Search Results (62)

Dual mycorrhizal symbiosis, i.e., the association with both arbuscular and ectomycorrhizal fungal symbionts, is an ambiguous phenomenon concurrently considered as common among various genetic lineages of trees and a result of bias in data analyses. Recent studies have shown that the ability to form dual mycorrhizal associations is a distinguishing factor for the continental-scale invasion of alien tree species. However, the phylogenetic mechanisms that drive it remain unclear. In this study, all the evidence on root-associated symbionts of Juglandaceae from South and North America, Asia, and Europe was combined and re-analysed following current knowledge and modern molecular-based identification methods. The Juglandaceae family was revealed to represent a specific pattern of symbiotic interactions that are rare among deciduous trees and absent among conifers. Closely related phylogenetic lineages of trees usually share the same type of symbiosis, but Juglandaceae contains several possible ones concurrently. The hyperdiversity of root symbionts of Juglandaceae, unlike other tree families, was concurrently found in Central and North America, Asia, and Europe, indicating its phylogenetic determinants, which endured geographical isolation. However, for many Juglandaceae, including the invasive Juglans and Pterocarya species, this was never studied or was studied only with outdated methods. Further molecular research on root symbionts of Juglandaceae, providing long sequences and high taxonomic resolutions, is required to explain their ecological roles. Full article

Arbuscular mycorrhizal (AM) fungi are root symbionts that play an important role in the growth of vascular plants. Four AM fungi, including three new species, Acaulospora citrusnsis, A. guangxiensis, A. jiangxiensis, and a new country record from China, Acaulospora herrerae, are reported based on morphological characteristics and molecular phylogenetic analysis. They were isolated and propagated from spores extracted from the rhizosphere soils of citrus. A. citrusnsis is characterized by forming hyaline to pale yellow globose to subglobose spores of (70.0–)85.0(−100.0) μm in diameter. Spores of A. guangxiensis are pale yellow to pale yellowish brown, with spherical to sub-spherical appearance and (103.1–)122.1(–147.1) μm in diameter. Young spores of A. jiangxiensis are hyaline, gradually turning pale yellow as they mature, with spherical to sub-spherical appearance and (78.7–)85.6(–90.0) μm in diameter. Spores of A. herrerae are hyaline and 86.3–127.2 μm in diameter. Four species have three spore wall layers, and spores form individually in the soil. The phylogenetic tree was constructed and inferred from sequences of 18S-ITS1-5.8S-ITS2-28S datasets by Bayesian inference and maximum likelihood analysis. Voucher specimens are deposited in the Center for Subtropical Arbuscular Mycorrhizal Fungi Culture Collection (CSMC). Full article

Arbuscular mycorrhizal fungi (AMF) and rhizobia are important symbiotic microorganisms in soil, which can symbiose with legumes to form mycorrhizal symbionts and nodules, respectively. Once a stable symbiotic relationship is established, these microorganisms have been found to enhance nitrogen absorption by legumes. Although plants can directly utilize ammonium through ammonium transporters (AMTs), there is limited research on the role of the AMT gene family in promoting ammonium transport in symbiotic relationships. Lotus japonicus, a common host of arbuscular mycorrhizal fungi and rhizobia, serves as a model legume plant. In this study, we examined the characteristics of the ammonium transporter LjAMT2;4 in L. japonicus and found that LjAMT2;4 is localized to the plasma membrane and is predominantly expressed in roots. The promoter region of LjAMT2;4 contains cis-acting elements induced by arbuscular mycorrhizal fungi and rhizomes, and the expression of LjAMT2;4 was induced by AM fungi and rhizobia. However, there was no significant difference in the mycorrhizal colonization rate of ljamt2;4 compared to the wild type, while the absence of LjAMT2;4 significantly increased the number of root nodules under nitrogen-starved conditions, enhancing nitrogen fixation and alleviating nitrogen stress in extremely nitrogen-starved environments, ultimately promoting plant growth. These findings suggest that manipulating the genes involved in symbiotic nitrogen fixation, such as LjAMT2;4, could offer new strategies for sustainable agricultural production. Given that AM and rhizobia symbiosis are critical for crop growth, our findings may inform strategies to improve agricultural management. Full article

