Indigenous Arbuscular Mycorrhizal Research Articles

Plant genotype and inoculation with indigenous arbuscular mycorrhizal (AM) fungi modulate wheat productivity and quality of processed products through changes in the frequency of root AM fungal taxa

ContextArbuscular mycorrhizal fungi (AMF) have been extensively applied as biofertilizers in wheat to promote crop productivity. However, variability in AM root colonization, grain yield, and nutrients was observed among wheat genotypes and according to AM genotype and environment. ObjectivesWe hypothesized that wheat response to AM inoculation is more affected by genotype than environment; the response is driven by increases in AM abundance and community structure changes, and not by modification of composition. MethodsWe inoculated an indigenous AM consortium on four old genotypes (Bianco Nostrale, Andriolo, Abbondanza, Sieve) and one modern variety (Bologna) of bread wheat for two years. The effect was evaluated by assessing grain yield, nutrients, and quality of processed products (flour and breadsticks), while the AM abundance and the community composition and structure in roots were characterized, at two plant growth stages, using morphological and molecular tools. ResultsThe functional traits of AMF and plant were better explained by inoculation than by genotype or environment (33 %, 17 %, 4 % of total explained variance), although significant interactions environment x genotype and genotype x inoculation were highlighted. Consistent increases in AM abundance in Sieve and Bologna were associated with positive changes in grain yield and nutrients, supporting the good responsiveness of these genotypes with inoculated AMF, while the plant response of other genotypes was shaped by air temperature and rainfall. However, we did not find significant correlations between changes in AM colonization and mycorrhizal response ratio, with the exception of P and K. After inoculation, AM community composition was similar in all wheat genotypes, but the structure greatly differed among genotypes in interaction with inoculation and plant growth stage. These changes were significantly related to wheat productivity. A Septoglomus taxon, present in the inoculum, was the best predictor of wheat performance. The characterization of the community structure at early crop development and maturity allowed the identification of fast and latest active AM colonizers. Our results showed for the first time that AM inoculation affect the rheological parameters and nutraceuticals of processed products, although the response was modulated by genotype. ConclusionsThe selection of responsive wheat genotypes is fundamental for the positive outcome of inoculation. The positive effects on wheat productivity and field persistence of the inoculated AMF support the use of indigenous consortia that have low impacts on resident AMF. SignificanceOur findings advance the understanding of the facilitative mechanisms that underlie compatibility between AMF and wheat genotypes.

Response of Two True Shallot Seed Varieties to Indigenous Arbuscular Mycorrhizal Fungi Inoculation

Seed availability poses a significant challenge for farmers, and True Shallot Seed (TSS) derived from seeds offers a potential solution to this problem. Currently, farmers primarily rely on bulb seeds for shallot cultivation. Therefore, extensive research on TSS seeds is crucial. This study aimed to investigate the impact of different indigenous FMA isolate types on the growth of various shallot varieties derived from seeds and the root infection of shallot plants. The research was conducted at the Wire House of the Faculty of Agriculture, Andalas University. A completely randomized design with two factors, namely the variety type and FMA dose, was employed, with three replications. The Lokananta and Sanren varieties were used, and the doses of FMA applied were 0, 10, 20, and 30 g/plant. The findings revealed no interaction between the variety type and FMA dose. The Sanren variety outperformed the Lokananta variety in plant height, number of leaves, percentage of root infection, root fresh weight, and root volume. Additionally, the FMA dose of 30 g/plant yielded better results regarding root fresh weight and volume.

