Mixed Arbuscular Mycorrhizal Fungi Research Articles

Inoculation with arbuscular mycorrhizal fungi improves plant biomass and nitrogen and phosphorus nutrients: a meta-analysis

Arbuscular mycorrhizal fungi (AMF) have profound effects on plant growth and nitrogen (N) and phosphorus (P) nutrition. However, a comprehensive evaluation of how plant N and P respond to AMF inoculation is still unavailable. Here, we complied data from 187 original researches and carried out a meta-analysis to assess the effects of AMF inoculation on plant growth and N and P nutrition. We observe overall positive effects of AMF inoculation on plant performance. The mean increases of plant biomass, N concentration, P concentration, N and P uptake of whole plant are 47%, 16%, 27%, 67%, and 105%, respectively. AMF inoculation induces more increases in plant concentrations and storage of P than N. Plant responses to AMF inoculation are substantially higher with single AMF species than with mixed AMF species, in laboratory experiments than in field experiments, and in legumes than in non-legumes. The response ratios of plant N and P nutrition are positively correlated with AMF colonization rate, N addition, P addition, and water condition, while unvaried with experiment duration. The biggest and smallest effect sizes of AMF inoculation on plant performance are observed in the application of nitrate and ammonium, respectively. Accordingly, this meta-analysis study clearly suggests that AMF inoculation improves both plant N and P nutrients and systematically clarifies the variation patterns in AMF effects with various biotic and abiotic factors. These findings highlight the important role of AMF inoculation in enhancing plant N and P resource acquisitions and provide useful references for evaluating the AMF functions under the future global changes.

Effects of organic contaminants on arbuscular mycorrhiza formation: A meta-analysis

Arbuscular mycorrhizal fungi (AMF) function mostly depends on their colonization to roots. However, it has not been systematically clear how arbuscular mycorrhiza (AM) formation is affected by organic contaminants. In this study, a meta-analysis was performed to estimate the effects of three groups of organic contaminants (polycyclic aromatic hydrocarbons (PAHs), crude oil, and pesticide) in soil on mycorrhizal colonization rates (MCRs) from various moderators, such as AMF (genus, species, and inoculation mode), contaminant (level, type, and source), and experimental conditions (plant type, duration, and soil sterilization). Our results showed that all MCRs (total, vesicular, arbuscular and hyphal) significantly decreased under the stresses of three contaminants. Generally, pesticide caused larger decrease in all MCRs than PAHs and crude soil except for vesicular MCRs. Mixed AMF showed larger decrease in the total and vesicular MCRs than single AM fungus, but contrary trends in the arbuscular and hyphal MCRs. Moreover, man-made contaminant seemed to produce larger negative effects on the total, vesicular, and arbuscular MCRs than industry contaminant. The inhibitive effects of three contaminants on the total and vesicular MCRs increased with increasing experimental duration, and were larger in the non-sterilized soil than in the sterilized soil. Hyphal and spore growth were also inhibited by three contaminants in most cases. Hyphal length and spore number of single AM fungus were lower than those of mixed AMF, and pesticide produced larger inhibition on the hyphal length and spore number than PAHs and crude oil. Similar trend was found in the non-sterilized soil relative to the sterilized soil. This study indicated that AM formation and AM structure were negatively affected by three organic contaminants, whereas the inhibitive degrees varied with AMF, organic contaminant and experimental conditions.

Positive Changes in Fruit Quality, Leaf Antioxidant Defense System, and Soil Fertility of Beni-Madonna Tangor Citrus (Citrus nanko × C. amakusa) after Field AMF Inoculation

