Ectomycorrhizal Root Research Articles

The poplar SWEET1c glucose transporter plays a key role in the ectomycorrhizal symbiosis.

The mutualistic interaction between ectomycorrhizal fungi and trees is characterized by the coordinated exchange of soil nutrients with soluble sugars. Despite the importance of this process, the precise mechanism by which sugars are transported from host roots to colonizing hyphae remains unclear. This study aimed to identify the specific membrane transporters responsible for the unloading of sugars at the symbiotic interface, with a focus on the role of the root Sugars Will Eventually Be Exported Transporter (SWEET) uniporters. Our study used RNA sequencing and quantitative PCR to identify PtaSWEET gene expression in Populus tremula × alba-Laccaria bicolor ectomycorrhizal root tips. Our results suggest that symbiosis-induced PtaSWEET1c is primarily responsible for transporting glucose and sucrose, as demonstrated by the yeast assays. Moreover, we used a promoter-YFP reporter to confirm the localization of the PtaSWEET1c expression in cortical cells of ectomycorrhizal rootlets, supporting its major role in supplying glucose at the symbiotic interface. Furthermore, our observations confirmed the localization of PtaSWEET1c-GFP in the plasma membrane. The inactivation of PtaSWEET1c reduced ectomycorrhizal root formation and 13C translocation to ectomycorrhizal roots. Our findings highlight the crucial role of PtaSWEET1c in facilitating glucose and sucrose transport at the symbiotic interface of Populus-L. bicolor symbiosis.

Root anatomical adaptations of contrasting ectomycorrhizal exploration types in Pinus sylvestris and Quercus petraea across soil horizons

Abstract Aims The anatomical characteristics of ectomycorrhizal exploration types in response to soil variability remain insufficiently understood. We examined the root anatomy of contact and long-distance exploration types in Pinus sylvestris and Quercus petraea, species with distinct ecological needs, across different soil horizons. Methods The diameter of ectomycorrhizal roots, the root absorptive traits i.e. proportion of cortex and mantle area, the percentage stele in the diameter, and the weighted average diameter of vessels (Ra) in the ectomycorrhizas were measured within ectomycorrhizas collected from organic and mineral soils across the soil profile. Results The absorptive traits varied along soil horizons, in which water and nutrient availability changed inversely. The proportion of cortex was associated with exploration type, but was not specific to tree species. However, the ectomycorrhizal diameter and the percentage of mantle within the root forming contact exploration type of P. sylvestris showed no variation among soil horizons. In contrast, the soil horizon significantly influenced all root anatomical traits in the contact exploration type of Q. petraea by enhancing the contribution of the absorption area of the root area, mainly in the illuvial horizon, but reaching the smallest value in the organic horizon. The Ra and the cell wall thickness of the vessels were strongly dependent on tree species. With increasing soil depth, Ra in Q. petraea increased, and stele proportion in root diameter decreased. Conclusion The results suggest that water acquisition traits differ among tree species, but traits associated with nutrient absorption (proportion of cortex and mantle area) within specific soil horizons are closely related to the ectomycorrhizal exploration type.

Soil Legacies of Tree Species Composition in Mature Forest Affect Tree Seedlings’ Performance

AbstractTrees affect the biotic and abiotic properties of the soil in which they grow. Tree species-specific effects can persist for a long time, even after the trees have been removed. We investigated to what extent such soil legacies of different tree species may impact tree seedlings in their emergence and growth. We performed a plant–soil feedback experiment, using soil that was conditioned in plots that vary in tree species composition in Białowieża Forest, Poland. Soil was taken from plots varying in proportion of birch, hornbeam, pine, and oak. In each soil, seeds of the same four target species were sown in pots. Seedling emergence and growth were monitored for one growing season. To further explore biotic implications of soil legacies, ectomycorrhizal root tip colonization of oak, a keystone forest species, was determined. We found no effect of soil legacies of tree species on the emergence measures. We, however, found a clear negative effect of pine legacies on the total biomass of all four seedling species. In addition, we found relationships between the presence of pine and soil fertility and between soil fertility and root tip colonization. Root tip colonization was positively correlated with the biomass of oak seedlings. We conclude that tree species can leave legacies that persist after that species has been removed. These legacies influence the growth of the next generation of trees likely via abiotic and biotic pathways. Thus, the choice of species in today’s forest may also matter for the structure and composition of future forests.

