Arbuscular Mycorrhizal Fungi Inoculation Research Articles

Effects of AMF inoculation on the eco-physiological characteristics of Imperata cylindrica under differing soil nitrogen conditions.

Arbuscular mycorrhizal fungi (AMF) play a key role in terrestrial ecosystems, while the ecological restoration application of AMF in mining areas has been progressively gaining attention. This study simulated a low nitrogen (N) environment in copper tailings mining soil to explore inoculative effects of four AMF species on the eco-physiological characteristics of Imperata cylindrica, and provided plant-microbial symbiote with excellent resistance to copper tailings. Results show that N, soil type, AMF species, and associated interactions significantly affected ammonium (), nitrate nitrogen (), and total nitrogen (TN) content and photosynthetic characteristics of I. cylindrica. Additionally, interactions between soil type and AMF species significantly affected the biomass, plant height, and tiller number of I. cylindrica. Rhizophagus irregularis and Glomus claroideun significantly increased TN and content in the belowground components I. cylindrica in non-mineralized sand. Moreover, the inoculation of these two fungi species significantly increased belowground content in mineralized sand. The net photosynthetic rate positively correlated to aboveground total carbon (TC) and TN content under the high N and non-mineralized sand treatment. Moreover, Glomus claroideun and Glomus etunicatum inoculation significantly increased both net photosynthetic and water utilization rates, while F. mosseae inoculation significantly increased the transpiration rate under the low N treatment. Additionally, aboveground total sulfur (TS) content positively correlated to the intercellular carbon dioxide (CO2) concentration, stomatal conductance, and the transpiration rate under the low N sand treatment. Furthermore, G. claroideun, G. etunicatum, and F. mosseae inoculation significantly increased aboveground and belowground TC content of I. cylindrica, while G. etunicatum significantly increased belowground content. Average membership function values of all physiological and ecological I. cylindrica indexes infected with AMF species were higher compared to the control group, while corresponding values of I. cylindrica inoculated with G. claroideun were highest overall. Finally, comprehensive evaluation coefficients were highest under both the low N and high N mineralized sand treatments. This study provides information on microbial resources and plant-microbe symbionts in a copper tailings area, while aiming to improve current nutrient-poor soil conditions and ecological restoration efficiency in copper tailings areas.

Growth Responses of Potted Vitis vinifera Cultivars Differ to a Mycorrhizal Inoculant and Phosphorus Fertilizer

Biological amendments, such as arbuscular mycorrhizal (AM) fungal inoculant products, are increasingly incorporated into agricultural management plans as a way to improve plant productivity. However, the effects of mycorrhizal inoculants on plant growth are context-dependent and can vary with soil fertility and among plant cultivars. To optimize the use of mycorrhizal inoculant products on wine grapes at the nursery stage, we tested the effect of a mycorrhizal inoculant product with and without the addition of phosphorus (P) fertilizer on the growth and tissue nutrients of two popular Vitis vinifera cultivars, Merlot and Chardonnay. We rooted dormant cuttings in the following respective treatments: no AM fungal inocula or P fertilizer; AM fungal inocula; P fertilizer; and co-amendment of AM fungal inocula and P fertilizer. We grew the grapevines in pots for 5 months in a greenhouse. Growth responses to treatments differed between cultivars. ‘Merlot’ vines had a stronger growth response to the mycorrhizal inoculant product than ‘Chardonnay’, especially when no P fertilizer was added. The co-amendment of AM fungi and P fertilizer resulted in larger root biomass for ‘Merlot’, but there was no effect of any treatment on the root biomass of ‘Chardonnay’. ‘Merlot’ vines grown with the AM fungal inoculant product also had higher tissue P than uninoculated vines, but there was no effect of inoculation on tissue nutrients of ‘Chardonnay’. This study provides evidence of grapevine cultivar-specific responses to an AM fungal inoculant product in a greenhouse, which may be useful when planning nursery management strategies for the incorporation of biological amendments into grapevine production.

Application of the arbuscular mycorrhizal fungi inoculant, organic and NPK fertilizers on the growth and yields of maize (Zea mays L.)

