Presence Of AMF Research Articles

Bacterial community changes in the presence of AMF in the context of maize with low phosphorus content

PurposeArbuscular mycorrhizal fungi (AMF) perform an ancestral and essential association with plant roots, where plants provide carbohydrates and lipids, and the fungi respond by translocating water and nutrients to the roots through the hyphae. There is a need to investigate the microbial community associated with the rhizosphere of mycorrhizal plants in response to the multiple benefits (e.g., improved nutrition and stress resistance) provided by the association. In this work, we analyzed the bacterial communities associated with the rhizosphere of plants and their response to mycorrhizae in low P conditions.MethodsFor this purpose, inoculated and non-inoculated B73 corn plants were grown with a consortium of mycorrhizal fungi under low phosphorus conditions. Mycorrhiza response in B73 and the interaction with rhizosphere microbiome were characterized by sequencing the bacterial 16S rRNA gene.ResultsInoculated plants showed increased greater growth in leaf and root parameters in low P conditions. Bacterial microbiome showed changes in beta diversity and some OUTs significantly regulated by AMF presence.ConclusionThese data confirm the importance of mycorrhizae in phosphorus stress and rhizosphere community changes as a possible mechanism to improve plant growth.

Growth and Yield of Pulses as Influenced by Intercropping with Finger Millet [Eleusine coracana (L.) Gaertn.] in the Southern Laterites of Kerala

Background: In the recent years, the yield plateau of the major cereals together with the climate change concerns, the potential of millets and pulses have been identified as pivotal for addressing the agrarian and nutritional challenges. The present study was conducted to assess the feasibility of intercropping green gram, black gram and cowpea in finger millet.Methods: A field experiment was conducted during summer 2019-2020 (February to May, 2020) to assess the variation in the growth and yield of pulses, viz., green gram, black gram and cowpea on intercropping with finger millet, along with and without AMF inoculation.Result: Pulses were observed to be significantly taller when intercropped with finger millet in the presence of AMF. Leaf area index (LAI), dry matter production, seed yield and haulm yield were higher for sole crops. Between the intercropping treatments, with and without AMF, LAI, dry matter production and seed yield were superior when pulses where intercropped in finger millet inoculated with AMF. Intercropping finger millet with cowpea recorded the highest finger millet equivalent yield (FMEY) followed by black gram and green gram. The treatment, T6 (finger millet with AMF + cowpea) registered the highest FMEY (3388 kg ha-1) followed by T5 (3234 kg ha-1). Intercropping finger millet (with AMF) with black gram (T4) and green gram (T2) recorded FMEY of 2708 kg ha-1 and 2497 kg ha-1 respectively.

The influence of forest litter on the endomicorritic fungi community in a natural regeneration area in São Paulo State, Brazil

ABSTRACT Natural areas of high biological diversity are being degraded to meet man’s need to convert them to various uses. The ecological restoration through litter transposition enables for the reestablishment of ecological processes and may contribute to the increase of microorganisms. It aimed to evaluate the influence of litter on the community of mycorrhizal fungi in an area of Cabreúva, São Paulo State, Brazil. Ten plots were delimited, five control and five treatment. Soil samples were collected during two distinct periods for physical, chemical and microbiological analysis. Results indicated that the edaphic conditions of the place are consistent with the presence of AMF; also, the transposed organic matter did not increase species richness and did not facilitate the colonization of plant species, whereas gravimetric humidity and grass may have influenced species richness.

Electromagnetism in taking concrete behavior on demand

Developing new techniques for improving concrete structures performances has resulted in invention of different methods, such as designing smart concrete elements. This study aims to evaluate effectiveness of employing Alternating Magnetic Field (AMF11Alternating magnetic field.) in enhancing concrete properties and controlling its behavior. Therefore, some experiments were conducted on some concrete cylindrical specimens, where the effect of applying AMF to fresh and hardened concrete on the compressive strength of 7 and 8-day specimens was investigated. For experiments a test setup was designed in a way that AMF (of power 0.5 T22Tesla. and frequency 50 Hz) and compressive force could be applied to concrete specimens, simultaneously. It was observed that exposing fresh and hardened concrete to AMF improves compressive strength, where this effect is more significant as to magnetizing hardened concrete. Moreover, the effectiveness of AMF was more significant for 7-day concrete compared to 28-day one. The fact that compressive strength of hardened concrete increases in the presence of AMF, in real time, was discussed as to feasibility of constructing smart concrete elements via this techniques.