Estructura de la comunidad bacteriana asociada con raíces de Pinus montezumae Lamb. inoculado con hongos ectomicorrízicos comestibles y bacteria auxiliar de la micorriza

Tree roots are associated with a high diversity of microorganisms that play key roles in soil fertility and plant nutrition and health. Here we examine the composition and diversity of bacterial community in ectomycorrhizal root (ECR) and their ectomycorrhizosphere (EMR) of the Neotropical tree Pinus montezumae inoculated with Laccaria laccata and Hebeloma mesophaeum, applied alone or co-inoculated with Azospirillum brasilense. For this, we used a 16S rRNA gene metabarcoding-sequencing approach in samples of ECR and EMR that were collected nine-months after inoculation in greenhouse. A total of 943 Operational Taxonomic Units (OTU) were differentiated and grouped in 32 bacterial phyla. The most abundant phyla were Proteobacteria (67%) and Actinobacteria (20.7%). Bacterial communities were structured in ECR and EMR (Anosim, R=0.77, P≤0.005), and were more diverse in EMR than ECR (Shannon-Weaver of 4.2 and 3.6, and Simpson inverse of 33.7 and 16.7, respectively). The abundance of Pseudomonas, Actinoplanes and Salinibacterium were promoted with L. laccata, while with H. mesophaeum an OTU from Burkholderiaceae was prominent. Our results showed that the ectomycorrhizal fungi strongly shaped the composition of the bacterial communities associated with roots of P. montezumae.

LbSakA-mediated phosphorylation of the scaffolding protein LbNoxR in the ectomycorrhizal basidiomycete Laccaria bicolor regulates NADPH oxidase activity, ROS accumulation and symbiosis development.

Ectomycorrhizal symbiosis, which involves mutually beneficial interactions between soil fungi and tree roots, is essential for promoting tree growth. To establish this symbiotic relationship, fungal symbionts must initiate and sustain mutualistic interactions with host plants while avoiding host defense responses. This study investigated the role of reactive oxygen species (ROS) generated by fungal NADPH oxidase (Nox) in the development of Laccaria bicolor/Populus tremula × alba symbiosis. Our findings revealed that L. bicolor LbNox expression was significantly higher in ectomycorrhizal roots than in free-living mycelia. RNAi was used to silence LbNox, which resulted in decreased ROS signaling, limited formation of the Hartig net, and a lower mycorrhizal formation rate. Using Y2H library screening, BiFC and Co-IP, we demonstrated an interaction between the mitogen-activated protein kinase LbSakA and LbNoxR. LbSakA-mediated phosphorylation of LbNoxR at T409, T477 and T480 positively modulates LbNox activity, ROS accumulation and upregulation of symbiosis-related genes involved in dampening host defense reactions. These results demonstrate that regulation of fungal ROS metabolism is critical for maintaining the mutualistic interaction between L. bicolor and P. tremula × alba. Our findings also highlight a novel and complex regulatory mechanism governing the development of symbiosis, involving both transcriptional and posttranslational regulation of gene networks.

Nonlinear responses of ericaceous and ectomycorrhizal Arctic shrubs across a long‐term experimental nutrient gradient

AbstractIn the Arctic tundra, warming is anticipated to stimulate nutrient release and potentially alleviate plant nutrient limitations. Typically simulated by fertilization experiments that saturate plant nutrient demand, future increases in soil fertility are thought to favor ectomycorrhizal (EcM) over ericaceous shrubs and have often been identified as a key driver of Arctic shrub expansion. However, the projected increases in fertility will likely vary in their alleviation of nutrient limitations. The resulting responses of shrubs and their mycorrhizae across the gradient of nutrient limitation may be nonlinear and could contradict the current predictions of tundra vegetation shifts. We compared the functional responses of two dominant shrubs, EcM dwarf birch (Betula nana) and ericaceous Labrador tea (Rhododendron tomentosum), across a long‐term nitrogen and phosphorus fertilization gradient experiment in Arctic Alaska. Using linear mixed‐effects modeling, we tested the responses of shrub cover, height, and root enzyme activities to soil fertility. We found that B. nana cover and height linearly increased with soil fertility. In contrast, R. tomentosum cover initially increased, but decreased after surpassing the intermediate levels of increased soil fertility. Its height did not change. Enzyme activity did not respond to soil fertility on EcM‐colonized B. nana roots, but sharply declined on R. tomentosum roots. Overall, the nonlinear responses of shrubs to our fertility gradient demonstrate the importance of experiments grounded in replicated regression design. Our results indicate that under moderate increases in soil fertility, Arctic shrub expansion may not only include deciduous EcM shrubs but also ericaceous shrubs. Regardless of shifts aboveground, changes in root enzyme activity belowground point to some EcM shrub species playing a more influential role in tundra soils; as EcM roots remained steady in their liberation of soil organic nutrients with heightened soil fertility, degradative root enzyme activity on the dominant ericaceous shrub dropped—in some instances with even the slightest increase in fertility.

