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Fruit bodies belonging to Hebeloma limbatum Beker, Vesterh. & U. Eberh. (Hymenogastraceae) were collected for the first time from Turkey and presented herein with field photos and a short discussion. The identification of the collection was made according to the data obtained from the field and the results of microscopic examination. The new record is identified with relatively small, sticky, orangey brown or whitish pileus; cream-colored or light brown lamellae; whitish stipe; almond-or lemon-shaped, ornamented, pale yellow, 10-14 × 5-7.5 µm sized basidiospores; club- or bottle-shaped, sometimes capped, and 30-100 × 5-14 µm sized cystidia. [ABSTRACT FROM AUTHOR]

Psathyloma is an agaricoid genus described recently to accommodate two species of brown-spored agarics from Australasia superficially similar to Psathyrella and Hebeloma. Phylogenetic analyses published along with the description of the genus determined that an unidentified species of Psathyloma was also present in Patagonia based on ITS sequences from ectomycorrhizal root tips of Nothofagaceae trees. Based on morphological and phylogenetic analyses of fresh mushroom collections from Patagonia, we determine that the unknown South American Psathyloma corresponds to Pholiota psathyrelloides, a species described by Rolf Singer in 1969 from Nothofagaceae forests in Argentina. Here we transfer this species to the genus Psathyloma and provide detailed morphological data and illustrations of fresh collections. Psathyloma is confirmed as an ectomycorrhizal genus with a disjunct southern Gondwanan distribution that is similar to what has been found for other Austral ectomycorrhizal fungal genera such as Austropaxillus and Descolea. [ABSTRACT FROM AUTHOR]

L-Amino acid oxidases (LAAOs) are flavoproteins, which use oxygen to deaminate L-amino acids and produce the corresponding α-keto acids, ammonia, and hydrogen peroxide. Here we describe the heterologous expression of LAAO4 from the fungus Hebeloma cylindrosporum without signal sequence as fusion protein with a 6His tag in Escherichia coli and its purification. 6His-hcLAAO4 could be activated by exposure to acidic pH, the detergent sodium dodecyl sulfate, or freezing. The enzyme converted 14 proteinogenic L-amino acids with L-glutamine, L-leucine, L-methionine, L-phenylalanine, L-tyrosine, and L-lysine being the best substrates. Methyl esters of these L-amino acids were also accepted. Even ethyl esters were converted but with lower activity. Km values were below 1 mM and vmax values between 19 and 39 U mg−1 for the best substrates with the acid-activated enzyme. The information for an N-terminal aldehyde tag was added to the coding sequence. Co-expressed formylglycine-generating enzyme was used to convert a cysteine residue in the aldehyde tag to a Cα-formylglycine residue. The aldehyde tag did not change the properties of the enzyme. Purified Ald-6His-hcLAAO4 was covalently bound to a hexylamine resin via the Cα-formylglycine residue. The immobilized enzyme could be reused repeatedly to generate phenylpyruvate from L-phenylalanine with a total turnover number of 17,600 and was stable for over 40 days at 25 °C. [ABSTRACT FROM AUTHOR]

Abstract Hebeloma mesophaeum is an ectomycorrhizal fungus frequently associated with metal disturbed environments. In this work, we examined Ag, Cd, and Zn tolerance of H. mesophaeum isolates from heavy metal-polluted (isolate Prib) and clean (isolate Rez) sites. Both mycelia showed essentially the same level of Ag and Zn tolerance, but Prib was more Cd tolerant. In short-term exposures, Prib accumulated slightly less Cd than Rez. Size exclusion chromatography of cell-free extracts and fluorescence microscopy of hyphae with a Cd-specific fluorescent tracer revealed that substantial proportion of Cd was contained in the vacuoles in both isolates. Considering that the proportion of Cd associated with fractions attributable to Cd complexes with cytosolic, metallothionein (MT) peptides was higher in Prib, we examined the copy number and basal levels of Hm MTs genes in Rez and Prib. While no difference between the isolates was observed in the gene copy numbers and basal levels of Hm MT1 transcripts, the basal transcription of Hm MT3 was 3-fold higher in Prib. These observations suggest that MTs provide in Prib better protection against Cd. Furthermore, the higher Cd tolerance in Prib can be to some extent also supported by the efflux or reduced uptake of Cd in the hyphae. Highlights • Metal tolerance of Hebeloma mesophaeum from metal-polluted and clean sites was compared. • "Prib" isolate from lead smelter site was significantly more Cd, but not Zn and Ag, tolerant. • Reduced accumulation of Cd can increase Cd tolerance in Prib isolate. • Higher basal levels of metallothionein Hm MT3 transcripts can add to Cd tolerance in Prib. [ABSTRACT FROM AUTHOR]

