Search

During an extended search in Western Canada for fungal root endophytes useful as biocontrol agents against soil-borne pathogens, we isolated Heteroconium chaetospira, as well as Phialocephala fortinii or similar taxa, from seven samples of forest soil using herbaceous seedlings of four different species (i.e., barley, Chinese cabbage, eggplant, and melon) as bait plants. Our results support a previous observation that eggplant is a particularly effective species for baiting H. chaetospira from soil and confirm the ability of this fungus to grow as an endophyte in the roots of axenically reared host plants. Cultural characters show that this species is similar to P. fortinii and other melanized fungi in the dark septate endophyte (DSE) group (e.g., Leptodontidium orchidicola, P. sphaeroides, and Cadophora finlandica) in that it produces darkly pigmented colonies on agar media. Heteroconium chaetospira differs from P. fortinii and other melanized members of the Leotiomycetes in the DSE group in that its conidia are fusiform and develop in blastic acropetal chains. Heteroconium chaetospira is phylogenetically distant from most DSE taxa because DNA sequences for the nuclear small subunit (SSU) ribosomal RNA gene (rDNA) indicate that the taxon is affiliated with the Herpotrichiellaceae of the Chaetothyriales rather than with the Leotiomycetes.

International audience; Several laboratory experiments and field observations demonstrate that saprotrophic and ectomycorrhizal fungi effectively use pollen cytoplasm and suggest pollen produced by wind-pollinated trees as a crucial nutrient source for fungi and their plant hosts in nutrient-limited environments. However, the role of such interactions is still underestimated or neglected in ecology and paleoecology. Here, we consider pollen attacked by fungi in palynological records from Holocene raised peat bogs as a nutrient source for ecosystems in the past. The attacks occurred through the pollen germination areas by a variety of saprotrophic, ericoid mycorrhizal, ectomycorrhizal or dark septate endophyte fungi. Large amounts of attacked pollen in phases rich in Calluna vulgaris highlight the importance of Ericaceae shrubs, hosting ericoid mycorrhizal fungi and forming hotspots of decomposition in nutrient-deficit bogs. Applying estimations of pollen rain from literature, and based on own observed pollen infection rates we estimate the annual release of nitrogen, phosphate and potassium from pollen, and highlight their significance in pushing the ecosystem nutrient cycle in early spring time, when several species release their pollen. We highlight the significant role of anthropogenic changes in pollen deposition for pre-industrial bogs and hypothesize about the consequences of the pollen-based interrelation between wind-pollinated plants and their mycorrhizal fungi in paleoecology and evolution. (C) 2015 Elsevier B.V. All rights reserved.

Our objective was to understand the cadmium (Cd) tolerance mechanisms by investigating the subcellular distribution, chemical forms of Cd and adsorptive groups in the mycelia of Exophiala pisciphila. We grew E. pisciphila in the liquid media with increasing Cd concentrations (0, 25, 50, 100, 200, and 400 mg L(-1)). Increased Cd in the media caused a proportional increase in the Cd uptake by E. pisciphila. Subcellular distribution indicated that 81 to 97% of Cd was associated with the cell walls. The largest amount and proportion (45-86%) of Cd was extracted with 2% acetic acid, and a concentration-dependent extraction was observed, both of which suggest that Cd-phosphate complexes were the major chemical form in E. pisciphila. A large distribution of phosphate and Cd on the mycelia surface was observed by scanning electron microscopy-energy dispersive spectrometer (SEM-EDS). The precipitates associated with the mycelia were observed to contain Cd by transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX). Fourier transform infrared (FTIR) identified that hydroxyl, amine, carboxyl, and phosphate groups were responsible for binding Cd. We conclude that Cd associated with cell walls and integrated with phosphate might be responsible for the tolerance of E. pisciphila to Cd.

Seagrasses, a small group of submerged marine macrophytes, were reported to lack mycorrhizae, i.e., the root-fungus symbioses most terrestrial plants use for nutrient uptake. On the other hand, several authors detected fungal endophytes in seagrass leaves, shoots, rhizomes, and roots, and an anatomically and morphologically unique dark septate endophytic (DSE) association has been recently described in the roots of the Mediterranean seagrass Posidonia oceanica. Nevertheless, the global diversity of seagrass mycobionts is not well understood, and it remains unclear what fungus forms the DSE association in P. oceanica roots. We isolated and determined P. oceanica root mycobionts from 11 localities in the northwest Mediterranean Sea with documented presence of the DSE association and compared our results with recent literature. The mycobiont communities were low in diversity (only three species), were dominated by a single yet unreported marine fungal species (ca. 90 % of the total 177 isolates), and lacked common terrestrial and freshwater root mycobionts. Our phylogenetic analysis suggests that the dominating species represents a new monotypic lineage within the recently described Aigialaceae family (Pleosporales, Ascomycota), probably representing a new genus. Most of its examined colonies developed from intracellular microsclerotia occupying host hypodermis and resembling microsclerotia of terrestrial DSE fungi. Biological significance of this hitherto overlooked seagrass root mycobiont remains obscure, but its presence across the NW Mediterranean Sea and apparent root intracellular lifestyle indicate an intriguing symbiotic relationship with the dominant Mediterranean seagrass. Our microscopic observations suggest that it may form the DSE association recently described in P. oceanica roots.

Acephala applanata gen. et sp. nov. is described. A. applanata is a dark-septate endophyte (DSE) of conifer roots and belongs to the Phialocephala fortinii species complex. Several genetic markers, including isozymes, inter-simple-sequence-repeat (ISSR) fingerprints, single-copy restriction fragment length polymorphisms (RFLP) and sequences of the internal transcribed spacers (ITS), let us unambiguously separate isolates of A. applanata from isolates of P. fortinii s.l. and other dark-septate endophytes. Alleles at four RFLP loci and two fixed nucleotides in the ITS region were diagnostic for A. applanata. One of the fixed nucleotides resulted in the addition of an Afa I restriction site. PCR amplification with primers prITS4 and the newly developed primer PF-ITS_F (ACT CTG AAT GTT AGT GAT GTC TGA GT) and restriction digestion with Afa I yielded three fragments (203 bp, 117 bp, 56 bp) in A. applanata but only two (260 bp and 117 bp) in P. fortinii s.l. Population differentiation (GST) between A. applanata and other cryptic species of P fortinii was pronounced, and the index of association (IA) did not deviate significantly from zero, showing that recombination occurs or had occurred in A. applanata. Although isolates of A. applanata never were observed to sporulate, it can be distinguished morphologically from P fortinii s.l. by the scarcity of aerial mycelium, significantly slower growth and denser mycelium on cellophane overlaid on water agar. These phenotypic characteristics, combined with diagnostic RFLP alleles and/or PCR-RFLP of the ITS fragment with the fixed Afa I restriction site, unequivocally allow identification of A. applanata.