The objective of this study was to examine the effect of Arbuscular Mycorrhizal Fungi (AMF) inoculant, NPK fertilizer, and organic fertilizers (chicken manure) on maize growth and yield. This study used a completely randomized design (CRD), with 8 fertilizer treatments, namely (1) control or without any fertilizer, (2) inoculation of AMF, (3) NPK fertilizer, (4) chicken manure (CM), (5) FMA + NPK, (6) FMA + CM, (7) NPK + CM and (8) FMA + NPK + CM. Each treatment was repeated 3 times. The results indicated that the fertilization treatment showed a significant and very significant effect for all variables, namely plant height, leaf number, fresh leaf weight, plant fresh weight per plant and per plot, ear diameter with and without husks, cob number per plot, ear weight per plant and per plot and ear weight without husk per plant and per plot, and ears number per plant. The application of AMF + NPK + CM and NPK + CM fertilizers produced the highest maize growth and yields, while each of the AMF and control treatments produced the lowest growth and yield components.

Invasive and Native Plants Differentially Respond to Exogenous Phosphorus Addition in Root Growth and Nutrition Regulated by Arbuscular Mycorrhizal Fungi.

Plant invasion has severely damaged ecosystem stability and species diversity worldwide. The cooperation between arbuscular mycorrhizal fungi (AMF) and plant roots is often affected by changes in the external environment. Exogenous phosphorus (P) addition can alter the root absorption of soil resources, thus regulating the root growth and development of exotic and native plants. However, it remains unclear how exogenous P addition regulates the root growth and development of exotic and native plants mediated by AMF, affecting the exotic plant invasion. In this experiment, the invasive plant Eupatorium adenophorum and native plant Eupatorium lindleyanum were selected and cultured under intraspecific (Intra-) competition and interspecific (Inter-) competition conditions, involving inoculation with (M+) and without AMF (M-) and three different levels of P addition including no addition (P0), addition with 15 mg P kg-1 soil (P15), and addition with 25 mg P kg-1 soil (P25) for the two species. Root traits of the two species were analyzed to study the response of the two species' roots to AMF inoculation and P addition. The results showed that AMF significantly promoted the root biomass, length, surface area, volume, tips, branching points, and carbon (C), nitrogen (N), and P accumulation of the two species. Under M+ treatment, the Inter- competition decreased the root growth and nutrient accumulation of invasive E. adenophorum but increased the root growth and nutrient accumulation of native E. lindleyanum relative to the Intra- competition. Meanwhile, the exotic and native plants responded differently to P addition, exhibiting root growth and nutrient accumulation of invasive E. adenophorum increased with P addition, whereas native E. lindleyanum reduced with P addition. Further, the root growth and nutrition accumulation of native E. lindleyanum were higher than invasive E. adenophorum under Inter- competition. In conclusion, exogenous P addition promoted the invasive plant but reduced the native plant in root growth and nutrient accumulation regulated by AMF, although the native plant outcompeted the invasive plant when the two species competed. The findings provide a critical perspective that the anthropogenic P fertilizer addition might potentially contribute to the successful invasion of exotic plants.

Dual Inoculation of Rhizobium and Arbuscular Mycorrhizal Fungi Increases Soil-Total Nitrogen, Available Phosphorus, and Yield of Soybean in Vertisols

Soybean is a protein source food crop with high economic value. So far, national production has not been able to meet domestic demand resulting in continuing import of soybean. The use of rhizobium and arbuscular mycorrhizal fungi (AMF) as biological fertilizers could be an alternative to increase soybean production. The research aimed to investigate the effect of dual inoculation of rhizobium and arbuscular mycorrhizal fungi (AMF) on root nodules formation, AMF development, total-N and available P of Vertisols, and yield of soybean. This study was designed in a completely randomized design) with 4 treatments namely no inoculation (R0), rhizobium inoculation (R1), AMF inoculation (R2), and dual inoculation of rhizobium and AMF (R3), with four replications. The variables observed were the number of effective root nodules, AMF spore density, AMF colonization, soil total-N, available P, plant height, number of pods, and seed weight. The results showed that dual inoculation of rhizobium and AMF had a better effect on the number of effective root nodules, AMF spore density, AMF colonization, soil total- N, available P, plant height, number of pods, and seed weight compared to the single inoculation and un-inoculated treatments