During the 1970s and 1980s, L. R. Hesler and A. H. Smith, alone, together, or Smith with other authors such as V. S. Evenson and D. H. Mitchel, described numerous North American taxa in Hebeloma . With the inclusion of an early work by Smith and a later work by E. Grilli, who described a species based on material from Smith, 130 taxa were described and form the subject of this paper. Apart from two taxa that were (deliberately) invalidly published and two that were illegitimately published, all others are valid and legitimate names. After study of morphology, habitat, and location of collection (based on available material and information) as well as molecular analysis (insofar as this was successful), of these 128 validly published taxa we regard 14 as being current names; the remaining 114 are synonymized with other current names. These 14 species are Hebeloma albomarginatum, H. alpinicola, H. angelesiense, H. caulocystidiosum, H. immutabile, H. incarnatulum, H. kelloggense, H. mackinawense, H. nitidum, H. olympianum, H. parcivelum, H. praeolidum, H. pungens , and H. sporadicum . This brings up the number of currently recognized, validly published, Hebeloma species in America to 72.

Summary: Through a mutualistic relationship with woody plant roots, ectomycorrhizal fungi provide growth‐limiting nutrients, including inorganic phosphate (Pi), to their host. Reciprocal trades occur at the Hartig net, which is the symbiotic interface of ectomycorrhizas where the two partners are symplasmically isolated. Fungal Pi must be exported to the symbiotic interface, but the proteins facilitating this transfer are unknown.In the present study, we combined transcriptomic, microscopy, whole plant physiology, X‐ray fluorescence mapping, 32P labeling and fungal genetic approaches to unravel the role of HcPT2, a fungal Pi transporter, during the Hebeloma cylindrosporum–Pinus pinaster ectomycorrhizal association.We localized HcPT2 in the extra‐radical hyphae and the Hartig net and demonstrated its determinant role for both the establishment of ectomycorrhizas and Pi allocation towards P. pinaster. We showed that the host plant induces HcPT2 expression and that the artificial overexpression of HcPT2 is sufficient to significantly enhance Pi export towards the central cylinder.Together, our results reveal that HcPT2 plays an important role in ectomycorrhizal symbiosis, affecting both Pi influx in the mycelium and efflux towards roots under the control of P. pinaster. [ABSTRACT FROM AUTHOR]

Between 1960 and 2009, regular visits to Svalbard were made and a number of Hebeloma spp. were collected by several mycologists. We have studied 249 such collections, many from the Herbarium in Oslo (O) and from the private herbarium of the first author. The collections represent 17 different species. Of the 17 species, five ( H. louiseae, H. pallidolabiatum, H. perexiguum, H. pubescens and H. spetsbergense ) are only known from Svalbard. In this paper we discuss the habitat and apparent associates of the 17 species recorded, as well as their frequency of occurrence within our sample, and compare this with our data from other regions of the northern hemisphere. A further analysis compares the records we have from the collection of basidiomes with data published from root analysis of mycorrhizal associates on Svalbard. Root associate data strongly suggest the occurrence of an unknown Hebeloma species, not close to any of the infrageneric groups known to occur in arctic habitats. [ABSTRACT FROM AUTHOR]