A comparison of published estimates of mycorrhizal and dark septate endophyte (DSE) colonisation from various ecosystems suggests that DSE may be as abundant as mycorrhizal fungi as judged by the proportion of host plants colonised in mixed plant communities, or by the extent of colonisation in sampled root systems. While many strides have been made in understanding the ecological significance of the mycorrhizal fungi, our knowledge about the role of DSE fungi is in its infancy. In order to provide a framework of testable hypotheses, we review and discuss the most likely functions of this poorly understood group of root-associated fungi. We propose that, like mycorrhizal symbioses, DSE-plant symbioses should be considered multifunctional and not limited to nutrient acquisition and resultant positive host growth responses. Admittedly, many mycorrhizal and endophyte functions, (e.g. stress tolerance, pathogen or herbivore deterrence) are likely to be mediated by improved nutritional status and increased fitness of the host. Accordingly, it is pivotal to establish whether or not the DSE fungi are involved in host nutrient acquisition, either from inorganic and readily soluble sources, or from organic and recalcitrant sources. Facilitation by DSE of the use of organic nitrogen, phosphorus and sulphur sources by plants is a topic that warrants further attention and research. Even in the absence of a clear nutrient uptake function, the extensive DSE colonisation that occurs is likely to pre-emptively or competitively deter pathogens by minimising the carbon available in host rhizosphere environment. The DSEs' high melanin levels and their potential production of secondary metabolites toxic or inhibitory to herbivores are also likely to be factors influencing host performance. Finally, the broad host ranges speculated for most DSE fungi thus far suggest that they are candidates for controlling plant community dynamics via differential host responses to colonisation. We emphasise the need for simple experiments that allow unravelling of the basic biological functions of DSE fungi when they colonise their hosts.

A wide range of ascomycetous microfungi inhabits roots without forming the anatomical features typical of mycorrhizas or causing overt signs of pathogenesis. The most-studied taxa have darkly pigmented hyphal walls and are referred to as "dark septate endophytes" (DSE). We provide a dichotomous key and annotated descriptions for a cross-section of the most common dark septate endophytes. The term DSE is sometimes used to imply taxonomic and physiological similarity even though a diverse range of root endophytic taxa form pigmented hyphae. Among these, Phialocephala fortinii Wang & Wilcox is a well-known representative; it is widespread, easily observed in roots, and readily grown in culture and with plants. Nevertheless, the basis of its symbiotic relationship with plants remains ambiguous. It may be a weak pathogen, a saprotroph on senescent root tissues, or a mutualist. More detailed studies of interactions between identified taxa of microfungal endophytes and host plants are necessary to elucidate the functional basis of these symbioses; it may be necessary to look beyond the paradigms of traditional mycorrhizal and pathogenic associations to understand the ecological roles of these fungi. Reports of cryptic speciation in Phialocephala fortinii emphasize the need for accurate identification of isolates of microfungal endophytes used in experiments.Key words: dark septate endophytes (DSE), Phialocephala fortinii, mycorrhiza, fungus–host interactions, fungi.

Summary • A survey of 12 plants colonized by six species of arbuscular mycorrhizal fungi was conducted to explore the diversity of Arum and Paris mycorrhizal structures. • Surveyed root material was sectioned both longitudinally and transversely, double-stained and mycorrhizal structures were identified. A detailed time course experiment using four plant, and four fungal species, was used to investigate the sequential development of hyphae, arbuscules, hyphal coils, arbusculate coils and vesicles. • The survey indicated that there was a continuum of mycorrhizal structures ranging from Arum to Paris, depending upon both the host plant and the fungus. The time course showed that total colonization increased, and that the establishment of the various mycorrhizal structures did not appear to change greatly over time. • It was concluded that identification of fungal structures and their subsequent development into morphological types is not easily defined. Visual inspection of root squashes is not always adequate, especially where transverse sections are needed to determine if longitudinal hyphae are inter or intracellular; this is essential to distinguish intermediate types.

Native grasses of semi-arid rangelands of the southwestern USA are more extensively colonized by dark septate endophytes (DSE) than by traditional mycorrhizal fungi. Roots of dominant grasses ( Bouteloua sp.) native to arid southwestern USA rangelands were prepared and stained using stains specific for fungi (trypan blue) and for lipids (sudan IV). This revealed extensive internal colonization of physiologically active roots by atypical fungal structures that appear to function as protoplasts, without a distinguishable wall or with very thin hyaline walls that escape detection by methods staining specifically for fungal chitin. These structures were presumed to be active fungal stages that progressed to form stained or melanized septate hyphae and microsclerotia characteristic of DSE fungi within dormant roots. The most conspicuous characteristic of these fungi were the unique associations that formed within sieve elements and the accumulation of massive quantities of lipids. This interface suggests a biologically significant location for carbon transfer between the plant and fungus. The continuous intimate association with all sieve elements, cortical and epidermal cells as well as external extension on the root surface and into the soil indicates that they are systemic and considerably more prevalent than previously thought. A fungal network associated with a mucilaginous complex observed on the root surface and its potential role in root function in dry soil is discussed. It is suggested that those fungi that non-pathogenically and totally colonize plant cells be classed as systemic endophytic fungi (SEF). This would refine the broad designation of DSE fungi. The potential mutualistic benefit of SEF for native plants in arid ecosystems based on the extent of lipid accumulation and its apparent distribution is discussed.

The growth response of an ornamentalRhododendron hybrid to the inoculation withPhialocephala fortinii was studied in two pot experiments in order to decide about the effectiveness of the inoculation of young rhododendron microplants. Two different substrates were used in both experiments, either sterilized or non-sterilized: a horticultural substrate and a soil collected from a field site with dominant ericoid vegetation. Two fungal isolates were used for an inoculation:P. fortinii strain P (UAMH 8433) andP. fortinii strain F, a dark septate endophyte (DSE) previously isolated from naturally-infected roots ofVaccinium myrtillus. BothPhialocephala strains successfully colonized the roots of the host plants forming typical DSE (=pseudomycorrhizal) colonization pattern including the formation of intracellular microsclerotia. However, pseudomycorrhizal colonization did not affect the growth parameters of the host rhododendrons. The results from both experiments indicate a neutral effect of the inoculation with DSE fungi on the growth ofRhododendron cv. Belle-Heller.

