinal plant cultivation, biological control, resource conservation, and the sustainable development of the traditional Chinese medicine industry.

Arbuscular mycorrhizal (AM) fungal diversity of arid lands : from AM fungal species to AM fungal communities

The application of microbial inoculants (biofertilizers) is a promising technology for future sustainable farming systems in view of rapidly decreasing phosphate stocks and the need to more efficiently use available nitrogen (N). Various microbial taxa are currently used as biofertilizers, based on their capacity to access nutrients from fertilizers and soil stocks, to fix atmospheric nitrogen, to improve water uptake or to act as biocontrol agents. Since the results of biofertilization in the field are inconsistent we conducted a meta-analysis to quantify benefits of biofertilizers in terms of yield increase, nitrogen and phosphorus use efficiency, based on 171 peer reviewed publications that met the eligibility criteria. Major findings are: i) the superiority of biofertilizer performance in dry climates over other climatic regions; ii) yield response due to biofertilizer application was generally small at low soil P levels; efficacy increased along higher soil P levels in the order arbuscular mycorrhizal fungi (AMF), P-solubilizers and N-fixers; iii) success of inoculation with AMF was greater at low organic matter content and at neutral pH. Our comprehensive analysis provides a basis and guidance for proper choice and application of biofertilizers. Rainfed farms on marginal lands will be most affected by scarcity of non-renewable resources such as fertilizers. Mutualistic root organisms like AMF can substantially contribute to a more resilient, sustainably intensified dryland farming system. We are interested to study the possibility to use AMF as “biofertilizers” in an intercropping system in Indian agriculture, planting pigeon pea (Cajanus cajan) seedlings pre-inoculated with AMF into a field sown with finger millet (Eleusine coracana). By destructive sampling over five weeks we estimated a hyphal growth of 4.1mm d-1 by C. etunicatum which is 1mm faster per day than all other estimates. To study the potential of Rhizophagus fasciculatus, Claroideoglomus etunicatum and Rhizophagus intraradices to spread from AMF-inoculated pigeon pea to un-inoculated finger millet seedlings, we established experimental microcosms in the greenhouse, in which the pigeon pea and two finger millet plantlets were kept in separate pots, connected by soil bridges of 5 or 12 cm length inaccessible to roots but accessible to fungal hyphae. We found that depending on the distance different AMF were promoting the growth of finger millet better. We also detected transport of fertilized nitrogen along the hyphae via stable isotope analysis over a distance of up to 12 cm. However these results also depended on the AMF species. We conclude that the row distance between the crops and the choice of AMF species play a crucial role for the application of AMF as biofertilizer and their growth promotion. To understand the effects the biofertilizers Pseudomonas fluorescens and two AMF species on the microbial community in the soil, both the bacterial community and the community of AMF were studied. Samples were collected at harvest from mono- and intercropped pigeon pea and finger millet at two field sites in South India at the University of Agricultural Sciences, GKVK campus, Bangalore and Kolli hills, Tamil Nadu state, India. DNA was extracted from rhizosphere soil surrounding the roots. To detect changes in the bacterial community automated ribosomal intergenic spacer analysis (ARISA) was conducted and treatments were compared using principal component analysis. The strongest effect was found to be exerted by the plant species; biofertilization had no effect on the bacterial community. To detect changes in the AMF community we amplified the whole ITS ribosomal unit and sequenced the barcoded samples with the PacBio platform. Although OTUs from Glomeromycota were found, the sequencing depth remained too little to make firm conclusions about the changes in the AMF community. Our second goal was to trace the applied inoculum at harvest and, although only few sequences were recovered, the inoculum of Rhizophagus fasciculatus could be traced in some treatments.

ABSTRACTPresent investigation studied plant water relations and soil physical properties through AM fungi (Glomus mosseae) to mitigate drought stress in Himalayan acid Alfisol having low water retentivity. Experimentation was carried out at Palampur, India during 2009–2011 in okra–pea cropping system in randomized block design (RBD) replicated thrice with 14 treatments comprising arbuscular mycorrhizal (AM) fungi, varying phosphorus nutrition and irrigation regimes at 40 and 80% available water holding capacity. Integrated use of AM fungi at varying phosphorus (P) levels and irrigation regimes led to significantly higher relative leaf water content (3% each) in okra and pea besides significantly higher xylem water potential (27%) in pea over non-AM fungi counterparts. AM fungi enhanced water-use-efficiency in okra (5–17%) and pea (12–35%) over non–AM fungi counterparts. AM fungi also improved water holding capacity (5–6%) and mean weight diameter of soil particles (4–9%) over non–AM fungi counterparts; but, had nominal or no effect on bulk density. Mycorrhizal plants maintained higher tissue water content imparting greater drought resistance to plants over non–mycorrhizal plants at moisture stress. It is inferred that integrated application of AM fungi and P at varying irrigation regimes improved the plant water relations vis-à-vis drought resistance, crop productivity, WUE, soil aggregation and water holding capacity in okra–pea sequence in Himalayan acid Alfisol.