Citrus plants rely heavily on arbuscular mycorrhizal fungi (AMF) due to their lack of root hairs. Most experiments have been conducted with AMF inoculation under potted conditions, while field inoculation of AMF on citrus, especially a high economic hybrid tangor variety Beni-Madonna (Citrus nanko × C. amakusa), has been rarely recorded. This study aimed to analyze the effects of two AMF inoculations (a single Funneliformis mosseae and a mixture of F. mosseae, Diversispora versiformis, and Rhizophagus intraradices) on the internal and external fruit quality, leaf antioxidant defense system, and soil fertility and structure of top-worked Beni-Madonna tangor citrus trees. Three and a half years after AMF inoculations, soil hyphal length and root mycorrhizal colonization rate increased by 61.2–101.8% and 15.85–29.6% in inoculated plants, respectively. Inoculated trees had higher external fruit coloration value, fruit horizontal diameter, and fruit weight, and lower fruit rigidity than uninoculated trees. AMF-inoculated trees had higher glucose levels of fruit peels, fructose and sucrose levels of fruit fleshes, and the ratio of fruit soluble solids/titratable acids, as well as lower titratable acids concentrations than non-AMF-inoculated trees. AMF inoculation significantly increased leaf nitrogen balance index, chlorophyll index, peroxidase, catalase, superoxide dismutase, and glutathione reductase activities, as well as reduced glutathione and oxidized glutathione concentrations, resulting in lower hydrogen peroxide and malondialdehyde levels when compared to the uninoculated treatment. In addition, inoculated trees presented higher soil nutrient levels, including organic carbon, available K, and Olsen-P as, well as soil aggregate stability (based on mean weight diameter) than uninoculated trees. This study concluded that field AMF inoculation improved fruit quality, enhanced leaf antioxidant defense system, and improved soil fertility of Beni-Madonna trees, with mixed AMF being prominent in improving fruit quality and F. mosseae being prominent in enhancing leaf antioxidant defense system and improving soil fertility.

Linking soil health to human health: Arbuscular mycorrhizae play a key role in plant uptake of the antioxidant ergothioneine from soils

Societal Impact StatementEvidence has emerged that the antioxidant ergothioneine may be important in preventing many inflammatory diseases in humans. However, ergothioneine is not produced by humans or plants and is only made by fungi and some bacteria in soils. As such, humans get ergothioneine from eating fungi (mushrooms) or plants that take it up from the soil. In this study, we found that growing plants with beneficial fungi called arbuscular mycorrhizal fungi increased the amount of ergothioneine in plant tissues. This suggests that promoting agricultural practices that maintain healthy populations of beneficial soil fungi may improve the nutritional quality of crops.Summary The amino acid ergothioneine (ERGO) has recently gained attention as an antioxidant that benefits human health. ERGO is produced by fungi and mycobacteria in soils and is acquired only from diet. The mechanism by which ERGO is transferred from soil to plant is unknown. Recent work has shown that tillage reduces the amount of ERGO in crops. As tillage also reduces arbuscular mycorrhizal fungi (AMF) populations, we examined the relationship between AMF and plant ERGO uptake. We grew asparagus, black beans, wheat, and oats with a variety of single and mixed species AMF inocula and compared ERGO levels of these plants to plants that were uninoculated. Mycorrhizal inoculation enhanced ERGO content across all plants. There was a positive correlation between AMF colonization level and plant ERGO content. AMF appear to be important mediators of plant ERGO uptake. Future research is needed to identify the mechanism that leads to higher ERGO in plants colonized by AMF in order to promote farming practices that enhance AMF populations and increase crop ERGO concentration in field settings.

Impacts of Drought Stress and Mycorrhizal Inoculation on the Performance of Two Spring Wheat Cultivars.

Cereal production is becoming challenging, given ongoing climate change. Arbuscular mycorrhizal fungi (AMF) are discussed to mitigate effects of drought for plants and enhance nutrient uptake. Thus, we investigated the impacts of drought and mycorrhiza on the growth and allocation patterns of two cultivars of spring wheat (Triticum aestivum). Plants were grown under three irrigation regimes (well-watered, continuous or pulsed drought) and in three substrates (absence or presence of one or three AMF species). Applied water use efficiency (WUEapplied), harvest index (HI) and contents of carbon (C), nitrogen (N) and phosphorous (P) were determined when grains were watery ripe. When grains were hard, again, WUEapplied, HI and the thousand-kernel weight were measured. The WUEapplied and HI were lowest in plants under pulsed drought stress at the second harvest, while the thousand-kernel weight was lower in mycorrhized compared to non-mycorrhized plants. The C/N ratio dropped with increasing drought stress but was enhanced by mycorrhiza, while the P content was surprisingly unaffected by mycorrhiza. The total root length colonization was higher in substrates with the AMF mix, but overall, fungal presence could not alleviate the effects of drought. Our results highlight the complexity of responses to challenging environments in this highly domesticated species.

