Native Arbuscular Mycorrhizal Fungi Communities Research Articles

Native mycorrhizal communities in maize roots as affected by plant genotype, starter fertilization and a seed-applied biostimulant

Background and aimsOne of the most promising strategies for sustainable intensification of crop production involves the utilization of beneficial root-associated microorganisms, such as plant growth-promoting bacteria and arbuscular mycorrhizal fungi (AMF). The aim of this study was to investigate whether a seed-applied biostimulant, based on the bacterial strain Bacillus amyloliquefaciens IT-45 and a plant polysaccharide extract, and crop enhancement tools, such as hybrids with contrasting early vigor and nitrogen (N) plus phosphorus (P) starter fertilization, and their interactions, shape the communities of native root-colonizing AMF symbionts in maize.MethodsA factorial growth chamber experiment was set up with two maize genotypes in natural soil. Mycorrhizal colonization was evaluated after root staining. The diversity and composition of AMF communities were assessed by PCR-DGGE of the 18S rRNA gene and amplicon sequencing.ResultsN and P fertilization determined a consistent reduction of AMF root colonization and, in combination of biostimulant, a reduction of AMF richness. The biostimulant alone generally did not affect AMF colonization or the community biodiversity. In addition the effect of the two factors were modulated by maize genotype. In all treatments, predominant AMF were represented by Glomus sp. and Funneliformis mosseae, while populations of the genus Rhizoglomus were rarely detected in biostimulant and NP fertilization treatments.ConclusionThe results of this study increase our understanding of how the biostimulant seed treatment may affect native AMF communities, depending on NP fertilization and maize genotype and may improve the implementation of innovative tools in sustainable and resilient agroecosystems.

AMF Inoculum Enhances Crop Yields of Zea mays L. 'Chenghai No. 618' and Glycine max L. 'Zhonghuang No. 17' without Disturbing Native Fugal Communities in Coal Mine Dump.

For the agricultural development of dumps, increase in land use efficiency and protection of food security, to verify the safety, efficacy and sustainability of field-applied arbuscular mycorrhizal fungi (AMF) inoculum, and to exclude the risk of potential biological invasion, in this study, we determined the effect of AMF inoculation and intercropping patterns (maize-soybean) on the temporal dynamics of soil parameters, native AMF communities and crop yields. AMF communities were analyzed using Illumina MiSeq. A total of 448 AMF operational taxonomic units (OTUs) belonging to six genera and nine families were identified. AMF inoculation treatment significantly improved the yield of intercropping maize and increased the content of available phosphorus. AMF diversity was significantly influenced by cropping pattern and growth stage, but not by the inoculation treatment. Inoculation altered the AMF community composition in the early growth stage and facilitated a more complex AMF network in the early and late growth stages. These results indicate that AMF inoculation affects native AMF only in the early stage, and its impact on yield may be the consequence of cumulative effects due to the advantages of plant growth and nutrient uptake in the early stage.

Arbuscular Mycorrhizal Fungi Improve Growth and Phosphate Nutrition of Acacia seyal (Delile) under Saline Conditions

Many plant species adapted to semi-arid environments are grown in the Sahelian region in northern Africa. One such species is Acacia seyal (Delile), a multipurpose leguminous tree grown in various agroecological zones, including saline soils. These challenging arid and semi-arid environments harbor a diversity of arbuscular mycorrhizal fungi (AMF) communities that can develop symbiotic associations with plants to improve their hydromineral nutrition. This study compared the effects of native AMF communities isolated from semi-arid sites (high, moderate, and low salinity zones Ndiafate, Ngane, and Bambey, respectively) and the AMF Rhizoglomus aggregatum on the development and phosphate nutrition of A. seyal seedlings subject to three salinity treatments (0, 340, and 680 mM). Plant height, dry matter weight of the shoots and roots, and phosphorus uptake from the soil were measured. Plants inoculated with AMF native species from each site that were provided with up to 340 mM of NaCl had greater shoot height than plants grown under 680 mM salinity. At NaCl concentrations above 340 mM, shoot and root development of A. seyal seedlings diminished. However, dry matter production of shoots (7%) and roots (15%) improved following AMF inoculation compared with the control (respectively 0.020 and 0.07 g for shoots and roots). When inoculated with AMF isolates from the high salinity zone (Ndiafate), phosphate content/nutrition was increased by 10% around 30 days after inoculation compared with non-inoculated seedlings (2.84 mg/kg of substrate). These results demonstrate that native AMF inoculants are capable of helping plants withstand environmental constraints, especially those exposing plants to harsh climatic conditions. We discuss insights on how AMF influences the interplay between soil phosphorus and perceived salinity that may have implications for broader relationships between plants and symbiotic fungi.