Aquatain AMF efficacy on juvenile mosquito stages in control of Culex pipiens complex and Aedes albopictus

AbstractAquatain® mosquito formulation (AMF) is a silicone‐based monomolecular film, which has recently been approved for use in the European Union. The physical mode of action based on lowering water surface tension prevents mosquito larvae/pupae respiration. Additionally, AMF disables gravid females from landing on the water surface and obstructs the natural oviposition process. Due to multistage effects on mosquitoes, AMF could be a product of choice for defined water body and container breeders such as Culex pipiens L. complex, principal vector of West Nile virus in Europe, and the invasive Aedes albopictus (Skuse) (both Diptera: Culicidae), vector of dengue and chikungunya viruses. The primary objectives of this study were to evaluate the efficacy of AMF, to determine the susceptibility of the immature forms of C. pipiens and A. albopictus, and the persistence/longevity of the product to suppress the eclosion of adults. AMF achieved high mortality rates of juvenile A. albopictus and C. pipiens under laboratory conditions. However, in the field C. pipiens larvae showed higher susceptibility to AMF than A. albopictus. Pupae of the two mosquito species were highly susceptible to the presence of AMF. When C. pipiens juveniles were exposed to AMF in the wild, effects lasted for 21 days in densely covered water bodies and 56 days in water recipients with less vegetation. In both breeding sites, natural habitat and artificial water recipient, the two mosquito species with high impact on public health in Europe could successfully be suppressed by application of AMF (1 ml m−2).

Activity in the Arbuscular Mycorrhizal Hyphosphere Warning Neighbouring Plants.

Pathogen infections of the phyllosphere have been investigated in detail, however, the changes induced by these infections on the arbuscular mycorrhizal hyphosphere, and the consequent signalling to the neighbouring plants have been scarcely investigated. Here, our objectives were to document that B.fabae infection of connected Vicia faba plants resulted in changes in the metabolism and microbial community of the hyphosphere, confirming the induction of plant defence in connected plants through gene-expression evaluations. Infected plants were challenged with B. fabae for 72 h. Changes in gene-expression of pathogenesis-related proteins 1,2, and 5 (PR1, PR2, PR5) of both infected- and non-infected plants were analysed, to confirm signalling through the hyphosphere. The primary metabolic profiles and changes in the level of microbiota in the hyphosphere were assessed. Changes in expression of PR1, PR2, and PR5 genes occurred in the neighbouring plants 24 hours after infection. Mannitol levels decreased in presence of AMF. A decrease in the level of actinobacteria in the hyphosphere of infected plants was detected. We conclude that B.fabae infection induced a signalling event through the AM hyphosphere, confirmed by changes in defence gene-expression in non-infected neighbouring plants, influenced primary metabolic activity of-, and affected the microbial composition within-, the AM hyphosphere.

Effect of Arbuscular Mycorrhizal Fungi Based Biofertilizer on Coconut Seedlings Growth in Nursery

The success of a coconut plantation, in terms of its field establishment as well as its future performance, is heavily dependent on the quality of the seedlings used. Coconut nurseries adopt different agronomic practices to produce good quality seedlings. Applying mycorrhizal inoculants is becoming an increasingly common practice in plant nurseries as it facilitates healthy seedling growth resulting in healthy and vigorous seedlings in the nursery, helps to reduce mortality rates of seedlings in the field and reduce water and fertilizer consumption. In this study effects of mycorrhizae based biofertilizer were evaluated for the growth of coconut seedlings in the nursery and field. The experiment was conducted at the Makadura Research Center in Sri Lanka. The nursery experiment treatments were, the presence of AMF based biofertilizer (50g per seedling or per bag) and absence of mycorrhizae based biofertilizer. In the field experiment, five treatments with 500g of AMF biofertilizerwith 25% recommended inorganic fertilizer mixture for young coconut palms (YPM) per seedling, 500g of AMF biofertilizer with 50% YPM per seedling, 500g of AMF biofertilizer with 75% YPM per seedling, 500g of AMF biofertilizer with 100% YPM per seedling and with only YPM per seedling. Root and shoot growth of seedlings were measured at monthly intervals in the nursery experiment. Leaf production rate and stem girth of the seedling were measured at six months interval in the field experiment. The application of bio fertilizer increased the volume and dry weight of primary, secondary, tertiary and quaternary roots in seedlings in the nursery significantly. A significantly higher leaf production rate and stem girth was observed in the field seedlings treatment with 500g of AMF biofertilizer with 75% YPM. The experiment concluded that application of bio fertilizer is beneficial for coconut seedlings in the nursery for the production good quality seedlings with well-developed roots resulting in better field establishment and in the field for fast and vigorous growth.

