Molecular study of arbuscular mycorrhizal fungi colonizing the sporophyte of the eusporangiate rattlesnake fern (Botrychium virginianum, Ophioglossaceae)

Fern mycorrhizae do not respond to fertilization in a tropical montane forest

Ferns are known to have a lower incidence of mycorrhization than angiosperms. It has been suggested that this results from carbon being more limiting to fern growth than nutrient availability, but this assertion has not been tested yet. In the present study, we took advantage of a fertilization experiment with nitrogen and phosphorus on cloud forest plots of the Ecuadorean Andes for 15 years. A previous analysis revealed changes in the abundances of fern species in the fertilized plots compared to the control plots and hypothesized that this might be related to the responses of the mycorrhizal relationships to nutrient availability. We revisited the plots to assess the root-associated fungal communities of two epiphytic and two terrestrial fern species that showed shifts in abundance. We sampled and analyzed the roots of 125 individuals following a metabarcoding approach. We recovered 1382 fungal ASVs, with a dominance of members of Tremellales (Basidiomycota) and Heliotales (Ascomycota). The fungal diversity was highly partitioned with little overlap between individuals. We found marked differences between terrestrial and epiphytic species, with the latter fundamentally missing arbuscular mycorrhizal fungi (AMF). We found no effect of fertilization on the diversity or relative abundance of the fungal assemblages. Still, we observed a direct impact of phosphorus fertilization on its concentration in the fern leaves. We conclude that fern-fungi relationships in the study site are not restricted by nutrient availability and suggest the existence of little specificity on the fungal partners relative to the host fern species.

Biotic and abiotic factors shape arbuscular mycorrhizal fungal communities associated with the roots of the widespread fern Botrychium lunaria (Ophioglossaceae)

Arbuscular mycorrhizal fungi (AMF) play central roles in terrestrial ecosystems by interacting with both above and belowground communities as well as by influencing edaphic properties. The AMF communities associated with the roots of the fern Botrychium lunaria (Ophioglossaceae) were sampled in four transects at 2400 m a.s.l. in the Swiss Alps and analyzed using metabarcoding. Members of five Glomeromycota genera were identified across the 71 samples. Our analyses revealed the existence of a core microbiome composed of four abundant Glomus operational taxonomic units (OTUs), as well as a low OTU turnover between samples. The AMF communities were not spatially structured, which contrasts with most studies on AMF associated with angiosperms. pH, microbial connectivity and humus cover significantly shaped AMF beta diversity but only explained a minor fraction of variation in beta diversity. AMF OTUs associations were found to be significant by both cohesion and co-occurrence analyses, suggesting a role for fungus-fungus interactions in AMF community assembly. In particular, OTU co-occurrences were more frequent between different genera than among the same genus, rising the hypothesis of functional complementarity among the AMF associated to B. lunaria. Altogether, our results provide new insights into the ecology of fern symbionts in alpine grasslands.

Features of development of hametophytes Botrychium multifidum (S.G. Gmel.) Rupr. culture in vitro

The work is devoted to studying the influence of the type of culture medium and pH on the development of gametophytes Botrychium multifidum in vitro. The spores obtained from sterilized sporangia were suspended in liquid nutrient media with initial inoculum of 10000 spores per 1 ml. Nutrient media tested in the study were composed of full Murashige and Skoog or Knudson mineral salts supplemented with kinetin (1 mg/l) and pH level 4.8-6.4. All stages of development, from spore germination to thallus and gametophyte formation, were observed in tissue culture. A low level of germinating spores was noted.