Summary: Ectomycorrhizal fungi play an essential role in the ecology of boreal and temperate forests through the improvement of tree mineral nutrition. Potassium (K+) is an essential nutrient for plants and is needed in high amounts. We recently demonstrated that the ectomycorrhizal fungus Hebeloma cylindrosporum improves the K+ nutrition of Pinus pinaster under shortage conditions. Part of the transport systems involved in K+ uptake by the fungus has been deciphered, while the molecular players responsible for the transfer of this cation towards the plant remain totally unknown. Analysis of the genome of H. cylindrosporum revealed the presence of three putative tandem‐pore outward‐rectifying K+ (TOK) channels that could contribute to this transfer. Here, we report the functional characterization of these three channels through two‐electrode voltage‐clamp experiments in oocytes and yeast complementation assays. The expression pattern and physiological role of these channels were analysed in symbiotic interaction with P. pinaster. Pine seedlings colonized by fungal transformants overexpressing two of them displayed a larger accumulation of K+ in shoots. This study revealed that TOK channels have distinctive properties and functions in axenic and symbiotic conditions and suggested that HcTOK2.2 is implicated in the symbiotic transfer of K+ from the fungus towards the plant. [ABSTRACT FROM AUTHOR]

Background. Metal contamination in soils affects both above- and belowground communities, including soil microorganisms. Ectomycorrhizal (ECM) fungi are an important component in belowground community and tolerant strains have great potential in enhancing plant-based remediation techniques. We assessed cadmium and zinc toxicity in five ECM species in liquid media (Hebeloma subsaponaceum; H. cylindrosporum; H. crustuliniforme; Scleroderma sp.; Austroboletus occidentalis) and investigated the potential of Zn to alleviate Cd toxicity. Due to highly divergent results reported in the literature, liquid and solid media were compared experimentally for the first time in terms of differential toxicity thresholds in Cd and Zn interactions. Methods. A wide range of Cd and Zn concentrations were applied to ectomycorrhizal fungi in axenic cultures (in mg L-1): 0; 1; 3; 9; 27; 81; 243 for the Cd treatments, and 0; 1; 30; 90; 270; 810; 2,430 for Zn. Combined Zn and Cd treatments were also applied to H. subsaponaceum and Scleroderma sp. Dry weight was recorded after 30 days, and in case of solid medium treatments, radial growth was also measured. Results and Discussion. All species were adversely affected by high levels of Cd and Zn, and A. occidentalis was the most sensitive, with considerable biomass decrease at 1 mg L-1 Cd, while Scleroderma sp. and H. subsaponaceum were the most tolerant, which are species commonly found in highly contaminated sites. Cd was generally 10 times more toxic than Zn, which may explain why Zn had little impact in alleviating Cd effects. In some cases, Cd and Zn interactions led to a synergistic toxicity, depending on the concentrations applied and type of media used. Increased tolerance patterns were detected in fungi grown in solid medium and may be the cause of divergent toxicity thresholds found in the literature. Furthermore, solid medium allows measuring radial growth/mycelial density as endpoints which are informative and in this case appeared be related to the high tolerance indices found in H. subsaponaceum. [ABSTRACT FROM AUTHOR]

The biological diversity in any ecosystem is fundamental for its existence and balance. Logging undoubtedly alters this diversity. An example is the modifications in the communities of ectomycorrhizal fungi, which are fundamental for the species of forest importance. Due to the above, it is essential for reforestation to carry out mycorrhization in the nursery and thereby favor the establishment of trees in the field, especially in highly disturbed or eroded areas. However, reintroducing ectomycorrhizal species is a challenge due to the ecological, biotechnological and financial implications. Particularly, there is scarce information that analyzes the production cost of ectomycorrhizal inoculants based on spores and the species or the criteria to choose the ectomycorrhizal fungus species suitable for preparation of inoculants. In the present work, the cost of production of Neotropical inoculants based on spores of edible ectomycorrhizal fungi species native to Mexico belonging to Laccaria spp. and Hebeloma spp. The production costs of the sporebased ectomycorrhizal inoculant evaluated in the present work were $2.00 Mexican pesos per gram for the powder inoculum and $0.05 pesos per mL for the liquid inoculum. Both inoculants are effective in the pine mycorrhizal colonization. We demonstrate the financial feasibility of the production of ectomycorrhizal inoculants to inoculate pine trees of forest importance. [ABSTRACT FROM AUTHOR]