Arbuscular mycorrhizal fungi suppress ammonia-oxidizing bacteria but not archaea across agricultural soils

Arbuscular mycorrhizal (AM) fungi are supposedly competing with ammonia-oxidizing microorganisms (AO) for soil nitrogen in form of ammonium. Despite a few studies directly addressing AM fungal and AO interactions, mostly in artificial cultivation substrates, it is not yet clear whether AM fungi can effectively suppress AO in field soils containing complex indigenous microbiomes. To fill this knowledge gap, we conducted compartmentalized pot experiments using four pairs of cropland and grassland soils with varying physicochemical properties. To exclude the interference of roots, a fine nylon mesh was used to separate the rhizosphere and mesh bags, with the latter being filled with unsterile field soils. Inoculation of plants with AM fungus Rhizophagus irregularis LPA9 suppressed AO bacteria (AOB) but not archaea (AOA) in the soils, indicating how soil nitrification could be suppressed by AM fungal presence/activity. In addition, in rhizosphere filled with artificial substrate, AM inoculation did suppress both AOB and AOA, implying more complex interactions between roots, AO, and AM fungi. Besides, we also observed that indigenous AM fungi contained in the field soils eventually did colonize the roots of plants behind the root barrier, and that the extent of such colonization was higher if the soil has previously been taken from cropland than from grassland. Despite this, the effect of experimental AM fungal inoculation on suppression of indigenous AOB in the unsterile field soils did not vanish. It seems that studying processes at a finer temporal scale, using larger buffer zones between rhizosphere and mesh bags, and/or detailed characterization of indigenous AM fungal and AO communities would be needed to uncover further details of the biotic interactions between the AM fungi and indigenous soil AO.

Natural grass coverage enriches arbuscular mycorrhizal fungal communities in subtropical citrus orchards through the regulation of Glomus on a regional scale

Arbuscular mycorrhizal (AM) fungi are ubiquitous soil fungi in orchard ecosystem, conferring a diverse array of benefits to citrus plants. However, how natural grass coverage, a common phenomenon in citrus orchards in southern China, shifts AM fungal communities in subtropical citrus orchards is far from being understood, especially on a regional scale, which impedes the understanding of the indigenous AM fungal adaptations. In this study, natural grass coverage rate, soil chemical properties, and soil AM fungal community in 80 sampling sites spanning 179, 700 km2 area in subtropical citrus orchards were investigated. The result of 18S rRNA gene high-throughput sequencing revealed that a total of eight AM fungal genera were identified and Glomus (90.15 %) was dominant genus in the community in citrus orchards. Natural grass coverage significantly increased soil organic matter (SOM), soil available phosphorus, and AM fungal alpha diversity, especially Glomus. Variation partitioning analysis revealed that grass coverage rate explained more variation in AM fungal alpha diversity than SOM. All the contrasting AM fungal species between different grass coverage rates and all the core AM fungal species belonged to Glomus. Null model analysis revealed that determinism played a slightly larger role in the assembly process of AM fungal communities than stochasticity with a distance-decay relationship. Moreover, natural grass coverage increased the relative importance of stochasticity in the community assembly. Taken together, these results suggest that maintaining natural grass coverage (naturally growing grass) is an effective nature-based solution for enriching AM fungal communities, which is essential for the sustainability of citrus production.

Earthworms facilitated pepper (Capsicum annuum L.) growth via enhancing the population and function of arbuscular mycorrhizal fungi in a low-density polyethylene-contaminated soil

Microplastics (MPs) produced by the decomposition of plastics exist persistently, interfering with soil fertility and plant nutrition. Both arbuscular mycorrhizal (AM) fungi and earthworms are beneficial in terrestrial ecosystems, but their interactions under MPs contamination are unclear so far. Here, the influences of inoculating earthworms (Eisenia fetida) on indigenous AM fungi and pepper (Capsicum annuum L.) growth were investigated in a vegetable soil treated with 0.1% low-density polyethylene (LDPE), while the specific interactions of earthworm and AM fungus (Funneliformis caledonium) under LDPE contamination were further resolved in another experiment using sterilized soil. Inoculation of earthworms shifted soil AM fungal community structure, replacing the predominant genus Glomus by Paraglomus, and increased the abundance, diversity (i.e., Shannon) index, and root colonization rate of AM fungi by 108, 34.6 and 45.0%, respectively. Earthworms also significantly decreased soil pH, and significantly increased soil alkaline phosphatase (ALP) activity, shoot biomass and fruit yield of pepper by 394, 82.8 and 188%, respectively. In the sterilized soil, both E. fetida and F. caledonium improved pepper growth, while the latter noticeably increased phosphorus (P) translocation efficiency from root to shoot, and the combination induced the highest soil ALP activity and pepper fruit yield. Furthermore, the significantly interactive effects between earthworm and AM fungus were observed in soil pH and available P concentration, as well as in shoot P concentration and fruit yield of pepper. This study revealed the interaction between earthworms and AM fungi under MPs contamination conditions for the first time, indicating that earthworms could facilitate vegetable growth via enhancing the propagation and P-promoting function of AM fungi in LDPE-contaminated soils.Graphical