Soil of the parent plant and AMF mix improve Cerrado’s seedlings growth in forest nurseries

The soil microbiota plays an extremely important role in the growth and survival of plants. The presence of some microorganisms can positively and significantly impact the growth of tree species, which can improve the performance of seedlings after planting for commercial purposes and/or for ecosystem restoration. The present study aimed to evaluate the initial growth of seedlings of Hancornia speciosa and Brosimum gaudichaudii associated with microorganisms from the soil of the parent tree and/or inoculated with arbuscular mycorrhizal fungi (AMF). Four substrates were tested: T1 (control) = Autoclaved dystrophic Red-Yellow Latosol (Aut-dRYL) + autoclaved commercial substrate (Aut-CS); T2 = Aut-dRYL + Aut-CS + inoculum of AMF (Mix); T3 = Aut-dRYL + Aut-CS + soil of the parent plant (SPP); and T4 = Aut-dRYL + Aut-CS + SPP + Mix. The AMF inoculum comprised a mix of the species Gigaspora decipiens, Rhizophagus clarus, and Scutellospora heterogama. Seedling growth was determined 270-350 days after transplanting by measuring the following parameters: mycorrhizal colonization rate (MC), abundance of spores (AS), height (H), stem diameter (D), H/D ratio, volume of roots (VR), dry matter of shoot (SDM), roots (RDM), total (TDM), shoot / root dry matter ratio (SDM/RDM), height / shoot dry matter ratio (H/SDM), and Dickson quality index (DQI). The results showed that the addition of SPP improved the growth and DQI of the seedlings, while the AMF mix minimally changed both growth and DQI. The use of symbiotic microorganisms in the nursery in Brazil is scarse due to the difficulty of acquiring these microorganisms and the lack of commercialization of specific isolates for species native to the Cerrado biome. The present study evaluated the use of soil from naturally occurring areas as a source of inoculum. The higher growth and biomass production of inoculated plants support the use of SPP as a form of inoculum and/or inoculation with native AMF to produce seedlings of H. speciosa and B. gaudichaudii.

Effect of single and mixed inoculation of arbuscular mycorrhizal fungi and phosphorus fertilizer application on corn growth in calcareous soil

Abstract. Ishaq L, Adu Tae ASJ, Airthur MA, Bako PO. 2021. Effect of single and mixed inoculation of arbuscular mycorrhizal fungi and phosphorus fertilizer application on corn growth in calcareous soil. Biodiversitas 22: 1920-1926. Low availability of soil phosphorus (P) in calcareous soil in West Timor has become a constraint in improving plant productivity. A field experiment was carried out in the calcareous soil to investigate the effect of single and mixed indigenous arbuscular mycorrhizal fungi (AMF) inoculation and P fertilizer application on growth and yield of corn in Kupang District, East Nusa Tenggara Timur Province, Indonesia. The experiment was laid out in a split-plot design consisting of indigenous AMF inoculation as the main plots and inorganic P fertilizer rates as the sub-plot treatments. The main plot treatments were: without AMF inoculation (M0), inoculated with single AMF inoculum (M1) and inoculated with mixed AMF inocula (M2). Sub-plots consisted of four P rates namely 25% (P1), 50% (P2), 75% (P3) and 100% (P4) of the recommended inorganic superphosphate dose of 200 kg SP36 ha-1. The results showed that there were significant interactions between AMF inoculation and P fertilizer dose on AMF spore density, AMF colonization and soil available P. Results indicated a strong correlation between AMF colonization and soil available P. Inoculation of both M1 and M2 significantly increased soil available P, plant growth and yield compared to the uninoculated plant. Spore production in the two AM responded differently to P fertilizer. Low doses of inorganic P fertilizer favored spore production in M1, whereas P fertilizer sporulation in M2 was adversely affected. The percentage of AMF root colonization of M1 and M2 decreased with an increase in P fertilizer applied. Further studies need to be conducted to evaluate the effectiveness of indigenous AMF in improving plant yield at low level of inorganic fertilizer application to achieve more sustainable agricultural practice in the region.