This study deals with the molecular systematics of Asian collections of Hebeloma theobrominum and H. mesophaeum which have not been previously reported from any Himalayan part of the world, and are new to Pakistan. Both were identified using morpho-anatomical and molecular characterization. The target rDNA of both species was amplified by using universal fungal primers. In phylogenetic analysis, both species distinctly clustered with their respective groups. These both species have been described first time from Asia using ITS-rDNA barcoding. The sequences of both species were compared with those of same European species from the GenBank. These species clustered with European species in phylogenetic tree proving their cosmopolitan distribution. [ABSTRACT FROM AUTHOR]

To clarify the early molecular interaction between ectomycorrhizal partners, we performed a RNA-Seq study of transcriptome reprogramming of the basidiomycete Hebeloma cylindrosporum before symbiotic structure differentiation with Pinus pinaster. Mycorrhiza transcriptome was studied for comparison. By reference to asymbiotic mycelium, 47 and 46 genes were specifically upregulated over fivefold ( p ≤ 0.05) upon rhizosphere colonization and root adhesion respectively. Other 45 were upregulated throughout the symbiotic interaction, from rhizosphere colonization to differentiated mycorrhizas, whereas 274 were specifically upregulated in mycorrhizas. Although exoproteome represents 5.6% of H. cylindrosporum proteome, 38.5% of the genes upregulated upon pre-infectious root colonization encoded extracellular proteins. The proportion decreased to 23.5% in mycorrhizas. At all studied time points, mycorrhiza-induced small secreted proteins (MiSSPs), representing potential effectors, were over-represented among upregulated genes. This was also the case for carbohydrate-active enzymes (CAZymes). Several CAZymes were upregulated at all studied stages of the interaction. Consistent with a role in fungal morphogenesis and symbiotic interface differentiation, CAZymes over-expressed before and upon root attachment targeted fungal and both fungal and plant polysaccharides respectively. Different hydrophobins were upregulated upon early root adhesion, in mycorrhizas or throughout interaction. The functional classification of genes upregulated only in mycorrhizas pointed to intense metabolic activity and nutritional exchanges. [ABSTRACT FROM AUTHOR]

William Alphonso Murrill was an American mycologist of the early 20th century. He described 1453 new species of Agaricales, Boletales, and Polyporales. Within these were 44 taxa that he described as Hebeloma or that he recombined into Hebeloma . Additionally, there are five species, of which we are aware, that Murrill described within other genera that should be referred to the genus Hebeloma . A further three species described from northern America by J. P. F. C. Montagne, and transferred to Hebeloma by Saccardo, were commented on by Murrill and not accepted within the genus. These 52 taxa are analyzed here, both morphologically and molecularly, as far as possible. For 18 of his types, internal transcribed spacer (ITS) sequences were generated. For two species ( H. harperi and H. subfastibile ), which were mixed collections, lectotypes are designated. Twenty-three of the taxa analyzed are Hebeloma , as the genus is recognized today, and six of these ( H. australe, H. harperi, H. paludicola, H. subaustrale, H. subfastibile , and H. viscidissimum ) are regarded as current, i.e., they are names that should be accepted and used. Hebeloma paludicola is an earlier name for H. hygrophilum , described from Europe. Gymnopilus viscidissimus is synonymous with H. amarellum but has priority and is here recombined into Hebeloma . The remaining 17 Hebeloma taxa are synonymized with other species that have priority. The remaining 29 species belong to a range of genera; molecularly supported were Agrocybe, Cortinarius, Inocybe, Inosperma, Phlegmacium, Pholiota, Pseudosperma , and Pyrrhulomyces . Recombinations and synonymizations are made as appropriate and necessary. The names H. alachuanum and H. vatricosum , respectively Inocybe vatricosa , are considered doubtful and should be avoided.

