Development Of Arbuscular Mycorrhizal Fungi Research Articles

Are Histidine Kinases of Arbuscular Mycorrhizal Fungi Involved in the Response to Ethylene and Cytokinins?

Signals are exchanged at all stages of the arbuscular mycorrhizal (AM) symbiosis between fungi and their host plants. Root-exuded strigolactones are well-known early symbiotic cues, but the role of other phytohormones as interkingdom signals has seldom been investigated. Here we focus on ethylene and cytokinins, for which candidate receptors have been identified in the genome of the AM fungus Rhizophagus irregularis. Ethylene is known from the literature to affect asymbiotic development of AM fungi, and in the present study, we found that three cytokinin forms could stimulate spore germination in R. irregularis. Heterologous complementation of a Saccharomyces cerevisiae mutant strain with the candidate ethylene receptor RiHHK6 suggested that this protein can sense and transduce an ethylene signal. Accordingly, its N-terminal domain expressed in Pichia pastoris displayed saturable binding to radiolabeled ethylene. Thus, RiHHK6 displays the expected characteristics of an ethylene receptor. In contrast, the candidate cytokinin receptor RiHHK7 did not complement the S. cerevisiae mutant strain or Medicago truncatula cytokinin receptor mutants and seemed unable to bind cytokinins, suggesting that another receptor is involved in the perception of these phytohormones. Taken together, our results support the hypothesis that AM fungi respond to a range of phytohormones and that these compounds bear multiple functions in the rhizosphere beyond their known roles as internal plant developmental regulators. Our analysis of two phytohormone receptor candidates also sheds new light on the possible perception mechanisms in AM fungi. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Assessment of Agricultural Practices Impact on the Development of Arbuscular Mycorrhizal Fungi

In natural environments, the development of plants depends on the interactions they maintain with their environment, in particular with soil microorganisms such as arbuscular mycorrhizal fungi, especially since the used of inputs is scarce by the majority of farmers in Côte d’Ivoire. The present study was carried out to study the endomycorrhizogenic potential of the soils on which tomato, cashew and banana are grown. Place and Duration of Study: Soil sampling in bananas, cashews and tomatoes fields (July and August 2016), spore trapping in WASCAL (West African Science Service Center on Climate Change and Adapted Land Use) greenhouse in the city of Bingerville and spore extraction and identification in Laboratory of Biotechnology, Agriculture and Development of Biological Resources (September 2016 to March 2017). Material and Methods: Soil samples were taken away from the same depth, 10 to 20 cm, in cashew, tomato or banana fields. They were then used for trap pot culture by sorghum [Sorghum bicolor (L.)] and cowpea [Vigna ungugulata (L.) Walp.]. The wet sieving revealed spore density and morphological diversity. Results: Spores were more abundant in the soils sampled under cashew (22 spores / gram of soil) in comparison to banana (9 spores / gram of soil) and tomato (3 spores / gram of soil). There were a real diversity of glomeromycete in the different agrosystems. There is a great richness and diversity of AMF spore form under cashew (18 morphotypes) in Côte d'Ivoire compared to tomato (2 morphotypes) and banana (4 morphotypes). Conclusion: Land use system impact spore richness and diversity. Controlled mycorrhization of cashew, tomato and banana could be considered.

Arbuscular mycorrhizal fungi mitigate earthworm-induced N2O emissions from upland soil in a rice-rotated wheat farming system

