Abstract Arbuscular Mycorrhizal Fungi Community Research Articles

Fungal symbiont diversity drives growth of Holcus lanatus depending on soil nutrient availability

Abstract Arbuscular mycorrhizal (AM) fungi frequently colonise plant roots and can affect plant morphology and physiology through their contribution to plant nutrition. However, the functional role of AM fungi in the presence of other microbial symbionts, including widespread Mucoromycotina ‘fine root endophytes’ (MFRE) fungi, remains largely unknown. While both AM fungi and MFRE transfer nutrients, including nitrogen, from inorganic and organic sources to host plants, their combined effects on co‐colonised plants have only been investigated in liverworts. Here, we compare the morphology and physiology of the grass Holcus lanatus grown with an AM fungal community versus a more diverse symbiotic fungal community containing both AM fungi and MFRE. Holcus lanatus plants were grown in the presence of either a diverse MFRE+AM fungi soil inoculum or a multi‐species AM fungal inoculum. Plant traits associated with growth were quantified, along with fungal transfer of 15N tracer to plants from a variety of sources (ammonium chloride, alanine, glycine and algal necromass). Holcus lanatus grown with the AM fungal community had greater root and shoot growth during early development and prior to the addition of 15N‐labelled sources, compared with plants grown with the more diverse symbiotic fungal community. When nitrogen sources were made available to the fungal symbionts in the pot microcosms, plants growing with the MFRE+AM fungi soil inoculum had a faster growth rate than plants growing with the AM fungal community. At harvest, H. lanatus grown with the AM fungal community had a larger biomass, and there were no differences in 15N tracer assimilation in plants across the two fungal community treatments. Our results demonstrate that the diversity of fungal inocula in conjunction with soil nutrient availability determine the benefits derived by plants from diverse fungal symbionts. Our research contributes to understanding host plant outcomes in diverse multi‐symbiont scenarios. Read the free Plain Language Summary for this article on the Journal blog.

High-Throughput DNA Sequence-Based Analysis of AMF Communities.

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts of most land plants. They have great ecological and economic impacts as they support plant nutrition and water supply, soil structure, and plant resistance to pathogens. Investigating AMF presence and distribution at small and large scales is critical. Therefore, research requires standard protocols to be easily implemented. In this chapter, we describe a workflow for AMF identification by high-throughput sequencing through Illumina MiSeq platform of two DNA target regions: small subunit (SSU) and internal transcribed spacer (ITS). The protocol can apply to both soil and root AMF communities.

Changes of mycorrhizal fungal community occurring during the natural restoration after the chi-chi earthquake in Taiwan

Arbuscular mycorrhizal (AM) fungi influence the plant establishment after disturbances, however, there were no reports on the succession of soil AM fungal communities after earthquakes. This study was carried out to monitor the changes of AM fungal species composition during plant succession after earthquakes. After a major earthquake, the ‘Chi-Chi’ event of 1999, a total of 4238 AM fungal spores belonging to 13 species were recorded. Higher AM fungal spore density was found in the crest area of the affected mountainside and the AM fungal community was significantly different between the crest and valley area. Scutellospora nigra, Acaulospora scrobiculata and Acaulospora tuberculata were dominant in the early succession stage. Glomus ambisporum, Glomus deserticola and Acaulospora mellea were more abundant in the late successional stage. These results demonstrated the dynamics of AM fungal community during succession and vegetation recovery.

