Disclosing arbuscular mycorrhizal fungal biodiversity in soil through a land-use gradient using a pyrosequencing approach.

The biodiversity of arbuscular mycorrhizal fungi (AMF) communities present in five Sardinian soils (Italy) subjected to different land-use (tilled vineyard, covered vineyard, pasture, managed meadow and cork-oak formation) was analysed using a pyrosequencing-based approach for the first time. Two regions of the 18S ribosomal RNA gene were considered as molecular target. The pyrosequencing produced a total of 10924 sequences: 6799 from the first and 4125 from the second target region. Among these sequences, 3189 and 1003 were selected to generate operational taxonomic units (OTUs) and to evaluate the AMF community richness and similarity: 117 (37 of which were singletons) and 28 (nine of which were singletons) unique AMF OTUs were detected respectively. Within the Glomeromycota OTUs, those belonging to the Glomerales order were dominant in all the soils. Diversisporales OTUs were always detected, even though less frequently, while Archaeosporales and Paraglomerales OTUs were exclusive of the pasture soil. Eleven OTUs were shared by all the soils, but each of the five AMF communities showed particular features, suggesting a meaningful dissimilarity among the Glomeromycota populations. The environments with low inputs (pasture and covered vineyard) showed a higher AMF biodiversity than those subjected to human input (managed meadow and tilled vineyard). A reduction in AMF was found in the cork-oak formation because other mycorrhizal fungal species, more likely associated to trees and shrubs, were detected. These findings reinforce the view that AMF biodiversity is influenced by both human input and ecological traits, illustrating a gradient of AMF communities which mirror the land-use gradient. The high number of sequences obtained by the pyrosequencing strategy has provided detailed information on the soil AMF assemblages, thus offering a source of light to shine on this crucial soil microbial group.

Lumini E ，Orgiazzi A ，Borriello R ，Bonfante P ，Bianciotto V ... -  《-》

Land-use intensity and host plant simultaneously shape the composition of arbuscular mycorrhizal fungal communities in a Mediterranean drained peatland.

Land-use change is known to be a major threat to biodiversity and ecosystem services in Mediterranean areas. However, the potential for different host plants to modulate the effect of land-use intensification on community composition of arbuscular mycorrhizal fungi (AMF) is still poorly understood. To test the hypothesis that low land-use intensity promotes AMF diversity at different taxonomic scales and to determine whether any response is dependent upon host plant species identity, we characterised AMF communities in the roots of 10 plant species across four land use types of differing intensity in a Mediterranean peatland system. AMF were identified using 454 pyrosequencing. This revealed an overall low level of AMF richness in the peaty soils; lowest AMF richness in the intense cropping system at both virtual taxa and family level; strong modulation by the host plant of the impact of land-use intensification on AMF communities at the virtual taxa level; and a significant effect of land-use intensification on AMF communities at the family level. These findings have implications for understanding ecosystem stability and productivity and should be considered when developing soil-improvement strategies in fragile ecosystems, such as Mediterranean peatlands.

Ciccolini V ，Ercoli L ，Davison J ，Vasar M ，Öpik M ，Pellegrino E ... -  《-》

Arbuscular Mycorrhizal Fungal Communities in the Roots of Maize Lines Contrasting for Al Tolerance Grown in Limed and Non-Limed Brazilian Oxisoil.

Gomes EA ，Oliveira CA ，Lana UG ，Noda RW ，Marriel IE ，de Souza FA ... -  《-》

Simulated nitrogen deposition affects community structure of arbuscular mycorrhizal fungi in northern hardwood forests.

Our previous investigation found elevated nitrogen deposition caused declines in abundance of arbuscular mycorrhizal fungi (AMF) associated with forest trees, but little is known about how nitrogen affects the AMF community composition and structure within forest ecosystems. We hypothesized that N deposition would lead to significant changes in the AMF community structure. We studied the diversity and community structure of AMF in northern hardwood forests after more than 12 years of simulated nitrogen deposition. We performed molecular analyses on maple (Acer spp.) roots targeting the 18S rDNA region using the fungal-specific primers AM1 and NS31. PCR products were cloned and identified using restriction fragment length polymorphism (RFLP) and sequencing. N addition significantly altered the AMF community structure, and Glomus group A dominated the AMF community. Some Glomus operational taxonomic units (OTUs) responded negatively to N inputs, whereas other Glomus OTUs and an Acaulospora OTU responded positively to N inputs. The observed effect on community structure implies that AMF species associated with maples differ in their response to elevated nitrogen. Given that functional diversity exists among AMF species and that N deposition has been shown to select less beneficial fungi in some ecosystems, this change in community structure could have implications for the functioning of this type of ecosystem.

VAN Diepen LT ，Lilleskov EA ，Pregitzer KS 《-》

Decrease in diversity and changes in community composition of arbuscular mycorrhizal fungi in roots of apple trees with increasing orchard management intensity across a regional scale.

Understanding which factors drive the diversity and community composition of arbuscular mycorrhizal fungi (AMF) is important due to the role of these soil micro-organisms in ecosystem functioning and current environmental threats to AMF biodiversity. Additionally, in agro-ecosystems, this knowledge may help to evaluate their use in making agriculture more sustainable. Here, we used 454-pyrosequencing of small subunit rRNA gene amplicons to quantify AMF diversity and community composition in the roots of cultivated apple trees across 24 orchards in central Belgium. We aimed at identifying the factors (soil chemical variables, organic vs. conventional farming, and geographical location) that affect AMF diversity and community composition. In total, 110 AMF OTUs were detected, of which the majority belonged to the Glomeraceae (73%) and the Claroideoglomeraceae (19%). We show that soil characteristics and farming system, rather than the geographical location of the orchards, shape AMF communities on apple trees. Particularly, plant-available P content of the soil was associated with lower AMF diversity. In orchards with a lower plant-available P content of the soil (P < 100 mg/kg soil), we also found a significantly higher AMF diversity in organically managed orchards as compared to conventionally managed orchards. Finally, the degree of nestedness of the AMF communities was related to plant-available P and N content of the soil, pointing at a progressive loss of AMF taxa with increasing fertilization. Overall, we conclude that a combination of organic orchard management and moderate fertilization may preserve diverse AMF communities on apple trees and that AMF in the roots of apple trees appear not to be dispersal limited at the scale of central Belgium.

van Geel M ，Ceustermans A ，van Hemelrijck W ，Lievens B ，Honnay O ... -  《-》