Dry-Season Soil and Co-Cultivated Host Plants Enhanced Propagation of Arbuscular Mycorrhizal Fungal Spores from Sand Dune Vegetation in Trap Culture.

The use of arbuscular mycorrhizal fungi (AMF) as biofertilizer in agriculture is a sustainable approach to fertilization. The first step in the production of AMF biofertilizer is inoculation of mycotrophic plants with a composite of soil and native plant roots, containing potentially viable AMF spores from natural habitats, to a trap culture. A single host plant or a consortium of host plants can be used to propagate AMF spores. However, the difference in the comparative efficiency of mono- and co-cultivated host plants used for the production of AMF spores and the maintenance of original AMF community composition has not been well elucidated. Here, we prepared trap culture with nutrient-poor soil from coastal sand dune vegetation collected during the dry season when the AMF spore density and relative abundance of Glomeromycota ITS2 sequences were significantly higher (p = <0.05) than in the wet season. The AMF communities in the soil were mainly composed of Glomus spp. Maize (Zea mays L.) and/or Sorghum (Sorghum bicolor (L.). Moench) were grown in trap cultures in the greenhouse. Our results demonstrated that co-cultivation of the host plants increased the production of AMF spores but, compared to mono-cultivation of host plants, did not better sustain the native AMF community compositions in the coastal sand dune soil. We propose that the co-cultivation of host plants in a trap culture broadens AMF-host plant compatibilities and thus sustains the symbiotic association of the natively diverse AMF. Therefore, the results of this study suggest that further research is needed to confirm whether the co-culturing of more than one host plant is as efficient a strategy as using a monoculture of a single host plant.

Infectividad micorrícica nativa en suelos de la Región Pampeana con cultivo de soja, diferentes historiales y características edáficas

The expansion of soybean crop in Argentina replaced other crops, extensive livestock and forest ecosystems. It’s unclear whether this has altered native microbial communities that could supply ecosystem services, such as arbuscular mycorrhizal fungi (AMF), symbionts of the roots of most higher plants and known to promote host nutrition and growth, and soil sustainability. However, the magnitude of the contribution by the AMFs depends, in part, on maintaining its abundance in the soil and their potential to form mycorrhizae with roots. Our objective was to analyze variations in mycorrhizal infectivity (IMS50) and in spontaneous arbuscular mycorrhizal colonization (AM) of soybean crops cropped at three agricultural sites from the north of the Pampean Region (Córdoba), in relation to the historical land use (Agricultural [soybeans for more than 60 years], Mixed agricultural-livestock [A-G, soybean in the last 35 years], and Sierras [soybean in the last 20 years]). An in vivo bioassay revealed that the highest IMS50 occurred at the Agricultural and Sierras sites, in relation to the Mixed A-G one, the site with the highest available soil P content. Both the IMS50 and AM negatively correlated with soil P, while IMS50 was negatively associated with sand content, and positively with water, carbon and clay content. A high degree of infective potential by native AMF was detected in soils destined for soybean crop at the Pampean Region with different historical land use. The IMS50 was a more sensitive detection method than the determination of AM colonization in the field. It is concluded that IMS 50 could be used to define agricultural management strategies to maintain/favor native AMF communities.

Effects of Dual Symbiotic Interactions Performed by the Exotic Tree Golden Wreath Wattle (Acacia cyanophylla Lindl.) on Soil Fertility in a Costal Sand Dune Ecosystem