Arbuscular mycorrhizal fungal communities associated with two dominant species differ in their responses to long‐term nitrogen addition in temperate grasslands

Abstract Arbuscular mycorrhizal (AM) fungi are important components of grassland ecosystems and are sensitive to enhanced atmospheric nitrogen (N) deposition. Enhanced N deposition has been widely reported to reduce species richness and alter species composition across different types of grasslands world‐wide. Despite extensive studies on effects of N deposition on AM fungal communities of grasslands, few studies have specifically focused on effects of N deposition on AM fungi associated with dominant species in grasslands. We investigated long‐term (12‐year) effects of N addition (80 kg ha−1 year−1) on AM fungal community richness in roots and rhizosphere biomass of two dominant plant species (forb Artemisia frigida and grass Stipa krylovii) in temperate steppes of northern China. We found that AM fungi associated with the two dominant plant species differed in their responses to N addition. Nitrogen addition led to a significant reduction in AM fungal richness colonized in roots, and biomass in the rhizosphere of A. frigida, while N addition had little impacts on AM fungi colonized in roots and rhizosphere of S. krylovii. Nitrogen addition significantly reduced AM fungal colonization in roots and AM fungal spore density in the rhizosphere soils of A. frigida. In contrast, N addition had no effect on AM fungal colonization in roots and spore density in the rhizosphere of S. krylovii. Nitrogen addition markedly suppressed photosynthetic rates in A. frigida due to excessive foliar accumulation of manganese. The N‐induced reduction in photosynthetic rates reduced allocation of C into roots in A. frigida, leading to a lower root/shoot ratio, and suppression of AM fungal community associated with A. frigida. The inhibition of AM fungi would render A. frigida less competitive in terms of acquisition of mineral nutrients in soils, thus contributing to its loss in the steppe community under conditions of elevated N deposition. These findings provide a mechanistic explanation for N‐evoked differential responses of AM fungal communities associated with A. frigida and S. krylovii by linking soil properties and host plants to AM fungal communities. A plain language summary is available for this article.

Plant community, geographic distance and abiotic factors play different roles in predicting AMF biogeography at the regional scale in northern China

Arbuscular mycorrhizal fungi (AMF) are ubiquitous mutualists of terrestrial plants and play key roles in regulating various ecosystem processes, but little is known about AMF biogeography at regional scale. This study aims at exploring the key predictors of AMF communities across a 5000-km transect in northern China. We determined the soil AMF species richness and community composition at 47 sites representative of four vegetation types (meadow steppe, typical steppe, desert steppe and desert) and related them to plant community characteristics, abiotic factors and geographic distance. The results showed that soil pH was the strongest predictor of AMF richness and phylogenetic diversity. However, abiotic factors only have a low predictive effect on AMF community composition or phylogenetic patterns. By contrast, we found a significant relationship between community composition of AMF and plants, which was a surprising result given the extent of heterogeneity in the plant community across this transect. Moreover, the geographic distance predominantly explained the AMF phylogenetic structure, implying that history evolutionary may play a role in shaping AMF biogeographic patterns. This study highlighted the different roles of main factors in predicting AMF biogeography, and bridge landscape-scale studies to more recent global-scale efforts. This article is protected by copyright. All rights reserved.

Impact of an invasive nitrogen-fixing tree on arbuscular mycorrhizal fungi and the development of native species.

Arbuscular mycorrhizal fungi (AMF) are obligate soil biotrophs that establish intimate relationships with 80 % of terrestrial plant families. Arbuscular mycorrhizal fungi obtain carbon from host plants and contribute to the acquisition of mineral nutrients, mainly phosphorus. The presence of invasive plants has been identified as a soil disturbance factor, often conditioning the structure and function of soil microorganisms. Despite the investigation of many aspects related to the invasion ofAcacia dealbata, the effect produced on the structure of AMF communities has never been assessed. We hypothesize thatA. dealbatamodifies the structure of AMF community, influencing the establishment and growth of plants that are dependent on these mutualisms. To validate our hypothesis, we carried out denaturing gradient gel electrophoresis (DGGE) analysis and also grew plants ofPlantago lanceolatain pots using roots of native shrublands or fromA. dealbata, as inoculum of AMF. Cluster analyses from DGGE indicated an alteration in the structure of AMF communities in invaded soils. After 15 weeks, we found that plants grown in pots containing native roots presented higher stem and root growth and also produced higher biomass in comparison with plants grown withA. dealbatainoculum. Furthermore, plants that presented the highest biomass and growth exhibited the maximum mycorrhizal colonization and phosphorus content. Moreover, fluorescence measurements indicated that plants grown withA. dealbatainoculum even presented higher photosynthetic damage. Our results indicate that the presence of the invaderA. dealbatamodify the composition of the arbuscular fungal community, conditioning the establishment of native plants.