Earthworms are important for soil processes in arable cropping systems, and affect the development of arbuscular mycorrhizal fungi (AMF) which may combinely play a crucial role in soil nitrogen (N) cycling. However, the information is limited about their interaction on N2O emissions. A two-factorial microcosm field experiment was established to identify the interactive effects of earthworms and AMF on N2O emissions from a rice-rotated wheat field and explore its underlying mechanisms about nitrification and denitrification processes. The results showed that earthworm addition (+E) increased cumulative N2O emissions during the whole growth stage by 236.7 % compared with no earthworms (−E). Cumulative N2O emissions during the jointing and booting stages contributed to 58.7 % of that during the whole growth stage. Higher N2O emissions under +E were attributed to changes in soil organic carbon (SOC) and NH4+ concentration. SOC was positively correlated to gene abundances associated with N2O reduction (e.g., nosZ), and earthworm activity enhanced SOC mineralization and reduced SOC concentration, thus increasing N2O emissions. A negative correlation between NH4+ and N2O emissions, and lower NH4+ under +E indicated that earthworms enhanced nitrification intensity using NH4+ as substrates. Interestingly, AMF normal (+A) significantly decreased cumulative N2O emissions by 37.3 % compared with mycorrhizal suppression (−A) and the interaction with earthworms can further decreased N2O emissions by 37.0 % compared with -E-A (P < 0.05). This can be explained by higher NH4+, lower NO3− concentrations, and lower abundance of nitrification-associated genes (e.g., AOA and AOB) at the booting stage under +A, suggesting that AMF reduced N2O emissions mainly through lowering nitrification intensity. The results highlight that earthworms increase N2O emissions while AMF can mitigate earthworm-induced N2O emissions, and enhance our understanding on the soil N cycle in terms of N2O production in the presence of AMF and earthworms.

Calling for comprehensive explorations between soil invertebrates and arbuscular mycorrhizas.

Arbuscular mycorrhizal (AM) fungi and soil invertebrates represent a large proportion of total soil biomass and biodiversity and are vital for plant performance, soil structure, and biogeochemical cycling. However, the role of soil invertebrates in AM fungi development remains elusive. In this opinion article, we summarize the ecological importance of AM fungi and soil invertebrates in the plant-soil continuum and highlight the effects of soil invertebrates on AM fungal hyphae development and functioning. In a context of global change, we envision that better mechanistic understanding of the complex feedback via chemical signaling pathways across the interactions between soil invertebrates and AM fungi is critical to predict their ecological consequences and will open new avenues for promoting ecosystem resilience and sustainability.

Metabolic Alterations in Pisum sativum Roots during Plant Growth and Arbuscular Mycorrhiza Development.

Intensive exchange of nutrients is a crucial part of the complex interaction between a host plant and fungi within arbuscular mycorrhizal (AM) symbiosis. For the first time, the present study demonstrates how inoculation with AMF Rhizophagus irregularis affects the pea (Pisum sativum L.) root metabolism at key stages of plant development. These correspond to days 21 (vegetation), 42 (flowering initiation), and 56 (fruiting-green pod). Metabolome profiling was carried out by means of a state-of-the-art GC-MS technique. The content shifts revealed include lipophilic compounds, sugars, carboxylates, and amino acids. The metabolic alterations were principally dependent on the stage of plant development but were also affected by the development of AM fungi, a fact which highlights interaction between symbiotic partners. The comparison of the present data with the results of leaf metabolome profiling earlier obtained did not reveal common signatures of metabolic response to mycorrhization in leaves and roots. We supposed that the feedback for the development and symbiotic interaction on the part of the supraorganismic system (root + AM fungi) was the cause of the difference between the metabolic profile shift in leaf and root cells that our examination revealed. New investigations are required to expand our knowledge of metabolome plasticity of the whole organism and/or system of organisms, and such results might be put to use for the intensification of sustainable agriculture.

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.

Arbuscular mycorrhizal fungal community was affected by tillage practices rather than residue management in black soil of northeast China

Arbuscular mycorrhizal (AM) fungi are one of the most important soil microbes in an agrarian ecosystem, and consequently affected by various agricultural practices. To elucidate the effects of tillage practices and residue management on AM fungi, a field trial was conducted on the Songnen Plain, Northeast China. We examined the effects of different tillage practices including no-tillage (NT), rotary tillage (RT), subsoil tillage (ST) and deep tillage (DT) on the AM fungal biomass, diversity and community under residue removal and residue retention. AM root colonization and extraradical hyphal (ERH) density were significantly higher in DT treatment compared with NT treatment, whereas an opposite trend was observed for AM fungal spore density. Structural equation modeling indicated that AM fungal spore density was directly affected by tillage practices. Albeit, the effect of tillage practices on ERH density was mainly mediated through root length of maize. By Miseq sequencing of 18S rDNA, 66 AM fungal operational taxonomic units (OTUs) were identified and Glomeraceae was the most abundant group in this study. AM fungal OTU richness was highest in treatment NT, and significantly higher than that in treatment DT. Non-metric multidimensional scaling analysis indicated that treatment DT and ST induced a distinct AM fungal community composition compared with treatment NT. On the other hand, residue did not significantly influence AM fungal biomass, OTU richness and community composition. Overall, our findings indicated that tillage practice is a stronger determinant than residue management in AM fungal development and community composition in black soil on the Songnen Plain.