Interdependency of efficient nodulation and arbuscular mycorrhization in Piptadenia gonoacantha, a Brazilian legume tree.

Tripartite interactions between legumes and their root symbionts (rhizobia and arbuscular mycorrhizal fungi, AMF) are poorly understood, although it is well established that only specific combinations of symbionts lead to optimal plant growth. A classic example in which to investigate such interactions is the Brazilian legume tree Piptadenia gonoacantha (Caesalpinioideae), for which efficient nodulation has been described as dependent on the presence of AMF symbiosis. In this study, we compared the nodulation behaviour of several rhizobial strains with or without AMF inoculation, and performed analyses on nodulation, nodule cytology, N-fixing efficiency, and plant growth response. Nodulation of P.gonoacantha does not rely on the presence of AMF, but mycorrhization was rhizobial strain-dependent, and nodule effectiveness and plant growth were dependent on the presence of specific combinations of rhizobial strains and AMF. The co-occurrence of both symbionts within efficient nodules and the differentiation of bacteroids within nodule cells were also demonstrated. Novel close interactions and interdependency for the establishment and/or functioning of these symbioses were also revealed in Piptadenia, thanks to immunocytochemical analyses. These data are discussed in terms of the evolutionary position of the newly circumscribed mimosoid clade within the Caesalpinioid subfamily and its relative proximity to non-nodulated (but AMF-associated) basal subfamilies.

Influence of arbuscular mycorrhizal fungi on antimony phyto-uptake and compartmentation in vegetables cultivated in urban gardens

1. ContextUrban areas are often contaminated with various forms of persistent metal (loid) and emerging contaminants such as antimony (Sb). Thus, in the context of urban agriculture where sustainable practices such as biofertilizers application (arbuscular mycorrhizal fungi, AMF) could improve nutrient transfer from the soil to the vegetables, the effect of AMF on metal (loid) mobility and human bioaccessibility is still poorly known. 2. MethodsThe role of AMF in Sb uptake by lettuce and carrot grown in artificial substrate spiked with different Sb chemical species was investigated. Plants were grown under hydroponic conditions and half of the treatments received a concentrated spore solution to obtain mycorrhized and non-mycorrhized plants. Three weeks before harvest, plants were exposed to 10 mg.L−1 of either Sb2O3 or KSbO-tartrate (KSb). 3. ResultsThe presence of AMF significantly increased its accumulation in carrots (all organs) with higher accumulation in roots. In lettuce, accumulation appeared to be dependent on the Sb chemical species. Moreover, it was observed for the first time that AMF changed the human bioaccessible fraction of Sb in edible organs. 4. ImplicationsThe present results highlight a possible risk of Sb transfer from soil to edible plants cultivated in soil naturally containing AMF propagules, or when AMF are added as biofertilizers. After validating the influence of soil environment and AMF on Sb behavior in the field, these results should be considered in health risk assessments.

An In Vitro Method for Studying the Three-Way Interaction between Soybean, Rhizophagus irregularis and the Soil-Borne Pathogen Fusarium virguliforme

In this work, we described an in vitro system adequate for investigating the pathosystem soybean/arbuscular mycorrhizal fungi (AMF)/Fusarium virguliforme. Pre-mycorrhized plantlets with Rhizophagus irregularis were infected by F. virguliforme either locally via a plug of gel supporting mycelium (Method 1) or via a macroconidia suspension applied to the medium surface (Method 2). Root colonization by the AMF and infection by the pathogen were similar to the usual observations in pot experiments. Within a period of 18 days, more than 20% of the roots were colonized by the AMF and infection by the pathogen was observed in all the plants. In presence of AMF, a decrease in symptoms and in the level of root tissue infection was noticed. With Method 1, smaller necrotic lesions were observed in the pre-mycorrhized plantlets. In Method 2, pathogen infection was slower but more homogenous. These results demonstrated the suitability of the in vitro cultivation system to study the pathosystem soybean/AMF/F. virguliforme. We propose this in vitro cultivation system for studying the mechanisms involved in the biocontrol conferred by AMF against F. virguliforme in soybean.

