A comparison of nine species of arbuscular mycorrhizal fungi on the development and nutrition of micropropagated Rubus idaeus L. cv. Glen Prosen (Red Raspberry)

Growth, development and nutrient status of micropropagated Rubus idaeus cv. Glen Prosen in response to inoculation with nine species of arbuscular mycorrhizal (AM) fungi from three different genera was investigated. The nine species of AM fungi included, Glomus clarum, G. etunicatum, G. intraradices, Gigaspora rosea, Gi. gigantea, Gi. margarita, Scutellospora calospora, S. heterogama and S. persica. Plant responses to AM fungi varied from growth enhancement to growth depression. Depressive growth effects were specific to Gigaspora species. Furthermore, particular species of AM fungi had unique effects on the mineral status of the raspberry plants. Importance of isolate selection for inoculation of micropropagated raspberry plants is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

Mycorrhizal associations in woody plant species at the Mt. Usu volcano,Japan

We investigated the association between ectomycorrhizal (ECM) and arbuscular mycorrhizal (AM) fungi and pioneer woody plant species in areas devastated by the eruption of Mt. Usu, Japan, in 2000. We observed eight woody plant species at the research site, most of which were associated with ECM and/or AM fungi. In particular, dominant woody plant species Populus maximowiczii, Salix hultenii var. angustifolia and Salix sachalinensis were consistently associated with ECM fungi and erratically associated with AM fungi. We found one to six morphotypes in the roots of each ECM host and, on average, two in the roots of each seedling, indicating low ECM fungal diversity. ECM colonization ranged from 17 to 42% of root tips. Using morphotyping and molecular analyses, 15 ECM fungi were identified. ECM fungi differed greatly between hosts. However, Laccaria amethystea, Hebeloma mesophaeum, Thelephora terrestris and other Thelephoraceae had high relative colonization, constituting the majority of the ECM colonization in the roots of each plant species. These ECM fungi may be important for the establishment of pioneer woody plant species and further revegetation at Mt. Usu volcano.     

Coinoculation of containerized Douglas-fir (Pseudotsuga menziesii) and maritime pine (Pinus pinaster) seedlings with the ectomycorrhizal fungi Laccaria bicolor and Rhizopogon spp.

 Coinoculations with mycelium of Laccaria bicolor and spores of Rhizopogon spp. included in alginate gel have been carried out to determine: (1) the ability of the mixed inoculum to produce dual-colonized containerized Douglas-fir and maritime pine planting stocks and (2) the colonization pattern of the two fungi in individual root systems. For both tree species, the maximal proportion of dual-colonized seedlings obtained almost never exceeded 50%. The rest of the seedlings remained colonized by a single fungus or were non-colonized. In Douglas-fir inoculations, the relationship between the dual-colonized seedlings obtained and the initial dose of the two fungi was highly significant. The highest proportion of dual-colonized seedlings was obtained when the highest dose of R. subareolatus was used (10⁶ spores/seedling), regardless of the dose of L. bicolor. Among the treatments producing 25% or more dual-colonized seedlings, differences in the proportion of Laccaria/Rhizopogon mycorrhizas and total root colonization percentages were not clearly related to the initial combination of doses. The proportion of dual-colonized maritime pine seedlings was not significantly related to the initial inoculation doses of the two fungi. The proportion of Laccaria/Rhizopogon mycorrhizas was not significantly different among treatments with 25% or more dual-colonized seedlings, whereas total colonization percentages ranged from 37% with the combination 0.08/10⁴ (g L. bicolor / spores R. roseolus per seedling) to 74% with the combination 0.08/10⁶, this difference being statistically significant. Accepted: 15 September 1998     

Survival of inoculated Laccaria bicolor in competition with native ectomycorrhizal fungi and effects on the growth of outplanted Douglasfir seedlings