Biogeography of arbuscular mycorrhizal fungal communities in saline ecosystems of northern China

Arbuscular mycorrhizal (AM) fungi, influencing many important ecosystem processes, widely occur in saline soils, and thus understanding their biogeographic patterns is of primary interest in saline ecosystem restoration. Fine roots and rhizosphere soils were sampled in black locust (Robinia pseudoacacia) plantations in four saline sites in northern China to detect soil properties and AM fungal attributes including their colonization level, spore density, hyphal density and community composition. Arbuscular mycorrhizal fungal attributes varied with sampling sites, and this variation was mostly attributed to changes in habitat characteristics and geographic distance. Habitat characteristics shape the root- and soil-inhabiting AM fungal communities to the same extent, whereas geographic distance seems to contribute more to root-inhabiting AM fungal assemblages. The level of root colonization by vesicles, arbuscules and hyphae and the density of AM fungal spores and hyphae in soils were found to be related to the relative abundance of AM fungal species such as root-inhabiting Rhizophagus intraradices and soil-inhabiting Sclerocystis sinuosa. All the results suggest that changes in habitat characteristics and geographic distance may induce biogeographic patterns of AM fungi, and these patterns are closely related to AM symbiosis in roots and the development of AM fungi in soils.

A novel in vitro methodology to cultivate arbuscular mycorrhizal fungi combining soil and synthetic media

Many studies have described the potential of root organ culture (ROC) to study the biology of arbuscular mycorrhizal (AM) fungi. The dual in vitro cultivation of AM fungi and ROC permits the establishment of the mycorrhizal symbiosis and the completion of fungal life cycle by producing new and infective propagules. However, some differences in AM fungal development are evident when growing in synthetic medium versus pot microcosms or in nature. We aimed to develop a new in vitro method that allows the study of AM symbiosis in a more natural environment, but under controlled conditions. This new culture method combines an artificial growth medium and differently sterilized soil samples for the cultivation of the AM fungal species Rhizophagus intraradices and Rhizophagus aggregatus. An extensive extraradical mycelia network and abundant viable spores, with similar morphological characteristics to those obtained under pot cultures developed under this in vitro soil-based cultivation system. Formation of sporocarp-like structures by R. aggregatus was also detected for the first time using this method.

Effect of salinity on spore germination, hyphal length and root colonization of the Arbuscular Mycorrhizal Fungi

Various environmental factors influence the growth and development of Arbuscular Mycorrhizal Fungi (AMF), one of which is salinity. Salinity can affect several stages of AMF growth. Theresearch aims to study the influence of salinity towards germination, growth, and performance of AMF, namely Gi. margarita and G. etunicatum. The level of salinity given ranges from 0 - 10,000 ppm with an interval of 2,000 ppm. Spore germination experiments were carried out in petri dish culture while evaluation was carried out in open pot culture with sorghum as host. The results showed that increasing salinity decreased the initial day of germination, the percentage of germination and hyphal growth. The effect is greater on Gi. margaritathanG. etunicatum on all parameters measured. An increase of salinity up to 10,000 ppm decreased the percentage of Gi. margarita root colonization by 69.07% and G. etunicatumby 37.78%. Nevertheless, the effect of salinity observed in this study towards germination and growth of AMF wasmore categorized as delaying rather than inhibiting or stopping.