Abiotic rather than biotic filtering shapes the arbuscular mycorrhizal fungal communities of European seminatural grasslands

Although it is well known that arbuscular mycorrhizal fungi (AMF) play a key role in the functioning of natural ecosystems, the underlying drivers determining the composition of AMF communities remain unclear. In this study, we established 138 sampling plots at 46 grassland sites, consisting of 26 acidic grasslands and 20 calcareous grasslands spread across eight European countries, to assess the relative importance of abiotic and biotic filtering in driving AMF community composition and structure in both the grassland soils and in the roots of 13 grassland plant species. Soil AMF communities differed significantly between acidic and calcareous grasslands. In root AMF communities, most variance was attributable to soil variables while very little variation was explained by host plant identity. Root AMF communities in host plant species occurring in only one grassland type closely resembled the soil AMF communities of that grassland type and the root AMF communities of other host plant species occurring in the same grassland type. The observed AMF-host plants networks were not modular but nested. Our results indicate that abiotic conditions, rather than biotic filtering through host plant specificity, are the most important drivers in shaping AMF communities in European seminatural grasslands.

Differences in Arbuscular Mycorrhizal Fungal Community Composition in Soils of Three Land Use Types in Subtropical Hilly Area of Southern China

Land use type is key factor in restoring the degraded soils due to its impact on soil chemical properties and microbial community. In this study, the influences of land use type on arbuscular mycorrhizal fungal (AMF) community and soil chemical properties were assessed in a long-run experimental station in subtropical hilly area of southern China. Soil samples were collected from forest land, orchard and vegetable field. Soil chemical properties were analyzed, and PCR-DGGE was performed to explore the AMF community structure. Cloning and sequencing of DGGE bands were conducted to monitor AMF community composition. Results indicate that the contents of total P, available P and available K were the highest while the contents of soil organic matter, total N, total K and available N were the lowest in vegetable field soils, with forest land soils vice versa. According to DGGE profiling, AMF community in forest soils was more closely related to that in orchard soils than that in vegetable field soils. Sequencing indicated that 45 out of 53 excised bands were AMF and 64.4% of AMF belonged to Glomeraceae, including some “generalists” present in all soils and some “specialists” present only in soils of particular land use. Category principle component analysis demonstrated that total N, soil organic matter and available P were the most important factors affecting AMF community, and some AMF phylotypes were closely associated with particular soil chemical properties. Our data suggest that AMF communities are different with different land use types.

Arbuscular mycorrhizal fungi communities in a coral cay system (Morrocoy, Venezuela) and their relationships with environmental variables

Knowledge of the natural diversity of arbuscular mycorrhizal fungi (AMF) and understanding of their biogeographical patterns and what drive them might help to the maintenance and preservation of ecosystems under a changing environment. The objective of this study was to evaluate the contribution of different environmental factors to the determination of the composition of AMF assemblages in representative sites within the Morrocoy National Park (Venezuela). The community structure of the AMF under the canopy of Coccoloba uvifera was investigated in four cays (Borracho, Muerto, Peraza, and Paiclás) and one mainland location (Las Luisas). Based on partial sequences of the nuclear small subunit ribosomal DNA gene, the AM fungi in soil samples were divided into 31 operational taxonomic units, grouped in eight families. The canonical correspondence analysis showed that environmental factors related to insularity (the mean annual rainfall, the distance to the mainland coast, and the cay land area) and a soil property related to biological activity (the total carbohydrate content) were significantly related to the distribution of the AMF communities.

Fungal associations in Horneophyton ligneri from the Rhynie Chert (c. 407 million year old) closely resemble those in extant lower land plants: novel insights into ancestral plant-fungus symbioses

Fungi (Eumycota) form close associations with plants, with which they have co-existed since the dawn of life on land, but their diversity in early terrestrial ecosystems is still poorly understood. We studied petrographic sections of exceptionally well-preserved petrified plants from the 407 million yr-old Rhynie Chert (Scotland, UK). For comparative purposes, we illustrate fungal associations in four extant lower land plants. We document two new endophytes in the plant Horneophyton lignieri: Palaeoglomus boullardii (sp. nov. Glomeromycota) colonizes parenchyma in a discontinuous zone of the outer cortex of the aerial axes, forming arbuscule-like structures, vesicles and spores; Palaeoendogone gwynne-vaughaniae (gen. nov., sp. nov. Mucoromycotina) colonizes parenchyma in the basal part of the plant, where it is present in intercellular spaces and as intracellular coils but absent from rhizoids. Critical comparisons between the newly discovered Horneophyton endophytes, fungi previously described from the Rhynie Chert and fungal colonization in extant lower land plants reveal several features characteristic of both Mucoromycotina and Glomeromycota. A reappraisal of fungal associations in early land plants indicates that they are more diverse than assumed hitherto, overturning the long-held paradigm that the early endophytes were exclusively Glomeromycota.