Interaction of rhizobia with native AM fungi shaped biochar effect on soybean growth

While biochar amendment is widely recommended as an excellent agricultural management practice, the biochar effect on the productivity of legume crops with symbiotic microorganisms has been poorly elucidated. Hence, a pot experiment was conducted by growing soybean with or without commercial rhizobia inoculation in an arbuscular mycorrhizal (AM) fungi rich sandy soil amended with wheat straw biochar produced respectively at 350 °C, 450 °C, and 550 °C. We tested the effect of biochar on soybean–rhizobia symbiosis and its impact on plant growth, leaf gas exchange and mycorrhizal colonisation. In brief, rhizobia inoculation, without biochar, increased net photosynthetic rate by 81% and plant total biomass by 44% compared to no inoculation (the control). Without inoculation, amendment of low-temperature biochar (350 ºC) resulted in higher (by 51%) plant biomass than high-temperature (550 °C) biochar. With rhizobia inoculation, low-temperature biochar decreased plant biomass by 9.3% compared to high-temperature biochar. Further, soybean with rhizobia under high-temperature biochar decreased plant biomass by 17% compared to rhizobia inoculation only but increased by 19% compared to the control. Soybean leaf gas exchange capacity and root morphological traits were consistent with plant biomass but symbiotic activity showed small differences among all the treatments. Overall, N-fixing rhizobia could alter the biochar effect on soybean in soil rich in indigenous AM fungi, depending on the pyrolysis temperature of the biochar used. Low-temperature biochar stimulated soybean growth greater than high-temperature biochar, while rhizobia shifted biochar’s positive effect. • Pyrolysis temperature shaped biochar effect on soybean growth with and without rhizobia inoculation in a sandy soil. • Soybean growth without rhizobia inoculation is promoted rather by biochar-350 °C than by biochar-550 °C. • A tradeoff on soybean plant growth between biochar and rhizobia inoculation. • Soil inorganic N correlated with root morphology while leaf gas exchange responded to soil NO 3 - .

Relationship between phosphorus uptake via indigenous arbuscular mycorrhizal fungi and crop response: A 32P-labeling study

Arbuscular mycorrhizal (AM) fungi form potentially symbiotic associations with most crop species and potentially increase crop phosphorus (P) uptake in intensive cropping systems. Their widespread use, however, remains restrained by our limited understanding of the processes that determine the outcome of the associations. Here, we have used 32P to quantify the delivery of P to maize (Zea mays L.) and wheat (Triticum aestivum L.) via indigenous AM fungi in compartmented pots under high- and low-P conditions. Soil P level was important in driving shoot P uptake via the direct root pathway (DP) or the mycorrhizal pathway (MP). The MP contribution reached 81.8 and 75.8%, respectively, in maize and wheat at low P status but declined to 40.6 and 9.1% at high P. The abundance of intraradical and extraradical colonization and the relative abundance of Rhizophagus and shoot P utilization efficiency (PUE) significantly impacted the MP contribution. Larger mycorrhizal P and growth responses were closely related to a higher MP contribution and shoot PUE in maize but only P response was significantly related to the latter in wheat. These results suggest that crops can acquire considerable amounts of P via the MP with indigenous AM fungi, especially at low P levels, and highlight the importance of plant and AM fungal identity in regulating the relationship between hidden P uptake and symbiotic outcomes. Therefore, manipulation of fertilizer P application rates to optimize the abundance and assemblage of the indigenous AM fungi and crop PUE to increase MP activity and symbiotic outcomes may contribute to the efficient utilization of AM fungi in intensive cropping systems.