Nutrient acquisition and fruit quality of Ponkan mandarin in response to AMF inoculation

Arbuscular mycorrhizal fungi (AMF) inhabited in citrus rhizosphere playing multiple roles in plant growth, nutrient acquisition, and stress tolerance are well known under potted conditions. However, information regarding response of AMF application in field citrus trees is scarce. In this study, single inoculation of Funneliformis mosseae and mixture of Diversispora versiformis, F. mosseae, and Rhizoglomus intraradices into the rhizosphere were compared with non-inoculated (control) three-yr-old Citrus reticulata Blanco var. Ponkan cv. Jinshuigan grafted on trifoliate orange grown under open field condition. After eight months of inoculation, root mycorrhiza colonization and soil hyphal length varied respectively from 43% to 56% and from 3.66 to 5.57 cm/g soil and also 1.7-2.2 times and 13.1-19.9 times higher in AM-treated trees than non-inoculated trees. Two AMF treatments collectively increased root P, K, Cu, Zn, and Mn concentrations, sarcocarp P, Mn, and Fe concentrations, peer coloration value, and fruit diameter longitudinal axis, as well as root vitality by 36%-76%. In addition, single F. mosseae inoculation dramatically increased juice soluble solid content and sarcocarp Zn concentrations than non-AMF treatment; mixed-AMF inoculation considerably increased single fruit weight and sarcocarp K and B contents. On the whole, these beneficial effects were superior under mixed AMF treatment than under single AMF treatment. Our study, hence, suggested that mixed culture of AMF inoculation, played an important role in quality production of Pokan mandarin as a viable biofertilizer use option.

Arbuscular mycorrhizal fungi (AMF) influences growth and insect community dynamics in Sorghum-sudangrass (Sorghum x drummondii)

Beneficial plant–microbe interactions in the rhizosphere have been found to enhance plant growth and development. Arbuscular mycorrhizal fungi (AMF), a major group among these microbes, have been found to improve plant fitness through mycorrhizal symbiosis. Despite being well documented in various natural and domesticated study systems, few studies have examined whether AMF also has cascading effects on other traits, such as influencing insect community dynamics through attraction/repulsion of beneficial and harmful insects. To test this, we planted Sorghum-sudangrass (Sorghum x drummondii), a fast-growing annual grain/forage crop, either inoculated with commercial AMF mix or left as control in lab and field experiments. We hypothesized that AMF would enhance plant growth and influence the recruitment of insect herbivores and their natural enemies due to possible alterations in plant defense pathways. Our results suggest that while AMF-inoculated plants had significantly better germination, growth, and establishment; they also experienced a lower initial incidence of Spodoptera frugiperda, a major herbivore on Sorghum in the Lower Rio Grande Valley. In addition, our insect community trapping experiment revealed that AMF-inoculated plants attracted significantly more beneficial insects (predators and parasitoids) and a lower number of damaging herbivores. Taken together, our field and lab data show that AMF can not only positively influence plant growth traits but can also provide defenses against herbivores by selectively attracting beneficial insects and repelling herbivores, with implications for sustainable pest management strategies.

Evaluation of the Mixed Effects of Some Indigenous Strains of Arbuscular Mycorrhizal Fungi on the Growth of Maize Seedlings Under Greenhouse Conditions

The objective of the study was to evaluate the joint effects of three groups of native arbuscular mycorrhizal fungi (AMF) (Glomeraceae, and Diversisporaceae) on the growth of Maize Seedlings. The mycorrhizal fungi were isolated by the wet sieving method through decreasing sieve (300 µm, 125 µm, 63 µm and 38 µm) followed by centrifugation on a sucrose gradient. The growth tests were evaluated in greenhouse conditions for 40 days. After opening a planting hole, two maize (2000 SYNEE-W) seeds, one coated with AMF and the other not coated (Control) were introduced into the planting hole for each treatment. Data on different parameters were evaluated. The results of this study revealed that the maximum heights, the largest noose diameters and the largest numbers of leaves were obtained with treatment Acaulosporaceae + 50% NPK-Urea having 20.55% and 17.04% respectively and 11.77% for that of the control. The produced biomass and the leaf area of the maize plants were improved by the treatment Glomeraceae+ 50NPK-Urea with a respective increase of 54.97% for fresh above biomass (FAB), 42.94% for fresh underground biomass (FUB) and 55.23% for the leaf area compared with the control. Also, very high frequency of mycorrhiza was recorded with treatment Glomeraceae while the largest numbers of mycorrhiza spores and intensity were recorded with treatment Acaulosporaceae. These results augur the possibility of using these mixed AMF bio-products as organic fertilizers to improve maize productivity in Benin.