Optimizing conditions of mycelial inoculum immobilized in Ca-alginate beads: a case study in ectomycorrhizal fungus Astraeus odoratus.

Ectomycorrhizal inoculum has emerged as a critical tool for forest restoration, especially under challenging climate change conditions. The inoculation of selective ectomycorrhizal fungi can enhance seedling survival and subsequent growth in the field. This study optimized the liquid media for mycelial growth of Astraeus odoratus strain K1 and the sodium alginate solution composition for enhanced mycelial viability after entrapment. Using Modified Melin-Norkrans as the optimal media for mycelial cultivation and 2% sodium alginate supplemented with Czapek medium, 0.25% activated charcoal, 5% sucrose, and 5% sorbitol in the alginate solution yielded the highest viability of A. odoratus mycelia. Preservation in distilled water and 10% glycerol at 25°C for 60 days proved to be the most effective storage condition for the alginate beads. Both fresh and preserved alginate beads were tested for colonizing on Hopea odorata Roxb. seedlings, showing successful colonization and ectomycorrhizal root formation, with over 49% colonization. This study fills a crucial gap in biotechnology and ectomycorrhizal inoculum, paving the way for more effective and sustainable forest restoration practices.

Characterization of ectomycorrhizal fungal community of Abies Pindrow using sporocarp sampling, morphotyping, and metabarcoding through next-generation sequencing.

Abies pindrow, commonly known as the West-Himalayan Fir, holds great ecological importance as a native tree species in the Himalayas. Beyond its value as a fuel and timber source, it serves as a keystone species within the ecosystem. However, over recent years, extensive degradation and deforestation have afflicted A. pindrow forests. Utilizing ectomycorrhizal fungal symbionts of A. pindrow could prove pivotal in restoring these deteriorated forests. This study aimed to evaluate the diversity and composition of the ectomycorrhizal fungal community associated with A. pindrow. We employed ectomycorrhizal root tip morphotyping, sporocarp sampling, and Illumina MiSeq metabarcoding of the ITS region of fungal nrDNA. The ectomycorrhizal root tips were categorized into 10 morphotypes based on their morphological characteristics, exhibiting an average colonization rate of 74%. Sporocarp sampling revealed 22 species across 10 genera, with Russula being the most prevalent. The metabarcoding yielded 285,148 raw sequences, identifying 326 operational taxonomic units (OTUs) belonging to 193 genera, 114 families, 45 orders, 22 classes, and 6 divisions. Of these, 36 OTUs across 20 genera were ectomycorrhizal, constituting 63.1% of the fungal community. Notably, Tuber was the most abundant, representing 37.42% of the fungal population, followed by Russula at 21.06%. This study provides a comprehensive understanding of mycorrhizal symbionts of A. pindrow. The findings hold significant implications for utilizing dominant ectomycorrhizal fungi in reforestation endeavors aimed at restoring this important Himalayan conifer.

Exploration capacity versus specific enzymatic activity of ectomycorrhizas in response to primary productivity and soil phosphorus availability in Bornean tropical rainforests.

Ectomycorrhizal (ECM) fungi are functionally important in biogeochemical cycles in tropical ecosystems. Extracellular enzymatic activity of ECM on a ground-area basis is the product of two attributes; exploration capacity (ECM surface-area) and specific enzymatic activity. Here, we elucidated which attribute better explained the ECM enzymatic activity in response to different levels of soil phosphorus (P) and Nitrogen (N) availability in five Bornean tropical rainforests. We determined the surface area of ECM root tips as well as the enzymatic activities per ECM surface area for carbon (C), N and P degrading enzymes in each site. We evaluated the relationship of ECM enzyme activities with the resource availabilities of C (Above-ground net primary production; ANPP), N, and P of ECM by a generalized linear mixed model. The ECM enzymatic activities on a ground-area basis were more significantly determined by specific enzymatic activity than by the exploration capacity. Specific enzymatic activities were generally negatively affected by C (ANPP) and soil P availability. ECM fungi enhance the specific enzyme activity rather than the exploration capacity to maintain the capacity of nutrient acquisition. The less dependence of ECM fungi on the exploration capacity in these forests may be related to the limitation of C supply from host trees. We highlighted the adaptive mechanisms of ECM fungi on nutrient acquisition in tropical ecosystems through the response of enzymatic activity to nutrient availability across the elements.