Colonización de micorrizas arbusculares en tres especies de pasturas del departamento de Sucre

El presente estudio se llevó a cabo durante el segundo semestre de 2015 en fincas ganaderas de cinco localidades del departamento de Sucre, establecidas con pastos colosuana (Bothrichloa pertusa (L) A. Camus), angletón (Dichanthium aristatum, Benth) y mombaza (Panicum maximum Jacq), con el objetivo de evaluar la colonización de hongos formadores de micorrizas arbusculares (HMA) en raíces de estas pasturas. El muestreo se realizo aleatoriamente en cada finca ganadera, recolectando muestra de suelos y raíces, determinándose el porcentaje de infección mediante técnica de coloración de raíces por HMA. Los resultados muestran que los porcentajes de colonización fueron de 52,73% entre el pasto colosoana y 50,46% para angletón, siendo estadísticamente similares; mientras que el pasto mombaza tuvo menor colonización 40,92%. El mayor valor de colonización de HMA por localidad correspondieron a Chapinero 70,06% y los menores para Cantagallo 37,06% y el Mamón 32,7%. El presente estudio confirmó la presencia de HMA en tres especies de pasturas de interes económico para las explotaciones ganaderas del departamento de Sucre. Así mismo, la colonizacón de HMA de raíces en el presente trabajo dependió del tipo de pastura y la localidad.

Combination of Crotalaria spectabilis with Rhizophagus irregularis MUCL41833 decreases the impact of Radopholus similis in banana

The past decade has seen substantial progress in our knowledge on microorganisms (e.g. arbuscular mycorrhizal fungi—AMF) and push-pull plants (e.g. Crotalaria spectabilis) that contribute to the biocontrol of nematodes. However, the application of microorganisms together with push-pull plants has seldom been considered. Therefore, the objective of the study was to investigate the combined effect of AMF and C. spectabilis on the control of the nematode Radopholus similis in banana. Banana plants, pre-colonized or not with the AMF Rhizophagus irregularis MUCL 41833 were grown in 3L pots in presence/absence of Crotalaria spectabilis. Above-ground parts were separated with a fixed talpa net to separate shoots and leaves of the two plants. Similarly, the pots were divided below-ground in two compartments by growing the banana roots in a pocket nylon mesh (30μm), to avoid roots of both plants to intermingle. The banana plants were established first and were followed three weeks later by C. spectabilis. Inoculation of nematodes was done in parallel to the planting of C. spectabilis. Half of the banana plants received 1000 monoxenically produced juveniles and adults of R. similis. Eight treatments were set up with 6 replications: mycorrhizal banana plantlets with/without C. spectabilis and with/without nematodes (+M+C+N, +M+C−N, +M−C+N, +M−C−N) and non-mycorrhizal banana plantlets with/without C. spectabilis and with/without nematodes (−M+C+N, −M+C−N, −M−C+N, −M−C−N). Plant growth parameters, root colonization by the AMF and infection by the nematode were evaluated. R. similis did not impact banana root colonization by the AMF. Conversely, the fungal symbiont as well as C. spectabilis significantly decreased the total number of nematodes as well as their multiplication rate. The multiplication rate in the controls (i.e. −M−C+N) was 280.3, while it decreased to 176.5, 106.7 and 83.8 in the −M+C+N, +M−C+N and +M+C+N treatments, respectively. The root necrosis index (RNI) was significantly decreased in presence of the AMF, C. spectabilis and the combination of both. The RNI of the control (i.e. −M−C+N) was 61.7% while it was 33.7, 19.8 and 17.2 in the −M+C+N, +M−C+N and +M+C+N treatments, respectively. Banana root fresh weight was significantly increased in presence of C. spectabilis and shoot dry weight in presence of AMF, but no increase was noticed in presence of both organisms together. This study reaffirmed that AMF and C. spectabilis are effective in decreasing the pressure caused by R. smilis in banana roots. It demonstrated further, for the first time, that their combination decreased even more drastically the surface of necrotic cortical tissues caused by the nematodes, opening new avenues for their concomitant use in an integrated pest management strategy.

Enhancement of faba bean competitive ability by arbuscular mycorrhizal fungi is highly correlated with dynamic nutrient acquisition by competing wheat.