The Synergistic Effects of AMF Inoculation and Boron Deficiency on the Growth and Physiology of Camellia oleifera Seedlings

Arbuscular mycorrhizal fungi (AMF) symbiosis has been shown to improve the ability to obtain nutrients and resist adverse environmental conditions. However, there are few studies on the functions of AMF in the absorption and accumulation of boron (B). Moreover, it is still unclear whether the root colonization rates of AMF are limited by B deficiency. In this study, Camellia oleifera seedlings were planted in normal and boron-deficient substrates, and the seedlings were inoculated with Funneliformis mosseae or left uninoculated. The growth and physiological indices of C. oleifera seedlings were determined. The results of this experiment indicate that AMF inoculation increased the plant biomass, B content, B accumulation, and antioxidant enzyme activity in both normal and boron-deficient C. oleifera seedlings. Furthermore, boron deficiency resulted in a decrease in the AMF root colonization efficiency and the inhibition of C. oleifera seedlings’ growth and physiological activity. These findings suggest that AMF inoculation could improve the resistance to B-deficiency stress. Additionally, the colonization efficiency of AMF was adversely affected by B deficiency; thus, AMF play a cooperative role with B in the growth and physiological functions of plants. The results provide a theoretical basis for taking measures to solve B-deficiency stress in C. oleifera and other plants’ cultivation.

Effects of Arbuscular Mycorrhizal Fungi on the Physiology and Saponin Synthesis of Paris polyphylla var. yunnanensis at Different Nitrogen Levels

Arbuscular mycorrhizal fungi (AMF) are important members of the plant microbiome and affect the uptake and transfer of mineral elements by forming a symbiotic relationship with plant roots. Nitrogen (N), as an important mineral element, can directly affect plant growth and development at different N levels. It has been confirmed that inoculation with AMF can improve the efficiency of N utilization by plants. However, there are still fewer reports on the dynamic relationship between arbuscular mycorrhizal and plant secondary metabolites at different nitrogen levels. In this experiment, the physiological indexes and genes related to saponin synthesis were determined by applying different concentration gradients of nitrogen to the medicinal plant P. polyphylla var. yunnanensis infested by AMF as the test material. It was found that nitrogen addition increased the biomass, chlorophyll content, and nutrient content of above- and below-ground plant parts and increased the content of saponin content of P. polyphylla var. yunnanensis to some extent, but AMF inoculation increased the saponin content of P. polyphylla var. yunnanensis more significantly. AMF inoculation also promoted the expression of genes related to the saponin synthesis pathway, including 3-hydroxy-3-methylglutaryl coenzyme A synthase (HMGS), squalene epoxidase 1 (SE1), and cycloartenol synthase (CAS), which is in according with the accumulation of saponin in plants. It also may increase the saponin content of AMF plants by altering the expression of P450s and UGTs related to saponin synthesis.

Contribution of Arbuscular Mycorrhizal and Endophytic Fungi to Drought Tolerance in Araucaria araucana Seedlings.

In its natural distribution, Araucaria araucana is a plant species usually exposed to extreme environmental constraints such as wind, volcanism, fires, and low rainfall. This plant is subjected to long periods of drought, accentuated by the current climate emergency, causing plant death, especially in its early growth stages. Understanding the benefits that both arbuscular mycorrhizal fungi (AMF) and endophytic fungi (EF) could provide plants under different water regimes would generate inputs to address the above-mentioned issues. Here, the effect of AMF and EF inoculation (individually and combined) on the morphophysiological variables of A. araucana seedlings subjected to different water regimes was evaluated. Both the AMF and EF inocula were obtained from A. araucana roots growing in natural conditions. The inoculated seedlings were kept for 5 months under standard greenhouse conditions and subsequently subjected to three different irrigation levels for 2 months: 100, 75, and 25% of field capacity (FC). Morphophysiological variables were evaluated over time. Applying AMF and EF + AMF yielded a noticeable survival rate in the most extreme drought conditions (25% FC). Moreover, both the AMF and the EF + AMF treatments promoted an increase in height growth between 6.1 and 16.1%, in the production of aerial biomass between 54.3 and 62.6%, and in root biomass between 42.5 and 65.4%. These treatments also kept the maximum quantum efficiency of PSII (Fv/Fm 0.71 for AMF and 0.64 for EF + AMF) stable, as well as high foliar water content (>60%) and stable CO2 assimilation under drought stress. In addition, the EF + AMF treatment at 25% FC increased the total chlorophyll content. In conclusion, using indigenous strains of AMF, alone or in combination with EF, is a beneficial strategy to produce A. araucana seedlings with an enhanced ability to tolerate prolonged drought periods, which could be of great relevance for the survival of these native species under the current climate change.