The community and Cd-resistance of endophytic fungi from roots of Salix variegata Franch. collected from the water-level-fluctuation zone of Three Gorges Reservoir Region, China, were investigated. A total of 53 strains were isolated and identified to 13 morphotaxa, in which Chromosporium, Fusarium and Gonatobotrys were dominant genera. Among them, 27 isolates were selected to measure their resistance to 0.02 mg ml(-1) Cd(2+) and 11 were growth stimulated (Tolerance index>100%). Of these active isolates, four dark septate endophyte (DSE) isolates (Paraphaeosphaeria sp. SR46, Pyrenochaeta sp. SR35, Rhizopycnis vagum SR37 and R. vagum SR44) were further tested for minimum inhibitory concentrations (MICs) against Cd and SR46 was found to be the most tolerant isolate with MIC of 0.39 mg ml(-1). Additionally, the maximum uptake values of these DSEs ranged from 3.01 to 7.89 mg g(-1), but there was no significant correlation between metal uptake with fungal biomass and metal tolerance. Subsequently, a pot experiment was conducted for investigating the impact of SR46 on corn seedlings in Cd-enriched soil. The results obtained suggested that SR46 reduced the Cd bioaccumulation of plant under low (100 mg kg(-1)) Cd stress and enhanced the Cd translocation from root zone to aerial parts under high (200 mg kg(-1)) Cd stress. Besides, it promoted plant growth without Cd stress. These findings indicated S. variegata harbors an endophytic fungal flora showing a high genetic diversity as well as a high level of metal resistance to Cd that has potential values in cadmium cycling and restoration of plant, soil and water system.

Two methods to determine variability among strains of Phialocephala fortinii and sterile DSE (dark septate endophyte) Type 1 were compared: inter-simple sequence repeat polymerase chain reaction analysis (ISSR–PCR) and sequence analysis of the two internal transcribed spacers and the 5.8S ribosomal DNA (ITS1-5.8S-ITS2). Both methods showed similar results for some strains, but different results for others. Phylogenetic analysis of various strains of P. fortinii and Type 1 based on ITS1-5.8S-ITS2 sequence information showed that Type 1 strains, with the exception of one Type 1 strain and a strain with a Type-1-like culture morphology, form a well-supported clade, whereas P. fortinii strains are much more variable and the relative position of many strains on the tree are unresolved. Two sterile DSE strains with Type 1 culture morphology form a well-supported clade, separate from the P. fortinii – Type 1 clade. Phylogenetic analysis of some species of the Leotiales and of Phialocephala and related species based on ITS1-5.8S-ITS2 sequences indicate that the genera Phialocephala and Sporendocladia are polyphyletic. One major clade, supported by a high bootstrap value, is positioned as a well-separated lineage among members of the Leotiales. Phialocephala fortinii, Phialocephala dimorphospora, Phialocephala compacta, Phialocephala scopiformis, and Type 1, all known as endophytes of woody plant species, are positioned in this clade. A second well-supported clade including Phialocephala humicola, Phialocephala xalapensis, and Phialocephala fusca was positioned outside the Leotiales. Phialocephala xalapensis and P. humicola had identical sequences and were not separable based on morphology. The two taxa were, therefore, considered to represent the same species. Phialocephala virens, Phialophora finlandia, Sporendocladia foliicola, and Leptodontidium orchidicola were not included in either of the two Phialocephala clades.Key words: Phialocephala, phylogenetic analysis, internal transcribed spacer, DSE.

Arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungal colonization of Alchemilla glomerulans, Carex vaginata, Ranunculus acris ssp. pumilus and Trollius europaeus growing in low-alpine meadows in the Finnish subarctic were studied at different times during the growing season. Fungal colonization was correlated to soil soluble phosphorus (P) concentration. The influence of flower bud removal on fungal colonization was investigated in A. glomerulans, C. vaginata and R. acris and the correlation between AM and DSE colonization was studied. The fungal colonization patterns were found to be species-specific. R. acris maintained a relatively high rate of fungal colonization throughout the summer, while the rates of colonization of T. europaeus were lower and decreased towards the end of the season. A. glomerulans had constant arbuscular and vesicular colonization throughout the summer, but hyphal and DSE colonization declined towards the end of the season. C. vaginata did not form arbuscular mycorrhiza, but was colonized by DSE fungi and hyaline septate hyphae throughout the season. The soil soluble P concentration showed some seasonal variation, but was also highly variable between the study sites. Bud removal decreased arbuscular colonization of R. acris, but no unique effects were seen in any other parameters or the other species studied. The root fungal parameters correlated with soil P in some species at some sites, but no consistent trend was found. DSE colonization was positively correlated with root vesicular and hyphal colonization in some cases. The differences in fungal colonization parameters may be related to species-specific phenologies.

Glutathione S-transferases (GSTs) compose a family of multifunctional enzymes that play important roles in the detoxification of xenobiotics and the oxidative stress response. In the present study, twenty four GST genes from the transcriptome of a metal-tolerant dark septate endophyte (DSE), Exophiala pisciphila, were identified based on sequence homology, and their responses to various heavy metal exposures were also analyzed. Phylogenetic analysis showed that the 24 GST genes from E. pisciphila (EpGSTs) were divided into eight distinct classes, including seven cytosolic classes and one mitochondrial metaxin 1-like class. Moreover, the variable expression patterns of these EpGSTs were observed under different heavy metal stresses at their effective concentrations for inhibiting growth by 50% (EC50). Lead (Pb) exposure caused the up-regulation of all EpGSTs, while cadmium (Cd), copper (Cu) and zinc (Zn) treatments led to the significant up-regulation of most of the EpGSTs (p < 0.05 to p < 0.001). Furthermore, although heavy metal-specific differences in performance were observed under various heavy metals in Escherichia coli BL21 (DE3) transformed with EpGSTN-31, the over-expression of this gene was able to enhance the heavy metal tolerance of the host cells. These results indicate that E. Pisciphila harbored a diverse of GST genes and the up-regulated EpGSTs are closely related to the heavy metal tolerance of E. pisciphila. The study represents the first investigation of the GST family in E. pisciphila and provides a primary interpretation of heavy metal detoxification for E. pisciphila.