Ozone does not diminish the beneficial effects of arbuscular mycorrhizas on Medicago sativa L. in a low phosphorus soil.

Enriched surface ozone (O3) can impose harmful effects on plants. Conversely, arbuscular mycorrhizal (AM) symbiosis can enhance plant tolerance to various environmental stresses and facilitate plant growth. The interaction of AM fungi and O3 on plant performance, however, seldom has been investigated. In this study, alfalfa (Medicago sativa L.) was used as a test plant to study the effects of O3 and AM symbiosis on plant physiology and growth under two O3 levels (ambient air and elevated O3 with 60nmol·mol-1 O3 enrichment) and three AM inoculation treatments (inoculation with exogenous or indigenous AM fungi and non-inoculation control). The results showed that elevated O3 decreased plant net photosynthetic rate and biomass, and increased malondialdehyde concentration, while AM inoculation (with both exogenous and indigenous AM fungi) could promote plant nutrient acquisition and growth irrespective of O3 levels. The positive effects of AM symbiosis on plant nutrient acquisition and antioxidant enzyme (superoxide dismutase and peroxidase) activities were most likely offset by increased stomatal conductance and O3 intake. As a result, AM inoculation and O3 generally showed no significant interactions on plant performance: although elevated O3 did not diminish the beneficial effects of AM symbiosis on alfalfa plants, AM symbiosis also did not alleviate the harmful effects of O3 on plants.

Breeding Practice Improves the Mycorrhizal Responsiveness of Cotton (Gossypium spp. L.).

Maximizing the function of indigenous arbuscular mycorrhizal (AM) fungi by choosing specific crop genotypes offers one of the few untapped opportunities to improve the sustainability of agriculture. In this study, the differences in mycorrhizal responsiveness (MR) in plant growth and shoot phosphorus (P) content among cotton (Gossypium spp. L.) genotypes from different release dates were compared and then the relationships between MR and P uptake-related traits were determined. The experimental design in a greenhouse included 24 genotypes released from 1950 to present in Xinjiang Province, inoculation with or without AM fungi, and P levels (15 and 150 mg P kg–1 added as KH2PO4). Results showed that the modern cotton genotypes exhibited a higher degree of mycorrhizal colonization, the hyphal length density (HLD), and mycorrhizae-induced changes in shoot growth than the old genotypes when inoculated with indigenous AM fungi at both the P levels. Moreover, MR was highly correlated with the HLD at low P levels and the HLD may provide useful insights for future cotton breeding aimed at delivering crop genotypes that can benefit more from AM fungi.

Effects of biochar amendment on wheat production, mycorrhizal status, soil microbial community, and properties of an Andisol in Southern Chile

Biochar (BC) production from agroforestry wastes and mycorrhizal fungi are potentially important agricultural practices for improving crops yields and increasing phosphorus (P) in volcanic soils. This study aimed to test the effect of BC application on wheat biomass and grain yield production, indigenous arbuscular mycorrhizal (AM) fungi propagules and soil microbial community and related to soil quality properties of an Andisol in Southern Chile. Biochars (BCs) were produced from oat hulls (OBC) and pine bark (PBC). Doses of 0, 5, 10, and 20 Mg ha−1 of BCs were applied on soil using wheat as the test crop. Wheat biomass (root and shoot portion) and grain yield, AM root colonization, spore, mycelium density, and glomalin content (glomalin related soil protein, EE-GRSP) were measured and related with soil quality properties such as bulk density, water-stable aggregates (WSA), and water holding capacity (WHC). The OBC had a significantly higher macronutrients content (N, P, K) than PBC. The highest dose of both BCs significantly improved shoot and root biomass and wheat grain yield. Application of 20 Mg ha−1 of OBC and PBC increased AM spore density and root colonization relative to control treatment. In the same way, the BC application significantly affects the AM mycelium density. The results showed that the application of higher BC dose changed the soil microbial community. The use of BCs in this volcanic soil is an effective strategy to increase wheat biomass, increase grain yield production, stimulate the indigenous AM fungi activity, enhance soil quality properties, and increase the sustainability levels of agricultural systems.