The present study aims to evaluate the effects of the exotic shrub Acacia cyanophylla Lindl. on soil fertility by studying 1) its ability to modify the soil physicochemical composition, 2) its contribution to the soil mycorrhizal potential and its impact on the richness and diversity of the arbuscular mycorrhizal fungi (AMF) community in the rhizospheric soil (RS), and finally 3) its atmospheric nitrogen fixation potential. The physicochemical analysis of the RS has shown that soil invasion by A. cyanophylla has a beneficial effect on its fertility; this advantage is demonstrated by the increase of the organic matter and the nutrient contents (N, P, K, Na, Ca) in the RS. Furthermore, the roots of this shrub exhibited broad AMF colonization, which confirms its high mycotrophic aspect. Four differentiated morphotypes of mycorrhizal spores were isolated from the RS of A. cyanophylla by use of the wet sieving method. In addition, the most probable number method showed that A. cyanophylla was capable of dramatically increasing the mycorrhizal potential of the soil. Indeed, more than 1,213 infectious propagules per one hundred grams of soil were detected in the RS of A. cyanophylla. Moreover, A. cyanophylla roots showed a significant presence of nodules indicating an active atmospheric nitrogen fixation. Counting revealed the presence of at least 130 nodules in the root fragments contained in 1 kg of soil. In conclusion, the biological invasion of sand dunes by the exotic shrub A. cyanophylla exhibited beneficial effects on the soil’s chemical composition and functioning, the activity of rhizobacteria in fixing atmospheric nitrogen, and phosphate bioavailability under the action of the native AMF community.

Diversity of Arbuscular Mycorrhizal Fungi in olive orchard soils in arid regions of Southern Tunisia

Arbuscular Mycorrhizal Fungi (AMF) play a fundamental role in the development and survival of plant species in arid regions. The objectives of the present research were (1) to characterize the native AMF communities in olive orchard soils collected from arid regions of southern Tunisia and (2) to study the AMF-host specificity hypothesis. AMF spores were extracted from soil-root samples collected from orchards planted with two indigenous olive cultivars (Chemlali and Zarrazi) and located at three sites (Matmata, Zarzis and Tataouine) along an aridity gradient. First, the abundance of AMF spores was determined; then the AMF spores were grouped into several morpho-types and molecularly characterized by 18S rDNA nested-PCR approach. AMF abundance and diversity varied among cultivars and sites. Olive orchard soil of Zarzis site had the highest spore density (140 spores/100g soil), while the Tataouine site had the lowest density (100 spore/100 g soil). Pooled data of morpho-typing and sequence-driven analyses allowed the identification of 10 AMF taxa with the dominance of Glomeraceae family, represented by Glomus, Rhizophagus and Funneliformis genera, followed by Diversisporaceae family. The less arid site (Matmata) exhibited the highest AMF diversity, while the most arid-site (Tataouine) showed the lowest one. The cultivar Zarrazi displayed a higher ability to associate with AMF than Chemlali. For all analyzed sequences, five AMF taxa were associated with Chemlali and eight were associated with Zarrazi.

Indigenous arbuscular mycorrhizal fungi play a role in phosphorus depletion in organic manure amended high fertility soil

The species richness and propagule number of arbuscular mycorrhizal fungi (AMF) are high in intensively-managed agricultural soils. Past research has shown that AMF improve crop phosphorus (P) uptake under low soil P conditions, however it is unclear if AMF play a role in high Olsen-P soils. In this study, we investigated whether native fungal benefits exist under high P input field conditions in-situ and contribute to P utilization. We installed in-grow tubes which were sealed with different membrane pore sizes (30 or 0.45 μm) to allow or prevent AMF hyphae access to the hyphal compartment and prevent cotton roots from penetrating the chamber. We used the depletion of soil available P (Olsen-P) in the hyphae accessed compartment to indicate P uptake by the native AMF community. Our results showed that the native AMF mediated P depletion and microbial biomass P (MBP) turnover and caused the largest Olsen-P depletion ratio and MBP turnover ratio in the high P treatments (Olsen-P: 78.29 mg kg−1). The cotton roots in each fertilization regime were colonized by a unique AMF community and Glomus and Paraglomus were the dominant genera, implying the long-term fertilization regimes domesticated the AMF community. We conclude that native AMF caused the P depletion and P turnover even under high soil Olsen-P conditions.

Host-Specific Effects of Arbuscular Mycorrhizal Fungi on Two Caragana Species in Desert Grassland.