High-elevation ecosystems are expected to be particularly sensitive to climate warming because cold temperatures constrain biological processes. Deeper understanding of the consequences of climate change will come from studies that consider not only the direct effects of temperature on individual species, but also the indirect effects of altered species interactions. Here we show that 20 years of experimental warming has changed the species composition of graminoid (grass and sedge) assemblages in a subalpine meadow of the Rocky Mountains, USA, by increasing the frequency of sedges and reducing the frequency of grasses. Because sedges typically have weak interactions with mycorrhizal fungi relative to grasses, lowered abundances of arbuscular mycorrhizal (AM) fungi or other root-inhabiting fungi could underlie warming-induced shifts in plant species composition. However, warming increased root colonization by AM fungi for two grass species, possibly because AM fungi can enhance plant water uptake when soils are dried by experimental warming. Warming had no effect on AM fungal colonization of three other graminoids. Increased AM fungal colonization of the dominant shrub Artemisia tridentata provided further grounds for rejecting the hypothesis that reduced AM fungi caused the shift from grasses to sedges. Non- AM fungi (including dark septate endophytes) also showed general increases with warming. Our results demonstrate that lumping grasses and sedges when characterizing plant community responses can mask significant shifts in the responses of primary producers, and their symbiotic fungi, to climate change. © 2014 by the Ecological Society of America.

The growth, oxidative damage and antioxidant response of Exophiala pisciphila ACCC32496, a dark septate endophyte isolated from an abandoned lead-zinc mining area, were measured at cadmium (Cd) concentrations of 0, 25, 50, 100, 200 and 400 mg L(-1). The EC50 values of E. pisciphila ACCC32496 to Cd were 332.2 mg L(-1) after 30 days on solid medium and 111.2 mg L(-1) after 7 days in liquid medium. Cd stress markedly stimulated the production of superoxide anion, H2O2 and malondialdehyde in the fungal mycelia. The activities of superoxide dismutase and catalase reached their maxima at 100 mg L(-1) Cd. The glutathione and non-protein thiol contents, along with the total antioxidant capability, reached their maxima at 50 mg L(-1) Cd. Low Cd concentrations induced a noticeable increase in antioxidant defense, while high Cd concentrations decreased the antioxidant defense.

Plants growing on an environmentally stressed glacier forefront on soil low in N and organic matter have abundant root colonizations by dark-septate fungi. As the plants appeared fit for this severe habitat, it was hypothesized that the dark-septate endophytes were neutral or beneficial rather than detrimental to the plants. To test this hypothesis, we designed a growth-room experiment with Pinus contorta grown on forefront soil inoculated with the dark-septate fungus Phialocephala fortinii in the absence of climatic stress. N and organic matter treatments were included to explore their interaction with the fungal inoculation. P. fortinii colonized roots inter- and intracellularly and occasionally formed microsclerotia. Inoculated plants absorbed significantly more P than noninoculated plants in all combinations of N and organic matter. Without added N, neither inoculation nor organic matter addition improved plant growth or N uptake, showing that N indeed limits plant growth in this substrate. With added N, however, both organic matter addition and inoculation significantly increased total pine biomass and N uptake. The enhanced P uptake by the P. fortinii-inoculated pine as well as the increased pine growth and N uptake in the treatment combining P. fortinii and N appear as typical mycorrhizal responses.

Dark septate (DS) fungal endophytes are the primary root colonizers of fourwing saltbush, Atriplex canescens (Pursh) Nutt, a dominant and ecologically important shrub in southwestern USA rangelands. These fungi are characteristically identified as stained or pigmented hyphae and microsclerotia in the root cortex using conventional fungus staining methods. A. canescens roots colonized by DS fungi were stained with sudan IV and analyzed with differential interference microscopy. This method revealed substantial internal colonization of the cortex and vascular cylinder by vacuolated hyaline hyphae that were not evident when stained with trypan blue. Hyaline hyphae were internal extensions of melanized DS hyphae and microsclerotia. Sudan IV intensely stained lipids in fungal vacuoles, further enhancing visibility of internal hyaline hyphae. Melanized hyphae and microsclerotia were more abundant in roots sampled from dormant and relatively inactive plants, while hyaline hyphae and lipid accumulation were most prevalent in roots of physiologically active plants. The polymorphic nature of DS fungal endophytes, their dynamic response to metabolic activity, and their similarities and differences relative to aseptate fungal colonization in A. canescens roots are discussed.

Dark septate endophytes (DSE) are a miscellaneous group of ascomycetous anamorphic fungi that colonize root tissues intracellularly and intercellularly. The limited selection of studies quoted here exemplifies the range of host responses to symbiotic DSE fungi. Like mycorrhizal associations, DSE associations vary from negative to neutral and positive when measured by host performance or host tissue nutrient concentrations. This range of host responses is partially attributable to variation between different fungus taxa and strains. Similarly, hosts differ in their responses to a single DSE strain. Experimental conditions may also govern the nature of the symbiotic association. It is concluded that DSE are capable of forming mutualistic associations functionally similar to mycorrhizas. If the variation in host response to mycorrhizal fungi is considered to represent a continuum ranging from parasitism to mutualism, DSE symbiosis must be considered mycorrhizal, at least under some conditions.

Seedlings of the annual grass Vulpia ciliata ssp. ambigua were grown in sterilized sand with a dark septate root fungus, Phialophora graminicola, which had been isolated from a natural population of the grass. Tiller number and shoot, root and total biomass of seedlings grown with P. graminicola were enhanced relative to uninoculated control plants in a growth room and a glasshouse experiment. Root length of seedlings grown with P. graminicola was significantly increased, but no effects of the fungus on root diameter, number of root hairs or specific root length were recorded. Root nitrogen content and shoot, root and total phosphorus contents of seedlings grown with the fungus were enhanced, but shoot nitrogen concentration of these plants was reduced. Shoot biomass and specific root length of inoculated plants were positively associated with the number of P. graminicola colonies re-isolated from roots. These data indicate that P. graminicola acts as a beneficial associate of V. ciliata ssp. ambigua seedlings under controlled conditions.

Posidonia oceanica is the most common, widespread and important monocotyledon seagrass in the Mediterranean Basin, and hosts a large biodiversity of species, including microorganisms with key roles in the marine environment. In this study, we ascertain the presence of a fungal endophyte in the roots of P.oceanica growing on different substrata (rock, sand and matte) in two Sicilian marine meadows. Staining techniques on root fragments and sections, in combination with microscope observations, were used to visualise the fungal presence and determine the percentage of fungal colonisation (FC) in this tissue. In root fragments, statistical analysis of the FC showed a higher mean in roots anchored on rock than on matte and sand. In root sections, an inter- and intracellular septate mycelium, producing intracellular microsclerotia, was detected from the rhizodermis to the vascular cylinder. Using isolation techniques, we obtained, from both sampling sites, sterile, slow-growing fungal colonies, dark in colour, with septate mycelium, belonging to the dark septate endophytes (DSEs). DNA sequencing of the internal transcribed spacer (ITS) region identified these colonies as Lulwoana sp. To our knowledge, this is the first report of Lulwoana sp. as DSE in roots of P.oceanica. Moreover, the highest fungal colonisation, detected in P.oceanica roots growing on rock, suggests that the presence of the DSE may help the host in several ways, particularly in capturing mineral nutrients through lytic activity.