Mycorrhizal fungi host diverse mycoviruses that contribute to our understanding of their diversity and evolution. Here we report on the identification and complete genome characterization of three novel partitiviruses naturally infecting the ectomycorrhizal fungus Hebeloma mesophaeum. During NGS derived viral sequence analyses, we identified a partitivirus that is conspecific with the previously reported partitivirus (LcPV1) described from a saprotrophic fungus Leucocybe candicans. The two distinct fungal specimens inhabited the same vicinity of a campus garden. RdRp sequences encoded by the LcPV1 isolates from both host fungi was found to be identical. Bio-tracking studies revealed that viral loads of LcPV1 drop significantly in L. candicans but not in H. mesophaeum within four years period. The physical proximity of the mycelial networks of both fungal specimens implied the occurrence of a virus transmission event with unknown mechanism. Nature of this virus transmission was discussed in relation to transient interspecific mycelial contact hypothesis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Most known species in the Strophariaceae are decomposers and grow on various kind of organic matter. Approximately 18 genera and 1,316 species in the Strophariaceae have been reported worldwide. Through an ongoing survey of indigenous fungi in Korea, 29 specimens belonging to the Strophariaceae were collected from 2012 to 2016. These specimens were identified based on morphological characteristics and molecular analysis of internal transcribed spacer sequences. Fifteen taxa were confirmed, with eight species matching those previously recorded. Seven species in five genera were shown to be new records in Korea: Galerina marginata, Gymnopilus crociphyllus, Gymnopilus picreus, Hebeloma birrus, Hebeloma cavipes, Pholiota multicingulata, and Psilocybe thaizapoteca. In this study, we provide detailed morphological descriptions of these species and investigate their evolutionary relationships by constructing phylogenetic trees. [ABSTRACT FROM AUTHOR]

The rare and interesting fungus Squamanita odorata (Cool) Imbach, a parasite on Hebeloma species, is reported for the first time from Poland, briefly described and illustrated based on Polish specimens. Its taxonomy, ecology and distribution are discussed. [ABSTRACT FROM AUTHOR]

It has been known that the agaric fungus Hebeloma radicosum fruits from mole latrines located in the ground and that ectomycorrhizas develop within the same latrines. But the identity between the fruit bodies on the ground and the mycosymbionts of the ectomycorrhizas below ground has not been established. Molecular genetic data revealed that the fungal hyphae composing the ectomycorrhizas are identical with the fruit bodies of H. radicosum . Furthermore, phylogenetic analysis clearly separated H. radicosum and H. radicosoides , suggesting that they are truly different species. [ABSTRACT FROM AUTHOR]

Hebeloma section Denudata includes the majority of the taxa commonly referred to as the Hebeloma crustuliniforme complex. In a recent paper we described in detail H. subsection Denudata and fifteen European species recognised within this subsection, using morphological and molecular methods. In this paper we continue this work and describe in detail three additional subsections and several new species. Within H. subsection Hiemalia we recognise just one species, Hebeloma hiemale . Here we propose an epitype in order to unambiguously define this taxon. Nine species occurring in Europe are assigned to H. subsect. Clepsydroida , namely Hebeloma ammophilum , H. cavipes , H. fragilipes , H. ingratum , H. laetitiae , H. limbatum sp. nov., H. matritense sp. nov., H. pseudofragilipes sp. nov., and H. vaccinum . Finally, we introduce H. subsection Echinospora with three species: Hebeloma echinosporum sp. nov., H. populinum , and H. rostratum sp. nov. We provide descriptions of all three of these species in order to clarify the taxonomy of this section. We provide a key to H. sect. Denudata and the discussed subsections. For the majority of the taxa there is good overall consistency between morphological and phylogenetic delimitation and, where the information exists, thanks to Aanen and Kuyper's work, biological delimitation. [ABSTRACT FROM AUTHOR]