The survival, development and mycorrhizal efficiency of a selected strain of Laccaria bicolor along with naturally occurring ectomycorrhizal fungi in a young plantation of Douglas fir was examined. Symbionts were identified and their respective colonization abilities were determined. Eight species of symbiotic fungi, which may have originated in adjacent coniferous forests, were observed on the root systems. Mycorrhizal diversity differed between inoculated (5 taxa) and control (8 taxa) seedlings. Ectomycorrhizal fungi which occurred naturally in the nursery on control seedlings (Thelephora terrestris and Suillus sp.) did not survive after outplanting. Both inoculated and naturally occurring Laccaria species, as well as Cenococcum geophilum, survived on the old roots and colonized the newly formed roots, limiting the colonization by other naturally occurring fungi. Other fungi, such as Paxillus involutus, Scleroderma citrinum and Hebeloma sp. preferentially colonized the old roots near the seedling's collar. Russulaceae were found mainly in the middle section of the root system. Mycorrhizal colonization by Laccaria species on inoculated seedlings (54%) was significantly greater than on controls (13%) which were consequently dominated by the native fungi. Significant differences (up to 239%) were found in the growth of inoculated seedlings, especially in root and shoot weight, which developed mainly during the second year after outplanting. Seedling growth varied with the species of mycorrhizae and with the degree of root colonization. Competitiveness and effectiveness of the introduced strain on improving growth performances of seedlings are discussed.     

The effects of insect pathogenic soil fungi and ectomycorrhizal inoculation of birch seedlings on the survival of Otiorhynchus larvae

• 1 Weevil larvae of the genus Otiorhynchus are a serious problem in agriculture and forestry, causing damage to a wide range of plant species, primarily by larval feeding on roots. Otiorhynchus larvae are a serious pest in forest plantations in Iceland, causing 10–20% mortality of newly‐planted seedlings.
• 2 We studied the effects of soil fungi on the survival of Otiorhynchus sulcatus larvae. The larvae were introduced into pots with birch seedlings grown in: (i) nursery peat; (ii) nursery peat inoculated with three different species of ectomycorrhizal fungi; (iii) nursery peat inoculated with insect pathogenic fungi; (iv) nursery peat inoculated with ectomycorrhizal fungi and insect pathogenic fungi; and (v) nursery peat inoculated with natural forest soil from Icelandic birch woodland.
• 3 Larval survival was negatively affected by inoculation of: (i) the ectomycorrhizal fungus Laccaria laccata; (ii) the ectomycorrhizal fungus Cenococcum geophylum; (iii) the insect pathogenic fungus Metarhizium anisopliae; and (iv) forest soil. Inoculation with the ectomycorrhizal fungus Phialophora finlandia did not have any significant effect on larval survival. No significant synergistic effect was found between insect pathogenic and ectomycorrhizal fungi.
• 4 It is concluded that ectomycorrhizal and insect pathogenic fungi have a significant potential in biological control of Otiorhynchus larvae in afforestation areas in Iceland. Further studies are needed to establish the effect of these fungi in the field and to analyse how mycorrhizal fungi affect root‐feeding larvae.

     

Invasion biology of Australian ectomycorrhizal fungi introduced with eucalypt plantations into the Iberian Peninsula

In the last two centuries, several species of Australian eucalypts (e.g. Eucalyptus camaldulensis and E.␣globulus) were introduced into the Iberian Peninsula for the production of paper pulp. The effects of the introduction of exotic root-symbitotic fungi together with the eucalypts have received little attention. During the past years, we have investigated the biology of ectomycorrhizal fungi in eucalypt plantations in the Iberian Peninsula. In the plantations studied, we found fruit bodies of several Australian ectomycorrhizal fungi and identified their ectomycorrhizas with DNA molecular markers. The most frequent species were Hydnangium carneum, Hymenogaster albus, Hysterangium inflatum, Labyrinthomyces donkii, Laccaria fraterna, Pisolithus albus, P. microcarpus, Rhulandiella berolinensis, Setchelliogaster rheophyllus, and Tricholoma eucalypticum. These fungi were likely brought from Australia together with the eucalypts, and they seem to have facilitated the establishment of eucalypt plantations and their naturalization. The dispersion of Australian fungal propagules may be facilitating the spread of eucalypts along watercourses in semiarid regions increasing the water lost. Because ectomycorrhizal fungi are obligate symbionts, their capacity to persist after eradication of eucalypt stands, and/or to extend beyond forest plantations, would rely on the possibility to find compatible native host trees, and to outcompete the native ectomycorrhizal fungi. Here we illustrate the case of the Australasian species Laccaria fraterna, which fruits in Mediterranean shrublands of ectomycorrhizal species of Cistus (rockroses). We need to know which other Australasian fungi extend to the native ecosystems, if we are to predict environmental␣risks associated with the introduction of Australasian ectomycorrhizal fungi into the Iberian Peninsula. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of mycorrhizal inocula on the growth of Sitka spruce seedlings in different soils

Summary Different mycorrhizal fungi were tested for their effectiveness in promoting growth of Sitka spruce seedlings, in two contrasting soils, in a glasshouse pot experiment. In nursery soil,Laccaria amethystina significantly improved growth of seedlings in comparison toL. laccata. Seedlings inoculated with a forest isolate ofThelephora terrestris were significantly larger than those inoculated with a nursery isolate when grown in forest soil. The effectiveness ofComplexipes moniliformis in forest soil was poor in comparison to other mycorrhizal fungi. Strains aswell as species of mycorrhizal fungi affect seedling growth differently. These effects are further influenced by soil type.     