Direct effects of soil cadmium on the growth and activity of arbuscular mycorrhizal fungi

A compartment cultivation system was developed to study the effect of cadmium (Cd) in soil on the development of arbuscular mycorrhizal fungi (AMF) under the same host conditions. Fungal compartments consisting of four levels of Cd addition rate (0, 5, 25 and 50 mg kg−1) were inserted into each porcelain pot in the greenhouse. Mycorrhizal development by Glaroideoglomus etunicatum and Glaroideoglomus claroideum was determined at three growth stages of Cucumis sativus. Both AMF isolates showed good root colonization during plant growth. Total extraradical mycelium (ERM) length and active ERM length reached a maximum at low Cd addition rate (5 mg kg−1) and were inhibited at the higher Cd addition rate (25 and 50 mg kg−1). The two AMF isolates showed different responses to Cd addition at the three growth stages and G. claroideum seemed to be more tolerant to Cd toxicity. These results showed a potential to use this technique to study the function of soil-grown AMF hyphae.

Shoot- and root-borne cytokinin influences arbuscular mycorrhizal symbiosis.

The arbuscular mycorrhizal (AM) symbiosis is functionally important for the nutrition and growth of most terrestrial plants. Nearly all phytohormones are employed by plants to regulate the symbiosis with AM fungi, but the regulatory role of cytokinin (CK) is not well understood. Here, we used transgenic tobacco (Nicotiana tabacum) with a root-specific or constitutive expression of CK-degrading CKX genes and the corresponding wild-type to investigate whether a lowered content of CK in roots or in both roots and shoots influences the interaction with the AM fungus Rhizophagus irregularis. Our data indicates that shoot CK has a positive impact on AM fungal development in roots and on the root transcript level of an AM-responsive phosphate transporter gene (NtPT4). A reduced CK content in roots caused shoot and root growth depression following AM colonization, while neither the uptake of phosphorus or nitrogen nor the root transcript levels of NtPT4 were significantly affected. This suggests that root CK may restrict the C availability from the roots to the fungus thus averting parasitism by AM fungi. Taken together, our study indicates that shoot- and root-borne CK have distinct roles in AM symbiosis. We propose a model illustrating how plants may employ CK to regulate nutrient exchange with the ubiquitous AM fungi.Electronic supplementary materialThe online version of this article (doi:10.1007/s00572-016-0706-3) contains supplementary material, which is available to authorized users.

Response of AM fungi spore population to elevated temperature and nitrogen addition and their influence on the plant community composition and productivity.

To examine the influence of elevated temperature and nitrogen (N) addition on species composition and development of arbuscular mycorrhizal fungi (AMF) and the effect of AMF on plant community structure and aboveground productivity, we conducted a 5-year field experiment in a temperate meadow in northeast China and a subsequent greenhouse experiment. In the field experiment, N addition reduced spore population diversity and richness of AMF and suppressed the spore density and the hyphal length density (HLD). Elevated temperature decreased spore density and diameter and increased the HLD, but did not affect AMF spore population composition. In the greenhouse experiment, AMF altered plant community composition and increased total aboveground biomass in both elevated temperature and N addition treatments; additionally, AMF also increased the relative abundance and aboveground biomass of the grasses Leymus chinensis (Poaceae) and Setaria viridis (Gramineae) and significantly reduced the relative abundance and aboveground biomass of the Suaeda corniculata (Chenopodiaceae). Although elevated temperature and N addition can affect species composition or suppress the development of AMF, AMF are likely to play a vital role in increasing plant diversity and productivity. Notably, AMF might reduce the threat of climate change induced degradation of temperate meadow ecosystems.

The relative importance of host vigor and hormonal response to pathogens in controlling the development of arbuscular mycorrhizal fungi

Plants are routinely colonized by both beneficial and detrimental microorganisms. These two microbial guilds may indirectly interact with each other via their host, either by modifying its vigor, or by altering its hormonal/defense status. Here, we studied indirect interactions between arbuscular mycorrhizal (AM) fungi and three plant pathogens. We show that AM fungal sporulation was only triggered by the least aggressive fungal pathogen, which is known to induce a jasmonate-based hormonal response by the host without affecting its vegetative growth and vigor. Conversely, the most aggressive fungal pathogen considerably reduced host vigor but did not alter AM fungal growth and sporulation. Our results thus suggest that the plant hormonal system is an important component of indirect interactions between AM fungi and plant pathogens.

