Mycorrhiza最新文献

Pesticides are essential agricultural inputs that help securing crop yields. However, they can affect non-target soil microorganisms, including arbuscular mycorrhizal (AM) fungi, that are potential indicators of the toxicity of pesticides on the soil microbiota. Here, we developed a fast-track high-throughput spore germination test, for AM fungi produced in vitro. This test allows the determination of EC₅₀ values and the nature of the effects of pesticides on AM fungal spores (fungicidal or fungistatic). First, 19 active ingredients were tested on Rhizophagus intraradices MUCL 49410. Secondly, five of these compounds, varying in their toxicity to R. intraradices, were tested on three additional AM fungi (Rhizophagus irregularis MUCL 41833, Rhizophagus clarus MUCL 46238 and Rhizophagus aggregatus MUCL 49408). Our results showed that the toxicity of pesticides varied according to their chemical nature, concentration and AM fungal species tested. With the exception of 3,5,6-trichloro-2-pyridinol (TCP, a transformation product of chlorpyrifos), insecticides and herbicides had no detrimental effect on spore germination at the concentration expected in soil upon application of the recommended dose, unlike most fungicides, which had an impact on one or more AM fungi. Fludioxonil and pyraclostrobin were by far the most problematic fungicide and R. aggregatus the most sensitive strain to pesticides. This AM fungus could thus be a good indicator to be used in standard ecotoxicity testing. In conclusion, we present a fast-track, high-throughput testing system for assessing the toxicity of pesticides on AM fungi, using spore germination as a relevant endpoint, that could be used as a first-tier screening tool in pesticide risk assessment.

Ecosystem functioning is influenced by biological diversity, ecological interactions, and abiotic conditions. Human interactions with ecosystems can cause major changes in how they function when involving changes in the vegetation cover and structure (i.e., land use change). This study examines how land use change affects the diversity of arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (EMF) in soil and rodent scats in temperate forest sites. We collected soil and rodent scat samples at five paired sites (i.e., disturbed vs. undisturbed) in Michoacan, Mexico. We identified 112 putative mycorrhizal fungi species using DNA barcoding based on partial internal transcribed region 1 (ITS) sequences. We found a higher richness of EMF in undisturbed soil samples compared to disturbed soil samples and a higher AMF diversity in rodent scat samples from disturbed than undisturbed sites. Scat samples had a high incidence of both AMF (75%) and EMF (100%). We found significant differences in the diversity of both AMF and EMF depending on the rodent species associated with them. We also found a higher diversity of EMF in scats in the wet season than in the dry season. We also report, for the first time, associations between Sigmodon hispidus and numerous AMF and EMF species. Overall, our study highlights the role of rodents as important dispersal vectors of mycorrhizal fungi, particularly for EMF that could be essential to build up mycorrhizal fungi spore banks in disturbed forests.

Tricholoma kakishimeji, a poisonous fungus containing the toxic compound ustalic acid, has sometimes been misidentified as closely related species (T. stans, T. matsushimeji, T. kakishimejioides) under the name T. ustale in Japan until recently. Tricholoma ustale s. str. was not found in Japan according to a recent study, and it has been only recorded in Europe. Here, we report the first comprehensive morphological comparison of ectomycorrhizae among these four Tricholoma species. Several cultured strains of these species were inoculated onto Pinus densiflora in vitro. The resulting ectomycorrhizal pine seedlings were subsequently used as mother plants to establish an ectomycorrhizal system on Fagaceae plants. Although all tested fungal strains formed ectomycorrhizae on pine, mycorrhizal colonization by T. kakishimejioides was limited. On Quercus hosts, T. matsushimeji exhibited discontinuous Hartig net development, whereas T. kakishimeji and T. stans produced distinct Hartig nets. Additionally, ectomycorrhizal biomass development on oak hosts was limited in T. stans and T. matsushimeji. These findings correspond to the habitat characteristics of these fungal species. Ectomycorrhizae of these Tricholoma species sampled from natural forests showed morphological and anatomical characteristics similar to their in vitro ectomycorrhizae, including species-specific hyphal arrangements of the mantle and rhizomorphs. We propose that the ectomycorrhizal specificity of Tricholoma can be experimentally assessed in relation to their genetic background on pine and oak hosts, as well as the phyloecological characteristics of these fungal species.