The mechanistic understanding of the dynamic processes linking nutrient acquisition and biomass production of competing individuals can be instructive in optimizing intercropping systems. Here, we examine the effect of inoculation with Funneliformis mosseae on competitive dynamics between wheat and faba bean. Wheat is less responsive to mycorrhizal inoculation. Both inoculated and uninoculated wheat attained the maximum instantaneous N and P capture approximately five days before it attained the maximum instantaneous biomass production, indicating that wheat detected the competitor and responded physiologically to resource limitation prior to the biomass response. By contrast, the instantaneous N and P capture by uninoculated faba bean remained low throughout the growth period, and plant growth was not significantly affected by competing wheat. However, inoculation substantially enhanced biomass production and N and P acquisition of faba bean. The exudation of citrate and malate acids and acid phosphatase activity were greater in mycorrhizal than in uninoculated faba bean, and rhizosphere pH tended to decrease. We conclude that under N and P limiting conditions, temporal separation of N and P acquisition by competing plant species and enhancement of complementary resource use in the presence of AMF might be attributable to the competitive co-existence of faba bean and wheat.

A Cr(VI)-reducing Microbacterium sp. strain SUCR140 enhances growth and yield of Zea mays in Cr(VI) amended soil through reduced chromium toxicity and improves colonization of arbuscular mycorrhizal fungi

Pot culture experiments were conducted in a glasshouse to evaluate the effects of four efficient Cr(VI)-reducing bacterial strains (SUCR44, SUCR140, SUCR186, and SUCR188) isolated from rhizospheric soil, and four arbuscular mycorrhizal fungi (AMF-Glomus mosseae, G. aggregatum, G. fasciculatum, and G. intraradices) alone or in combination, on Zea mays in artificially Cr(VI)-amended soil. Presence of a strain of Microbacterium sp. SUCR140 reduced the chromate toxicity resulting in improved growth and yields of plants compared to control. The bioavailability of Cr(VI) in soil and its uptake by the plant reduced significantly in SUCR140-treated plants; the effects of AMF, however, either alone or in presence of SUCR140 were not significant. On the other hand, presence of AMF significantly restricted the transport of chromium from root to the aerial parts of plants. The populations of AMF chlamydospores in soil and its root colonization improved in presence of SUCR140. This study demonstrates the usefulness of an efficient Cr(VI)-reducing bacterial strain SUCR140 in improving yields probably through reducing toxicity to plants by lowering bioavailability and uptake of Cr(VI) and improving nutrient availability through increased mycorrhizal colonization which also restricted the transport of chromium to the aerial parts.

Detection of buccal perimandibular neurovascularisation associated with accessory foramina using limited cone-beam computed tomography and gross anatomy

To investigate buccal perimandibular neurovascularisation associated with the mandibular accessory buccal foramina (ABF) which were detected using a limited cone-beam computed tomography (limited CBCT). Five Japanese cadaveric mandibles had been examined using helical CT to investigate the presence or absence of ABF. Two mandibles indicating the presence of AMF were examined more minutely using a limited CBCT. Following the three-dimensional radiological observation of ABF, the mandibles were removed from the cadavers and dissected with referring to the findings of AMF on the limited CBCT images. Four ABF of the three mandibular sides, which were depicted with limited CBCT, had different perimandibular neurovascularisation. Three accessory foramina were associated with the following arteries: a branch of the submental, facial, and buccal artery, and one was associated with a branch of the mental nerve. A branch of the mental nerve re-entered the mandible through the accessory foramen after it exited from a mental foramen. Limited CBCT is useful for pre-operative three-dimensional assessment of mandible since high-resolution analysis demonstrates not only the skeletal conditions but also the assessment and suggestions of perimandibular neurovascularisation.

Activation of Leukemia-associated RhoGEF by Gα13 with Significant Conformational Rearrangements in the Interface

The transient protein-protein interactions induced by guanine nucleotide-dependent conformational changes of G proteins play central roles in G protein-coupled receptor-mediated signaling systems. Leukemia-associated RhoGEF (LARG), a guanine nucleotide exchange factor for Rho, contains an RGS homology (RH) domain and Dbl homology/pleckstrin homology (DH/PH) domains and acts both as a GTPase-activating protein (GAP) and an effector for Galpha(13). However, the molecular mechanism of LARG activation upon Galpha(13) binding is not yet well understood. In this study, we analyzed the Galpha(13)-LARG interaction using cellular and biochemical methods, including a surface plasmon resonance (SPR) analysis. The results obtained using various LARG fragments demonstrated that active Galpha(13) interacts with LARG through the RH domain, DH/PH domains, and C-terminal region. However, an alanine substitution at the RH domain contact position in Galpha(13) resulted in a large decrease in affinity. Thermodynamic analysis revealed that binding of Galpha(13) proceeds with a large negative heat capacity change (DeltaCp degrees ), accompanied by a positive entropy change (DeltaS degrees ). These results likely indicate that the binding of Galpha(13) with the RH domain triggers conformational rearrangements between Galpha(13) and LARG burying an exposed hydrophobic surface to create a large complementary interface, which facilitates complex formation through both GAP and effector interfaces, and activates the RhoGEF. We propose that LARG activation is regulated by an induced-fit mechanism through the GAP interface of Galpha(13).