Role of gibberellins during arbuscular mycorrhizal formation in tomato: new insights revealed by endogenous quantification and genetic analysis of their metabolism in mycorrhizal roots.

Gibberellins (GAs) are key regulators of plant growth and development and recent studies suggest also a role during arbuscular mycorrhizal (AM) formation. Here, complementary approaches have been used to obtain a clearer picture that correlates AM fungal development inside roots with GA metabolism. An extensive analysis of genes associated with GA metabolism as well as a quantification of GA content in roots was made. Application of GA3 and its biosynthesis inhibitor prohexadione calcium (PrCa) combined with a GA-constitutive response mutant (procera) were used to determine whether fungal colonization is altered by the level of these hormones or by changes in the GA-signaling pathway. The increased levels of specific GAs from the 13-hydroxylation pathway in mycorrhizal roots correlate closely with the increased expression of genes coding enzymes from the GA biosynthetic trail. The imbalance of GAs in tomato roots caused by exogenous applications of GA3 or PrCa affects arbuscules in both negative and positive ways, respectively. In addition, procera plants were adversely affected by the mycorrhization process. Our findings demonstrate that an imbalance in favor of an increased amount of GAs negatively affects the frequency of mycorrhization and particularly the arbuscular abundance in tomato mycorrhizal roots and the results point out that AM formation is associated with a change in the 13-hydroxylation pathway of GAs.

Combining Metabolomics and Gene Expression Analysis Reveals that Propionyl- and Butyryl-Carnitines Are Involved in Late Stages of Arbuscular Mycorrhizal Symbiosis

The arbuscular mycorrhizal (AM) symbiosis is a widespread mutualistic association between soil fungi (Glomeromycota) and the roots of most plant species. AM fungi are obligate biotrophs whose development is partially under the control of their plant host. We explored the possibility to combine metabolomic and transcriptomic approaches to find putative mycorrhiza-associated metabolites regulating AM fungal development. Methanol extracts of Medicago truncatula roots colonized or not with the AM fungus Rhizophagus irregularis were analyzed and compared by ultra-high-performance liquid chromatography (UHPLC), high-resolution mass spectrometry (Q-TOF), and multivariate statistical discrimination. We detected 71 mycorrhiza-associated analytes exclusively present or at least 10-fold more abundant in mycorrhizal roots. To identify among these analytes those that could regulate AM fungal development, we fractionated by preparative and semi-preparative HPLC the mycorrhizal and non-mycorrhizal root extracts and established how the 71 analytes were distributed among the fractions. Then we tested the activity of the fractions on germinating spores of R. irregularis by quantifying the expression of 96 genes known for their diverse in planta expression patterns. These investigations reveal that propionyl- and butyryl-carnitines accumulated in mycorrhizal roots. The results suggest that these two molecules regulate fungal gene expression in planta and represent interesting candidates for further biological characterization.

Phosphorus and carbon availability regulate structural composition and complexity of AM fungal mycelium

The regulation of the structural composition and complexity of the mycelium of arbuscular mycorrhizal (AM) fungi is not well understood due to their obligate biotrophic nature. The aim of this study was to investigate the structure of extraradical mycelium at high and low availability of carbon (C) to the roots and phosphorus (P) to the fungus. We used monoxenic cultures of the AM fungus Rhizophagus irregularis (formerly Glomus intraradices) with transformed carrot roots as the host in a cultivation system including a root-free compartment into which the extraradical mycelium could grow. We found that high C availability increased hyphal length and spore production and anastomosis formation within individual mycelia. High P availability increased the formation of branched absorbing structures and reduced spore production and the overall length of runner hyphae. The complexity of the mycelium, as indicated by its fractal dimensions, increased with both high C and P availability. The results indicate that low P availability induces a growth pattern that reflects foraging for both P and C. Low C availability to AM roots could still support the explorative development of the mycelium when P availability was low. These findings help us to better understand the development of AM fungi in ecosystems with high P input and/or when plants are subjected to shading, grazing or any management practice that reduces the photosynthetic ability of the plant.