Sugar beet (Beta vulgaris L.) is cultivated extensively worldwide as an important cash crop, and soil salinity is a critical factor influencing both its yield and sugar content. Consequently, enhancing the salt tolerance of sugar beet is of paramount importance. Arbuscular mycorrhizal (AM) fungi form symbiotic associations with approximately 80% of vascular plants, thereby improving the adaptability of host plants to adverse conditions. However, the mechanisms by which the AM symbiosis assists sugar beet in coping with salt stress remain poorly understood. To investigate the adaptation strategies employed by AM symbiotic sugar beet under salt stress, we examined physiological and transcriptomic changes in sugar beet seedlings subjected to various treatments, using the KWS1176 variety as the experimental material. The results indicated that AM symbiotic sugar beet demonstrated superior performance under salt stress, characterized by improved seedling growth, alterations in antioxidant enzyme activities, modifications in osmoregulatory substance levels, reduced Na⁺ uptake, and enhanced K⁺ influx within the root system. Notably, most of the differentially expressed genes were implicated in pathways related to reactive oxygen species scavenging, phenylpropanoid biosynthesis, and phytohormone signal transduction. Furthermore, pivotal genes identified through weighted gene co-expression network analysis were validated via reverse transcription-quantitative PCR, revealing that the salt tolerance of AM symbiotic sugar beet may be associated with its ionic homeostasis, antioxidant enzyme activities, and regulation of photosynthesis at both transcriptional and physiological levels.

Fully mycoheterotrophic (FMH) orchids rely entirely on mycorrhizal fungi for carbon and nutrients, with tropical Asian FMH orchids typically associating with saprotrophic fungi, though some known relationships also with ectomycorrhizal fungi, leaving much to learn about their fungal partners. Didymoplexis belongs to tribe Gastrodieae, which represents one of the largest fully mycoheterotrophic orchid lineages. Although mycorrhizal associations of its sister genus Gastrodia have been relatively well-studied, those of Didymoplexis remain largely unexplored. Here, we used molecular barcoding to analyze fungal associations and stable isotope analysis to elucidate the nutritional strategies of Didymoplexis micradenia, Didymoplexis pallens, and Didymoplexis siamensis in subtropical and tropical forests across Taiwan. In Didymoplexis pallens and Didymoplexis micradenia, most fungal partners were litter-decaying fungi (Mycena, Clitocybula, Marasmius, Gymnopus) with smaller contributions from ectomycorrhizal and rhizoctonia fungi. In Didymoplexis siamensis, ectomycorrhizal fungi dominated, particularly Sebacinales, however, with additional associations with wood-decaying Delicatula. The pattern of carbon and nitrogen isotope enrichments found for the three Didymoplexis species was in the typical range known for fully mycoheterotrophic orchids associated with litter- or wood-decaying fungi. ¹⁵N enrichments of all investigated Didymoplexis species distinguished from fully mycoheterotrophic orchids associated with ectomycorrhizal fungi. Despite its ectomycorrhizal association, Didymoplexis siamensis was weakly enriched in ¹⁵N and more enriched in ¹³C than found for exclusively ectomycorrhizal fully mycoheterotrophic orchids. Thus, Didymoplexis siamensis covered its carbon and nitrogen demand obviously through the additional association with wood-decaying Delicatula. These findings enhance our understanding of the diverse fungal associations and physiological ecology of Didymoplexis species in subtropical and tropical ecosystems.

Earthworms and arbuscular mycorrhizal fungi (AMF) are two different organisms playing crucial role in soil mechanisms. The integration of earthworms and AMF in phytoremediation strategies leverages their combined ability to improve soil structure, nutrient availability, and microbial activity while modulating metal bioavailability. These entities promote soil-plant interactions and enhance the phytoremediation process of heavy metals-contaminated soil. This review explores the mechanisms by which earthworms and AMF function individually and in combination in the phytoremediation of heavy metal-contaminated soil. The main objectives of this were determine earthworms heavy metals tolerance, absorption and transformation, as well as the synergistic effect between earthworms and plants. Further, the effects of AMF on heavy metals phytoremedoation process was also analyzed as well as the potential interactions between earthworms and AMF on heavy metals removal. This partnership can optimize plant health and remediation efficiency, making it a promising approach for restoring heavy metal-contaminated soils. Thus an integrated empirical study was conducted to summarize the effects earthworms and AMF interactions on heavy metals phytoremediation and to highlight the impact of their individual and combined actions on the phytoremediation paramters. Avenue for further studies towards improved phytoremediation process we discussed. This review emphasize that earthworms and AMF can be employed as biological method to enhance the phytoextraction by hyperaccumulator plants on severely heavy metal-contaminated soil. Alternatively, in moderately and lowly contaminated farmland, the transfer of heavy metals to the above-ground parts of crops can be reduced to promote safe production.