Arbuscular mycorrhizal fungi (AMF), which form symbioses with most land plants, could benefit their hosts and potentially play important roles in revegetation of degraded lands. However, their application in revegetation of desert grasslands still faces challenges and uncertainties due to the unclear specificity of AMF-plant interactions. Here, Caragana korshinskii and Caragana microphylla were inoculated with either conspecific (home) or heterospecific (away) AM fungal communities from the rhizosphere of three common plant species (C. korshinskii, C. microphylla and Hedysarum laeve) in Kubuqi Desert, China. AMF communities of the inocula and their home and away effects on growth and nutrition status of two Caragana species were examined. Results showed that AMF communities of the three inocula from C. korshinskii, H. laeve and C. microphylla were significantly different, and were characterized by high abundance of Diversispora, Archaeospora, and Glomus, respectively. The shoot biomass, photosynthetic rate, foliar N and P contents of C. korshinskii only significantly increased under home AMF inoculation by 167.10%, 73.55%, 9.24%, and 23.87%, respectively. However, no significant effects of AMF on C. microphylla growth were found, regardless of home or away AMF. Positive correlations between C. korshinskii biomass and the abundance of AMF genus Diversispora were found. Our study showed strong home advantage of using native AMF community to enhance C. korshinskii growth in the desert and presented a potentially efficient way to use native AMF in restoration practices.

Native AMF Communities in an Italian Vineyard at Two Different Phenological Stages of Vitis vinifera.

Arbuscular mycorrhizal fungi (AMF) are beneficial soil microorganisms that can establish symbiotic associations with Vitis vinifera roots, resulting in positive effects on grapevine performance, both in terms of water use efficiency, nutrient uptake, and replant success. Grapevine is an important perennial crop cultivated worldwide, especially in Mediterranean countries. In Italy, Piedmont is one of the regions with the longest winemaking tradition. In the present study, we characterized the AMF communities of the soil associated or not with the roots of V. vinifera cv. Pinot Noir cultivated in a vineyard subjected to conventional management using 454 Roche sequencing technology. Samplings were performed at two plant phenological stages (flowering and early fruit development). The AMF community was dominated by members of the family Glomeraceae, with a prevalence of the genus Glomus and the species Rhizophagus intraradices and Rhizophagus irregularis. On the contrary, the genus Archaeospora was the only one belonging to the family Archaeosporaceae. Since different AMF communities occur in the two considered soils, independently from the plant phenological stage, a probable role of V. vinifera in determining the AMF populations associated to its roots has been highlighted.

Tolerance of arbuscular mycorrhizal fungi and microorganisms associated to their hyphosphere to aluminum in soil

Background: The elements that are toxic to arbuscular mycorrhizal fungi (AMF) and soil microorganisms, and the levels at which they affect them, are poorly known.&#x0D; Objective: To quantify the effects of: 1) aluminum added to the soil (0, 50 and 100 mg kg-1) and 2) inoculation with AMF (two isolates without prior exposure to aluminum, Acaulospora delicata and Gigaspora margarita, the native AMF community of a soil contaminated with Al, and a control without AMF) on the development of AMF mycelium and the hyphosphere-associated microbiota.&#x0D; Methods: A system with two compartments was used, a central compartment in which maize was sown and AMF were inoculated and a side compartment without root passage, where only the external mycelium was exposed to the different concentrations of Al. AMF external mycelium exposed to Al was quantified with the fatty-acid biomar-ker 16:1w5.&#x0D; Results and conclusions: Al concentrations up to 100 mg kg-1, controlling the pH of the soil, did not alter mycelium growth of any of the inoculated HMA either in the soil or in the roots. Aluminum added up to 100 mg kg-1 did not have a direct toxic effect on the growth of AMF mycelium and the hyphosphere-associated microbiota.

The effects of field inoculation of arbuscular mycorrhizal fungi through rye donor plants on grapevine performance and soil properties

Grapevines are highly dependent on arbuscular mycorrhizal fungi (AMF) for normal growth and development. However, vineyard soils may have low AMF abundance and diversity due to conventional soil management practices that are detrimental for these fungi. In this context, the establishment of AMF-inoculated cover crops can be a highly convenient strategy to reestablish soil mycorrhizal potential, as it combines the advantages of a vigorous inoculum source coming from mycorrhizal donor plants with the overall benefits of green covers for grape quality, microbial diversity and soil health. In this work, the potential benefits of Funneliformis mosseae-inoculated under-vine cover crops on grapevine growth, physiology and production were compared to those derived from 1) the establishment of non-inoculated under-vine cover crops, and 2) conventional herbicide-based weed control in the under-vine space. In addition, grapevine root AMF community composition was analyzed to assess if the introduction of a non-native AMF species induced changes on resident mycorrhizal community assemblies and to unveil potential variations in AMF diversity associated to herbicide replacement by green covers. Results indicated that under-vine cover crops, inoculated or not, led to a general vigor decrease in grapevines, probably due to competition between the two species. However, after a heat wave that occurred at harvest time in the second year of the experiment, grapevines growing in plots with inoculated cover crops had the highest photochemical reflectance indices and net photosynthesis rates, and partially compensated production losses due to berry sunburn. Root mycorrhizal community analysis by the end of the experiment revealed that the inoculated F. mosseae isolate colonized grapevine roots from inoculated plots, while it was absent in the other ones. Moreover, inoculation of this AMF did not lead to a replacement of native root AMF communities, but allowed further colonization by other resident Glomeraceae and non-Glomeraceae AMF taxa. Overall, the work herein demonstrates that the introduction of F. mosseae through donor plants is a suitable field inoculation method for grapevines and can help them to better withstand heat waves.