Ability of native ectomycorrhizal fungi from northern Spain to colonize Douglas-fir and other introduced conifers

 Thirty-six isolates from 27 species of native ectomycorrhizal fungi collected in northern Spain were tested for ectomycorrhiza formation with Pseudotsuga menziesii seedlings in pure culture syntheses. Thirteen of those species were also tested for ectomycorrhiza formation with six other species of conifers (two native and four introduced) to compare their colonization potential. Twenty-three fungal isolates from 18 species formed ectomycorrhizas with Pseudotsuga menziesii. The colonization level of the root system varied markedly among the different fungal species. Eight fungi colonized over 50% of the short roots. Nine fungi did not form ectomycorrhizas even though some of them were collected in pure stands of Pseudotsuga menziesii. Laccaria laccata, Lyophyllum decastes, Pisolithus tinctorius, and Scleroderma citrinum formed abundant ectomycorrhizas on all the conifers tested. Lactarius deliciosus, Rhizopogon spp., and Suillus luteus showed the greatest host specificity. The success in the introduction of some exotic conifers for reforestation in northern Spain is discussed in relation to their compatibility with native ectomycorrhizal fungi. Accepted: 28 August 1995     

Prior host feeding experience influences ovipositional but not feeding preference in a polyphagous insect herbivore

Black vine weevils, Otiorhynchus sulcatus (Fabricius) (Coleoptera: Curculionidae), are globally‐distributed polyphagous pests of many horticultural crops. We investigated how adult weevils were affected by host switching and, in particular, how host plant species nutritional and defensive chemistry affected subsequent host plant species selection and oviposition. Adults were fed one of three host plant species, blackcurrant [Ribes nigrum L. (Grossulariaceae)], raspberry [Rubus idaeus L. (Rosaceae)], or strawberry [Fragaria x ananassa Duchesne (Rosaceae)], throughout their pre‐reproductive periods and then subjected to behavioral choice assays with these plants. Foliar chemistry differed significantly among the three host plant species. Compared to raspberry and strawberry foliage, blackcurrant foliage was 13% lower in nitrogen, 3% higher in carbon, and 28% higher in phenolic compounds. Initial host plant species had a significant effect on weevil mortality, with more weevils dying when previously fed blackcurrant (12%) than strawberry (3%) or raspberry (0%) regardless of subsequent host. Initial host plant species also affected oviposition, with weevils laying only ca. two eggs per week when previously fed blackcurrant, compared to those on raspberry or strawberry (ca. 11 and 15 eggs per week, respectively). When given a choice, weevils discriminated among host plant species and tended to oviposit on plants on which they had previously fed, even when the plant was nutritionally inferior for egg production and adult survival. In contrast, feeding behavior was only affected by the current host plant species. Feeding and oviposition were related to leaf chemistry only in blackcurrant, as leaf consumption was negatively correlated with foliar carbon and zinc concentrations, and positively correlated with foliar phosphorus and potassium concentrations.     

Mycorrhiza and root-associated fungi in Spitsbergen

Summary Roots of 76 plant species collected in West Spitsbergen (Svalbard), in the middle-northern Arctic zone, were examined for mycorrhiza and root-associated fungi. Dryas octopetala, Pedicularis dasyantha and Salix polaris were ectomycorrhizal and Cassiope tetragona and Empetrum hermaphroditum ericoid mycorrhizal. Pedicularis dasyantha was only slightly infected. Structures resembling vesicular-arbuscular mycorrhizal (VAM) fungi were not found in the roots, and soil samples screened for VAM fungi contained only one spore. Root endophytic fungi commonly occurred in Spits-bergen, but only Olpidium brassicae, Pleospora herbarum, Papulaspora, Microdochium bolleyi and Rhizoctonia solani were identified with reasonable certainty. A sterile endophytic dark-septate fungus (DSF) was in 39.5% of the flowering-plant species examined, especially in the Brassicaceae, Caryophyllaceae, Saxifragaceae and Poaceae. DSF were categorized into four slightly overlapping groups. Sterile endophytic hyaline septate fungi were rare. In the literature it is suggested that at least some of the DSF species or the hyaline septate fungi are functionally mutualistic rather than saprophytic or pathogenic. The literature on ectomycorrhizal fungi and plants in Spitsbergen is reviewed, including about 50 species, mainly of the genera Cortinarius, Hebeloma, Inocybe, Laccaria, Lactarius and Russula. These are symbiotic with the above-mentioned ectomycorrhizal plants. Four further ectomycorrhizal plants (Betula nana, Salix spp.) are very rare in the area.     

