Differential effects of abiotic factors and host plant traits on diversity and community composition of root-colonizing arbuscular mycorrhizal fungi in a salt-stressed ecosystem

Host genotype and age shape the microbial community in the rhizosphere soils of Camellia forests

Microbiota living in the rhizosphere influences plant growth and fitness, from the opposite perspective; whether host genotypes control its root microbiota is of great interest to forest breeders and microbiologists. To improve low-yield plantations and promote sustainable management of Camellia oleifera, high-throughput sequencing was used to study the chemical properties and microbiome in rhizosphere soil of Camellia forests under three genotypes (common C. oleifera, local C. gauchowensis, and C. chekiangoleosa) and three growth stages (sapling stage at 4-year-old, primary fruit stage at 7-year-old, and full fruiting stage at 11-year-old). The results showed that the rhizosphere soil organic matter (OM), nutrient concentrations, diversity, and community composition of the microbiome were significantly varied among different Camellia genotypes. The relative abundance of symbiotic and pathotrophic fungi in the rhizosphere soil of C. chekiangoleosa was significantly higher than that of C. gauchowensis. Concentrations of OM, available phosphorus (AP), and bacterial alpha diversity increased with tree age. Fungi of Saitozyma, Mortierella, and Glomeromycota and bacteria of Burkholderia-Caballeronia-Paraburkholderia and Vicinamibacterales had potential for fertilizer development for Camellia plantation. Camellia genotypes and growth stages were significantly correlated with the rhizosphere soil pH, OM, and available potassium (AK). Soil pH and OM were key factors that affected the microbiome in the Camellia rhizosphere soils. In conclusion, tree genotypes and growth stages shaped microbial communities in Camellia rhizosphere soils, and some plant growth-promoting rhizobacteria were identified as preliminary candidates for improving Camellia plantation growth.

Soil organic matter and water content affect the community characteristics of arbuscular mycorrhizal fungi in Helan mountain, an arid desert grassland area in China

Introduction

Arbuscular mycorrhizal fungi (AMF) are vital in terrestrial ecosystems. However, the community structure characteristics and influencing factors of AMF in the forest ecosystems of arid desert grassland areas require further investigation.

Methods

Therefore, we employed high-throughput sequencing technology to analyze the soil AMF community characteristics at different elevations in the Helan mountains.

Results

The results revealed that significant differences (P < 0.05) were observed in the soil physicochemical properties among different elevations, and these properties exhibited distinct trends with increasing elevation. Through high-throughput sequencing, we identified 986 operational taxonomic units (OTUs) belonging to 1 phylum, 4 classes, 6 orders, 12 families, 14 genera, and 114 species. The dominant genus was Glomus. Furthermore, significant differences (P < 0.05) were observed in the α-diversity of the soil AMF community across different elevations. Person correlation analysis, redundancy analysis (RDA), and Monte Carlo tests demonstrated significant correlations between the diversity and abundance of AMF communities with soil organic matter (OM) (P < 0.01) and soil water content (WC) (P < 0.05).

Discussion

This study provides insights into the structural characteristics of soil AMF communities at various altitudes on the eastern slope of Helan mountain and their relationships with soil physicochemical properties. The findings contribute to our understanding of the distribution pattern of soil AMF and its associations with environmental factors in the Helan mountains, as well as the stability of forest ecosystems in arid desert grassland areas.

Plant species identity and mycorrhizal type explain the root-associated fungal pathogen community assembly of seedlings based on functional traits in a subtropical forest

Introduction

As a crucial factor in determining ecosystem functioning, interaction between plants and soil-borne fungal pathogens deserves considerable attention. However, little attention has been paid into the determinants of root-associated fungal pathogens in subtropical seedlings, especially the influence of different mycorrhizal plants.

Methods

Using high-throughput sequencing techniques, we analyzed the root-associated fungal pathogen community for 19 subtropical forest species, including 10 ectomycorrhizal plants and 9 arbuscular mycorrhizal plants. We identified the roles of different factors in determining the root-associated fungal pathogen community. Further, we identified the community assembly process at species and mycorrhizal level and managed to reveal the drivers underlying the community assembly.