Is root DNA a reliable proxy to assess arbuscular mycorrhizal community structure?

Arbuscular mycorrhizal (AM) fungi are widespread plant symbionts that extensively colonize both soil and roots. Given their influence on ecosystem processes, such as plant growth, soil carbon storage, and nutrient cycling, there is great interest in understanding the drivers of their community structure. AM fungal communities are increasingly characterized by selectively amplifying their DNA from plant roots, thus assuming that AM fungal community structure within roots provides a reliable portrait of the total (i.e., soil + roots) community. Through numerical simulations, we test this assumption using published data. We show that community structure and diversity is well preserved when analyzing only a subset of the community biomass (i.e., roots or soil), provided that the community shows a typical skewed abundance distribution, with few very dominant species and a high prevalence of rare species. Given that this community structure has been shown to be common in natural AM fungal communities, the present work would suggest that characterizing AM fungal communities using only roots or soil can provide a reliable portrait of the overall community. However, we show through additional analyses that the proportion of sample biomass used for molecular methods must be over a minimal threshold to properly characterize the community. Using published molecular data sets, we validate those results, which suggest that typical molecular protocols using low amounts of biomass may strongly influence AM fungal community characterization. Finally, we also discuss other assumptions implied by the molecular analysis of AM fungal communities, and point out urgent knowledge gaps.

English

Arbuscular mycorrhizal fungi (AMF) are obligatory biotrophs that have a symbiotic evolutionary relationship with about 80% of all terrestrial plant species. The fungus mainly supplies water and nutrients to the plant and receives photoassimilates. The AMF diversity affects both the competition among species and floristic composition of an area. Fluctuations in the population of this group of microorganisms can cause fluctuations in plant populations above ground. In this work, the AMF community profile in areas with different ages of revegetation was evaluated by morphological identification of spores and denaturing gradient gel electrophoresis (DGGE) techniques. We found 12 AMF species and dominance of the species Glomus macrocarpum determined by spore density. Since the richness level observed in each plot was low and there was predominance of one species of AMF, it can be concluded that these areas still present a high degree of disturbance. It was possible to detect complex band profiles by DGGE analyses for the two plant species studied, Visnia latifolia and Cecropia hololeuca. No relationship between AMF diversity and revegetation time was observed in these areas. Key words: Denaturing gradient gel electrophoresis (DGGE), symbiosis, succession, survey.

A comparative study of arbuscular mycorrhizal fungi in forest, grassland and cropland in the Tibetan Plateau, China

Arbuscular mycorrhizal (AM) fungus community composition and diversity among the forest, grassland, and cropland ecosystems in the Tibetan Plateau were carried out in this study. A total of 44 AM fungi belonging to six genera were isolated from 144 soil samples collected from forest, grassland, and cropland. Of these AM fungi, 40 taxa were found in forest, 19 in grassland, and 19 in cropland. Glomus was the dominant genus in the three ecosystems, as well as Acaulospora was dominant in forest and grassland. Acaulospora laevis and A. scrobiculata were the dominant species in forest. Acaulospora laevis and Glomus mosseae were dominant in grassland and cropland. The spore density, species richness, and Shannon diversity index of AM fungi from high to low were forest > grassland > cropland. The Sorenson's similarity coefficients of AM fungus community composition ranged from 0.58 to 0.63 between the forest, grassland, and cropland. The results revealed that there was high diversity of AM fungi and the AM fungal community composition varied among the three ecosystems.