Part 1: Ecology and Biodiversity.- Chapter 1.Diversity and ecology of endophytic and epiphytic fungi of tree leaves in Japan: a review.- Chapter 2. Endophytic actinobacteria: diversity and ecology.- Chapter 3.Foliar fungal endophytes in herbaceous plants: a marriage of convenience?.- Part 2: Entomopathogenic endophytes.- Chapter 4. Entomopathogenic and nematophagous fungal endophytes .- Part 3: Host-endophyte interactions.- Chapter 5. Interactions of meristem-associated endophytic Bacteria.- Chapter 6. Unraveling the dark septate endophyte functions: Insights from the Arabidopsis model .- Chapter 7. Asexual endophytes of grasses: Invisible symbionts, visible imprints in the host neighborhood .- Part 5: Bioactive compounds from endophytes.- Chapter 8 . Microbial endophytes their resilience for innovative treatment solution to neglected tropical diseases .- Chapter 9. Endophytes and plant secondary metabolite synthesis: molecular and evolutionary perspective.- Chapter 10. Endophytes as a novel source of bioactive new structures .- Chapter 11.Host-mimetic metabolomics of endophytes: looking back into the future.- Chapter 12. Myconanosynthesis: Redefining the role of microbial endophytes .- Part 6: Bio-control and bioremediation.- Chapter 13. Biological control of insect-pest and diseases by endophytes.- Chapter 14. Biocontrol and bioremediation: two areas of endophytic research which hold great promise.- Chapter 15. Biosourcing endophytes as biocontrol agents of wilt diseases .- Chapter 16. Ecology and functional potential of endophytes in bioremediation: a molecular prospective.- Chapter 17 Ecological aspects of endophyte-based biocontrol of forest diseases .- Chapter 18 Endophyte mediated biocontrol of herbaceous and non-herbaceous plants .- Part 7: Endophytes and cancer.- Chapter 19. Implication of endophytic metabolite and their derivatives in cancer chemotherapy: a prospective study.- Chapter 20. Endophytic fungi: novel sources of anticancer molecules.- Part 8: Future challenges.- Chapter 21. A functional view of plant microbiomes: Endosymbiotic systems that enhance plant growth and survival.- Chapter 22. Microbial endophytes: future challenges.

Investigations on the prevalence of arbuscular mycorrhizal (AM) and dark septate endophyte (DSE) fungal symbioses are limited for plants growing in tropical aquatic and wetland habitats compared to those growing on terrestrial moist or dry habitats. Therefore, we assessed the incidence of AM and DSE symbiosis in 8 hydrophytes and 50 wetland plants from four sites in south India. Of the 58 plant species examined, we found AM and DSE fungal symbiosis in 21 and five species, respectively. We reported for the first time AM and DSE fungal symbiosis in seven and five species, respectively. Intermediate-type AM morphology was common, and AM morphology is reported for the first time in 16 plant species. Both AM and DSE fungal colonization varied significantly across plant species and sites. Intact and identifiable AM fungal spores occurred in root zones of nine plant species, but AM fungal species richness was low. Though no clear relationship between AM and DSE fungal colonization was recognized, a significant negative correlation between AM colonization and spore numbers was established. Our study suggests that the occurrence of AM and DSE fungal symbiosis in plants growing in hydrophytic and wetland habitats is not as common as in terrestrial habitats.

A great diversity of plants and fungi engage in mycorrhizal associations. In natural habitats, and in an ecologically meaningful time span, these associations have evolved to improve the fitness of both plant and fungal symbionts. In systems managed by humans, mycorrhizal associations often improve plant productivity, but this is not always the case. Mycorrhizal fungi might be considered to be parasitic on plants when net cost of the symbiosis exceeds net benefits. Parasitism can be developmentally induced, environmentally induced, or possibly genotypically induced. Morphological, phenological, and physiological characteristics of the symbionts influence the functioning of mycorrhizas at an individual scale. Biotic and abiotic factors at the rhizosphere, community, and ecosystem scales further mediate mycorrhizal functioning. Despite the complexity of mycorrhizal associations, it might be possible to construct predictive models of mycorrhizal functioning. These models will need to incorporate variables and parameters that account for differences in plant responses to, and control of, mycorrhizal fungi, and differences in fungal effects on, and responses to, the plant. Developing and testing quantitative models of mycorrhizal functioning in the real world requires creative experimental manipulations and measurements. This work will be facilitated by recent advances in molecular and biochemical techniques. A greater understanding of how mycorrhizas function in complex natural systems is a prerequisite to managing them in agriculture, forestry, and restoration.

The global occurrence of plant root-associated fungal endophytes and their great abundance in many habitats necessitate studies to decipher their potential functions. Improved understanding of the basic endophyte ecology including host range, host preference, and host responses to endophyte colonization has been made possible through populations of endophytes (e.g., Periconia macrospinosa and Microdochium sp.) isolated from North American native tallgrass prairie. The recent demonstration of the endophyte symbiosis of the model plant Arabidopsis thaliana has provided additional tools to further elucidate the ecology of these endophytes. The availability of a large number of Arabidopsis ecotypes and mutants, microarrays, and databases allows the molecular dissection of endophyte symbiosis to better understand the importance of fungal endophytes in host nutrient uptake, defenses, and/or responses to pathogens and stress. In this chapter, we discuss the ecology and functions of endophytic fungi through experiments utilizing the Arabidopsis model system. We draw parallels with another deeply dissected Piriformospora indica root endophyte symbiosis, which has been demonstrated to promote growth of model and non-model plants.