Three new species of arbuscular mycorrhizal fungi discovered at one location in a desert of Oman: Diversispora omaniana, Septoglomus nakheelum and Rhizophagus arabicus

Three new species of arbuscular mycorrhizal (AM) fungi (Glomeromycota) were isolated from soil samples collected from a hyperarid sandy plain of South Arabia. Morphological characteristics of the spores clearly differentiated them from closely related AM species. Molecular analyses were performed on rDNA sequences obtained from single spores including a ~1700 bp region comprising partial SSU, ITS, partial LSU and the ~600 bp ITS region only. The phylogenetic trees based on these regions showed that the three species belong to well described genera but are clearly distinct from known species. Consequently, we describe them here as Diversispora omaniana, Septoglomus nakheelum and Rhizophagus arabicus spp. nov. D. omaniana and R. arabicus were isolated from the native, arid habitat, while S. nakheelum was isolated from a nearby irrigated date palm plantation. The discovery of three new species of AM fungi from this location suggests that a number of additional undescribed AM taxa may be present in such desert ecosystems. Further work to understand the diversity and functional significance of these new AM taxa may offer new opportunities for conservation, re-vegetation, and sustainable agriculture in extremely arid environments.

Arbuscular mycorrhiza formation in cordate gametophytes of two ferns, Angiopteris lygodiifolia and Osmunda japonica

Mycorrhizal symbiosis is common among land plants including pteridophytes (monilophytes and lycophytes). In pteridophytes with diplohaplontic life cycle, mycorrhizal formations were mostly reported for sporophytes, but very few for gametophytes. To clarify the mycorrhizal association of photosynthetic gametophytes, field-collected gametophytes of Angiopteris lygodiifolia (Marattiaceae, n = 52) and Osmunda japonica (Osmundaceae, n = 45) were examined using microscopic and molecular techniques. Collected gametophytes were mostly cut into two pieces. One piece was used for light and scanning microscopic observations, and the other for molecular identification of plant species (chloroplast rbcL sequences) and mycorrhizal fungi (small subunit rDNA sequences). Microscopic observations showed that 96 % (50/52) of Angiopteris and 95 % (41/43) of Osmunda gametophytes contained intracellular hyphae with arbuscules and/or vesicles and fungal colonization was limited to the inner tissue of the thick midribs (cushion). Fungal DNA analyses showed that 92 % (48/52) of Angiopteris and 92 % (35/38) of Osmunda have sequences of arbuscular mycorrhizal fungi, which were highly divergent but all belonged to Glomus group A. These results suggest that A. lygodiifolia and O. japonica gametophytes consistently form arbuscular mycorrhizae. Mycorrhizal formation in wild fern gametophytes, based on large-scale sampling with molecular identification of host plant species, was demonstrated for the first time.