Arbuscular mycorrhizal (AM) fungi occur in the interface between soils and plants. Yet, the impacts of the plant community functional composition and soil properties on AM fungal communities remain poorly understood in the face of ongoing climate change. Here, we investigated the AM fungal community in alpine meadow habitats of the Tibetan Plateau by linking fungal species richness to plant community functional composition and soil parameters at three latitudinal sites. High-throughput sequencing of the AM fungal small subunit rRNA gene was performed to characterize fungal communities. We found that AM fungal diversity and plant functional diversity, as well as the contents of soil nutrients, were significantly higher in the southernmost site, Hongyuan (HY). Total soil nitrogen and soil-available phosphorus explained the variation in AM fungal diversity, while AM fungal biomass was best predicted by the plant community-weighed mean nitrogen:phosphorus ratio (CWM-N:P). Glomus species preferentially occurred in the northernmost site of Hezuo (HZ). Distance-based redundancy analysis (db-RDA) revealed that AM fungal community structure was influenced by not only CWM-N:P but also by plant community-weighed mean photosynthetic rate (CWM-Pn), soil total carbon, and plant community functional dispersion (FDis). We conclude that plant traits and soil properties are crucial for nutrient–carbon (C) exchange, as fungal symbionts may shape AM communities in this vast alpine meadow ecosystem. Our findings provide timely insight into AM fungal community assembly from the perspective of nutrient–C exchange dynamics in the Tibetan Plateau’s alpine meadow habitats. Full article

Arbuscular mycorrhizal (AM) fungi are one of the most widely distributed microorganisms in all terrestrial ecosystems, playing an important role in supplying nitrogen (N) and phosphorus (P) to plants and in nutrient cycling. The contribution discusses the responses of rises in temperature and atmospheric N deposition to stoichiometric features of plant–soil–litter–microorganism–soil hydrolases in forest ecosystems. It summarizes the role that AM fungi play in the context of global change in carbon (C), N, and P stoichiometric characteristics of forest plant–soil systems. In this study, under conditions of warming with N application, it said the AM fungi will strongly influence the stoichiometric characteristics of C, N, and P in forest ecosystems. In addition to that, the presence of AM fungi may weaken certain impacts of global change on nutrient limitations in plants, increasing their plant dependency on mycorrhizal symbionts. AM fungi also seem to control soil nutrient transformation but simultaneously enhance soil nutrient stability, accelerate litter decomposition, and shorten the cycling time of litter C, N, and P. Full article

Arbuscular mycorrhizal fungi (AMF) can form symbionts with plant roots, acquire soil nitrogen, and affect nitrous oxide (N₂O) production. Biochar, as a soil additive for the management of agricultural soil, affects soil nitrogen (N) utilization and plant growth. However, how AMF regulates soil N unitization, the denitrification process, and N₂O emissions in plant–soil systems remains largely unknown, particularly under the biochar amendment. In this study, a microcosm experiment was conducted to investigate the impacts of different mycorrhizal treatments (CK: neither AMF hyphae nor plant roots; AMF: only AMF hyphae; AMF + R: AMF hyphae and plant roots) on plant growth, soil N fertilizer utilization, N₂O production and consumption, functional gene abundance, and N₂O emission at two biochar addition levels (B0: no biochar; B1: biochar addition rate of 10 g·kg⁻¹ soil) in a maize planting soil system. The results revealed that AMF alone and AMF with plant root treatments enhanced the fresh weight of maize plants by 10.15% and 19.23% and decreased soil inorganic N contents by 33.28% and 75.56%, respectively. The combination of biochar, AMF, and plant roots showed the largest increase in maize plant biomass. The AMF and AMF with root treatments all significantly decreased the nirS + nirK/nosZ ratio and N₂O emissions at two biochar levels. The presence of AMF and plant roots during biochar amendment showed the smallest nirS + nirK/nosZ ratio and N₂O emissions. The AMF combined with biochar and AMF and plant roots combined with biochar treatments increased nirS + nirK/nosZ by 24.32% and 26.90% and decreased N₂O accumulation emission by 21.12% and 38.13%, respectively. The results imply that biochar, AMF, and plant roots reduced N₂O emissions directly by reducing soil N and increasing soil N unitization efficiency and indirectly by shifting the N₂O production and consumption gene abundance in agroecosystems. These findings suggest that the addition of biochar and AMF and/or the presence of plant roots can interact to alleviate soil N₂O emissions by manipulating plant inorganic N acquisition and the soil denitrification process. Full article