The role of inoculum identity for growth, photosynthesis, and chlorophyll fluorescence of zinnia plants by arbuscular mycorrhizal fungi under varying water regimes

This experiment aimed to determine effects of three arbuscular mycorrhizal fungi (AMF), i.e., Rhizophagus irregularis, Rhizophagus intraradices, and Funneliformis mosseae, either singly or their mix inoculation on dry mass, photosynthesis, chlorophyll (Chl) fluorescence, leaf pigment contents, and water-use efficiency (WUE) in Zinnia elegans (var. Magellan Red) plants under different water regimes (WR). The greenhouse experiment was performed under a complete randomized design at four different WR [100% of field capacity (FC) as control, 80, 60, and 40% FC]. Our results suggested that arbuscular mycorrhizal symbiosis protected zinnia plants against WR through improving gas-exchange capacity, higher Chl and carotenoid concentrations, Chl fluorescence, and WUE. Regardless of WR, comparison of colonization percentage demonstrated that the highest colonization was recorded for mixed AMF, while mixed inoculation was not so effective for the growth promotion as the corresponding single inoculation.

Arbuscular Mycorrhizal Fungi in the Phytostabilization of Soil Degraded by Manganese Mining

Mining and processing of manganese (Mn) minerals are activities that may result in the generation of large amounts of wastes and serious environmental impacts. Several strategies have been employed to remediate areas with high Mn concentrations, but many of them imply high investments and high risk of secondary pollution. This study aimed to evaluate the phytostabilization potential of Mimosa caesalpiniaefolia Benth. in Mn mining soil influenced by inoculation with arbuscular mycorrhizal fungi (AMF). The experimental design was completely randomized, with four treatments [not inoculated (control), inoculated with Rhizophagus clarus; inoculated with Claroideoglomus etunicatum and inoculated with Rhizophagus clarus + Claroideoglomus etunicatum (Mix)], and four replicates. Inoculation with Mix and C. etunicatum had higher efficiency in protecting plants against excess Mn, due to the greater retention of this element in the roots and lower translocation to the shoots. Inoculation with R. clarus did not influence plant development and reduction of Mn contents in the shoots. The association of the AMF Mix and C. etunicatum with the species Mimosa caesalpiniaefolia Benth. enhances Mn phytostabilization in mining soils with high concentration of this element. The use of multivariate analyses proved to be an important tool with respect to the behavior of biometric, chemical and microbiological variables in mining soil with high Mn concentration.

Arbuscular mycorrhizal fungi and sewage sludge enhance growth and adaptation of Metrosideros laurifolia on ultramafic soil in New Caledonia: A field experiment

The ecological restauration of nickel mining-degraded areas in New Caledonia is strongly limited by soil mineral nutrient deficiencies, heavy metal toxicity and slow growth rate of the native plant species. The improvement of revegetation technics needs multidisciplinary knowledge. A field experiment with relocated topsoil was assessed to test plant inoculation with a mix of three selected arbuscular mycorrhizal fungi (AMF) combined with sewage sludge amendment of the soil. Metrosideros laurifolia seedlings, an endemic Myrtaceae, were inoculated with the mixed AMF isolates and grown in a nursery for 18 months before being planted. 528 days after plantation, the dry weight of inoculated plants was 4 times higher than non-inoculated ones. AMF inoculated plants growing in sewage sludge amended soil showed a dry weight more than seven times higher than control plants. These differences were positively correlated with mycorrhizal colonization. However at this stage, AMF inoculated isolates were reduced in roots of M. laurifolia and replaced by several AMF indigenous species. This AMF diversity was higher in inoculated plants and in non-amended plots. Inoculated plants were characterized by a better mineral nutrition, a higher Ca/Mg ratio and a lower heavy metal translocation. In conclusion, this study showed that AMF inoculation combined with sewage sludge amendment of soil can improve ecological restoration of ultramafic mine-degraded areas.