Septoglomus fuscum and S. furcatum, two new species of arbuscular mycorrhizal fungi (Glomeromycota)

Two new arbuscular mycorrhizal fungal species, (Glomeromycota) Septoglomus fuscum and S. furcatum, are described and illustrated. Spores of S. fuscum usually occur in loose hypogeous clusters, rarely singly in soil or inside roots, and S. furcatum forms only single spores in soil. Spores of S. fuscum are brownish orange to dark brown, globose to subglobose, (20-)47(-90) μm diam, rarely ovoid, 21-50 × 23-60 μm. Their spore wall consists of a semi-persistent, semi-flexible, orange white to golden yellow, rarely hyaline, outer layer, easily separating from a laminate, smooth, brownish orange to dark brown inner layer. Spores of S. furcatum are reddish brown to dark brown, globose to subglobose, (106-) 138(-167) μm diam, rarely ovoid, 108-127 × 135-160 μm, usually with one subtending hypha that is frequently branched below the spore base, or occasionally with two subtending hyphae located close together. Spore walls consists of a semipermanent, hyaline to light orange outermost layer, a semipermanent, hyaline to golden yellow middle layer, and a laminate, smooth, reddish brown to dark brown innermost layer. None of the spore-wall layers of S. fuscum and S. furcatum stain in Melzer's reagent. In the field, S. fuscum was associated with roots of Arctotheca populifolia colonizing maritime dunes located near Strand in South Africa and S. furcatum was associated with Cordia oncocalyx growing in a dry forest in the Ceará State, Brazil. In single-species cultures with Plantago lanceolata as host plant, S. fuscum and S. furcatum formed arbuscular mycorrhizae. Phylogenetic analyses of the SSU, ITS and LSU nrDNA sequences placed the two new species in genus Septoglomus and both new taxa were separated from described Septoglomus species.

Temporal dynamics of arbuscular mycorrhizal fungi colonizing roots of representative shrub species in a semi-arid Mediterranean ecosystem

Arbuscular mycorrhizal (AM) symbiosis plays an important role in improving plant fitness and soil quality, particularly in fragile and stressed environments, as those in certain areas of Mediterranean ecosystems. AM fungal communities are usually affected by dynamic factors such as the plant community structure and composition, which in turn are imposed by seasonality. For this reason, a one-year-round time-course trial was performed by sampling the root system of two representative shrubland species (Rosmarinus officinalis and Thymus zygis) within a typical Mediterranean ecosystem from the Southeast of Spain. The 18S rDNA gene, of the AM fungal community in roots, was subjected to PCR-SSCP, sequencing, and phylogenetic analysis. Forty-three different AM fungal sequence types were found which clustered in 16 phylotypes: 14 belonged to the Glomeraceae and two to the Diversisporaceae. Surprisingly, only two of these phylotypes were related with sequences of morphologically defined species: Glomus intraradices and Glomus constrictum. Significant differences were detected for the relative abundance of some phylotypes while no effects were found for the calculated diversity indices. These results may help to design efficient mycorrhizal-based revegetation programs for this type of ecosystems.

Arbuscular mycorrhizal fungi in national parks, nature reserves and protected areas worldwide: a strategic perspective for their in situ conservation

Soil fungi play a crucial role in producing fundamental ecosystem services such as soil fertility, formation and maintenance, nutrient cycling and plant community dynamics. However, they have received little attention in the field of conservation biology. Arbuscular mycorrhizal fungi (AMF) are beneficial soil symbionts fulfilling a key function in the complex networks of belowground/aboveground biotic interactions as they live in association with the roots of most (80%) land plant families and influence not only soil fertility but also plant nutrition, diversity and productivity. The diversity of AMF communities can decline due to habitat loss and anthropogenic disturbance, especially in agro-ecosystems, and many valuable ecotypes could become extinct before they are even discovered. Consequently, long-term strategies are urgently needed to ensure their conservation in habitats where they naturally occur and have evolved. Protected areas, where living organisms are under the care of national and international authorities, represent an appropriate place for the in situ conservation of AMF, providing them with adapted situations together with established complex networks of interactions with different components within each specific ecosystem. Here, we review data available about the main present-day threats to AMF and the current state of knowledge about their occurrence in protected sites worldwide, providing a checklist of national parks and nature reserves where they have been reported. The aim was to offer a strategic perspective to increase awareness of the importance of conserving these beneficial plant symbionts and of preserving their biodiversity in the years to come.