Planting nitrogen-fixing plants in post-mining sites and similar degraded areas is a common approach to speed up soil development and buildup of the nitrogen pool in soil organic matter. The aim of this study was to explore if slower growth of alder seedlings in initial post-mining sites results from adverse soil conditions or lack of microbial symbionts. To address this question, we sampled young soil (age 15 years) and more developed soil (age 70 years) from heaps after coal mining near Sokolov (Czech Republic). Soil samples were sterilized and not inoculated or inoculated with arbuscular mycorrhizal fungi (AMF) or AMF + Frankia, followed by planting with alder (Alnus glutinosa) seedlings germinated and precultured under sterile conditions. The effect of soil age on alder growth appeared to be non-significant. The only significant growth effect was seen with Frankia inoculation, implicating this inoculum as a key factor in later succession in post-mining soils. When the soil was fully inoculated, alder biomass was higher in developed soil supplied with iron (Fe) and phosphorus (P), indicating that iron and phosphorus availability may affect alder growth. In young soil, alder growth was highest with a combination of iron, phosphorus, and sulfur (S), and a positive effect of sulfur in young soil may correspond with a reduced, alkaline soil pH and increased phosphorus and iron availability. Full article

Grasslands play a crucial role in exchanges between global ecosystems and the atmosphere and form an integral part of the agricultural industry. Arbuscular mycorrhizal fungi (AMF) are mutualistic symbionts of most grassland plant species and thereby influence the functional capacity of grassland systems. Agricultural grasslands are primarily used for livestock farming and are subjected to various management practices designed to increase production, but which also alter both plant and soil communities in the process. This research investigated the effects of a selection of management practices and environmental factors on the presence and abundance of AMF in upland Welsh grasslands. The aim was to identify how these management practices affected the abundance of AMF, assessed through microscopic observations of four AMF structures: spores, hyphae, vesicles and arbuscules. The results suggest grazing sheep and cattle together had the highest overall influence on AMF abundance compared to grazing sheep or cattle separately. High plant diversity correlated with high arbuscule and vesicle abundance, but conversely, the application of lime reduced vesicle abundance. These findings offer new insights into the effects of management practices on AMF. Mixing livestock, increasing plant diversity and reducing lime applications are shown here to improve the abundance of AMF and could, therefore, help to inform sustainable farm management decisions in the future. Full article

Soil salinity is an emerging phenomenon threatening arid and semiarid areas due to changing climatic events. Salinity, in combination with other elemental contaminants, can often harm crop performance and productivity. This experiment was conducted to evaluate the mitigating effect of Claroideoglomus etunicatum, an arbuscular mycorrhizal fungus (AMF), on combined boron (B) toxicity and salt stress symptoms in maize plants. After the stress and AMF treatments, plants were subjected to a wide range of analyses, such as AMF colonization rates, ion leakage, plant biomass, and concentration of B, phosphorus, sodium, potassium, iron, zinc, copper, and manganese in root and shoot tissues. The results showed that the combined stress did not affect the AMF colonization rate. AMF inoculation significantly increased plant biomass, the K⁺/Na⁺ ratio, and shoot B, sodium, and copper concentrations, but reduced root B concentrations and ion leakage. AMF inoculation slightly increased root dry weight and the sodium, potassium, zinc, copper and Mn contents in shoots under combined B and salinity stress, while AMF reduced the electrolyte leakage in leaves. It is inferred that AMF can ameliorate B toxicity in maize by improving biomass and reducing B concentration in plant tissues. Our research implies that C. etunicatum could be a valuable candidate for assisting in the remediation of boron-contaminated and saline soils. Full article