Role of melatonin in enhancing arbuscular mycorrhizal symbiosis and mitigating cold stress in perennial ryegrass (Lolium perenne L.).

Melatonin is a biomolecule that affects plant development and is involved in protecting plants from environmental stress. However, the mechanisms of melatonin's impact on arbuscular mycorrhizal (AM) symbiosis and cold tolerance in plants are still unclear. In this research, AM fungi inoculation and exogenous melatonin (MT) were applied to perennial ryegrass (Lolium perenne L.) seedlings alone or in combination to investigate their effect on cold tolerance. The study was conducted in two parts. The initial trial examined two variables, AM inoculation, and cold stress, to investigate the involvement of the AM fungus Rhizophagus irregularis in endogenous melatonin accumulation and the transcriptional levels of its synthesis genes in the root system of perennial ryegrass under cold stress. The subsequent trial was designed as a three-factor analysis, encompassing AM inoculation, cold stress, and melatonin application, to explore the effects of exogenous melatonin application on plant growth, AM symbiosis, antioxidant activity, and protective molecules in perennial ryegrass subjected to cold stress. The results of the study showed that compared to non-mycorrhizal (NM) plants, cold stress promoted an increase in the accumulation of melatonin in the AM-colonized counterparts. Acetylserotonin methyltransferase (ASMT) catalyzed the final enzymatic reaction in melatonin production. Melatonin accumulation was associated with the level of expression of the genes, LpASMT1 and LpASMT3. Treatment with melatonin can improve the colonization of AM fungi in plants. Simultaneous utilization of AM inoculation and melatonin treatment enhanced the growth, antioxidant activity, and phenylalanine ammonia-lyase (PAL) activity, while simultaneously reducing polyphenol oxidase (PPO) activity and altering osmotic regulation in the roots. These effects are expected to aid in the mitigation of cold stress in Lolium perenne. Overall, melatonin treatment would help Lolium perenne to improve growth by promoting AM symbiosis, improving the accumulation of protective molecules, and triggering in antioxidant activity under cold stress.

Rhizoglomus intraradices Is More Prominent in Improving Soil Aggregate Distribution and Stability Than in Improving Plant Physiological Activities

Arbuscular mycorrhizal fungi (AMF) confer positive and negative effects on many plants, but it is unclear whether AMF has an effect on soil fertility, aggregate distribution, and stability. The aim of this study was to analyze the effects of Rhizoglomus intraradices on plant growth, root morphology, leaf chlorophyll and gas exchange, sugar concentrations, and soil nutrients, aggregate distribution, and stability in marigold (Tagetes erecta L.), maize (Zea mays L.), white clover (Trifolium repens L.), and vetch (Vicia villosa Roth.) plants. Twelve weeks after R. intraradices inoculation, maize presented the highest mycorrhizal development, while mycorrhizal dependence was shown to be the decreasing trend in marigold > white clover > vetch > maize. AMF inoculation significantly increased the chlorophyll index of marigold and white clover, the net photosynthetic rate of white clover, the stomatal conductance of maize and white clover, and the transpiration rate of maize. Fructose, glucose, and sucrose in the four plants were differentially affected by R. intraradices. R. intraradices significantly increased the soil organic carbon (SOC) of marigold, maize, and white clover, the Olsen-P of white clover, the available K content of marigold, the easily extractable glomalin-related soil protein (GRSP) of maize, and the difficultly extractable and total GRSP levels of marigold and vetch. In addition, R. intraradices significantly increased the stability of soil water-stable aggregates (WSAs) in all four plants, plus it increased WSA at 0.5–4 mm sizes. Root AMF colonization was significantly positively correlated with WSA stability, SOC, difficultly extractable GRSP, and total GRSP. It is concluded that AMF-triggered changes in plant growth, physiological activities, and soil fertility depended on plant species, but AMF-improved WSA distribution and stability were not dependent on plant species.