Effect of Bacteria Inoculation on Colonization of Roots by Tuber melanosporum and Growth of Quercus ilex Seedlings.

Tuber melanosporum is an ascomycete that forms ectomycorrhizal (ECM) symbioses with a wide range of host plants, producing edible fruiting bodies with high economic value. The quality of seedlings in the early symbiotic stage is important for successful truffle cultivation. Numerous bacterial species have been reported to take part in the truffle biological cycle and influence the establishment of roots symbiosis in plant hosts and the development of the carpophore. In this work, three different bacteria formulations were co-inoculated in Quercus ilex L. seedlings two months after T. melanosporum inoculation. At four months of bacterial application, the T. melanosporum ECM root tip rate of colonization and bacterial presence were assessed using both morphological and molecular techniques. A 2.5-fold increase in ECM colonization rate was found in the presence of Pseudomonas sp. compared to the seedlings inoculated only with T. melanosporum. The same treatment caused reduced plant growth either for the aerial and root part. Meanwhile, the ECM colonization combined with Bradyrhizobium sp. and Pseudomonas sp. + Bradyrhizobium sp. reduced the relative density of fibrous roots (nutrient absorption). Our work suggests that the role of bacteria in the early symbiotic stages of ECM colonization involves both the mycorrhizal symbiosis rate and plant root development processes, both essential for improve the quality of truffle-inoculated seedlings produced in commercial nurseries.

Re-examination of the Southern Hemisphere truffle genus Amylascus (Pezizaceae, Ascomycota) and characterization of the sister genus Nothoamylascus gen. nov.

Amylascus is a genus of ectomycorrhizal truffles within Pezizaceae that is known from Australia and contains only two described species, A. herbertianus and A. tasmanicus. Species of Amylascus are closely related to truffles (Pachyphlodes, Luteoamylascus) and cup fungi (Plicariella) from the Northern Hemisphere. Here we reevaluate the species diversity of Amylascus and related taxa from southern South America and Australia based on new morphological and molecular data. We identify previously undocumented diversity and morphological variability in ascospore color, ascospore ornamentation, hymenial construction, epithecium structure and the amyloid reaction of the ascus in Melzer's reagent. We redescribe two Amylascus species from Australia and describe seven new Amylascus species, five from South America and two from Australia. This is the first report of Amylascus species from South America. We also describe the new South American genus Nothoamylascus as sister lineage to the Pachyphlodes-Amylascus-Luteoamylascus clade (including Amylascus, Luteoamylascus, Pachyphlodes, and Plicariella). We obtained ITS sequences of mitotic spore mats from Nothoamylascus erubescens gen. & sp. nov. and four of the seven newly described Amylascus species, providing the first evidence of mitotic spore mats in Amylascus. Additional ITS sequences from mitotic spore mats reveal the presence of nine additional undescribed Amylascus and one Nothoamylascus species that do not correspond to any sampled ascomata. We also identify three additional undescribed Amylascus species based on environmental sequences from the feces of two grounddwelling bird species from Chile, Scelorchilus rubecula and Pteroptochos tarnii. Our results indicate that ascomata from Amylascus and Nothoamylascus species are rarely collected, but molecular data from ectomycorrhizal roots and mitotic spore mats indicate that these species are probably common and widespread in southern South America. Finally, we present a time-calibrated phylogeny that is consistent with a late Gondwanan distribution. The time since the most recent common ancestor of: 1) the family Pezizaceae had a mean of 276 Ma (217-337 HPD); 2) the Amylascus-Pachyphlodes-Nothoamylascus-Luteoamylascus clade had a mean of 79 Ma (60-100 HPD); and 3) the Amylascus-Pachyphlodes clade had a mean of 50 Ma (38-62 HPD). The crown age of Pachyphlodes had a mean of 39 Ma (25-42 HPD) and Amylascus had a mean age of 28 Ma (20-37 HPD), falling near the Eocene-Oligocene boundary and the onset of the Antarctic glaciation (c. 35 Ma). Citation: Healy RA, Truong C, Castellano MA, et al. 2023. Re-examination of the Southern Hemisphere truffle genus Amylascus (Pezizaceae, Ascomycota) and characterization of the sister genus Nothoamylascus gen. nov. Persoonia 51: 125-151. doi: 10.3767/persoonia.2023.51.03.