We studied the actual links between mycorrhizal fungi, nutrient availability and plant development in several sites of fragmented Chaco forests. Specifically, we evaluated whether arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) colonization and availability of soil nutrients are related to growth (biomass and plant height) and reproductive traits (pollen size and pollen and fruit production) of two ruderal, annual, congeneric Euphorbia species along a gradient of forest fragmentation. We assessed relationships between forest fragment size and isolation, nutrient availability, mycorrhizal fungal variables and plant development at eleven Chaquean forest fragments (0.5?1000 ha) immersed in an agricultural landscape in central Argentina. Mycorrhizal colonization was not related to forest fragment isolation, positively related to forest fragment size and negatively related to soil nutrient availability in both hosts along the fragmentation gradient. Plant reproductive and vegetative traits were related to mycorrhizal colonization. In general, plant height, biomass, and fruit production were negatively related to AMF, and pollen production was positively related to DSE, in both ruderal hosts (native and exotic). We found remarkable relationships along a forest fragmentation gradient that reliably link forest fragment size to lower nutrient availability and increased mycorrhizal colonization in native/exotic ruderal hosts, while negatively linking AMF colonization to plant development and reproductive success. Fil: Grilli, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Urcelay, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Galetto, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina

Individual plants typically interact with multiple mutualists and enemies simultaneously. Plant roots encounter both arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungi, while the leaves are exposed to herbivores. AMF are usually beneficial symbionts, while the functional role of DSE is largely unknown. Leaf herbivory may have a negative effect on root symbiotic fungi due to decreased carbon availability. However, evidence for this is ambiguous and no inoculation-based experiment on joint effects of herbivory on AM and DSE has been done to date. We investigated how artificial defoliation impacts root colonization by AM (Glomus intraradices) and DSE (Phialocephala fortinii) fungi and growth of Medicago sativa host in a factorial laboratory experiment. Defoliation affected fungi differentially, causing a decrease in arbuscular colonization and a slight increase in DSE-type colonization. However, the presence of one fungal species had no effect on colonization by the other or on plant growth. Defoliation reduced plant biomass, with this effect independent of the fungal treatments. Inoculation by either fungal species reduced root/shoot ratios, with this effect independent of the defoliation treatments. These results suggest AM colonization is limited by host carbon availability, while DSE may benefit from root dieback or exudation associated with defoliation. Reductions in root allocation associated with fungal inoculation combined with a lack of effect of fungi on plant biomass suggest DSE and AMF may be functional equivalent to the plant within this study. Combined, our results indicate different controls of colonization, but no apparent functional consequences between AM and DSE association in plant roots in this experimental setup.

The ecology of weed plants includes their interactions with soil microorganisms, such as mutualistic partners that may contribute to their adaptation and competitive success in the agricultural fields. Despite the importance of microorganisms to plant growth, knowledge on weed-symbiont associations is still incipient compared to crops. Thus, a survey for the presence of arbuscular mycorrhiza (AM) and dark septate endophyte (DSE) associations in the roots of 50 weed species was done in three distinct areas during the dry and rainy seasons. We found that 41 and 29 out of the 50 species were associated with AM fungi and DSE, respectively, and 27 species presented both associations. All the plant species not forming AM belong to families thought to be nonmycorrhizal, such as Amaranthaceae, Commelinaceae, Brassicaceae, and Cyperaceae. The most common morphotype of AM observed was the Arum-type. No significant differences were found in root length colonization between the areas or seasons. For 19 species surveyed, this is the first report on their mycorrhizal status.

Resynthesis studies were done to determine the ecological role of Leptodontidium orchidicola, a dematiaceous hyphomycete commonly associated with roots of plants growing in cool and humus-rich soils. Results were compared with those of Phialocephala fortinii, another common root endophyte with similar cultural and vegetative characteristics. In axenic culture with Salix glauca seedlings, L. orchidicola caused a marked increase in host root length but also invaded the stele, causing extensive cellular lysis. Phialocephala fortinii formed a Hartig net and a thin, patchy mantle. In pot monocultures with Potentilla fruticosa, Dryas octopetala, S. glauca, and Picea glauca seedlings, the effects of four L. orchidicola strains on host dry weight were strain- and host-specific; the effects of Phialocephala fortinii were also host-specific. Leptodontidium orchidicola formed a range of symbiotic associations that could be considered mycorrhizal to parasitic, whereas the effects of Phialocephala fortinii suggest amensal, parasitic, or neutral association. In pot combination cultures, the Phialocephala fortinii – Potentilla fruticosa symbiosis resulted in a significant increase in shoot weight in contrast with the results of the same symbiosis in monoculture resynthesis. The resynthesis experiments demonstrated that the effects of both L. orchidicola and Phialocephala fortinii also vary according to cultural conditions. Keywords: Leptodontidium orchidicola, Phialocephala fortinii, Mycelium radicis atrovirens, fungus–plant symbiosis, subalpine plants.

The mutualism pattern of the dark septate endophyte (DSE) Harpophora oryzae in rice roots and its biocontrol potential in rice blast disease caused by Magnaporthe oryzae were investigated. Fluorescent protein-expressing H. oryzae was used to monitor the colonization pattern. Hyphae invaded from the epidermis to the inner cortex, but not into the root stele. Fungal colonization increased with root tissue maturation, showing no colonization in the meristematic zone, slight colonization in the elongation zone, and heavy colonization in the differentiation zone. H. oryzae adopted a biotrophic lifestyle in roots accompanied by programmed cell death. Real-time PCR facilitated the accurate quantification of fungal growth and the respective plant response. The biocontrol potential of H. oryzae was visualized by inoculation with eGFP-tagged M. oryzae in rice. H. oryzae protected rice from M. oryzae root invasion by the accumulation of H2O2 and elevated antioxidative capacity. H. oryzae also induced systemic resistance against rice blast. This systemic resistance was mediated by the OsWRKY45-dependent salicylic acid (SA) signaling pathway, as indicated by the strongly upregulated expression of OsWRKY45. The colonization pattern of H. oryzae was consistent with the typical characteristics of DSEs. H. oryzae enhanced local resistance by reactive oxygen species (ROS) and high antioxidative level and induced OsWRKY45-dependent SA-mediated systemic resistance against rice blast.

We surveyed the non-mycorrhizal model plant Arabidopsis thaliana microscopically for its ability to form dark septate endophyte (DSE) symbioses in field, greenhouse, and laboratory studies. The laboratory studies were also used to estimate host growth responses to 34 Periconia macrospinosa and four Microdochium sp. isolates. Consistent with broad host range observed in previous experiments, field-, greenhouse-, and laboratory-grown A. thaliana were colonized by melanized inter- and intracellular hyphae and microsclerotia or chlamydospores indicative of DSE symbiosis. Host responses to colonization were variable and depended on the host ecotype. On average, two A. thaliana accessions (Col-0 and Cvi-0) responded negatively, whereas one (Kin-1) was unresponsive, a conclusion consistent with our previous analyses with forbs native to the field site where the fungi originate. Despite the average negative responses, examples of positive responses were also observed, a conclusion also congruent with earlier studies. Our results suggest that A. thaliana has potential as a model for more detailed dissection of the DSE symbiosis. Furthermore, our data suggest that host responses are controlled by variability in the host and endophyte genotypes.