Mycorrhizal and saprotrophic macromycetes contribute strongly to the carbon and nitrogen cycles of forest ecosystems, often studied by tracing stable isotope composition of carbon and nitrogen. The phenomenon of the saprotrophic-mycorrhizal divide highlights the difference in the stable isotope composition of fruiting bodies of mycorrhizal and saprotrophic fungi. Much less is known about the isotopic composition of the mycelium, which plays an important role in the formation of the soil organic matter and fuels the fungal trophic channel in soil food webs. In this study, we assessed whether the saprotrophic-mycorrhizal divide in the natural δ¹³С and δ¹⁵N values can be traced throughout entire fungal organisms. This hypothesis was tested using 16 species of ectomycorrhizal and six species of saprotrophic basidiomycetous fungi. We showed that not only fruiting bodies, but also the mycelium of ectomycorrhizal and saprotrophic fungi differs in the δ¹³C and δ¹⁵N values. In both ectomycorrhizal and saprotrophic fungi, the δ¹³C and δ¹⁵N values increased from mycelium to hymenophores and correlated positively with the total N content in the corresponding tissues. The differences between ectomycorrhizal and saprotrophic mycelium can be used to reconstruct the fungal-driven belowground carbon and nitrogen allocation, and the contribution of saprotrophic and mycorrhizal fungi to soil food webs.

The normal development of mycorrhizal symbiosis is a dynamic process, requiring elaborately regulated interactions between plant roots and compatible fungi, mandatory for both partners´ survival. In the present study, we further elucidated the mycorrhizal development of the desert truffles Terfezia claveryi with the host plant Helianthemum almeriense as an ectendomycorrhizal symbiosis model under greenhouse conditions. To investigate this, we evaluated the morphology of mycorrhizal colonization, concomitantly with the dynamic expression of selected marker genes (6 fungal and 11 plant genes) measured every week until mycorrhiza maturation (three months). We were able to determine 3 main stages in the mycorrhization process, 1) pre-symbiosis stage where mycelium is growing in the soil with no direct interaction with roots, 2) early symbiosis stage when the fungus spreads along the roots intercellularly and plant-fungal signaling is proceeding, and 3) late symbiosis stage where the fungus consolidates and matures with intracellular hyphal colonization; this is characterized by the regulation of cell-wall remodeling processes.

Robusta coffee, grown by 25 million farmers across more than 50 countries, plays an important role in smallholder farmers' livelihoods and the economies of many low-income countries. Coffee establishes a mutualistic symbiosis with arbuscular mycorrhizal fungi (AMF); however, the impact of agricultural practices and soil characteristics on AMF diversity and community composition is not well understood. To address this, we characterised the AMF community composition of robusta coffee in part of its region of origin, the Democratic Republic of Congo. AMF diversity and community composition were compared between coffee monoculture, agroforestry systems and wild robusta in its native rainforest habitat. Using Illumina sequencing on 304 root samples, we identified 307 AMF operational taxonomic units (OTUs), dominated by the genera Glomus and Acaulospora. OTU richness did not vary across the three studied systems, yet large differences in community composition were found. Many unique OTUs were only observed in the coffee in the rainforest. In general, lower available soil phosphorus (P) and lower soil bulk density increased AMF diversity, yet higher available soil P and pH increased AMF diversity in the wild forest coffee. Shifts in AMF community composition across coffee systems were driven by canopy closure, soil pH, available soil P and soil bulk density. Our study is the first to characterise mycorrhizal communities in wild robusta coffee in its region of origin and shows that even low-input agricultural practices result in major AMF community shifts as compared to a natural baseline.

Mycoheterotrophic plants, which depend entirely on mycorrhizal fungi for carbon acquisition, often exhibit high specificity toward their fungal partners. Members of Thismiaceae are generally recognized for their extreme mycorrhizal specialization and rarity. In this study, we examined the mycorrhizal associations of Relictithismia, a recently discovered monotypic genus within Thismiaceae, and Thismia abei, a Thismia species with a similar distribution in southern Japan, by employing high-throughput DNA sequencing of the 18S rRNA gene. Our analyses revealed that both R. kimotsukiensis and T. abei are predominantly associated with two specific virtual taxa (VTX00295 and VTX00106) of the genus Rhizophagus (Glomeraceae). These shared associations may reflect either phylogenetic niche conservatism, in which the common ancestor of R. kimotsukiensis and T. abei retained the same AM fungal partners, or convergent evolution, in which the AM fungal phylotypes were independently recruited due to their potential benefits for these mycoheterotrophic plants. Furthermore, BLAST searches demonstrated that VTX00295 and VTX00106 are widely distributed globally, suggesting that highly specialized mycorrhizal interactions are unlikely to be the primary drivers of the limited distribution and rarity of R. kimotsukiensis and T. abei. Overall, our findings enhance our understanding of high mycorrhizal specificity in Thismiaceae. However, broader investigations, combining extensive sampling of Thismiaceae species with ancestral state reconstruction, are needed to determine whether the shared associations detected here reflect phylogenetic niche conservatism or convergent evolution.