ASSOCIATED BACTERIA INCREASE THE PHYTOEXTRACTION OF CADMIUM AND ZINC FROM A METAL-CONTAMINATED SOIL BY MYCORRHIZAL WILLOWS

In order to enhance phytoremediation efficiency, we investigated the effects of dual inoculation with ectomycorrhizal fungi and the ectomycorrhiza associated bacteria Micrococcus luteus and Sphingomonas sp. on the growth and metal accumulation of willows (Salix viminalis x caprea) on contaminated soil. The bacterial strains were previously collected from sporocarps of ectomycorrhizal fungi. The bacteria increased plant growth and the mycorrhizal dependency of willows colonized with the ectomycorrhizal fungus Hebeloma crustuliniforme. The total cadmium (Cd) and zinc (Zn) accumulation in the shoot biomass was increased after inoculation with the fungal strain Hebeloma crustuliniforme in combination with Micrococcus luteus up to 53% and in combination with Sphingomonas sp. up to 62%, respectively. The dual inoculation in combination with Laccaria laccata did not increase the accumulation of Cd and Zn in the willows. We conclude that associated bacteria can enhance the ectomyorrhiza formation and growth of willows and, thereby, the Cd and Zn accumulation in the plant biomass. The results suggest that bacterial support of root growth promoting ectomycorrhizal fungi may be a promising approach to improve the remediation of metal-contaminated soils by using willows.     

Molecular approaches to ectomycorrhizal diversity studies: variation in ITS at a local scale

In most ectomycorrhizal (EM) community studies involving molecular identification methods there is a poor correspondence between fungi that appear dominant as sporocarps and those that appear dominant on EM roots and the species richness belowground is higher than that above ground. As a consequence, many fungi from root tip samples remain unidentified. In most studies, genetic data from multiple samples of an EM morphotype collected from various sampling locations are compared to genetic data from one to a few sporocarps of each species for identification purposes. The mismatch between above- and belowground species richness may be influenced by these different sampling efforts. To address this, intra-specific variation in the ITS region first investigated in Kårén et al. (1997) is revisited here, but at a spatial scale in which variation is expected to be low. Sporocarps were collected across a 7 km region of the Oregon Dunes National Recreation Area in western North America. ITS–RFLP data are presented for 3-18 sporocarps from each of 44 EM species in 18 genera. A total of 311 sporocarps were analyzed. Fifty-three ITS–RFLP types were observed. Of the 44 species, 38 (86% of total) yielded a single, species specific, RFLP type. No 2 species had the same RFLP type. Polymorphic ITS–RFLP types were observed in six species (14%). The following three species had two ITS-RFLP types with one type dominating: Inocybe lacera, Laccaria proxima, and Rhizopogon subcaerulescens. The following three species had three RFLP types with no type dominating: Laccaria laccata, Lactarius deliciosus, and Tricholoma flavovirens. A phylogenetic analysis of ITS sequences in Tricholoma revealed that two of the RFLP types in T. flavovirenswere apparently the result of intra-specific variation, while the third RFLP type was likely a cryptic species. All the other RFLP types observed in Tricholoma represented unique phylogenetic species. These results suggest that ITS–RFLP data from single samples (sporocarp or EM) are robust for characterizing most of the species at this scale. However, restriction endonucleases detect a limited amount of existing nucleotide variation and thus have limited value to detect cryptic species. Therefore, additional analyses of sequence data should be added to the RFLP matching technique to identify unknown RFLP types. These data also suggest that polymorphic RFLP types within species do not adequately explain the mismatch between above- and belowground views of EM species richness.     