Results

We found that plant species identity, plant habitat, and plant mycorrhizal type accounted for the variations in fungal pathogen community composition, with species identity and mycorrhizal type showing dominant effects. The relative importance of different community assembly processes, mainly, homogeneous selection and drift, varied with plant species identity. Interestingly, functional traits associated with acquisitive resource-use strategy tended to promote the relative importance of homogeneous selection, while traits associated with conservative resource-use strategy showed converse effect. Drift showed the opposite relationships with functional traits compared with homogeneous selection. Notably, the relative importance of different community assembly processes was not structured by plant phylogeny. Drift was stronger in the pathogen community for ectomycorrhizal plants with more conservative traits, suggesting the predominant role of stochastic gain and loss in the community assembly.

Discussion

Our work demonstrates the determinants of root-associated fungal pathogens, addressing the important roles of plant species identity and plant mycorrhizal type. Furthermore, we explored the community assembly mechanisms of root-associated pathogens and stressed the determinant roles of functional traits, especially leaf phosphorus content (LP), root nitrogen content (RN) and root tissue density (RTD), at species and mycorrhizal type levels, offering new perspectives on the microbial dynamics underlying ecosystem functioning.

Electrical Conductivity and pH Are Two of the Main Factors Influencing the Composition of Arbuscular Mycorrhizal Fungal Communities in the Vegetation Succession Series of Songnen Saline-Alkali Grassland

Arbuscular mycorrhizal fungi (AMF) are widely distributed microorganisms in the soil, playing an important role in vegetation succession, plant community diversity, and improving soil physicochemical properties. In this study, morphological identification and high-throughput sequencing technology were used to comprehensively analyze the AMF community composition and diversity at different succession stages of Songnen saline-alkali grassland. To determine the root colonization status of plants collected in the field, a colonization system was established using late-succession plants as host plants to verify the existence of mycorrhizal symbiosis and the matching phenomenon of AMF in Songnen saline-alkali grassland. The results indicated that both morphological methods and high-throughput sequencing technology showed that glomus was the dominant genus of AMF in Songnen saline grassland. Redundancy analysis (RDA) and linear regression analysis showed that electrical conductivity (EC) and pH were the main environmental factors affecting AMF species diversity and community structure in the succession sequence of Songnen saline grassland. In addition, the results of root colonization identification and the colonization system test in the field showed that AMF successfully colonized vegetation at different succession stages and had mycorrhizal symbiosis. The results of this study could help to understand the AMF community of Songnen saline-alkali grassland as well as provide a reference and basis for optimizing the AMF community structure of Songnen saline-alkali grassland through human intervention in the future and using mycorrhizal technology to restore and rebuild the degraded ecosystem of Songnen saline-alkali grassland.

Genetic Mapping of the Root Mycobiota in Rice and its Role in Drought Tolerance

BACKGROUND

Rice is the second most produced crop worldwide, but is highly susceptible to drought. Micro-organisms can potentially alleviate the effects of drought. The aim of the present study was to unravel the genetic factors involved in the rice-microbe interaction, and whether genetics play a role in rice drought tolerance. For this purpose, the composition of the root mycobiota was characterized in 296 rice accessions (Oryza sativa L. subsp. indica) under control and drought conditions. Genome wide association mapping (GWAS) resulted in the identification of ten significant (LOD > 4) single nucleotide polymorphisms (SNPs) associated with six root-associated fungi: Ceratosphaeria spp., Cladosporium spp., Boudiera spp., Chaetomium spp., and with a few fungi from the Rhizophydiales order. Four SNPs associated with fungi-mediated drought tolerance were also found. Genes located around those SNPs, such as a DEFENSIN-LIKE (DEFL) protein, EXOCYST TETHERING COMPLEX (EXO70), RAPID ALKALINIZATION FACTOR-LIKE (RALFL) protein, peroxidase and xylosyltransferase, have been shown to be involved in pathogen defense, abiotic stress responses and cell wall remodeling processes. Our study shows that rice genetics affects the recruitment of fungi, and that some fungi affect yield under drought. We identified candidate target genes for breeding to improve rice-fungal interactions and hence drought tolerance.