Over the last few decades, argan trees (Argania spinosa L.) skeels have faced harsh ecological conditions and anthropogenic pressure, leading to a dramatic decline in surface and density of cultivation. Nowadays, most techniques used to regenerate argan trees have failed. Arbuscular mycorrhizal fungi (AMF) are root symbionts that increase plant resistance to biotic and abiotic stresses during transplantation. The exploration of these symbiotic fungi from different soils of argan stands is the starting point for the selection and production of high-performance organisms adapted to the reforestation sites. The objective of this study is to investigate the composition of the AMF community associated with the argan tree rhizosphere. Forty adult argan trees were sampled in eight forest sites representative of the distribution and genetic diversity of argan forest stands. Five sub-samples of rhizospheric soil were taken around each tree. Our results revealed the presence of different AMF structures (i.e., hyphae, vesicles/and arbuscules) in root samples. Based on morphological characterization, six genera of AMF spores were identified with a dominance of the genera Septoglomus (34%). In addition, soil organic matter and phosphorus concentrations showed a highly significant correlation with AMF spore density. The chi-square test showed a highly significant dependence of the distribution of genera on the site conditions of forest stands. These AMF could be tested and used during the inoculation of argan seedlings in forest nurseries for the success of restoration and reforestation programs, as well as for the development and sustainable improvement of this agroforestry system. Full article

The old Zn-Pb-contaminated (calamine) tailings in southern Poland are spontaneously colonized by metal-tolerant Anthyllis vulneraria L. (Fabaceae), which can form simultaneously symbiotic association with nitrogen-fixing rhizobia and phosphorus-acquiring arbuscular mycorrhizal fungi (AMF). So far, fungal colonization and the AMF diversity of calamine-inhabiting legumes have been poorly studied. Thus, we determined AMF spore density in the substratum and the mycorrhizal status of nodulated A. vulneraria plants occurring on calamine tailings (M) and on a reference non-metallicolous (NM) site. The results indicate the presence of the Arum-type of arbuscular mycorrhiza in the roots of both Anthyllis ecotypes. Despite the presence of AM fungi in M plant roots, the dark septate endophyte (DSE) fungi (hyphae and microsclerotia) were occasionally also detected. Metal ions were accumulated mainly in the nodules and intraradical fungal structures rather than thick plant cell walls. Mycorrhization parameters (frequency of mycorrhization and intensity of root cortex colonization) for M plants were markedly higher and differed in a statistically significant manner from the parameters for NM plants. Heavy metal excess had no negative effect on the number of AMF spores, the amounts of glomalin-related soil proteins and AMF species composition. Molecular identification of AMF using PCR-DGGE analysis based on the 18S rDNA ribosomal gene by nested-PCR with primers AM1/NS31 and NS31-GC/Glo1 revealed similar genera/species of AMF in the roots of both Anthyllis ecotypes: Rhizophagus sp., R. fasciculatus, and R. iranicus. The results of this work indicate the presence of unique fungal symbionts, which may enhance A. vulneraria tolerance to heavy metal stress and plant adaptation to extreme conditions on calamine tailings. Full article

Plants are colonized by various fungi with both pathogenic and beneficial lifestyles. One type of colonization strategy is through the secretion of effector proteins that alter the plant’s physiology to accommodate the fungus. The oldest plant symbionts, the arbuscular mycorrhizal fungi (AMF), may exploit effectors to their benefit. Genome analysis coupled with transcriptomic studies in different AMFs has intensified research on the effector function, evolution, and diversification of AMF. However, of the current 338 predicted effector proteins from the AM fungus Rhizophagus irregularis, only five have been characterized, of which merely two have been studied in detail to understand which plant proteins they associate with to affect the host physiology. Here, we review the most recent findings in AMF effector research and discuss the techniques used for the functional characterization of effector proteins, from their in silico prediction to their mode of action, with an emphasis on high-throughput approaches for the identification of plant targets of the effectors through which they manipulate their hosts. Full article