Incidence and genetic diversity of raspberry bushy dwarf virus (RBDV) in Rubus spp. in Turkey

Raspberry bushy dwarf virus (RBDV), recently renamed to Idaeovirus rubi, is one of the most common viruses infecting Rubus species worldwide but there is still a limited number of genome sequences available in the GenBank database and the majority of the sequences include partial sequences of RNA-1 and RNA-2. The distribution and incidence of RBDV in main raspberry and blackberry growing provinces in Turkey were monitored during 2015–2019 and 537 Rubus spp. samples were tested by both DAS-ELISA and RT-PCR. Among the tested samples, 36 samples tested positive for RBDV by DAS-ELISA and 67 samples by RT-PCR. There was relatively low nucleotide diversity among the Turkish isolates. Turkish isolates shared 93%–97.7%, 84.3%–98.9%, and 85%–99.2% nucleotide sequence identities with available sequences in the GenBank, in partial RNA-1, movement protein (MP) and coat protein (CP) genes, respectively. In the phylogenetic tree constructed for RNA-1, MP, and CP sequences, all Turkish raspberry isolates were clustered in a distinct clade. However, the blackberry isolates showed considerable variation in nucleotide sequences and were placed in three distinct groups. The divergent blackberry isolates showed high variability in MP (84.5%–89.3%) and CP (85.5%–89.7%) regions and were placed in a distinct group. The rest of blackberry isolates clustered together with sweet cherry RBDV isolates adjacent to the grapevine clade or together with raspberry isolates. The comparative analysis conducted on three RNA segments of RBDV highlighted the high sequence diversity of Turkish RBDV isolates. This study also emphasizes the importance of regular monitoring of RBDV infections in Turkey, with special regard to those Rubus spp. and grapevine accessions employed in conservation and selection programmes. In particular, the presence of new RBDV genetic variants and infection of Rubus species must be taken into account to choose a correct detection protocol and management strategy.     

Seed-transmission of nematode-borne viruses

Transmission through seed of crop and weed plants seems to be characteristic of nematode-borne viruses. It occurred with tomato black ring virus (TBRV) in nineteen species (thirteen botanical families), with arabis mosaic virus (AMV) in thirteen species (eleven families), with raspberry ringspot virus (RRV) in six species (five families), and also, in more limited tests, with tomato ringspot, cherry leaf roll and tobacco rattle viruses. A remarkable feature was that infected seedlings, except those containing tobacco rattle virus, often appeared healthy. The occurrence and extent of seed-transmission depended on both the virus and the host plant. In many progenies more than 10%, and in some 100%, of seedlings were infected. The viruses were transmitted through at least two or three generations of seed of those host species tested. After 6 years' storage, TBRV- and RRV-containing seed of Capsella bursa-pastoris and Stellaria media germinated to give infected seedlings. In controlled crossing experiments with strawberry and raspberry, virus was transmitted to seed from both male and female parents but, at least in raspberry, the presence of competing virus-free pollen much decreased the ability of pollen from infected plants to set seed. There was no evidence that healthy mother plants became infected when their flowers were pollinated with infected pollen.     

Detecting the heavy metal tolerance level in ectomycorrhizal fungi <Emphasis Type="Italic">in vitro</Emphasis>

Summary Eight isolates of ectomycorrhizal fungi namely, Laccaria fraterna (EM-1083),Laccaria laccata (EM-1191), Pisolithus tinctorius (EM-1081),Pisolithus tinctorius (EM-1293), Scleroderma cepa (EM-1233),Scleroderma flavidum (EM-1235),Scleroderma verucosum, (EM-1283) and Hysterangium incarceratum (EM-1185) were grown on specially designed cocktail media prepared by adding various concentrations of different heavy metals namely Al, As, Cd, Cr, Ni and Pb. The heavy metals were selected keeping in view their relative abundance in coal ash and potential toxicity. The fungal isolates were grown on such designed cocktail media. The colony diameter was used for the measurement of the fungal growth. Total heavy metal accumulated in the mycelia was assayed by atomic absorption spectrophotometry.In relation to metal tolerance ability in general,Hysterangium incarceratum (EM-1185) showed maximum tolerance with respect to growth, Laccaria fraterna (EM-1083) and Pisolithus tinctorius (EM-1293) also showed considerable tolerance to the heavy metals tested. In relation to metal uptake in particular, Pisolithus tinctorius (EM-1293), has reported maximum uptake of Al (34642.58 ppm), Cd (302.12 ppm) and Pb (3501.96 ppm). In Laccaria fraterna (EM-1083), As (130.57 ppm) and Cr (402.38 ppm) uptake was recorded maximum; and Hysterangium incarceratum (EM-1185) has recorded maximum Ni (2648.59 ppm) uptake among the three suitable isolates documented here.     