Late activation of the 9-oxylipin pathway during arbuscular mycorrhiza formation in tomato and its regulation by jasmonate signalling

The establishment of an arbuscular mycorrhizal (AM) symbiotic interaction is a successful strategy for the promotion of substantial plant growth, development, and fitness. Numerous studies have supported the hypothesis that plant hormones play an important role in the establishment of functional AM symbiosis. Particular attention has been devoted to jasmonic acid (JA) and its derivates, which are believed to play a major role in AM symbiosis. Jasmonates belong to a diverse class of lipid metabolites known as oxylipins that include other biologically active molecules. Recent transcriptional analyses revealed up-regulation of the oxylipin pathway during AM symbiosis in mycorrhizal tomato roots and indicate a key regulatory role for oxylipins during AM symbiosis in tomato, particularly those derived from the action of 9-lipoxygenases (9-LOXs). Continuing with the tomato as a model, the spatial and temporal expression pattern of genes involved in the 9-LOX pathway during the different stages of AM formation in tomato was analysed. The effects of JA signalling pathway changes on AM fungal colonization were assessed and correlated with the modifications in the transcriptional profiles of 9-LOX genes. The up-regulation of the 9-LOX oxylipin pathway in mycorrhizal wild-type roots seems to depend on a particular degree of AM fungal colonization and is restricted to the colonized part of the roots, suggesting that these genes could play a role in controlling fungal spread in roots. In addition, the results suggest that this strategy of the plant to control AM fungi development within the roots is at least partly dependent on JA pathway activation.

Benzo[a]pyrene induced lipid changes in the monoxenic arbuscular mycorrhizal chicory roots

Arbuscular mycorrhizal (AM) colonization may be one of the means that protects plants and allows them to thrive on polycyclic aromatic hydrocarbon-polluted soils including the carcinogenic benzo(a)pyrene (B[a]P). To understand the mechanisms involved in the AM symbiosis tolerance to B[a]P toxicity, the purpose of this study was to compare the lipid compositions as well as the contents between mycorrhizal and non-mycorrhizal chicory root cultures grown in vitro under B[a]P pollution. Firstly, B[a]P induced significant decreases of the Glomalean lipid markers: C16:1ω5 and 24-methyl/methylene sterol amounts in AM roots indicating a reduced AM fungal development inside the roots. Secondly, whereas increases in fatty acid amounts after B[a]P application were measured in non-mycorrhizal roots, no changes were shown in mycorrhizal roots. On the other hand, while, after treatment with B[a]P, the total phospholipid contents were unmodified in non-mycorrhizal roots in comparison with the control, drastic reductions were observed in mycorrhizal roots, mainly owing to decreases in phosphatidylethanolamine and phosphatidylcholine. Moreover, B[a]P affected AM root sterols by reducing stigmasterol. In conclusion, the findings presented in this paper have highlighted, for the first time, significant changes in the AM root lipid metabolism under B[a]P pollution and have culminated on their role in the defense/protection mechanisms.

Dynamics of arbuscular mycorrhizal fungi associated with desert ephemeral plants in Gurbantunggut Desert

Previous studies documented that most desert plants can be colonized by arbuscular mycorrhizal (AM) fungi, however, little is known about how the dynamics of AM fungi are related to ephemerals in desert ecosystems. The dynamics of AM fungi with desert ephemerals were examined to determine the effects of host plant life stages on the development of AM fungi. Mean colonization of ephemeral annual plants was 45% lower than that of ephemeral perennial plants. The colonizations were much higher in the early part of the growing season than in later parts, peaking at flowering times. The phenology of AM fungi in root systems varied among different ephemerals. The density of AM fungal spores increased with the development of ephemeral annual plants, reached its maximum at flowering times, and then plateaued about 20 days after the aboveground senescence. A significant positive correlation was found between AM fungi spore density and biomass of ephemeral annual plants. The life cycles of AM fungi associated with desert ephemerals were very short, being about 60–70 days. Soil temperature and water content had no direct influence on the development of AM fungal spores. We concluded that the development of AM fungi was in response to desert ephemeral phenology and life history strategy.