Spatial changes of arbuscular mycorrhizal fungi in peach and their correlation with soil properties.

Arbuscular mycorrhizal (AM) fungi have beneficial effects on host plants, but their growth is influenced by various factors. This study was carried out to analyze the variation of AM fungi in soils and roots of peach (Prunus persica L. var. Golden Honey 3, a yellow-flesh variety) trees in different soil layers (0–40 cm) and their correlation with soil properties. The peach tree could be colonized by indigenous AM fungi (2.2–8.7 spores/g soil and 1.63–3.57 cm hyphal length/g soil), achieving 79.50–93.55% of root AM fungal colonization degree. The mycorrhizal growth, root sugars, soil three glomalins, NH4+-N, NO3−-N, available P and K, and soil organic matter (SOM) had spatial heterogeneity. Soil spores, but not soil hyphae contributed to soil glomalin, and soil glomalin also contributed to SOM. There was a significant correlation of soil hyphae with spore density, soil NO3−-N, and SOM. Root mycorrhiza was positively correlated with spore density, NH4+-N, NO3−-N, and easily extractable glomalin-related soil protein. Notably, spore density positively correlated with NO3−-N, available K, SOM, and root fructose and glucose, while negatively correlated with available P and root sucrose. These findings concluded that mycorrhiza of peach showed spatial distribution, and soil properties mainly affected/altered based on the soil spore density.

The relative contribution of indigenous and introduced arbuscular mycorrhizal fungi and rhizobia to plant nutrient acquisition in soybean/maize intercropping in unsterilized soils

It has been demonstrated that intercropped crops may benefit from inoculation with rhizobia or arbuscular mycorrhizal (AM) fungi in soybean/maize intercropping systems under sterilized conditions. Little is known about the relative contribution of indigenous and introduced AM fungi and rhizobia to nutrient acquisition of intercropped soybean and maize in unsterilized soils. In this study, we evaluated the effectiveness of indigenous and introduced AM fungi and rhizobia in a soybean/maize intercropping system under unsterilized soil conditions. The results show that introduced rhizobial inoculation promoted soybean nodulation and growth. Single AM fungal inoculation promoted indigenous rhizobial nodulation and increased maize AM root colonization, but had little effect on maize growth. Co-inoculation strongly increased plant dry weight, and nitrogen (N) and phosphorus (P) content of the intercropped soybean compared to those with only indigenous rhizobial and AM fungal communities, but had no effect on those of maize in the same intercropped system. These results indicate that AM fungal inoculation promoted nodulation by indigenous rhizobia. Effective rhizobial inoculation combined with introduced AM fungi may not only promote symbiotic N2 fixation, but also enhance rhizosphere processes, which has the potential to improve nutrient acquisition in the field. Soybean is a weak competitor compared with maize in intercropping systems. Inoculation with introduced AM and rhizobia ameliorated the growth suppression of intercropped soybean, but inhibited growth of intercropped maize, indicating that inoculation of introduced AM fungi and/or rhizobia partly shifted the competitive advantage from maize to soybean. In conclusion, introduced AM fungi and rhizobia contributed more than indigenous populations to promoting growth and nutrient acquisition of the intercropped soybean in unsterilized soils.

Effect of Poultry Manure Compost and Arbuscular Mycorrhizal Fungi on Cu Immobilization and Soil Microbial Communities in a Cu-Contaminated Soil Using the Metallophyte Oenothera Picensis