Liquid Organic Fertilizer Amendment Alters Rhizosphere Microbial Community Structure and Co-occurrence Patterns and Improves Sunflower Yield Under Salinity-Alkalinity Stress

Response of rhizosphere microbial community structure and co-occurrence patterns to liquid organic fertilizer in sunflower cropland was investigated. Moderate and severe saline-alkaline soils were treated with liquid organic fertilizer containing mainly small molecular organic compounds (450 g L^-1) at a rate of 4500 L ha^-1 year^-1 over 2 years. Compared with the untreated soils, organic fertilizer treatment increased soil nutrient concentrations by 13.8-137.1% while reducing soil pH and salinity by 5.6% and 54.7%, respectively. Organic fertilizer treatment also improved sunflower yield, plant number, and plant height by 28.6-67.3%. Following organic fertilizer treatment, fungal α-diversity was increased, and the effects of salinity-alkalinity stress on rhizosphere microbial communities were alleviated. The relative abundances of some halotolerant microbes and phytopathogenic fungi were reduced in organic fertilizer-treated soils, in contrast to increases in the relative abundances of plant growth-promoting microbes and organic matter decomposers, such as Nocardioides, Rhizophagus, and Stachybotrys. Network analysis revealed that severe salinity-alkalinity stress stimulated cooperation among bacteria, while organic fertilizer treatment tended to stimulate the ecosystem functions of fungi with higher proportions of fungi-bacteria and fungi-fungi links. More keystone taxa (e.g., Amycolatopsis, Variovorax, and Gemmatimonas) were positively correlated with soil nutrient concentrations and crop yield-related traits in organic fertilizer-treated soils. Overall, liquid organic fertilizer amendment could attenuate the adverse effects of salinity-alkalinity stress on sunflower yield by improving soil quality and optimizing rhizosphere microbial community structure and co-occurrence patterns.

High Variability of Fungal Communities Associated with the Functional Tissues and Rhizosphere Soil of Picea abies in the Southern Baltics

Climate change, which leads to higher temperatures, droughts, and storms, is expected to have a strong effect on both health of forest trees and associated biodiversity. The aim of this study was to investigate the diversity and composition of fungal communities associated with the functional tissues and rhizosphere soil of healthy-looking Picea abies to better understand these fungal communities and their potential effect on tree health in the process of climate change. The study sites included 30 P. abies stands, where needles, shoots, roots, and the rhizosphere soil was sampled. DNA was isolated from individual samples, amplified using ITS2 rRNA as a marker and subjected to high-throughput sequencing. The sequence analysis showed the presence of 232,547 high-quality reads, which following clustering were found to represent 2701 non-singleton fungal OTUs. The highest absolute richness of fungal OTUs was in the soil (1895), then in the needles (1049) and shoots (1002), and the lowest was in the roots (641). The overall fungal community was composed of Ascomycota (58.3%), Basidiomycota (37.2%), Zygomycota (2.5%), Chytridiomycota (1.6%), and Glomeromycota (0.4%). The most common fungi based on sequence read abundance were Aspergillus pseudoglaucus (7.9%), Archaeorhizomyces sp. (3.6%), and Rhinocladiella sp. (2.0%). Pathogens were relatively rare, among which the most common were Phacidium lacerum (1.7%), Cyphellophora sessilis (1.4%), and Rhizosphaera kalkhoffii (1.4%). The results showed that the detected diversity of fungal OTUs was generally high, but their relative abundance varied greatly among different study sites, thereby highlighting the complexity of interactions among the host trees, fungi, and local environmental conditions.

Changes in Intraspecific Diversity of the Arbuscular Mycorrhizal Community Involved in Plant-Plant Interactions Between Sporobolus robustus Kunth and Prosopis juliflora (Swartz) DC Along an Environmental Gradient