Arbuscular mycorrhizal fungi improve the growth and drought tolerance of Zenia insignis seedlings under drought stress

Drought is one of the most critical limiting environmental factors for plant survival and restoration in areas of rocky desertification in southwestern China. Here, we aimed to understand how arbuscular mycorrhizal fungi (AMF) affect the growth and drought tolerance of tree species used for afforestation, with the ultimate aim of using them to restore degraded karst ecosystems. A pot experiment was conducted in which Zenia insignis seedlings were inoculated separately with three AMF (Funneliformis mosseae, Rhizoglomus intraradices, and Diversispora versiformis) and a mixture of all three species under two water regimes (drought stress and normal water) in a greenhouse. The results showed that AMF have a positive effect on plant biomass, osmolytes, and antioxidant enzyme activity under drought conditions. Shoot/root biomass increased by 12.5–33.8% and plant height increased by 13.6–32.1% after inoculation with AMF under drought conditions. The phosphorus content of the shoots significantly increased in mycorrhized plants, whereas nitrogen content was minimally affected. Superoxide dismutase and catalase activity was higher under drought stress in mycorrhized plants than in non-mycorrhized plants. The same pattern was found for soluble sugar and proline content in mycorrhized seedings under water deficit conditions. Mixed AMF inoculation had a more beneficial effect on plant growth than single AMF inoculation. In conclusion, our results indicate that AMF inoculation could help restore degraded ecosystems in desertified karst regions.

Short Communication: Growth response and dependency of endangered nedun tree species (Pericopsis mooniana) affected by indigenous Arbuscular Mycorrhizal Fungi inoculation

Husna, Tuheteru FD, Wigati E. 2017. Short Communication: Growth response and dependency of endangered nedun tree species (Pericopsis mooniana) affected by indigenous Arbuscular Mycorrhizal Fungi inoculation. Nusantara Bioscience 9: 57-61. Arbuscular mycorrhizal fungi (AMF) were isolated from the rhizosphere of local nedun tree or kayu kuku (Pericopsis mooniana (Thw.) Thw.) and based on the results of previous studies which showed that inoculation with AMF mix enhanced growth and nutrient uptake of seedlings P. mooniana on ultisol and serpentine soil media. Thus study aimed to determine the effectiveness of indigenous AMF on the growth and dependence of P. mooniana. P. mooniana seedlings were grown on ultisol soil medium and inoculated with and without AMF (Clareodeglomus etunicatum, Glomus sp. (HA), Glomus sp. (KDI)) and mixed (C. etunicatum, Glomus sp. (HA), Glomus sp. (KDI) for 12 weeks under greenhouse conditions. The results showed that inoculation with Glomus sp. (HA) significantly increased plant height, stem diameter, number of leaves, dry weight (roots, shoots, total), nodulation, root length and leaf length. It was better than results on control of P. mooniana seedling but it was not significantly different from other types of AMF, except on Glomus sp. (HA) on plant height. The width of the leaf and shoot-root ratio was not influenced by the AMF. P. mooniana has a high dependency (<75%) with mycorrhizal dependency (MD) value ranging from 54-68%. Glomus sp. (HA) and other types of AMF have potential to be developed to support the conservation of P. mooniana.

Dependency and Response of Apuleia leiocarpa to Inoculation with Different Species of Arbuscular Mycorrhizal Fungi