Growth, heavy metal uptake, and photosynthesis in 'Paulsen 1103' (Vitis berlandieri x rupestris) grapevine rootstocks inoculated with arbuscular mycorrhizal fungi from vineyard soils with high copper contents

Soils in old vineyards in southern Brazil have high copper accumulation due to fungicide applications over the years, which can affect physiology and growth of young grapevine plants. Arbuscular mycorrhizal fungi (AMF) alleviate toxic effects of metals and increase photosynthesis and plant growth. We evaluated whether inoculation with Rhizophagus clarus (Rh) from a mining area or with a trap-culture-enriched AMF community (Tc) isolated from a high-copper vineyard soil, improved growth and photosynthesis in grapevine rootstocks planted in young ( 60 years) vineyards soils of Vale da Uva Goethe, SC, Brazil. Mycorrhizal colonization was higher in grapevines installed in young vineyard soil than those planted in old vineyard soil. Plants grew more in the old vineyard soil than in the soil from a young vineyard, and that was related to plant nutrient concentration in the soil. In both soils, Tc-inoculated grapevines had higher photosynthetic activity, while those inoculated with R. clarus had higher carbon assimilation. In conclusion, grapevines showed a positive response to AMF inoculation in different soil conditions, and the native AMF community from high copper soils are promising for inoculation of grapevines.

Different sensitivity of a panel of Rhizophagus isolates to AMF-suppressive soils

Suppression of the activity of arbuscular mycorrhizal fungi (AMF) in unsterile soils, as determined by transfer of 33P from soils to plants, has been recently demonstrated, and soils differ in their degree of suppressiveness. The previous experiments included only one R. irregularis isolate, BEG87. The aim of this study was to analyze the sensitivity to suppression of different cultivated AMF isolates as well of native AMF communities using shoot 33P content as a proxy of AMF activity in mesh-enclosed patches of unsterile soil. We found that the suppression of a panel of Rhizophagus isolates differed from the suppression of R. irregularis BEG87. Suppression overall correlated with low soil pH and high soil phosphorus, but there were large differences between the isolates. Some Rhizophagus isolates were less sensitive to soil suppression than BEG87, and tolerance to suppression may be a relevant property to consider when choosing future AMF inoculants. For native AMF communities showing high root colonization, we found one example of a community that was not suppressed by its ‘home’ soil, while BEG87 activity in that soil was completely suppressed. Hence, some AMF communities appear to be reservoirs for inoculants with high tolerance towards suppression.

Arbuscular mycorrhizal fungi communities associated with wild plants in a coastal ecosystem

Arbuscular mycorrhizal fungi (AMF) form a near-ubiquitous mutualistic association with roots to help plants withstand harsh environments, and play a key role in the establishment of coastal beach plant communities. Yet little is known about the structure and composition of AMF communities on coastal beaches of eastern China. In this study, we investigated the occurrence, community composition and diversity of AMF associated with common wild plants on a coastal beach of North Jiangsu, China. Almost all of the local wild species were colonized by AMF except for Chenopodium album L. Thirty-seven AMF species were isolated from the rhizosphere belonging to 12 genera in seven families. Glomus was the dominant genus and Funneliformis mosseae the dominant species. The colonization, spore composition and diversity of AMF were strongly related to edaphic factors. Sodium (Na+) ions in the soil significantly and negatively affected the colonization rate by AMF and both soil Na+ levels and pH had a significant negative effect on AMF spore density and evenness. However, there was a significant positive correlation between species richness and total organic carbon. The results provide insights into soil factors affecting native AMF communities in coastal beach habitats which could benefit vegetation recovery and soil reclamation efforts.