Soil metal contamination has emerged as a global environmental issue due to toxicity to living organisms. Traditional remediation techniques applied to metal-contaminated soils are intrusive and expensive, by which more environmental-friendly methods, such as phytoremediation, are necessary to remediate metal-contaminated soils. This study aimed to evaluate the combined effect of poultry manure compost (PMC) and indigenous arbuscular mycorrhizal (IM) fungi inoculation over copper (Cu) immobilization and the effectiveness of these elements promoting the plant growth and the soil microbial communities in a Cu-contaminated soil. A sandy Cu-contaminated soil (338 mg kg−1 of extractable Cu) was amended with PMC (2 and 4% w/w) in a pot experiment using the metallophyte Oenothera picensis. The plants were inoculated with the IM fungi isolated from the Cu-contaminated soils and grown for 3 months. PMC produced a liming effect, reduced the exchangeable Cu, and increased the amount of Cu-bound to organic and residual fractions. In addition, PMC also increased the biomass of O. picensis, which grew 8.5 times than the ones in unamended soil. Moreover, PMC incorporation stimulated soil microorganisms, increasing basal respiration and dehydrogenase activity modifying also the microbial community composition probably by reducing Cu availability and increasing carbon and nutrient sources to microorganism. On the contrary, the IM fungi inoculation reduced the plant biomass and increased the Cu translocation to the aboveground tissues. Therefore, the PMC is an effective amendment for remediating Cu-contaminated soils since it buffered soil pH, decreased Cu availability, supported the growth of O. picensis, and promoted mainly microbial activities in special shifting bacterial communities.

Plant invasion alters community structure and decreases diversity of arbuscular mycorrhizal fungal communities

Invasive plants often pose serious threats to the natural biodiversity of invaded ecosystems and in this way are likely to alter ecosystem services. This applies to arbuscular mycorrhizal (AM) fungi, in which the invaders have been reported to modify community structure, which facilitates their further intrusion. Information as to the impact of such invasion on AM fungal communities is insufficient and therefore needed. In particular, little is known about how AM fungal communities shift in response to individual invasive species. To ascertain whether invasion changes the structure of indigenous AM fungal communities, we examined changes in AM fungal community composition and diversity in soil and in roots of native neighboring plants in response to incursion of five invasive plant species from the family Asteraceae: Conyza canadensis, Erigeron annuus, Echinops sphaerocephalus, Solidago canadensis, and Symphyotrichum novi-belgii. We found that invasions of tested invasive plant species altered composition of the AM fungal community and reduced the diversity of AM fungi in soil and in the roots of some native plants. Statistical significance of the invasions' effects depended on composition of AM fungal communities in roots of the native plant species and/or site and was not connected with changes in soil parameters. Our results confirm the notable influence of plant invasion on indigenous AM fungal biodiversity and the need for further study in various environmental conditions.

Arbuscular mycorrhizal enhancement of phosphorus uptake and yields of maize under high planting density in the black soil region of China

Arbuscular mycorrhizal (AM) symbioses are an attractive means of improving the efficiency of soil phosphorus (P) that difficult to be used by plants and may provide a sustainable way of maintaining high yields while reducing P applications. However, quantifying the contribution of indigenous AM fungi on phosphorus uptake and yields of maize (Zea mays L.) under field conditions is not particularly clear. Mesh-barrier compartments were applied to monitor the distribution of hyphal P uptake throughout the experimental period under different planting densities and soil depths, over two consecutive years. AM symbioses enhanced plant P-acquisition efficiency, especially during the silking stage, and hyphae of AM fungi was assessed to contribution 19.4% at most to total available P content of soil. Moreover, the pattern of AM depletion of soil P generally matched shoot nutrient demand under the high planting density, which resulted in significantly increased yield in 2014. Although the hyphal length density was significantly decreased with soil depth, AM fungi still had high potential for P supply in deeper soil. It demonstrates the great potential of indigenous AM fungi to maize productivity in the high-yield area of China, and it would further provide the possibility of elimination P fertilizer applications to maintain high yields.

Poultry Litter Biochar Increases Mycorrhizal Colonisation, Soil Fertility and Cucumber Yield in a Fertigation System on Sandy Soil