Hebeloma subsection Denudata includes the type of H. section Denudata, Hebeloma crustuliniforme, as well as the majority of the taxa commonly included in the Hebeloma crustuliniforme complex. Complementing the work of D.K. Aanen and coworkers, and using refined morphological and molecular methods we were able to recognize further individual taxa within the section. Fifteen species occurring in Europe are assigned to H. subsect. Denudata. Of these, we describe eight species as new, namely H. aanenii, H. aurantioumbrinum, H. geminatum, H. louiseae, H. luteicystidiatum, H. pallidolabiatum, H. perexiguum and H. salicicola. Naucoria bellotiana, a species very similar to H. alpinum is recombined into Hebeloma. A key to Hebeloma subsect. Denudata is provided. We demonstrate that within this subsection there is good overall consistency between morphological, phylogenetic and biological species concepts. In contrast to current opinion, in this group there is little species overlap, particularly when also considering species frequencies, between arctic and alpine floras on one hand and temperate on the other. [ABSTRACT FROM AUTHOR]

Between 2002 and 2012 regular visits to the Carpathians were made and a number of Hebeloma spp. were collected from the alpine area. In total 44 collections were made that represent 11 species, two of which, Hebeloma grandisporum and H. oreophilum, are described here as new. Of the 11 species, four (H. alpinum, H. marginatulum and the two species described as new) are known only from alpine or Arctic habitats. Hebeloma dunense and H. mesophaeum are commonly found in, but not restricted to, alpine habitats. The other five species (H. aanenii, H. laterinum, H. naviculosporum, H. vaccinum, H. velutipes) are usually found in lowland or boreal habitats. Hebeloma naviculosporum is reported for the first time from the alpine zone and H. alpinum for the first time as growing with Helianthemum. All but two species (H. alpinum, H. marginatulum) are reported for the first time from the Carpathian alpine zone. In this paper we discuss the habitat, the 11 recorded species and give detailed descriptions of the two new species, both morphologically and molecularly. A key for Hebeloma species from sect. Hebeloma occurring in Arctic-alpine habitats is provided. [ABSTRACT FROM AUTHOR]

Four alnicolous (Alnicola citrinella, A. suavis, Cortinarius alnetorum, and Gyrodon lividus), 2 cortinarioid (Cortinarius alnetorum and C. scutulatus), 3 entolomatoid (Entoloma conferendum, E. pallescens, and E. sordidulum), 1 hebelomatoid (Hebeloma aff. aestivale), and 2 clitocyboid (Clitocybe applanata and C. elegantula) fungi were collected, studied, illustrated, and first reported for the Turkish mycota from Trabzon. Cortinarius alnetorum was evaluated as both an alnicolous and cortinarioid species. Field trips were made in 2012 and 2013, and the microscopical studies were performed in January and February 2014. Identification of the collections was made according to morphological investigations and field characteristics. [ABSTRACT FROM AUTHOR]

Hebeloma ifeleletorum is described as a new species from American Samoa. Based on analyses of ITS and combined nLSU-ITS datasets H. ifeleletorum clusters with but is distinct from described species that have been placed in the genus Anamika by some. The phylogenetic relationship of H. ifeleletorum to the genus Anamika from Asia and to other species from Australia and New Caledonia suggests that H. ifeleletorum has origins in the western Pacific. [ABSTRACT FROM AUTHOR]