Plant growth stage, fertiliser management and bio-inoculation of arbuscular mycorrhizal fungi and plant growth promoting rhizobacteria affect the rhizobacterial community structure in rain-fed wheat fields

The goal of this study was first to assess the dynamics of the bacterial community during a growing season in three Indian rain-fed wheat fields which differ mainly through their fertilizer management and yield and then to study the effects of PGPR/AMF bio-inoculations on the bacterial community structure and wheat growth. The bacterial community structure of the rhizosphere soil (RS) and the rhizoplane/endorhizosphere (RE) was determined by PCR-denaturing gradient gel electrophoresis. Seed treatments consisted of consortia of two PGPR strains alone or combined with AMF or AMF alone. The PGPR strains were Pseudomonas spp. which included some or all of the following plant growth promoting properties: phosphate solubilisation and production of indole-3-acetic acid, siderophores, 1-aminocyclopropane-1-carboxylate deaminase and diacetyl-phloroglucinol. The mycorrhizal inoculum was an indigenous AMF consortium isolated from the field with the lowest level of fertilization and yield. Variation partitioning analysis of the DGGE data indicated a predominant effect of the wheat growth stage (30.4% of the variance, P=0.001) over the type of field (9.0%, P=0.027) on the bacterial community structure in the RE. The impact of plant age in the RS was less than in the RE and the bacterial community structure of the field with the highest input of fertilization was very different from the low input fields. The bio-inoculants induced a significant modification in the bacterial community structure. In the RS, the bacterial consortia explained 28.3% ( P=0.001) and the presence of AMF 10.6% ( P=0.02) of the variance and the same trend was observed in the RE. Plant yield or grain quality was either increased or remained unaffected. For example, protein content was significantly higher in the treated plants' grain compared to the control plants; maximum values were obtained when the PGPR were co-inoculated with the AMF. The percentage of root colonization by AMF was significantly higher in the treatments containing a mycorrhizal inoculum than in the untreated control and remained unaffected by the PGPR treatments. In conclusion, the wheat rhizobacterial community structure is highly dynamic and influenced by different factors such as the plant's age, the fertilizer input and the type of bio-inoculant. In addition, there is a distance-related effect of the root on the bacterial community. Finally, a combined bio-inoculation of diacetyl-phloroglucinol producing PGPR strains and AMF can synergistically improve the nutritional quality of the grain without negatively affecting mycorrhizal growth.

Plant and arbuscular mycorrhizal fungal diversity – are we looking at the relevant levels of diversity and are we using the right techniques?

Plant and arbuscular mycorrhizal fungal diversity – are we looking at the relevant levels of diversity and are we using the right techniques?

The influence of arbuscular mycorrhizae on the relationship between plant diversity and productivity

Ecological theory predicts a positive and asymptotic relationship between plant diversity and ecosystem productivity based on the ability of more diverse plant communities to use limiting resources more fully. This is supported by recent empirical evidence. Additionally, in natural ecosystems, plant productivity is often a function of the presence and composition of mycorrhizal associations. Yet, the effect of mycorrhizal fungi on the relationship between plant diversity and productivity has not been investigated. We predict that in the presence of AMF, productivity will saturate at lower levels of species richness because AMF increase the ability of plant species to utilize nutrient resources. In this study we manipulated old‐field plant species richness in the presence and absence of two species of AMF. We found that in the absence of AMF, the relationship between plant species richness and productivity is positive and linear. However, in the presence of AMF, the relationship is positive but asymptotic, even though the maximum plant biomass was significantly different between the two AMF treatments. This is consistent with the hypothesis that AMF increase the redundancy of plant species in the productivity of plant communities, and indicates that these symbionts must be considered in future investigations of plant biodiversity and ecosystem function.