Uncovering the impact of AM fungi on wheat nutrient uptake, ion homeostasis, oxidative stress, and antioxidant defense under salinity stress

The growth of wheat (Triticum aestivum) is constrained by soil salinity, although some fungal species have been shown to enhance production in saline environments. The yield of grain crops is affected by salt stress, and this study aimed to investigate how arbuscular mycorrhizal fungus (AMF) mitigates salt stress. An experiment was conducted to assess the impact of AMF on wheat growth and yield in conditions of 200 mM salt stress. Wheat seeds were coated with AMF at a rate of 0.1 g (108 spores) during sowing. The results of the experiment demonstrated that AMF inoculation led to a significant improvement in the growth attributes of wheat, including root and shoot length, fresh and dry weight of root and shoot. Furthermore, a significant increase in chlorophyll a, b, total, and carotenoids was observed in the S2 AMF treatment, validating the effectiveness of AMF in enhancing wheat growth under salt stress conditions. Additionally, AMF application reduced the negative effects of salinity stress by increasing the uptake of micronutrients such as Zn, Fe, Cu, and Mn while regulating the uptake of Na (decrease) and K (increase) under salinity stress. In conclusion, this study confirms that AMF is a successful strategy for reducing the negative effects of salt stress on wheat growth and yield. However, further investigations are recommended at the field level under different cereal crops to establish AMF as a more effective amendment for the alleviation of salinity stress in wheat.

Arbuscular mycorrhizal fungi improve growth and tolerance of Platycladus orientalis under lead stress

Platycladus orientalis is a significant woody plant for phytoremediation in heavy metals contaminated soils. The growth and tolerance of host plants under the lead (Pb) stress were enhanced by arbuscular mycorrhizal fungi (AMF). To evaluate the adjustment by AMF on growth and activity of antioxidant system of P. orientalis under Pb stress. The two-factor pot experiment was conducted with three AM fungal treatments (noninoculated, Rhizophagus irregularis, and Funneliformis mosseae) and four Pb levels (0, 500, 1000, and 2000 mg kg−1). AMF increased dry weight, phosphorus uptake, root vitality, and total chlorophyll content of P. orientalis in spite of Pb stress. Compared with nonmycorrhizal treatments, mycorrhizal P. orientalis had lower H2O2 and malondialdehyde (MDA) contents under Pb stress. AMF increased Pb uptake in roots and decreased the Pb translating to the shoots yet under Pb stress. Total glutathione and ascorbate in roots of P. orientalis were decreased by AMF inoculation. Mycorrhizal P. orientalis had higher superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione S-transferase (GST) activities in shoots and roots than nonmycorrhizal counterparts. Mycorrhizal P. orientalis under Pb stress showed higher expression of PoGST1 and PoGST2 in roots than that in CK treatments. Future studies will explore the function of induced tolerance genes by AMF of P. orientalis under Pb stress.

A Commercial Arbuscular Mycorrhizal Inoculum Alleviated the Effects of Acid Water on Lupinus angustifolius Grown in a Sterilized Mining Dump.