Fungal endophytic communities and potential host preference of root-inhabiting fungi of boreal forest understory plants are poorly known. The objective of this study was to find out whether two neighboring plant species, Deschampsia flexuosa (Poaceae) and Trientalis europaea (Primulaceae), share similar root fungal endophytic communities and whether the communities differ between two sites. The study was carried out by analysis of pure culture isolates and root fungal colonization percentages. A total of 84 isolates from D. flexuosa and 27 isolates from T. europaea were obtained. The roots of D. flexuosa harbored 16 different isolate types based on macromorphological characteristics, whereas only 4 isolate types were found in T. europaea. The root colonization by dark septate and hyaline septate hyphae correlated with isolate numbers being higher in D. flexuosa compared to T. europaea. The different isolate types were further identified on the basis of internal transcribed spacer sequence and phylogenetic analysis. An isolate type identified as dark septate endophyte Phialocephala fortinii colonized 50 % of the T. europaea and 21 % of the D. flexuosa specimens. In addition, Meliniomyces variabilis, Phialocephala sphaeroides, and Umbelopsis isabellina were found colonizing the grass, D. flexuosa, for the first time and Mycena sp. was confirmed as an endophyte of D. flexuosa. Site-specific differences were observed in the abundance and diversity of endophytic fungi in the roots of both study plants, but the differences were not as predominant as those between plant species. It is concluded that D. flexuosa harbors both higher amount and more diverse community of endophytic fungi in its roots compared to T. europaea.

The colonization of 120 plant species by dark septate endopytes (DSE) in the valley-type savanna of Jiansha River, southwest China was investigated. It was found that about 84% of plants were colonized by DSE to some extent. Morphological polymorphism of DSE was observed and 8 plant families were recorded as potential hosts for DSE. High colonization rate of DSE in the savanna vegetation implies that these fungi may play an important role in the adaption of plants to the dry-hot stress environment. Key words: Valley-type savanna, dark septate endophyte.

Background Fungi are asexually and sexually reproducing organisms that can combine the evolutionary advantages of the two reproductive modes. However, for many fungi the sexual cycle has never been observed in the field or in vitro and it remains unclear whether sexual reproduction is absent or cryptic. Nevertheless, there are indirect approaches to assess the occurrence of sex in a species, such as population studies, expression analysis of genes involved in mating processes and analysis of their selective constraints. The members of the Phialocephala fortinii s. l. - Acephala applanata species complex (PAC) are ascomycetes and the predominant dark septate endophytes that colonize woody plant roots. Despite their abundance in many ecosystems of the northern hemisphere, no sexual state has been identified to date and little is known about their reproductive biology, and how it shaped their evolutionary history and contributes to their ecological role in forest ecosystems. We therefore aimed at assessing the importance of sexual reproduction by indirect approaches that included molecular analyses of the mating type (MAT) genes involved in reproductive processes. Results The study included 19 PAC species and > 3, 000 strains that represented populations from different hosts, continents and ecosystems. Whereas A. applanata had a homothallic (self-fertile) MAT locus structure, all other species were structurally heterothallic (self-sterile). Compatible mating types were observed to co-occur more frequently than expected by chance. Moreover, in > 80% of the populations a 1:1 mating type ratio and gametic equilibrium were found. MAT genes were shown to evolve under strong purifying selection. Conclusions The signature of sex was found in worldwide populations of PAC species and functionality of MAT genes is likely preserved by purifying selection. We hypothesize that cryptic sex regularely occurs in the PAC and that further field studies and in vitro crosses will lead to the discovery of the sexual state. Although structurally heterothallic species prevail, it cannot be excluded that homothallism represents the ancestral breeding system in the PAC., BMC Evolutionary Biology, 11, ISSN:1471-2148

Plants support numerous root colonists that may share morphological characteristics with mycorrhizal fungi but may play different roles in the rhizosphere. To determine the function of one such root-colonizing fungus, Chaetomium elatum, the infectivity and composition of inoculum containing C. elatum were varied independently of and in association with the known mutualist Glomus intraradices under two light intensities. Maximum plant benefit occurred with mixtures of both G. intraradices and C. elatum and under high light intensity. Under low light intensity and in monoculture, C. elatum functioned as a weak pathogen that was able to kill host plants. Here, maximum plant mortality was associated with the highest levels of C. elatum infectivity. When G. intraradices was present, no negative impact of C. elatum was detected. Intraspecific interactions were important in predicting sporulation rates for both fungi, whereas no interspecific fungal interactions were detected. In the presence of G. intraradices, C. elatum appears to function as a "commensalistic associate," neither impacting plant growth nor sporulation by G. intraradices. Overall, C. elatum appears to be multifunctional, serving as both a rhizoplane and rhizophere fungus, opportunistically colonizing plant roots and only becoming pathogenic when resources are severely limited and intraspecific competition is high. This multifunctional strategy may be shared with other fungi that form similar structures in roots.

Dark septate endophytes (DSE) are ubiquitous root associated fungi; however, our understanding of their ecological function remains unclear. Here, we investigated the positive effect of a DSE fungus on its host plant Lycium barbarum L. A DSE isolate, LBF-2, isolated from the roots of L. barbarum, was inoculated onto the roots of plants, which were grown under greenhouse conditions for five weeks. The result of molecular analyses of internal transcribed spacer regions indicated that LBF-2 was 96% similar to Paraphoma chrysanthemicola. Melanized septate hyphae were observed in the root cortical cells of L. barbarum using a light microscope. Inoculation with LBF-2 increased the total biomass by 39.2% and also enhanced chlorophyll fluorescence. Inoculation increased the concentration of total chlorophyll by 22.8% and of chlorophyll a by 21.3%, relative to uninoculated controls. These data indicate that the LBF-2 isolate might be used to facilitate the cultivation of L. barbarum, which has medicinal applications.

Native tallgrass prairies support distinct dark septate endophyte (DSE) communities exemplified by Periconia macrospinosa and Microdochium sp. that were recently identified as common root symbionts in this system. Since these DSE fungi were repeatedly isolated from grasses and forbs, we aimed to test their abilities to colonize different hosts. One Microdochium and three Periconia strains were screened for colonization and growth responses using five native grasses and six forbs in an in vitro system. Previously published data for an additional grass (Andropogon gerardii) were included and reanalyzed. Presence of indicative inter- and intracellular structures (melanized hyphae, microsclerotia, and chlamydospores) demonstrated that all plant species were colonized by the DSE isolates albeit to varying degrees. Microscopic observations suggested that, compared to forbs, grasses were colonized to a greater degree in vitro. Host biomass responses varied among the host species. In broad comparisons, more grass species than forbs tended to respond positively to colonization, whereas more forb species tended to be non-responsive. Based on the suspected differences in the levels of colonization, we predicted that tallgrass prairie grasses would support greater DSE colonization than forbs in the field. A survey of field-collected roots from 15 native species supported this hypothesis. Our study supports the “broad host range” of DSE fungi, although the differences in the rates of colonization in the laboratory and in the field suggest a greater compatibility between grasses and DSE fungi. Furthermore, host responses to DSE range from mutualism to parasitism, suggesting a genotype-level interplay between the fungi and their hosts that determines the outcome of this symbiosis.