Ectomycorrhizas of Rhizopogon himalayensis on Cedrus deodara.

The ectomycorrhizal (EcM) roots of Cedrus deodara associated with a unique hypogeous EcM fungus-Rhizopogon himalayensis is meticulously characterized and comprehensively described based on well-established standard morphological and anatomical features. The mycobiont-R. himalayensis was found organically associated with the roots of C. deodara. The EcM morphotypes are distinguished by differences in the shape and color of the roots, type of ramification, surface texture, type of mantle, as well as different chemical reactions. All the examined morphotypes were having similar mycorrhizal system and anatomically (Mantle and Hartig net) no disparities were seen, that is, nonsignificant (p > 0.05) variations were observed. The majority of mycorrhizal systems were irregularly pinnate, dichotomous type with 0-1 order of ramification and occasional coralloid type. Mantle surface was densely cottony to loosely wooly. The outer and inner mantles were H & Q type. Hartig net was a complex net-like structure with uniseriate to mutiseriate type of hyphal cell arrangement. Rhizomorph were smooth and round, consistently growing along roots. Moreover, extraradical hyphae were hyaline, septate, and without clamp connections. Sclerotia and cystidia were absent. Our findings will contribute to the biology of ectomycorrhizae associated with primitive and economically valuable conifers, thriving in the face of shifting environmental conditions in the northwestern Himalayas.

Aseptic In vitro Synthesis of Pinus gerardiana Ectomycorrhizae with Amanita ceciliae and Lactarius sanguifluus

ABSTRACT: The present investigations are aimed to synthesize in vitro ectomycorrhizae between Pinus gerardiana and two gilled ectomycorrhizal (ECM) mushrooms (Amanita ceciliae and Lactarius sanguifluus). To carry out in vitro synthesis, pure cultures of ECM mushrooms (A. ceciliae and L. sanguifluus) were isolated on Potato Dextrose Agar (PDA) and Modified Melin-Norkans (MMN) Medium respectively. The synthesis was achieved successfully in the surfaced sterilized seedlings of P. gerardiana geminated under aseptic conditions by using vermiculite, peat, medium for ECM fungi and inoculum of each fungus in the test tubes. Mycorrhization was checked periodically in the test tubes. P. gerardiana seedlings were lifted from test tubes after five months to observe ectomycorrhizae formation on the root system with A. ceciliae and L. sanguifluus. The synthesized ectomycorrhizae were dark brown in case of A. ceciliae whereas in case of L. sanguifluus the colour of ECM roots was yellowish brown. Anatomy of synthesized ectomycorrhizae with both ECM fungi showed fully developed fungal mantle and Hartig net. The seedlings with ECM synthesis showed a significant effect on the growth and development.

Riverbank lupine’s (Lupinus rivularis) influence on conifer growth, ectomycorrhizal colonization, and neighboring vegetation in coarse sediments left behind after dam removal

IntroductionUntil recently, much of the Elwha River was inaccessible to anadromous fish species due to the Elwha and Glines Canyon dams. Dam deconstruction resulted in approximately 325 ha of formerly inundated lake beds devoid of natural riparian corridors or adjacent forests. Efforts to restore the vegetation have had varying success. Areas where fine sediments settled along the valley walls quickly regenerated, while coarse terraces were slower to revegetate from plantings and directed seeding. One seeded species, riverbank lupine (Lupinus rivularis), quickly established on the coarse-textured terraces. Riverbank lupine is a pioneering species that assimilates nitrogen (N) through N-fixing bacteria; thus, it enriches the soil with bioavailable N and organic matter upon decomposition.MethodsThe goal of this study was to investigate lupine’s influence on conifer establishment in the coarse sediments of the former Lake Mills basin along the Elwha River. Conifers planted 3 years prior to the study in plots with different levels of lupine cover (sparse, medium, or dense) were measured for growth, foliar total nitrogen, and ectomycorrhizal (ECM) root colonization. Soil N, organic matter (OM), and surrounding plant community composition were also evaluated at this time.ResultsAfter 3 years, conifers did not statistically differ in height or basal diameter among differing levels of lupine cover. However, conifers in the medium- and dense-cover plots had significantly greater foliar N concentrations (β = 0.25, SE = 0.08, p < 0.001). The roots of conifers in the dense- and medium-cover plots had significantly less ECM colonization than those in the sparse-cover plots (β = 0.14, SE = 0.03, p = 0.03). No differences existed regarding soil total N or OM. Plant community composition differed among lupine cover classes (permutational multivariate analysis of variance (PERMANOVA), (F(2,21) = 2.02, p = 0.01). Higher lupine cover resulted in lower species richness (β = 25.9, SE = 0.61, p = 0.04).DiscussionBased on our findings, the inclusion of native lupine in coarse, N-limiting soils contributes to the N pools without reducing the growth of planted conifers, which may accelerate forest succession leading to closed canopies much faster than passive recovery.