Lupinus species have been sporadically reported to be colonized by arbuscular mycorrhizal fungi (AMF). The interactions between AMF and lupine plants could also be non-symbiotic, from positive to negative, as controlled by the stress conditions of the plant. The goal of the study was to reveal the existence of such positive interactions and provide preliminary data for a myco-phytoremediation technology of mining dumps using L. angustifolius as a first crop. The objective was to test the hypothesis that the AMF inoculation of an acidified dump material contaminated with heavy metals would improve the growth of L. angustifolius and decrease oxidative stress. The design consisted of a one-month bivariate pot experiment with plants grown in a mining dump soil inoculated and not inoculated with a commercial AMF inoculum sequestered in expanded clay and watered with acidic and neutral water. There was no AMF root colonization under the experimental conditions, but under neutral and acidic water conditions, the phosphorus concentrations in roots and leaves increased, and the superoxide dismutase and peroxidase activities significantly decreased due to AMF inoculation. The increase in leaf phosphorus concentration was correlated with the decrease in peroxidase activity. The fresh weight of shoots and leaves significantly increased due to the commercial inoculum (under acidic water conditions). At the end of the experiment, the ammonium concentration in the substrate was higher in the inoculated treatments than in the not inoculated ones, and the concentrations of many elements in the dump material decreased compared to the start of the experiment. A comprehensive discussion of the potential mechanisms underlying the effects of the commercial AMF inoculum on the non-host L. angustifolius is completed.

Improvements in the biochemical responses and Pb and Ni phytoremediation of lavender (Lavandula angustifolia L.) plants through Funneliformis mosseae inoculation

BackgroundHeavy metals (HMs) phytoremediation is a well-recognized protocol to remove toxic elements from the soil. As known, arbuscular mycorrhizal fungi (AMF) enhance the plants' growth responses. The idea of the present study was to assay the response of lavender plants to HMs stress under AMF inoculation. We hypothesized that mycorrhiza will enhance the phytoremediation and simultaneously reduce the harmful effects of heavy HMs. So, lavender (Lavandula angustifolia L.) plants were inoculated with AMF (0 and 5 g Kg−1 soil) under Pb [150 and 225 mg kg−1 soil from Pb (NO3)2] and Ni [220 and 330 mg kg−1 soil from Ni (NO3)2] pollution, in the greenhouse conditions. The control treatment was plants not treated with AMF and HMs. Doing this, the root colonization, HMs uptake, enzymatic and non-enzymatic antioxidants pool, MDA, proline, total phenolics (TPC), flavonoids (TFC), anthocyanins, and essential oil (EO) components were evaluated.ResultsAccording to the findings, the AMF inoculation enhanced shoot and root Pb and Ni content, antioxidant enzymes activity, the total antioxidant activity by DPPH and FRAP methods, TPC, TFC, anthocyanins, and H2O2 content in the lavender plants subjected to Pb and Ni stress. Moreover, the highest (28.91%) and the least (15.81%) percentages of borneol were identified in the lavender plants subjected to AMF under 150 mg kg−1 of Pb and the control plants without AMF application, respectively. Furthermore, the top 1,8-cineole (12.75%) content was recorded in AMF-inoculated plants.ConclusionsThe overall results verify that AMF inoculation can be a reliable methodology to enhance the phytoremediation of Pb and Ni by lavender plants while maintaining reliable growth potential. The treatments improved the main EO constituents content, especially under moderate HMs stress conditions. With more detailed studies, the results will be advisable for the extension section for the phytoremediation of polluted soils.

Effect of Arbuscular Mycorrhizal Fungi on Nitrogen and Phosphorus Uptake Efficiency and Crop Productivity of Two-Rowed Barley under Different Crop Production Systems.

Arbuscular Mycorrhizal Fungi (AMF) constitute a ubiquitous group of soil microorganisms, affecting plant and soil microorganism growth. Various crop management practices can have a significant impact on the AM association. This study investigated the AMF inoculation contribution on growth and productivity of two-rowed barley crop by identifying the underlying mechanisms both in conventional and organic cropping systems. A two-year field trial was set up as a split-plot design with 2 main plots [AMF inoculation: with (AMF+) and without (AMF-)] and five sub-plots (fertilization regimes: untreated, 100% recommended dose of fertilizer in organic and inorganic form, and 60% recommended dose of fertilizer in organic and inorganic form) in three replications. According to the results, AMF+ plants presented higher plant height and leaf area index (LAI), resulting in increased biomass and, as a result, higher seed yield. With regard to the quality traits, including the nitrogen and phosphorus uptake and their utilization indices, the AMF inoculated plants showed higher values. Furthermore, the level of fertilization, particularly in an inorganic form, adversely affected AMF root colonization. Consequently, it was concluded that substitution of inorganic inputs by organic, as well as inputs reduction, when combined with AMF inoculation, can produce excellent results, thus making barley crop cultivation sustainable in Mediterranean climates.