Applications of silicon (Si) and arbuscular mycorrhizal fungi (AMF) to soils to increase plant resistance and plant growth and development are potential alternatives in soybean cultivation. Si and AMF promote growth and stress tolerance through increased absorption of essential micro and macronutrients, restriction of toxic ion uptake, increased root hydraulic conductance and water uptake, thus contributing to increased water use efficiency and improved defense response and development. Many studies highlight the importance of both in regulating plant growth under stressful conditions. Furthermore, recent studies have revealed the cumulative effects of Si and AMF in imparting stress tolerance when applied together. The objectives of this work were to evaluate the effects of soil application of Si and AMF on the development of soybean and the resistance and tolerance of soybean to different species of insect pests in the field. The experiments showed that the application of AMF and Si to the soil individually or in combination positively influenced soybean development and improved some aspects of the tolerance of soybean. The results of this work are important for the development of sustainable alternatives in the cultivation and protection of this important crop, as they demonstrate that the application of Si and AMF in the soil is beneficial for soybean crops.

Arbuscular mycorrhizal (AM) fungi are one of the important microbiota involved in a relationship with plant roots in which the plants and fungi both share and exchange nutrients and shelter. Cereal crops are the most essential sources of carbohydrates, dietary protein, and vitamin B for humans, and they supply the most fundamental diets. AM fungi are introduced as the optimal approach for real agricultural systems for increasing growth and productivity. According to a study from the previous decade, AM fungi were shown to promote crop growth and production, particularly in cereal crops. The AM fungi symbiosis provides a pleasant environment for microorganisms in the root and soil system, which promotes plant nutrition and water availability. AM fungi increase nutrient uptake and assimilation and also increase photosynthetic activity, which is directly associated with plant growth. Furthermore, AM fungi increase the primary and secondary metabolites, as well as soluble proteins and carbohydrates, in cereals crops. AM fungi have been shown to improve plant biomass, yield, and productivity in cereal crops. Additionally, the use of AM fungi enhances plants’ stress tolerance against various environmental stresses. In this review, we integrate the recent findings regarding the effects of AM fungi application on soil, root systems, nutrient availability and uptake, photosynthesis, metabolites, plant growth, and productivity. Furthermore, a large number of studies have been reviewed, and several limitations and research gaps have been identified that must be addressed in future studies.

The poor soil nutrients in the degraded karst region frequently restrict vegetation growth. Soil bacterial communities are essential drivers of biogeochemical cycling and regulate soil nutrient availability. Arbuscular mycorrhizal (AM) fungi play a fundamental role in shaping rhizosphere bacterial communities and promoting plant growth and nutrient acquisition. Nevertheless, how AM fungi mediated bacterial community interaction and assembly involved in nutrient cycling to promote plant growth and nutrient acquisition in karst soil remains unclear. In this study, a greenhouse pot experiment was conducted using γ-sterilized karst soil to cultivate four herbaceous plant species with AM fungal inoculation (AM treatment) or the control of non-inoculation (CK treatment). The results showed that plant biomass, nitrogen and phosphorus accumulation, hyphal length and soil organic carbon were significantly higher in the AM treatment than CK treatment, indicating that AM fungus promoted plant growth. The AM treatment also increased the abundance of specific functional bacterial taxa, including Nocardioides, Sphingomonas, and Massilia. Functional annotation of prokaryotic taxa analysis showed that AM treatment significantly enhanced soil functions related to ureolysis, nitrate reduction, and aromatic compound degradation. Furthermore, the co-occurrence network analysis showed that AM treatment decreased the average clustering coefficient and path length while increasing modularity compared to CK treatment, with Haliangium and Devosia identified as keystone species. In addition, Mantel’s test showed a significant relationship among the abundance of functional and keystone bacteria, soil metabolic functions and nutrients, and plant biomass and nutrient accumulation. In conclusion, AM fungus alters the abundance of specific functional bacteria associated with nutrient cycling, concomitant with the promotion of plant growth and nutrient accumulation. These findings highlight the important role of AM fungi in mediating the assembly of soil bacterial communities and enhancing host growth, and advancing understanding of the application of AM fungi for vegetation restoration in degraded karst ecosystem.

The impact of soil amendment with compost and/or application of arbuscular mycorrhizal fungi (AMF) on the resistance of tomato to Verticillium dahliae was evaluated. The frequency and intensity of mycorrhization decreased in V. dahliae inoculated plants. Application of compost and AMF significantly improved plant growth, stomatal conductance and chlorophyll fluorescence compared to infected and non infected controls. The combination of these biostimulants reduced the disease severity and incidence and the leaf alteration index compared to pathogen-infected control plants. Mycorrhized and compost amended soil recorded a maximum decrease in plants malonyldialdehyde accumulation in the presence of V. dahliae. The combination of compost and AMF resulted in a significant improvement of superoxide dismutase, catalase, peroxidase and polyphenoloxidase activities in tomato leaves and roots compared to the control treatment in the presence of the pathogen. Similarly, yield and quality of tomato fruits were significantly improved by the dual application of compost and AMF.