Unique arbuscular mycorrhizal fungal communities uncovered in date palm plantations and surrounding desert habitats of Southern Arabia

The main objective of this study was to shed light on the previously unknown arbuscular mycorrhizal fungal (AMF) communities in Southern Arabia. We explored AMF communities in two date palm (Phoenix dactylifera) plantations and the natural vegetation of their surrounding arid habitats. The plantations were managed traditionally in an oasis and according to conventional guidelines at an experimental station. Based on spore morphotyping, the AMF communities under the date palms appeared to be quite diverse at both plantations and more similar to each other than to the communities under the ruderal plant, Polygala erioptera, growing at the experimental station on the dry strip between the palm trees, and to the communities uncovered under the native vegetation (Zygophyllum hamiense, Salvadora persica, Prosopis cineraria, inter-plant area) of adjacent undisturbed arid habitat. AMF spore abundance and species richness were higher under date palms than under the ruderal and native plants. Sampling in a remote sand dune area under Heliotropium kotschyi yielded only two AMF morphospecies and only after trap culturing. Overall, 25 AMF morphospecies were detected encompassing all study habitats. Eighteen belonged to the genus Glomus including four undescribed species. Glomus sinuosum, a species typically found in undisturbed habitats, was the most frequently occurring morphospecies under the date palms. Using molecular tools, it was also found as a phylogenetic taxon associated with date palm roots. These roots were associated with nine phylogenetic taxa, among them eight from Glomus group A, but the majority could not be assigned to known morphospecies or to environmental sequences in public databases. Some phylogenetic taxa seemed to be site specific. Despite the use of group-specific primers and efficient trapping systems with a bait plant consortium, surprisingly, two of the globally most frequently found species, Glomus intraradices and Glomus mosseae, were not detected neither as phylogenetic taxa in the date palm roots nor as spores under the date palms, the intermediate ruderal plant, or the surrounding natural vegetation. The results highlight the uniqueness of AMF communities inhabiting these diverse habitats exposed to the harsh climatic conditions of Southern Arabia.

The diversity of Terfezia desert truffles: new species and a highly variable species complex with intrasporocarpic nrDNA ITS heterogeneity

Desert truffles belonging to Terfezia are well known mycorrhizal members of the mycota of the Mediterranean region and the Middle East. We aimed to test (i) whether the morphological criteria of Terfezia species regularly collected in Spain enable their separation and (ii) whether the previously hypothesized edaphic/biotic specificity of one group could be confirmed by study of a larger number of specimens. The species T. arenaria and T. claveryi can be identified unambiguously by morphological characters. We consider T. leptoderma as a distinct species while several lineages of similar spiny spored Terfezia truffles with cellular peridium were detected that have no obvious anatomical differences. Several species treated generally as synonyms of T. olbiensis have been described in this group, and because they cannot be unambiguously assigned to separate lineages we propose to consider the group as the T. olbiensis species complex. A high level of intrasporocarpic variation of the nrDNA ITS was detected in the T. olbiensis species complex, especially in one of its lineages. We detected no exclusive specificity to either plant associates or soil, except in T. leptoderma, which was associated with Quercus spp. and cistaceous plants on acidic soils. Nevertheless the clades showed a tendency either to associate with Quercus/Helianthemum/Cistus or Pinus hosts. Specimens having distinct anatomical features, reticulate spores and cellular peridium formed a separate group in the molecular phylogenetic analyses of nrDNA ITS and LSU regions; for these specimens we propose a new species, Terfezia alsheikhii sp. nov.