Arbuscular mycorrhizal fungi trigger danger-associated peptide signaling and inhibit carbon-phosphorus exchange with nonhost plants.

In soil, arbuscular mycorrhizal fungi (AMF) meet the roots of both host and presumed nonhost plants, but the interactional mechanisms of AMF with and functional relevance for nonhost plants is little known. Here we show AMF can colonize an individually grown nonhost plant, Arabidopsis thaliana, and suppress the growth of Arabidopsis and two nonhost Brassica crops. This inhibitory effect increased with increasing AMF inoculum density, and was independent of AMF species or nutrient availability. 13 C isotope labeling and physiological analyses revealed no significant carbon-phosphorus exchange between Arabidopsis and AMF, indicating a lack of nutritional function in this interaction. AMF colonization activated the danger-associated peptide Pep-PEPR signaling pathway, and caused clear defense responses in Arabidopsis. The impairment of Pep-PEPR signaling in nonhost plants greatly compromised AMF-triggered defensive responses and photosynthesis suppression, leading to higher colonization rates and reduced growth suppression upon AMF inoculation. Pretreatment with Pep peptide decreased AMF colonization, and largely substituted for AMF-induced growth suppression in nonhosts, confirming that the Pep-PEPR pathway is a key participant in resistance to AMF colonization and in mediating growth suppression of nonhost plants. This work greatly increases our knowledge about the functional relevance of AMF and their mechanisms of interactions with nonhost plants.

Arbuscular mycorrhizal fungus Rhizophagus irregularis alleviates drought stress in soybean with overexpressing the GmSPL9d gene by promoting photosynthetic apparatus and regulating the antioxidant system

Drought is the most destructive abiotic stress and negatively affects crop growth and productivity. Modern breeding efforts have produced numerous cultivars with distinct genetic traits that improve crop growth and drought stress tolerance. Arbuscular mycorrhizal fungi (AMF) can enhance drought tolerance in soybean plants by directly providing nutrients to plants, promoting photosynthesis, or influencing interspecific plant interactions in natural communities. However, the interactions between AMF and wild and transgenic soybean genotypes remain unclear. Therefore, in the present study, we evaluated the effect of arbuscular mycorrhizal fungi on the growth performance of drought-stressed transgenic soybean lines (ZXOE-11 and ZXOE-13) overexpressing GmSPL9d gene and their wild soybean Tianlong 1 (TL1) at the seedling stage (45 d after sowing). The results showed that colonization of wild and transgenic soybean with Rhizophagus irregularis significantly decreased the adverse effects of drought on plant growth. AMF inoculation significantly increased plant biomass, root activity, chlorophyll metabolism, photosynthesis, and chlorophyll fluorescence in wild-type and transgenic plants under both control and drought stress conditions. Drought causes the production of ROS, such as hydrogen peroxide, which enhances MDA, thereby decreasing the membrane stability index (MSI). However, AMF-inoculated plants exhibited decreased ROS accumulation and increased MSI. Moreover, AMF treatment significantly improved osmolyte, nitrogen, and nitrate reductase activity under control and drought conditions, which increased the relative water content. Furthermore, AMF treatment enhanced the antioxidant systems of drought-stressed plants by increasing the activities of peroxidase, superoxide dismutase, catalase, and ascorbate peroxidase. AMF improved the growth performance, photosynthesis, and antioxidant activity of transgenic plants under drought stress conditions. The present findings indicate that the AMF contribution to soybean seedling drought tolerance was more significant for the transgenic plants than for the wild plants under drought conditions. The current findings emphasize the possibility of growth and photosynthetic variation in the degree of AMF-associated drought resistance in soybean plants. Our findings suggest that future crop breeding challenges include developing cultivars for sustainable production and maximizing crop cultivar and fungal species (AMF) combinations in drought-stressed regions.