Small-scale soil heterogeneity affects the distribution of arbuscular mycorrhizal fungal species in a hot-spot field in a Mediterranean site

Arbuscular mycorrhizal fungi (AMF) establish mutualistic symbioses with the roots of most plant species, playing a key role in crop productivity and ecosystem functioning. The characterization of local AMF genotypes assemblages is a prerequisite for the reproduction, both ex situ and on farm, of efficient native AMF communities, in order to improve soil quality and fertility through agricultural management and to use selected AMF as inoculants in sustainable agriculture. Contrasting evidences have been found by studies addressing the influence of different environmental drivers, among which geographical distance, on the diversity and composition of AMF communities in agricultural soils.In the present study, a Mediterranean “hot-spot” of AMF species richness was studied to assess whether AMF display a spatial structure at a local scale and whether their spore distribution is affected by soil variables. AMF distribution patterns were estimated by spore analysis, in 12 field plots, which were characterized for their chemical and physical variables. Plots were distributed along a transect across the field, and sampling points distances ranged from 4 to 102 m. While most taxa displayed an aggregated distribution, no significant spatial correlation was detected among AMF communities. On the contrary, AMF communities were significantly correlated with the entire set of soil variables, and with distinct soil characteristics, such as pH and total N, but not P. Among the most abundant taxa, Funneliformis geosporus, Septoglomus constrictum, Funneliformis mosseae, Ambispora granatensis and Glomus badium, were positively affected by total N, and Paraglomus occultum negatively affected by pH. Multiple regression analysis revealed that distribution of most AMF species was significantly related to nitrogen, clay, cation exchange capacity and pH. Multivariate (RDA) analysis confirmed results of multiple regression, with the best model selecting three soil variables (N, clay and pH). Variance partitioning analysis also showed that AMF distribution was mostly explained by environmental variables (36.4%) and by environmental variables spatial structure (16.4%). Overall, the results of this work revealed the importance of soil variables in shaping AMF community composition and spatial heterogeneity, within a site characterized by high AMF richness.

Field performance of different maize varieties in growth cores at natural and reduced mycorrhizal colonization: yield gains and possible fertilizer savings in relation to phosphorus application

The benefits of arbuscular mycorrhizal fungi (AMF) on yield and phosphorus (P) uptake of crops have commonly been studied by inoculating a single mycorrhizal fungal species in pot experiments. Yet, how the native AMF community affects the performance of different maize varieties under field conditions remains obscure. In-growth cores with and without rotation were used in three soils that differed in P application to assess shoot biomass, P uptake, and mycorrhizal colonization of three maize varietal groups, encompassing four inbred lines, 12 hybrids, and four landraces. Rotating cores drastically reduced mycorrhizal colonization, biomass and P uptake for each varietal group at every P level. Performance of plants at natural mycorrhizal colonization at 30 kg P ha−1 was equal to that of reduced-mycorrhizal plants at 60 kg P ha−1, suggesting the potential for adequate mycorrhizal management to save P fertilizer. There were no significant differences between varietal groups for mycorrhizal responsiveness, confirming that the ability to associate with and benefit from AMF has been maintained in modern breeding. Mycorrhizal plants both exhibited higher P acquisition efficiency and higher P use efficiency than reduced-mycorrhizal plants. Disadvantages of in-growth cores should be duly considered.

Field evidence for maize-mycorrhiza interactions in agroecosystems with low and high P soils under mineral and organic fertilization

Plant growth promotion traits of arbuscular mycorrhizal fungi (AMF) are well-known, though documented mainly under controlled greenhouse conditions with little evidence from field experiments. Here we examined the contribution of native AMF communities to maize growth in two field experiments in luvisols with low and high P bioavailability and various mineral (without, NK, NPK) and organic fertilization schemes (without and with Bokashi (fermented soil amendment)). In the first experiment, maize was grown in field mesocosms with high P soil using soil sterilization to obtain non-mycorrhiza control treatments. In the second experiment, maize was grown in a low P soil in the same geographic region as in the first experiment, but now with the fungicide Benomyl (carbendazim) as a non-mycorrhiza control treatment. Main results show that eradicating AMF and other soil microbiota in the high P soil increased plant growth, resulting in a negative mycorrhiza growth response most strongly expressed in the absence of fertilization. In the low P soil experiment, positive mycorrhiza growth responses were observed in the vegetative growth phase, but this trend did not translate into increased yields. In conclusion, under the experimental conditions employed in the present field study in luvisols with low and high P bioavailability, in general the mycorrhiza growth response in the vegetative maize growth phase was respectively positive and negative. Our results confirm that soil P bioavailability determines mycorrhiza growth response in maize, which should be considered when managing AMF in maize agroecosystems.