Mycocentric fertilisation of ectomycorrhizae-inoculated Pinus radiata during containerised production alters root microbiome and growth outcomes

ABSTRACT During containerised production in forest nurseries, seedlings are often intensively fertilised to maximise seedling survival and growth. However, this practice can inadvertently harm the development of a robust root microbiome needed for plant resilience post-planting. In this controlled study using Pinus radiata, we combined reduced fertilisation and seedling inoculation with a diverse ectomycorrhizal (ECM) community as an alternative to intensive, industry-standard fertilisation. After 9 months, we investigated growth responses and changes to ECM and non-ECM root fungal communities. Reduced fertilisation improved the belowground growth and mycorrhizal root colonisation of inoculated seedlings. Isotopic nutrient tracing determined that, under moderate fertilisation, more photosynthetically fixed carbon was allocated belowground, and root-tip nitrogen (N) accumulation, a proxy for N uptake from the soil, also increased. Fertilisation level resulted in shifts in both ECM and non-ECM fungal community composition and substantial changes in the abundance of certain fungi. This study demonstrates that employing more-mycocentric fertilisation regimes may improve plantation nursery outcomes and that interactions between ECM and non-ECM fungi within inocula should be considered when studying the role of the soil microbiome in supporting P. radiata growth during containerised production.

Identification of microRNAs involved in ectomycorrhizal formation in Populus tomentosa.

The majority of woody plants are able to form ectomycorrhizal (ECM) symbioses with fungi. During symbiotic development, plants undergo a complex re-programming process involving a series of physiological and morphological changes. MicroRNAs (miRNAs) are important components of the regulatory network underlying symbiotic development. To elucidate the mechanisms of miRNAs and miRNA-mediated mRNA cleavage during symbiotic development, we conducted high-throughput sequencing of small RNAs and degradome tags from roots of Populus tomentosa inoculated with Cenococcum geophilum. This process led to the annotation of 51 differentially expressed miRNAs between non-mycorrhizal and mycorrhizal roots of P. tomentosa, including 13 novel miRNAs. Increased or decreased accumulation of several novel and conserved miRNAs in ECM roots, including miR162, miR164, miR319, miR396, miR397, miR398, novel-miR44 and novel-miR47, suggests essential roles for these miRNAs in ECM formation. The degradome analysis identified root transcripts as miRNA-mediated mRNA cleavage targets, which was confirmed using real-time quantitative PCR. Several of the identified miRNAs and corresponding targets are involved in arbuscular mycorrhizal symbioses. In summary, increased or decreased accumulation of specific miRNAs and miRNA-mediated cleavage of symbiosis-related genes indicate that miRNAs play important roles in the regulatory network underlying symbiotic development.

DNA‐based fungal diversity in Madagascar and arrival of the ectomycorrhizal fungi to the island