Talpine moles are reported to nest at the same site for periods longer than their known longevity. The present study verifies experimentally in situ that during such long-term nesting, the inhabitants of the nest change, with the new inhabitant constructing its own nest if the existing nest has been removed. The principal methods involved removal of both the nest and inhabiting mole from the nesting site, the site that had been located by observing the fruiting of the mushroom species Hebeloma radicosum. This treatment was followed by observation of refruiting of the mushroom at the same site; refruiting indicated renesting by another mole. Verification was made at three sites in the cool temperate forests of central Japan where three talpine species live. At two of the sites, the inhabiting Euroscaptor mizura mole was replaced by another E. mizura mole. At the third site, a Mogera wogura mole was replaced by a Mogera imaizumii mole. The causes and circumstances for such persistent nesting are discussed, with emphasis on habitat-cleaning symbiosis. [ABSTRACT FROM AUTHOR]

Highlights: [•] Metal species in Hebeloma mesophaeum sporocarps and mycelia have been characterized. [•] Zinc (Zn) and cadmium (Cd) are sequestered in subcellular compartments. [•] Accumulated silver (Ag) and the excess cytosolic Zn and Cd are associated with metallothioneins. [•] Three metallothionein genes characterized: HmMT1 and sequence-related HmMT2 and HmMT3. [•] HmMT1 specifically increased Zn and HmMT2 and HmMT3 Ag tolerance in yeasts. [ABSTRACT FROM AUTHOR]

To investigate whether root colonisation of Scots pine (Pinus sylvestris L.) seedlings with symbiotic mycorrhizal fungi (Hebeloma sp. and Suillus luteus) could be detected in situ, classification analysis of the electric impedance spectra (IS) of the root system was carried out. The seedlings were inoculated either with Hebeloma or Suillus with some left as controls. The seedlings were firstly cultivated in long-day and high temperature (LDHT) conditions. Half of the seedlings remained in LDHT and half were moved to short-day and low temperature conditions (SDLT) to acclimatise to the cold. The electrical impedance spectra of the root systems were measured at a frequency range of 5 Hz–100 kHz. The results of principal component analysis (PCA) showed that current delivery through root system, sensed by real and imaginary parts of IS, depended upon the cold acclimation and mycorrhizal treatment. Comparison of SDLT to LDHT via correlation analysis indicated a 13% and a 27% change in PCA responses for the real and imaginary parts of the impedance, respectively. When the mycorrhizal treatments were compared with a non-mycorrhizal treatment, the respective changes in the correlation coefficients were 30% for Hebeloma sp. and 39% for S. luteus in the real part and 28% and 38% in the imaginary part, respectively. These changes in the correlation coefficients appear to indicate physicochemical changes (e.g. ionic behaviour) in the roots as a result of fungal colonisation. [Copyright &y& Elsevier]

Mycorrhizal associations are known to improve the hydro-mineral nutrition of their host plants. However, the importance of mycorrhizal symbiosis for plant potassium nutrition has so far been poorly studied. We therefore investigated the impact of the ectomycorrhizal fungus Hebeloma cylindrosporum on the potassium nutrition of Pinus pinaster and examined the involvement of the fungal potassium transporter Hc Trk1., Hc Trk1 transcripts and proteins were localized in ectomycorrhizas using in situ hybridization and EGFP translational fusion constructs. Importantly, an overexpression strategy was performed on a H. cylindrosporum endogenous gene in order to dissect the role of this transporter., The potassium nutrition of mycorrhizal pine plants was significantly improved under potassium-limiting conditions. Fungal strains overexpressing Hc Trk1 reduced the translocation of potassium and phosphorus from the roots to the shoots of inoculated plants in mycorrhizal experiments. Furthermore, expression of Hc Trk1 and the phosphate transporter Hc PT1.1 were reciprocally linked to the external inorganic phosphate and potassium availability., The development of these approaches provides a deeper insight into the role of ectomycorrhizal symbiosis on host plant K+ nutrition and in particular, the K+ transporter Hc Trk1. The work augments our knowledge of the link between potassium and phosphorus nutrition via the mycorrhizal pathway. [ABSTRACT FROM AUTHOR]