Fungal Facilitation in Rangelands: Do Arbuscular Mycorrhizal Fungi Mediate Resilience and Resistance in Sagebrush Steppe?

Arbuscular mycorrhizal fungi (AMF) may exert profound influences on ecosystem resilience and invasion resistance in rangelands. Maintenance of plant community structure through ecological feedback mechanisms such as facilitation of nutrient cycling and uptake by host plants, physical and chemical contributions to soil structural stability, and mediation of plant competition suggest AMF may be important facilitators in stressful arid environments. Plant-AMF interactions could influence succession by increasing native plant community resilience to drought, grazing, and fire and resistance to exotic plant invasion. However, invasive exotic plants may benefit from associations with, as well as alter, native AMF communities. Furthermore, questions remain on the role of AMF in stressful environments, specifically the mycorrhizal dependency of sagebrush (Artemisia spp.) steppe plant species. Here, we review scientific literature relevant to AMF in rangelands, with specific focus on impacts of land management, disturbance, and invasion on AMF communities in sagebrush steppe. We highlight the nature of AMF ecology as it relates to rangelands and discuss the methods used to measure mycorrhizal responsiveness. Our review found compelling evidence that AMF mediation of resilience to disturbance and resistance to invasion varies with plant and fungal community composition, including plant mycorrhizal host status, plant functional guild, and physiological adaptations to disturbance in both plants and fungi. We conclude by outlining a framework to advance knowledge of AMF in rangeland invasion ecology. Understanding the role of AMF in semiarid sagebrush steppe ecosystems will likely require multiple study approaches due to the highly variable nature of plant-AMF interactions, the complex mechanisms of resilience conference, and the unknown thresholds for responses to environmental stressors. This may require shifting away from the plant biomass paradigm of assessing mycorrhizal benefits in order to obtain a more holistic view of plant dependency on AMF, or lack thereof, in sagebrush steppe and other semiarid ecosystems.

Temporal and spatial variation of arbuscular mycorrhizal fungi under the canopy of Hedysarum scoparium in the northern desert, China

Despite the evident importance of arbuscular mycorrhizal fungi (AMF) associated with the root system of plants inhabiting desert regions, limit is known about the distribution and activity of AMF in desert ecosystems. Accordingly, AMF diversity, community composition and glomalin were investigated in the northern desert of China. Soil samples from 0 to 30 cm in depth over seven plots were collected under the canopy of Hedysarum scoparium in July of 2015 and 2016. A total of 51 molecular operational taxonomic units (OTUs) were identified by MiSeq sequencing based on small subunit (SSU) ribosomal RNA genes, and Diversispora celata and Diversispora trimurales were discovered for the first time in a desert ecosystem in China. The abundant genera included Glomus (56.4%), Diversispora (25.1%), Claroideoglomus (6.0%), Funneliformis (6.1%) and Paraglomus (5.5%). Archaeospora and Scutellospora sequences represented <1.0% of total sequences. AMF community composition and diversity and two Bradford-reactive soil protein (BRSP) assays were significantly different among the seven studied plots and sampling times. Moreover, AMF diversity and richness tended to increase first and then decrease as the precipitation decreased in the barren sandy grey desert and aeolian sandy soil. Correlation coefficient analysis demonstrated that the Shannon-Wiener index was significantly and positively correlated with acid phosphatase (P < 0.05) and precipitation (P < 0.01) and was significantly and negatively correlated with soil pH (P < 0.01). The richness of AMF was significantly and positively correlated with precipitation (P < 0.01) and negatively correlated with soil organic carbon (SOC) (P < 0.05) and soil pH (P < 0.01). The BRSP fractions were also significantly and positively correlated with edaphic factors (e.g., soil moisture, soil organic carbon) and soil enzymes (e.g., soil acid and alkaline phosphatase). The means of total BRSP and easily extractable BRSP were 5.86 mg·g−1 and 1.90 mg·g−1, respectively. The levels of BRSP in the desert soil were slightly lower than those in native and arable soils, but the ratios of BRSP to SOC were much higher than in farmland soils. Our findings provide insights into important factors affecting the native AMF community and glomalin in the northern desert of China and suggest that AMF diversity and glomalin might be useful for monitoring desertification and soil degradation.