The intensification of biological processes coping with salt stress became a major issue to mitigate land degradation. The Sine-Saloum Delta in Senegal is characterized by salt-affected soils with vegetation dominated by salt-tolerant grass Sporobolus robustus and shrubs like Prosopis juliflora. Plant experiments in controlled conditions suggested that arbuscular mycorrhizal (AM) fungi might be the key actors of facilitation process observed between S. robustus and P. juliflora, but the AM fungal community determinants are largely unknown. The current field-based study aimed at (1) characterizing the environmental drivers (rhizosphere physico-chemical properties, plant type and season) of the AM fungal community along an environmental gradient and (2) identifying the AM fungal taxa that might explain the S. robustus-mediated benefits to P. juliflora. Glomeraceae predominated in the two plants, but a higher richness was observed for S. robustus. The pH and salinity were the main drivers of AM fungal community associated with the two plants, negatively impacting richness and diversity. However, while a negative impact was also observed on mycorrhizal colonization for S. robustus, P. juliflora showed opposite colonization patterns. Furthermore, no change was observed in terms of AM fungal community dissimilarity between the two plants along the environmental gradient as would be expected according to the stress-gradient and complementary hypotheses when a facilitation process occurs. However, changes in intraspecific diversity of shared AM fungal community between the two plants were observed, highlighting 23 AM fungal OTUs associated with both plants and the highest salinity levels. Consequently, the increase of their abundance and frequency along the environmental gradient might suggest their potential role in the facilitation process that can take place between the two plants. Their use in ecological engineering could also represent promising avenues for improving vegetation restoration in saline Senegalese's lands.

Plant hosts may influence arbuscular mycorrhizal fungal community composition in mangrove estuaries

We investigated the role of plant host and soil variables in determining arbuscular mycorrhizal fungi (AMF) community composition in plant roots of two spatially separated mangrove estuaries on the rivers Aghanashini (14° 30' 30″ N-74° 22' 44″ E) and Gangavali (14° 35' 26″ N-74° 17' 51″ E) on the west coast of India. Both mangrove estuaries had similar plant species composition but differed in soil chemistries.We amplified a 550-bp portion of 18S small subunit (SSU) rDNA from mangrove plant roots and analysed it by restriction fragment length polymorphism (RFLP). Clones representing unique RFLP patterns were sequenced. A total of 736 clones were obtained from roots of seven and five plant species sampled at Aghanashini and Gangavali, respectively. AMF phylotype numbers in plant roots at Aghanashini (12) were higher than at Gangavali (9) indicating quantitative differences in the AMF community composition in plant roots at the two mangrove estuaries. Because both estuaries had similar plant species composition, the quantitative difference in AMF communities between the estuaries could be an attribute of the differences in rhizospheric chemistry between the two sites.Non-metric multidimensional scaling (NMDS) revealed overlap in the AMF communities of the two sites. Three and two AMF phylotypes had significant indicator value indices with specific hosts at Aghanashini and Gangavali, respectively. Environmental vector fitting to NMDS ordination did not reveal a significant effect of any soil variable on AMF composition at the two sites. However, significant effects of both plant hosts and sites were observed on rhizospheric P. Our results indicate that root AMF community composition may be an outcome of plant response to rhizospheric variables. This suggests that plant identity may have a primary role in shaping AMF communities in mangroves.

Diverse and abundant arbuscular mycorrhizal fungi in ecological floating beds used to treat eutrophic water

An increasing number of investigations have shown the universal existence of arbuscular mycorrhizal fungi (AMF) in aquatic ecosystems. However, little is known about the accurate distribution and function of AMF inhabiting aquatic ecosystems, especially ecological floating beds (EFBs), which are constructed for the remediation of polluted water bodies. In this study, we collected root samples of Canna generalis, Cyperus alternifolius, and Eichhornia crassipes from three EFBs on two eutrophic lakes in Wuhan, China. We aimed to investigate the resources and distribution of AMF in EFBs using Illumina Mi-seq technology. A total of 229 operational taxonomic units (OTUs) and 21 taxa from 348,799 Glomeromycota sequences were detected. Glomus and Acaulospora were the most dominant and second most dominant genera of AMF in the three EFBs, respectively. Different aquatic plant species showed varying degrees of AMF colonization (3.83-71%), diversity (6-103 OTUs, 3-15 virtual taxa), and abundance (14-57,551 sequences). Low AMF abundance, but relatively high AMF diversity, was found in C. alternifolius, which is usually considered non-mycorrhizal. This finding indicated the high accuracy of Illumina sequencing. Our results also revealed a lognormal species abundance distribution that was observed across AMF taxa in the three plant species. The AMF community composition was closely related to nitrogen and phosphorus contents. Overall, our data show that EFBs harbor diverse and abundant AMF communities. Additionally, the AMF community composition is closely related to the water quality of eutrophic lakes treated by the EFBs, indicating the potential application of AMF in plant-based bioremediation of wastewater. KEYPOINTS: • Aquatic plants in EFBs harbor diverse (229 OTUs) and abundant (348,799 sequences) AMF. • Different plant species host different taxa of AMF. Cyperaceae, originally considered non-mycorrhizal, may in fact be a variable mycorrhizal plant family. • The AMF community composition in EFBs is closely related to nutrient concentrations (nitrogen and phosphorus).