A greater understanding of the relationship between native orchids and their mycorrhizal symbionts is needed to ensure more effective orchid conservation strategies. A protocol for symbiotic seed germination and seedling development was developed for E. geminiflorum. Mature seeds were collected from a naturally occurring orchid population in Ecuador. Putative mycorrhizal fungi isolated from other native orchid species were used to screen their ability to facilitate germination and seedling development in vitro in either a 0/24 h or 12/12 h light/dark photoperiod at 20 °C. The mycorrhizal fungus Tulasnella calospora (UAMH 9824) isolated from Spiranthes brevilabris in Florida, USA, was also included in this study. Sterilization treatments using 0.3%, 0.5% sodium hypochlorite/ethanol or 2% calcium hypochlorite were tested for their effectiveness as sterilant and their subsequent effects on seed germination percentage. Effective surface seed sterilization was achieved with either 0.5% NaClO/ethanol or 2% calcium hypochlorite. However, significantly higher percentages of germinated embryos developed into protocorms when NaOCl solutions were used compared to the other treatments. Seed germination occurred in both photoperiods tested; however, delayed germination was observed under complete darkness. Seeds of E. geminiflorum germinated without fungal inoculation; however, co-culture with Tulasnella strains improved germination significantly. Seedling development was only observed when seeds were cultured in asymbiotic medium or co-cultured with T. caloscopa (UAMH 9824). Significantly longer seedlings were obtained when T. calospora was present in the culture compared with seedlings cultured in asymbiotic medium. The establishment of mycorrhizal associations was confirmed by the presence of pelotons in the roots of E. geminiflorum seedlings. Full article

The plant domestication process led to crops with strongly modified growth-defense tradeoff features, and crops that were much more pampered in terms of nutrition, irrigation and defense measures, showing less ability to trigger adaptation strategies with respect to their wild relatives. It is worth noting that plants are not alone, they share their environment with a myriad of microbes supporting them with many relevant functions. We have already demonstrated that an arbuscular mycorrhizal fungal (AMF) inoculum (formed by two AMF species, i.e., Rhizophagus irregularis and Funneliformis mosseae) is able to balance growth and defense responses in two grapevine rootstocks with opposite tradeoff features. In the present study, we evaluated the persistence of AMF-mediated balancing effects under field conditions, confirming the positive impact of the symbiosis in vineyards. In detail, some genes related to nitrogen (N) uptake and metabolism were specifically modulated by the presence of the symbionts, while others were not. Additionally, photosynthetic performances and stilbenes accumulation were influenced by the AMF presence. Overall, our results open new questions about the timing of AMF inoculation in grapevine to obtain a stable and functional symbiosis, suggesting that an early inoculation can facilitate the interaction between grapevine roots and these beneficial microorganisms. Full article

Abies beshanzuensis, an extremely rare and critically endangered plant with only three wild adult trees globally, is strongly mycorrhizal-dependent, leading to difficulties in protection and artificial breeding without symbiosis. Root hair morphogenesis plays an important role in the survival of mycorrhizal symbionts. Due to the lack of an effective genome and transcriptome of A. beshanzuensis, the molecular signals involved in the root hair development remain unknown, which hinders its endangered mechanism analysis and protection. Herein, transcriptomes of radicles with root hair (RH1) and without root hair (RH0) from A. beshanzuensis in vitro plantlets were primarily established. Functional annotation and differentially expressed gene (DEG) analysis showed that the two phenotypes have highly differentially expressed gene clusters. Transcriptome divergence identified hormone and sugar signaling primarily involved in root hair morphogenesis of A. beshanzuensis. Weighted correlation network analysis (WGCNA) coupled with quantitative real-time PCR (qRT-PCR) found that two hormone–sucrose–root hair modules were linked by IAA17, and SUS was positioned in the center of the regulation network, co-expressed with SRK2E in hormone transduction and key genes related to root hair morphogenesis. Our results contribute to better understanding of the molecular mechanisms of root hair development and offer new insights into deciphering the survival mechanism of A. beshanzuensis and other endangered species, utilizing root hair as a compensatory strategy instead of poor mycorrhizal growth. Full article