The online database MaarjAM reveals global and ecosystemic distribution patterns in arbuscular mycorrhizal fungi (Glomeromycota)

• Here, we describe a new database, MaarjAM, that summarizes publicly available Glomeromycota DNA sequence data and associated metadata. The goal of the database is to facilitate the description of distribution and richness patterns in this group of fungi. • Small subunit (SSU) rRNA gene sequences and available metadata were collated from all suitable taxonomic and ecological publications. These data have been made accessible in an open-access database (http://maarjam.botany.ut.ee). • Two hundred and eighty-two SSU rRNA gene virtual taxa (VT) were described based on a comprehensive phylogenetic analysis of all collated Glomeromycota sequences. Two-thirds of VT showed limited distribution ranges, occurring in single current or historic continents or climatic zones. Those VT that associated with a taxonomically wide range of host plants also tended to have a wide geographical distribution, and vice versa. No relationships were detected between VT richness and latitude, elevation or vascular plant richness. • The collated Glomeromycota molecular diversity data suggest limited distribution ranges in most Glomeromycota taxa and a positive relationship between the width of a taxon's geographical range and its host taxonomic range. Inconsistencies between molecular and traditional taxonomy of Glomeromycota, and shortage of data from major continents and ecosystems, are highlighted.

Phylogenetic affinity of arbuscular mycorrhizal symbionts in Psilotum nudum

Many lineages of land plants (from lycopsids to angiosperms) have non-photosynthetic life cycle phases that involve obligate mycoheterotrophic arbuscular mycorrhizal (AM) associations where the plant host gains organic carbon through glomalean symbionts. Our goal was to isolate and phylogenetically identify the AM fungi associated with both the autotrophic and underground mycoheterotrophic life cycle phases of Psilotum nudum. Phylogenetic analyses recovered 11 fungal phylotypes in four diverse clades of Glomus A that form AM associations with P. nudum mycoheterotrophic gametophytes and autotrophic sporophytes, and angiosperm roots found in the same greenhouse pots. The correspondence of identities of AM symbionts in P. nudum sporophytes, gametophytes and neighboring angiosperms provides compelling evidence that photosynthetic heterospecific and conspecific plants can serve as the ultimate sources of fixed carbon for mycoheterotrophic gametophytes of P. nudum, and that the transfer of carbon occurs via shared fungal networks. Moreover, broader phylogenetic analyses suggest greenhouse Psilotum populations, like field-surveyed populations of mycoheterotrophic plants, form AM associations with restricted clades of Glomus A. The phylogenetic affinities and distribution of Glomus A symbionts indicate that P. nudum greenhouse populations have the potential to be exploited as an experimental system to further study the physiology, ecology and evolution of mycoheterotrophic AM associations.

Molecular diversity of arbuscular mycorrhizal fungi in onion roots from organic and conventional farming systems in the Netherlands

Diversity and colonization levels of naturally occurring arbuscular mycorrhizal fungi (AMF) in onion roots were studied to compare organic and conventional farming systems in the Netherlands. In 2004, 20 onion fields were sampled in a balanced survey between farming systems and between two regions, namely, Zeeland and Flevoland. In 2005, nine conventional and ten organic fields were additionally surveyed in Flevoland. AMF phylotypes were identified by rDNA sequencing. All plants were colonized, with 60% for arbuscular colonization and 84% for hyphal colonization as grand means. In Zeeland, onion roots from organic fields had higher fractional colonization levels than those from conventional fields. Onion yields in conventional farming were positively correlated with colonization level. Overall, 14 AMF phylotypes were identified. The number of phylotypes per field ranged from one to six. Two phylotypes associated with the Glomus mosseae-coronatum and the G. caledonium-geosporum species complexes were the most abundant, whereas other phylotypes were infrequently found. Organic and conventional farming systems had similar number of phylotypes per field and Shannon diversity indices. A few organic and conventional fields had larger number of phylotypes, including phylotypes associated with the genera Glomus-B, Archaeospora, and Paraglomus. This suggests that farming systems as such did not influence AMF diversity, but rather specific environmental conditions or agricultural practices.

Fern-associated arbuscular mycorrhizal fungi are represented by multiple Glomus spp.: do environmental factors influence partner identity?