Inoculation with arbuscular mycorrhizal fungi (AMF) is a strategy to improve the efficiency of forest plantations, reducing costs and increasing the survival of plant species. The objective of this study was to assess the response and mycorrhizal dependency of seedlings of the forest species Apuleia leiocarpa (Vogel) J.F. Macbr to inoculation with AMF. The experiment was conducted in a completely randomized design using a 5 × 5 factorial arrangement with six replications. The treatments consisted of combinations of five P rates (0, 24, 71, 213, and 650 mg kg-1) with five types of inoculations with AMF (inoculation with the fungi Rhizophagus clarus, Gigaspora margarita, Dentiscutata heterogama, inoculation with an AMF mix of these three species, and a treatment without inoculation). The A. leiocarpa showed the highest biomass accumulations in inoculation with D. hetorogama combined with the P rates of 213 and 650 mg kg-1, and in the AMF mix combined with the P rates of 71, 213, and 650 kg-1. Biomass accumulation showed a linear, positive response to inoculation with D. heterogama combined with the different P rates, and a positive square root fit to inoculation with the AMF mix. The plants inoculated with G. margarita had no significant biomass accumulation. The plant species had a positive response to inoculation with R. clarus combined with the lowest P rates; however, it had a negative response to combination with the highest P rate (650 mg kg-1). The relative benefit of inoculation with these fungi was more than 100 % in most treatments, showing the high mycorrhizal dependency of A. leiocarpa and the nutritional benefit of AMF inoculation for this species. However, this response is dependent on the fungus species that colonize the plant roots. The best combination between fungus and P rate was inoculation with the AMF mix combined with the P rate of 71 mg kg-1.

Meta-Analysis of Crop and Weed Growth Responses to Arbuscular Mycorrhizal Fungi: Implications for Integrated Weed Management

Integrated weed management (IWM) relies upon multiple chemical, physical, or biological weed management techniques to achieve an acceptable level of weed control. Agents that selectively suppress weeds but not crops and that can be manipulated in agriculture will be promising components for inclusion in IWM. We used a meta-analytic approach to investigate the potential of arbuscular mycorrhizal fungi (AMF) to contribute to IWM. We quantified the effect of crop and weed host status (strong and weak AMF hosts are divided in this study by a 10% root length colonization threshold), AMF diversity (single vs. mixed), and soil N and P fertility management on plant mycorrhizal growth responses (MGRs). Our results indicated that weak host weeds had consistently lower MGRs than strong host crops in both controlled and field conditions. Moreover, these differences in MGRs between weak host weeds and strong host crops were more pronounced under mixed AMF inoculum and low N and P nutrient availability. In contrast, MGR of strong host weeds was not different from strong host crops in general. However, we observed a wide range of MGRs among strong host weeds, some of which had much lower MGRs than strong host crops. In addition, in the presence of N and P fertilizers, strong host crops had a stronger positive response to AMF than strong host weeds. Thus, our meta-analysis indicates that AMF have potential to contribute to weed control by direct and indirect pathways: directly suppress weak host weeds, and indirectly suppress some strong host weeds mediating by competitive effects exerted by strong host crops. We suggest that management practices affecting AMF diversity and crop and weed mycorrhizal responses could be chosen to improve the contribution of AMF to IWM. Better understanding is needed of crop–weed–AMF interactions and management practices that enhance this form of weed management.

Mycorrhizal Symbiotic Efficiency on C3 and C4 Plants under Salinity Stress - A Meta-Analysis.

A wide range of C3 and C4 plant species could acclimatize and grow under the impact of salinity stress. Symbiotic relationship between plant roots and arbuscular mycorrhizal fungi (AMF) are widespread and are well known to ameliorate the influence of salinity stress on agro-ecosystem. In the present study, we sought to understand the phenomenon of variability on AMF symbiotic relationship on saline stress amelioration in C3 and C4 plants. Thus, the objective was to compare varied mycorrhizal symbiotic relationship between C3 and C4 plants in saline conditions. To accomplish the above mentioned objective, we conducted a random effects models meta-analysis across 60 published studies. An effect size was calculated as the difference in mycorrhizal responses between the AMF inoculated plants and its corresponding control under saline conditions. Responses were compared between (i) identity of AMF species and AMF inoculation, (ii) identity of host plants (C3 vs. C4) and plant functional groups, (iii) soil texture and level of salinity and (iv) experimental condition (greenhouse vs. field). Results indicate that both C3 and C4 plants under saline condition responded positively to AMF inoculation, thereby overcoming the predicted effects of symbiotic efficiency. Although C3 and C4 plants showed positive effects under low (EC < 4 ds/m) and high (>8 ds/m) saline conditions, C3 plants showed significant effects for mycorrhizal inoculation over C4 plants. Among the plant types, C4 annual and perennial plants, C4 herbs and C4 dicot had a significant effect over other counterparts. Between single and mixed AMF inoculants, single inoculants Rhizophagus irregularis had a positive effect on C3 plants whereas Funneliformis mosseae had a positive effect on C4 plants than other species. In all of the observed studies, mycorrhizal inoculation showed positive effects on shoot, root and total biomass, and in nitrogen, phosphorous and potassium (K) uptake. However, it showed negative effects in sodium (Na) uptake in both C3 and C4 plants. This influence, owing to mycorrhizal inoculation, was significantly higher in K uptake in C4 plants. For our analysis, we concluded that AMF-inoculated C4 plants showed more competitive K+ ions uptake than C3 plants. Therefore, maintenance of high cytosolic K+/Na+ ratio is a key feature of plant salt tolerance. Studies on the detailed mechanism for the selective transport of K in C3 and C4 mycorrhizal plants under salt stress is lacking, and this needs to be explored.