AbstractMadagascar is known for its high diversity and endemism of fauna and flora. Fungi, however, have been largely overlooked in diversity and evolution studies on the island, and whether fungi exhibit the same patterns as animals and plants has yet to be further examined. We collected fungal sporocarps and ectomycorrhizal (EcM) roots during three opportunistic surveys in five forests in Madagascar and generated a dataset of fungal Internal Transcribed Spacer (ITS) DNA sequences. We analyzed them together with all publicly available fungal ITS DNA sequences and identified 620 Operational Taxonomic Units (OTUs) from Madagascar, 10% of which contained only sequences from our surveys. Two hundred and ninety‐two OTUs belonged to EcM species with /russula‐lactarius, /boletus, /tomentella‐telephora, /cortinarius, and /amanita being the most abundant EcM lineages. Overall, 60% of all fungi and 81% of the EcM species from Madagascar appear to be endemic. We conducted a phylogenetic analysis using all the OTUs in Amanitaceae, Boletaceae, and Russulaceae families to elucidate their relative timing of arrival in Madagascar. We found that most EcM species from Madagascar in the three families diverged less than 22 million years ago (mya), long after the separation of India and Madagascar (88 mya), which is consistent with a dispersal mediated process of arrival to the island. Our study provides the first comprehensive view of the overall DNA‐based fungal diversity in Madagascar and the current state of knowledge of EcM fungi based on DNA sequences, useful for further ecological and evolutionary studies.Abstract in Malagasy is available with online material.

Preliminary assessment of the ectomycorrhizal fungi ofQuercus garryanaon Vancouver Island, British Columbia, Canada

Garry oak ( Quercus garryana Douglas ex Hook.) is the only oak native to British Columbia (BC), where it occupies the northernmost extent of its range. The ecosystem it occupies in BC has been greatly reduced in size and fragmented by European settlement. Garry oak forms ectomycorrhizas that are essential to its existence and will likely play an important role in the response of this tree to climate change. Yet, relatively little is known about the ectomycorrhizal fungi associated with Garry oak in BC. In this study, we have documented the occurrence of fungi forming ectomycorrhizas with Garry oak at six locations on Vancouver Island by sequencing the internal transcribed spacer region of ectomycorrhizal root tips collected from Garry oak stands. Of the 47 species we detected, only about 20% can be confidently assigned to known species because not all species have been sequenced and many sequences in public databases are incorrectly or incompletely identified, but the majority of them belong to a community of fungi associated primarily with oaks or other members of Fagaceae. The uniqueness of this community of ectomycorrhizal fungi indicates that the possible expansion of the range of Garry oak in BC in response to climate change may be limited by the co-migration of its ectomycorrhizal fungi.

Primary succession of ectomycorrhizal fungi associated with Alnus sieboldiana on Izu-Oshima Island, Japan

The primary succession of ectomycorrhizal (ECM) fungi has been well described for Pinus and Salix, but the succession for other pioneer hosts is almost unknown. Here, we investigated ECM fungal communities of Alnus sieboldiana at different host growth stages in a primary successional volcanic site on Izu-Oshima Island, Japan. ECM root tips were collected from 120 host individuals, encompassing seedling, sapling, and mature tree stages. The taxonomic identity of the ECM fungi was determined based on rDNA internal transcribed spacer region sequences. Nine molecular taxonomic units were detected from a total of 807 root tips. The initial ECM fungal community on the pioneer seedlings was composed of only three species, where an undescribed Alpova species (Alpova sp.) was exclusively frequent. With host growth, other ECM fungal species were added to the communities, while the initial colonizers remained even at mature tree stages. Thus, the ECM fungal composition significantly changed along host growth stages and showed the nested community structure. Although most of the ECM fungi confirmed in this study had a broad Holarctic geographical distribution, the Alpova sp. had no previous records in other regions. These results suggest that a locally evolved Alpova sp. plays an essential role in the initial seedling establishment of A. sieboldiana at early successional volcanic sites.

Ectomycorrhizal diversity, taxon-specific traits and root N uptake in temperate beech forests.

Roots of forest trees are colonized by a diverse spectrum of ectomycorrhizal (EM) fungal species differing in their nitrogen (N) acquisition abilities. Here, we hypothesized that root N gain is the result of EM fungal diversity or related to taxon-specific traits for N uptake. To test our hypotheses, we traced 15 N enrichment in fine roots, coarse roots and taxon-specific ectomycorrhizas in temperate beech forests in two regions and three seasons, feeding 1 mM NH4 NO3 labelled with either 15 NH4 + or 15 NO3 - . We morphotyped > 45 000 vital root tips and identified 51 of 53 detected EM species by sequencing. EM root tips exhibited strong, fungal taxon-specific variation in 15 N enrichment with higher NH4 + than NO3 - enrichment. The translocation of N into the upper parts of the root system increased with increasing EM fungal diversity. Across the growth season, influential EM species predicting root N gain were not identified, probably due to high temporal dynamics of the species composition of EM assemblages. Our results support that root N acquisition is related to EM fungal community-level traits and highlight the importance of EM diversity for tree N nutrition.