Mycorrhizal Fungi Prevent Disease in Stressed Pine Seedlings

The common rhizospheric fungus Cylindrocarpon destructans caused severe root damage leading to mortality in light-starved, stunted seedlings of Pinus sylvestris. This effect was, however, almost fully prevented by the presence of mycorrhizal fungi; i.e. Laccaria laccata, Pisolithus tinctorius, or unidentified species present in small amounts of conifer soil. Protection took place even before visible mycorrhizae were found on the roots. This is the first time that protection ofstressed plants against non-parasitic (non-invasive) pathogens has been reported. The results indicate that root protection by mycorrhizal fungi may not only be effective inside the root but probably also extends out into the rhizoplane or rhizosphere.     

Nitrate reductase activity of nonmycorrhizal Douglas-fir rootlets and of some associated mycorrhizal fungi

Douglas-fir root tips reduced nitrate at much higher rates than seven mycorrhizal fungi, which also differed between species in rate of nitrate reduction. Results are related to nitrogen nutrition of Douglas-fir.Excised, nonmycorrhizal root tips of Douglas-fir reduced nitrate at much higher rates than seven mycorrhizal fungi commonly associated with Douglas-fir. The fungi differed significantly in degree of activity:Cenococcum geophilum, Piloderma bicolor, andRhizopogon vinicolor were highest;Amanita muscaria was intermediate; andHebeloma crustuliniforme, Thelephora terrestris, andLaccaria laccata were lowest.     

Changes in hyphal morphology and activity of phenoloxidases during interactions between selected ectomycorrhizal fungi and two species of <Emphasis Type="Italic">Trichoderma</Emphasis>

Patterns of phenoloxidase activity can be used to characterize fungi of different life styles, and changes in phenoloxidase synthesis were suspected to play a role in the interaction between ectomycorrhizal and two species of Trichoderma. Confrontation between the ectomycorrhizal fungi Amanita muscaria and Laccaria laccata with species of Trichoderma resulted in induction of laccase synthesis, and the laccase enzyme was bound to mycelia of ectomycorrhizal fungi. Tyrosinase release was noted only during interaction of L. laccata strains with Trichoderma harzianum and T. virens. Ectomycorrhizal fungi, especially strains of Suillus bovinus and S. luteus, inhibited growth of Trichoderma species and caused morphological changes in its colonies in the zone of interaction. In contrast, hyphal changes occurred less often in the ectomycorrhizal fungi tested. Species of Suillus are suggested to present a different mechanism in their interaction with other fungi than A. muscaria and L. laccata.     

ROOTS OF METAL HYPERACCUMULATING POPULATION OF THLASPI PRAECOX (BRASSICACEAE) HARBOUR ARBUSCULAR MYCORRHIZAL AND OTHER FUNGI UNDER EXPERIMENTAL CONDITIONS

Thlaspi praecox (Brassicaceae) is a recently discovered metal hyperaccumulating plant species colonized by arbuscular mycorrhizal fungi (AMF). The identity and diversity of the AMF colonizing its roots have not been determined so far. Therefore, T. praecox was inoculated with an indigenous fungal mixture from a metal polluted site and grown in original polluted soil/ commercial substrate mixtures (i.e., 100%, 50%, and 25%). Low to moderate mycorrhizal frequencies (F = 33–68%) and only rare arbuscules were observed. Densities of vesicles and microsclerotia, typical structures of dark septate endophytes (DSE), were greater in pots with 100% original polluted soil. In contrast, the highest diversity of fungal genotypes was observed in the roots from 25% polluted soil/ commercial substrate mixture, with the lowest soil concentrations of Cd, Zn, and Pb. The sequences obtained corresponded to Glomus species (Glomeromycota), to putative DSE Phialophora verrucosa and Rhizoctonia sp. and to some other fungi from Asco- and Basidiomycota, that are known to associate with plants, namely Capnobotryella sp., Penicillium brevicompactum, Rodotorula aurantiaca and Rodotorula slooffiae. This is the first report of DSE occurrence in roots of hyperaccumulating T. praecox, a promising candidate for phytoextraction.