There is a continuing argument about the benefits of biochar on arbuscular mycorrhizal (AM) symbiosis, crop growth, yield, and fertility of soil. There is also limited research on the effects of biochar on AM colonization, cucumber yield, and soil fertility improvement. Therefore, this investigation aimed to determine the impact of poultry litter biochar (PLB) on colonization of roots by indigenous AM fungi in agricultural soil and their contribution to cucumber yield, nutrition, and soil fertility improvement. A field trial was conducted to assess the effect of PLB combined with compound poultry manure (CPM) and nitrophos (NP) fertilizer to investigate the response of treatments on nutrient-deficient sandy soils. Plant growth responses to biochar showed better plant growth and yield of cucumber. Application of biochar with and without CPM and NP reduced the negative impact of nutrient deficiency stress on cucumber growth. AM fungal colonization, soil fertility, and cucumber yield were improved with the combined application of biochar, CPM, and NP fertilizer. Post-harvest, soil C, N, P, K, Ca, Mg, S, Zn, Cu, Fe, and Mn increased with application of biochar applied with CPM and NP. Biochar application with CPM and NP also increased the percent root colonization of cucumber. Use of biochar with CPM and NP has the potential to improve plant growth, yield, nutrient uptake, and soil fertility. Further studies in various agro-ecological conditions would help utilize this technology in sustainable crop production.

Similar Arbuscular Mycorrhizal Fungal Communities in 31 Durum Wheat Cultivars (Triticum turgidum L. var. durum) Under Field Conditions in Eastern Canada.

Wheat is among the important crops harnessed by humans whose breeding efforts resulted in a diversity of genotypes with contrasting traits. The goal of this study was to determine whether different old and new cultivars of durum wheat (Triticum turgidum L. var. durum) recruit specific arbuscular mycorrhizal (AM) fungal communities from indigenous AM fungal populations of soil under field conditions. A historical set of five landraces and 26 durum wheat cultivars were field cultivated in a humid climate in Eastern Canada, under phosphorus-limiting conditions. To characterize the community of AMF inhabiting bulk soil, rhizosphere, and roots, MiSeq amplicon sequencing targeting the 18S rRNA gene (SSU) was performed on total DNAs using a nested PCR approach. Mycorrhizal colonization was estimated using root staining and microscope observations. A total of 317 amplicon sequence variants (ASVs) were identified as belonging to Glomeromycota. The core AM fungal community (i.e., ASVs present in > 50% of the samples) in the soil, rhizosphere, and root included 29, 30, and 29 ASVs, respectively. ASVs from the genera Funneliformis, Claroideoglomus, and Rhizophagus represented 37%, 18.6%, and 14.7% of the sequences recovered in the rarefied dataset, respectively. The two most abundant ASVs had sequence homology with the 18S sequences from well-identified herbarium cultures of Funneliformis mosseae BEG12 and Rhizophagus irregularis DAOM 197198, while the third most abundant ASV was assigned to the genus Paraglomus. Cultivars showed no significant difference of the percentage of root colonization ranging from 57.8% in Arnautka to 84.0% in AC Navigator. Cultivars were generally associated with similar soil, rhizosphere, and root communities, but the abundance of F. mosseae, R. irregularis, and Claroideoglomus sp. sequences varied in Eurostar, Golden Ball, and Wakooma. Although these results were obtained in one field trial using a non-restricted pool of durum wheat and at the time of sampling, that may have filtered the community in biotopes. The low genetic variation between durum wheat cultivars for the diversity of AM symbiosis at the species level suggests breeding resources need not be committed to leveraging plant selective influence through the use of traditional methods for genotype development.

Salinity changes root occupancy by arbuscular mycorrhizal fungal species

Understanding the diversity and community composition of arbuscular mycorrhizal (AM) fungi in stressful conditions is fundamental to predicting the occurrence and function of indigenous AM fungal associations in a changing soil environment. Here, using whole-soil inoculum, we investigated the effects of salinity on community structure and colonization rate of AM fungi in roots, and assessed their influence on maize (Zea mays L.) performance. Three different salinity treatments (0, 75, and 150 mM NaCl) were applied to mycorrhizal inoculated and non-inoculated plants. Results showed that salinity levels significantly influenced AM fungal composition and diversity as well as vesicular and hyphal colonization in roots. The AM fungal community composition and diversity index differed slightly under the 0 and 75 mM NaCl treatments, but changed significantly under the 150 mM NaCl treatment. Increased vesicular and declined hyphal colonization were observed under 75 and 150 mM NaCl treatments relative to the control. Further analyses uncovered that plants under the 0 and 75 mM NaCl treatments, where Glomeraceae predominated as root symbionts, had a higher mycorrhizal growth response than plants under the 150 mM NaCl treatment, where Claroideoglomeraceae abundance increased significantly. This study provides evidence that saline stress plays a vital role in community structure and root colonization by AM fungal communities. Additionally, our data suggested that community composition may be more important for mycorrhizal symbiotic function than the rate of root colonization. Finally, while the relative abundance of Claroideoglomeraceae was found to increase with stress in saline soil, their role needs to be further clarified in future studies.