Locally adapted arbuscular mycorrhizal fungi improve vigor and resistance to herbivory of native prairie plant species

Soil microbial communities contribute to ecosystem function and structure plant communities, but are altered by anthropogenic disturbance. Successful restoration may require microbial community restoration. Inoculation of plants with arbuscular mycorrhizal fungi (AMF) may improve ecological restoration, but AMF species that are locally adapted to native plant communities are often unavailable and commercially propagated AMF are not necessarily locally adapted to the desired plant community target. The disconnect between readily available commercial fungi and later‐successional plants may inhibit successful establishment of the restoration. We tested this concept using four mid‐ to late successional prairie plant species planted with one of three inoculum sources: a locally adapted AMF mix cultured from native prairie, a non‐locally adapted commercial AMF product, or a sterilized background soil control. The inoculated plants (termed nurse plants) were planted in the middle of field plots. In each plot, uninoculated plants (test plants) were planted at 0.5, 1, and 2 m from the nurse plants in order to test whether growth and survival of test plants could be affected by inoculum source. Generally, plants grew larger when inoculated with native AMF compared to commercial inoculum or the control. Later successional species responded most positively to native AMF. Benefits of inoculation also spread to neighbors, as uninoculated late successional test plant, Sporobolus heterolepis, grew larger when its' neighbors were inoculated with native AMF than with commercial AMF or the control. Due to an unanticipated herbivory event, we also assessed the degree to which rate of herbivory or plant tolerance to herbivory is affected by inoculum source. The mid‐ successional nurse plant, Ratibida pinnata, received the majority of the herbivore damage, and when it was inoculated with commercial AMF, it experienced significantly more herbivory than plants inoculated with native AMF or the control. R. pinnata inoculated with native AMF grew significantly larger one month following herbivory, though there was no significant difference in growth in the second year of sampling. This study suggests that native, locally adapted AMF can improve restoration of prairie plant species and these benefits can extend to neighbors up to two meters from the inoculation point.

Growth and nutritional responses to arbuscular mycorrhizal fungi are dependent on onion genotype and fungal species

Plant roots associate with diverse communities of arbuscular mycorrhizal fungi (AMF), providing the plant with mineral nutrients in exchange for carbohydrates. We investigated how onion genotype and fungal species interact to determine the benefit of the symbiosis to the plant and the potential benefit of a mixed AMF community. Ten onion genotypes were inoculated with five different AMF species, or a mixture of all five, then plant growth/nutrient uptake was compared to non-inoculated controls. 18S ribosomal RNA (rRNA) terminal restriction fragment length polymorphism was used to compare the abundance of each AMF species between genotypes. Growth and nutrient uptake were significantly different between genotypes and AMF species, but no genotype × AMF interaction was observed, indicating a general response to AMF. Potentially useful pre-breeding material was identified for use in low-input systems. Inoculation of plants with AMF led to significant increases in the concentrations of N, P and Cu, whereas significant decreases in Ca, K, Na, Fe, Mn and Zn were observed. There were significant differences between AMF species in their effect on plant nutrition. Inoculation with Acaulospora spinosa led to a significant increase in shoot S concentration which may have implications for plant defence and pungency. No additive effect of a mixed community was observed. Contrasting genotypes showed subtly different preferences for associating with AMF from a mixed community, suggesting a selection process controlled by the plant and/or the fungi. The implications of this work for the development of sustainable, low-input systems are discussed.