Summary •Dark septate endophytes (DSE) frequently colonize roots in the natural environment, but the effects of these fungi on plants are obscure, with previous studies indicating negative, neutral or positive effects on plant performance. •In order to reach a consensus for how DSE influence plant performance, meta-analyses were performed on data from 18 research articles, in which plants had been inoculated with DSE in sterile substrates. •Negative effects of DSE on plant performance were not recorded. Positive effects were identified on total, shoot and root biomass, and on shoot nitrogen (N) and phosphorus contents, with increases of 26–103% in these parameters for plants inoculated with DSE, relative to uninoculated controls. Inoculation increased total, shoot and root biomass by 52–138% when plants had not been supplied with additional inorganic N, or when all, or the majority, of N was supplied in organic form. Inoculation with the DSE Phialocephala fortinii was found to increase shoot and root biomass, shoot P concentration and shoot N content by 44–116%, relative to uninoculated controls. •The analyses here suggest that DSE enhance plant performance under controlled conditions, particularly when all, or the majority, of N is available in organic form.

The impact of transgenic white spruce [ Picea glauca (Moench) Voss] containing the endochitinase gene ( ech 42) on soil fungal biomass and on the ectendomycorrhizal fungi Wilcoxina spp. was tested using a greenhouse trial. The measured level of endochitinase in roots of transgenic white spruce was up to 10 times higher than that in roots of nontransformed white spruce. The level of endochitinase in root exudates of three of four ech 42-transformed lines was significantly greater than that in controls. Analysis soil ergosterol showed that the amount of fungal biomass in soil samples from control white spruce was slightly larger than that in soil samples from ech 42-transformed white spruce. Nevertheless, the difference was not statistically significant. The rates of mycorrhizal colonization of transformed lines and controls were similar. Sequencing the internal transcribed spacer rRNA region revealed that the root tips were colonized by the ectendomycorrhizal fungi Wilcoxina spp. and the dark septate endophyte Phialocephala fortinii . Colonization of root tips by Wilcoxina spp. was monitored by real-time PCR to quantify the fungus present during the development of ectendomycorrhizal symbiosis in ech 42-transformed and control lines. The numbers of Wilcoxina molecules in the transformed lines and the controls were not significantly different ( P > 0.05, as determined by analysis of covariance), indicating that in spite of higher levels of endochitinase expression, mycorrhization was not inhibited. Our results indicate that the higher levels of chitinolytic activity in root exudates and root tissues from ech 42-transformed lines did not alter the soil fungal biomass or the development of ectendomycorrhizal symbiosis involving Wilcoxina spp.

Summary 1 Summary All plants in natural ecosystems appear to be symbiotic with fungal endophytes. This highly diverse group of fungi can have profound impacts on plant communities through increasing fitness by conferring abiotic and biotic stress tolerance, increasing biomass and decreasing water consumption, or decreasing fitness by altering resource allocation. Despite more than 100 yr of research resulting in thousands of journal articles, the ecological significance of these fungi remains poorly characterized. Historically, two endophytic groups (clavicipitaceous (C) and nonclavicipitaceous (NC)) have been discriminated based on phylogeny and life history traits. Here, we show that NC-endophytes represent three distinct functional groups based on host colonization and transmission, in planta biodiversity and fitness benefits conferred to hosts. Using this framework, we contrast the life histories, interactions with hosts and potential roles in plant ecophysiology of C- and NC-endophytes, and highlight several key questions for future work in endophyte biology.

Both mycorrhizal fungi and systemic fungal endophytes in the Order Clavicipitales have been extensively studied. Compared to these groups, root-associated fungal endophytes have received very little attention, even though they seem common in many ecosystems. Based on published reports, comparisons between host colonization by the root endophytes and mycorrhizal fungi from various habitats suggest that endophytes are possibly as abundant as mycorrhizas (Mandyam and Jumpponen 2005). As more reports that document the abundance of root endophytes in different habitats become available, a better understanding of the ecology and functions of these endophytes seems not only logical but critical. The term ‘endophyte’ is used to describe either bacterial or fungal intracellular symbionts of plants that do not cause any visible signs of tissue damage or adverse effects on the host (Petrini 1991; Wilson 1995; Stone et al. 2000; Schulz and Boyle 2005). Fungal root endophytes are a paraphyletic group primarily occurring in the Ascomycota, although some examples also exist for Basidiomycetous endophytes (see Verma et al. 1998; Barazani et al. 2005). In this group, we usually include all root-inhabiting fungi that are considered non-mycorrhizal based on the morphology of the colonized host roots and on fungal structures produced in colonized roots typically considered indicative of dark septate endophytes (DSE). We also include fungi that produce hyaline structures when colonizing hosts intracellularly (O’Dell et al. 1993; Barrow and Aaltonen 2001; Ohki et al. 2002; Narisawa et al. 2003), but do not form typical DSE structures. These hyaline fungi can routinely be isolated from the roots of many plant species. Well-studied systemic and foliar endophytes of grasses, such as Acremonium sp., Epichoe sp. and Neotyphodium sp., will be excluded from this discussion. Many of the studies of fungal root endophytes have either made no effort to identify the fungi or have focused on one fungus isolated at a single site. This gives the impression that the species diversity of fungal root endophytes is low. Phialocephala

An investigation on heavy metals (HMs), Pb, Zn and Cd pollution and accumulation in maize grown in arable soils along a lead and zinc slag heap in Yunnan, Southwest China was conducted using multivariate statistical methods. Calculation of the Nemerow pollution index revealed that all sampled soils were heavily polluted. The concentrations of Pb, Zn and Cd in the maize samples presented a decreasing trend from roots to shoots to seeds, except for Zn (roots > seeds > shoots), and the content of HMs in the maize roots was positively correlated with both soil total and extractable HMs. Arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) intensively colonised in the maize roots, and their functional roles are discussed in the soils contaminated by HMs. The study results showed that intensive mining and smelting activities contributing to soil metal contamination present a high metal-pollution risk for crops grown.