Soil phosphorus availability modifies the relationship between AM fungal diversity and mycorrhizal benefits to maize in an agricultural soil

Arbuscular mycorrhizal (AM) fungi are very abundant in many agricultural soils and are important in increasing and maintaining the sustainability of agricultural systems. However, high soil fertility, especially high available soil phosphorus (P) status, often limits AM fungal development in intensively managed agricultural systems and results in the C-costs to the host plant outweighing any benefits from AM colonization. Some promising approaches can minimize negative effects on soil biota while providing the desired agricultural benefits (e.g. reduced soil tillage and organic amendments). However, the influence of these agricultural practices on the benefits of root mutualistic associations remains poorly understood. Here, we collected indigenous AM fungi from a long-term field experiment with different application rates of cow manure and conducted a pot experiment with different soil P levels. Using high throughput sequencing we demonstrate that increasing cow manure application changed the community composition of AM fungi and reduced community diversity in the field. Phosphorus addition in a bioassay experiment produced a mycorrhizal growth response (MGR) and the mycorrhizal P response (MPR) shifted from positive to negative, regardless of the origin of the inoculum. An increase in intraradical and extraradical AM fungal structures enhanced maize shoot biomass and P uptake under low (no P added) and moderate (20 mg P added kg−1 soil) P levels but the opposite occurred at a high P level (250 mg P added kg−1 soil). The MGR was higher in the treatment with higher community diversity at the moderate P level but there was no significant correlation at the other two P levels examined. We conclude that available soil P may regulate the abundance and diversity of AM fungi and their symbiotic function in intensive cropping systems. Our results indicate that managing the soil phosphorus level to favor a rich and diverse AM fungal community can enhance crop production and result in a more sustainable agricultural system.

Molecular diversity of arbuscular mycorrhizal fungal communities across the gradient of alkaline Fe ore tailings, revegetated waste rock to natural soil sites.

Arbuscular mycorrhizal (AM) fungi are important to the establishment of native vegetation for mined land rehabilitation, particularly in semi-arid and infertile landscapes. However, the information has been scarce about the colonization of AM fungal community in alkaline magnetite Fe ore tailing sites (without toxic metal (loid) contamination). The present study has characterized the diversity of AM fungi across typical domains of a magnetite Fe ore mine located in 200km south-east of Geraldton, Western Australia, by adopting high throughput Illumina Miseq sequencing. The investigated domains included two tailing sites without top soil covering (T1 and T2), a rehabilitated area of tailings with top soil covering (R1), a revegetated waste rock area (R2), and two native undisturbed soil sites (S1 and S2). The results indicated that the T1/T2 sites had different AM fungal community structure, compared with R1/R2 and S1/S2 sites. The dominant families were Glomeraceae, Claroideoglomeraceae, Archaeosporaceae, Ambisporaceae, and Paraglomeraceae, with Paraglomeraceae (more than 50%) as the most abundant in the T1/T2 and R1/R2 sites. At genus level, Ambispora spp. and Archaeospora spp. were rich in T1/T2 sites (> 10%), while Glomus spp. were preferably dominant in S1/S2 sites (> 10%). Furthermore, amorphous Fe and available P were found to explain the variations associated with AM fungal community composition, particularly the abundance of Archaeosporaceae and Glomeraceae. The study revealed the AM fungal community composition shift across the gradient of Fe ore mine sites, as well as the effects of revegetation on AM fungal community development. The findings indicate the possible restoration of AM fungal community in the tailings undergoing revegetation, and potential adoption of indigenous AM fungi to rapid phytostabilization of the Fe ore tailings under semi-arid climatic conditions.