Symbioses involving arbuscular mycorrhizal fungi (AMF) are among the most important ecological associations for many plant species. The diversity of AMF associated with ferns, however, remains poorly studied. Using recently designed Glomus-specific primers, we surveyed the AMF community associated with ferns from deciduous, broad-leaved second-growth forest habitats at the eastern edge of the piedmont region of central Virginia, USA. Results indicate that this molecular approach may be a useful tool for detecting AMF in ferns compared to traditional techniques based on morphology. Over 30 potential fungal ribotypes were identified from eight fern species using denaturing gradient gel electrophoresis. Fungal ribotypes were found to differ widely in terms of (1) the number of fern partners with which they interact and (2) their relative frequency within each fern. Sequence analysis of fungal isolates from three species of fern indicated that the primers were generally highly specific for Glomus species but some non-target DNA was also amplified. Cloned polymerase chain reaction (PCR) products from Polystichum acrostichoides and Osmunda regalis revealed several phylogenetically distinct Glomus species. A single Glomus species was identified in the cloned PCR products from Botrychium virginianum. These findings challenge the hypothesis that the extent or degree of fern-fungal symbiosis is somehow tied to root complexity. Environmental factors appear to influence the suite of AMF that form partnerships with ferns. Some species of fern from similar habitats associated with dissimilar fungal partners (e.g., P. acrostichoides and Athyrium filix-femina var. asplenioides), whereas others harbored uniform fungal communities (e.g., Asplenium platyneuron). The significance of these data in terms of ecological and evolutionary dynamics of the AMF-fern symbiosis is discussed.

Glomus perpusillum, a new arbuscular mycorrhizal fungus

A new arbuscular mycorrhizal fungal species of genus Glomus, G. perpusillum (Glomeromycota), forming small, hyaline spores is described and illustrated. Spores of G. perpusillum were formed in hypogeous aggregates and occasionally inside roots. They are globose to subglobose, (10-)24(-30) microm diam, rarely egg-shaped, oblong to irregular, 18-25 x 25-63 microm. The single spore wall of G. perpusillum consists of two permanent layers: a finely laminate, semiflexible to rigid outer layer and a flexible to semiflexible inner layer. The inner layer becomes plastic and frequently contracts in spores crushed in PVLG-based mountants and stains reddish white to grayish red in Melzer's reagent. Glomus perpusillum was associated with roots of Ammophila arenaria colonizing sand dunes of the Mediterranean Sea adjacent to Calambrone, Italy, and this is the only site of its occurrence known to date. In single-species cultures with Plantago lanceolata as host plant, G. perpusillum formed vesicular-arbuscular mycorrhiza. Phylogenetic analyses of partial SSU sequences of nrDNA placed the species in Glomus group A with no affinity to its subgroups. The sequences of G. perpusillum unambiguously separated from the sequences of described Glomus species and formed a distinct clade together with in planta arbuscular mycorrhizal fungal sequences found in alpine plants.

Complexity of semiarid gypsophilous shrub communities mediates the AMF biodiversity at the plant species level

The community composition of arbuscular mycorrhizal fungi (AMF) was analyzed in roots of Gypsophila struthium growing in gypsum soils under semiarid conditions. In order to investigate the effect of plant community degradation on the AMF biodiversity at the single species level, on the basis of the plant community complexity level, we selected four areas affected by degradation and shrub species spatial heterogeneity. The AM fungal community colonizing G. struthium was investigated from the morphological and molecular points of view. All plants were well colonized and showed a high level of infective AM propagules. Roots were analyzed by polymerase chain reaction, restriction fragment length polymorphism screening, and sequence analyses of the ribosomal DNA small subunit region. Four AM fungal types were identified and clustered into the AM fungal family: Glomeraceae, Glomus being the only taxon present. One fungal type was present in all the selected areas. Two fungal types are distinct from any previously published sequences and could be specific to gypsum soils. The chemical-physical properties of the soil were not correlated with the AMF diversity in roots. Our data show vegetation cover complexity-dependent differences in the AM fungal community composition.