Ameliorating the drought stress tolerance of a susceptible soybean cultivar, MAUS 2 through dual inoculation with selected rhizobia and AM fungus

BackgroundDrought stress is currently the primary abiotic stress factor for crop loss worldwide. Although drought stress reduces the crop yield significantly, species and genotypes differ in their stress response; some tolerate the stress effect while others not. In several systems, it has been shown that, some of the beneficial soil microbes ameliorate the stress effect and thereby, minimizing yield losses under stress conditions. Realizing the importance of beneficial soil microbes, a field experiment was conducted to study the effect of selected microbial inoculants namely, N-fixing bacteria, Bradyrhizobium liaoningense and P-supplying arbuscular mycorrhizal fungus, Ambispora leptoticha on growth and performance of a drought susceptible and high yielding soybean cultivar, MAUS 2 under drought condition.ResultsDrought stress imposed during flowering and pod filling stages showed that, dual inoculation consisting of B. liaoningense and A. leptoticha improved the physiological and biometric characteristics including nutrient uptake and yield under drought conditions. Inoculated plants showed an increased number of pods and pod weight per plant by 19% and 34% respectively, while the number of seeds and seed weight per plant increased by 17% and 32% respectively over un-inoculated plants under drought stress condition. Further, the inoculated plants showed higher chlorophyll and osmolyte content, higher detoxifying enzyme activity, and higher cell viability because of less membrane damage compared to un-inoculated plants under stress condition. In addition, they also showed higher water use efficiency coupled with more nutrients accumulation besides exhibiting higher load of beneficial microbes.ConclusionDual inoculation of soybean plants with beneficial microbes would alleviate the drought stress effects, thereby allowing normal plants’ growth under stress condition. The study therefore, infers that AM fungal and rhizobia inoculation seems to be necessary when soybean is to be cultivated under drought or water limiting conditions.

Pioneer Tree Bellucia imperialis (Melastomataceae) from Central Amazon with Seedlings Highly Dependent on Arbuscular Mycorrhizal Fungi.

Bellucia imperialis is one of the most abundant pioneer tree species in anthropized areas of the Central Amazon, and has ecological importance for the environmental resilience of phosphorus (P)-depleted areas. Thus, we investigated whether B. imperialis depends on symbiosis with arbuscular mycorrhizal fungi (AMF) to grow and establish under the edaphic stresses of low nutrient content and low surface moisture retention capacity of the substrate. We tried three AMF inoculation treatments: (1) CON-no mycorrhizae; (2) MIX-with AMF from pure collection cultures, and (3) NAT-with native AMF, combined with five doses of P via a nutrient solution. All CON treatment seedlings died without AMF, showing the high mycorrhizal dependence of B. imperialis. Increasing P doses significantly decreased the leaf area and shoot and root biomass growth for both the NAT and MIX treatments. Increasing P doses did not affect spore number or mycorrhizal colonization, but decreased the diversity of AMF communities. Some species of the AMF community showed plasticity, enabling them to withstand shortages of and excess P. B. imperialis was shown to be sensitive to excess P, promiscuous, dependent on AMF, and tolerant of scarce nutritional resources, highlighting the need to inoculate seedlings to reforest impacted areas.

Plant propagation Litsea garciae Vidal. with shoot cutting technique inoculated with arbuscular mycorrhizal fungi

Litsea garciae Vidal. (engkala, kalangkala) is a fruit-producing plant useful as a potential medicinal plant and food. The availability of seedlings is a must if their potential is to be developed. The study aimed to evaluate the formation and growth of roots and shoots of L. garciae shoot cuttings in response to growth regulators and arbuscular mycorrhizal fungi (AMF) inoculation. The study used a factorial experiment with a completely randomized design. The treatments tested were growth regulators (without and with rootone-F) and AMF inoculation (without and with AMF). The shoot cuttings were planted in a mixture of cocopeat and husk charcoal (2:1 v/v) and placed in a propagation box in a screen house for 12 weeks. The live percentage, the percentage of callus cuttings, the percentage of rooted cuttings, and the percentage of cuttings sprouting all shoot cuttings planted reached 100%. The interaction between rootone-F and AMF had no significant effect on initiating root and shoot growth. However, cuttings treated without or with rootone-F showed a positive response to AMF inoculation, particularly in primary root formation and secondary root count. The secondary roots’ length and wet and dry weights of the cuttings with rootone-F were significantly lower than those without rootone-F.