Specificity of assemblage, not fungal partner species, explains mycorrhizal partnerships of mycoheterotrophic Burmannia plants

Mycoheterotrophic plants (MHPs) growing on arbuscular mycorrhizal fungi (AMF) usually maintain specialized mycorrhizal associations. The level of specificity varies between MHPs, although it remains largely unknown whether interactions with mycorrhizal fungi differ by plant lineage, species, and/or by population. Here, we investigate the mycorrhizal interactions among Burmannia species (Burmanniaceae) with different trophic modes using high-throughput DNA sequencing. We characterized the inter- and intraspecific dynamics of the fungal communities by assessing the composition and diversity of fungi among sites. We found that fully mycoheterotrophic species are more specialized in their fungal associations than chlorophyllous species, and that this specialization possibly results from the gradual loss of some fungal groups. In particular, although many fungal species were shared by different Burmannia species, fully MHP species typically host species-specific fungal assemblages, suggesting that they have a preference for the selected fungi. Although no apparent cophylogenetic relationship was detected between fungi and plants, we observe that evolutionarily closely related plants tend to have a greater proportion of shared or closely related fungal partners. Our findings suggest a host preference and specialization toward fungal assemblages in Burmannia, improving understanding of interactions between MHPs and fungi.

Coastal reclamation alters soil microbial communities following different land use patterns in the Eastern coastal zone of China

Coastal reclamation seriously disturbs coastal wetland ecosystems, while its influences on soil microbial communities remain unclear. In this study, we examined the impacts of coastal reclamation on soil microbial communities based on phospholipid fatty acids (PLFA) analysis following the conversion of Phragmites australis wetlands to different land use types. Coastal reclamation enhanced total soil microbial biomass and various species (i.e., gram-positive bacterial, actinomycete, saturated straight-chain, and branched PLFA) following the conversion of P. australis wetland to aquaculture pond, wheat, and oilseed rape fields. In contrast, it greatly decreased total soil microbial biomass and various species following the conversion of P. australis wetland to town construction land. Coastal reclamation reduced fungal:bacterial PLFA, monounsaturated:branched PLFA ratios, whereas increasing gram-positive:gram-negative PLFA ratio following the conversion of P. australis wetland to other land use types. Our study suggested that coastal reclamation shifted soil microbial communities by altering microbial biomass and community composition. These changes were driven primarily by variations in soil nutrient substrates and physiochemical properties. Changes in soil microbial communities following coastal reclamation impacted the decomposition and accumulation of soil carbon and nitrogen, with potential modification of carbon and nitrogen sinks in the ecosystems, with potential feedbacks in response to climate change.

Interactions of Arbuscular Mycorrhizal Fungi with Hyphosphere Microbial Communities in a Saline Soil: Impacts on Phosphorus Availability and Alkaline Phosphatase Gene Abundance

The limited availability of soil phosphorus to plants under salinity stress is a major constraint for crop production in saline soils, which could be alleviated by improving mycorrhizal and soil microbial interactions. This study investigated the effects of Funneliformis mosseae (Fm) inoculation on phosphorus (P) availability to Sorghum bicolor, and alkaline phosphatase (ALP) activity and gene abundance (phoD) in a P-deficient naturally saline soil. A greenhouse study was conducted in order to compare the experimental treatments of Fm inoculated vs. control plants grown in saline soil with and without (sterilized soil) native microbial community. A separate hyphosphere (root-free) compartment was constructed within the mycorrhizosphere and amended with phosphate. After four weeks of transplanting, shoot, roots, mycorrhizosphere, and hyphosphere samples were collected and analyzed for soil and plant P concentrations, root colonization, and abundance of ALP and phoD. The results showed significantly higher colonization in Fm-inoculated treatments compared to uninoculated. Plant available P concentrations, phoD gene abundance and ALP activity were significantly reduced (p < 0.05) in sterilized-hyphosphere as compared to unsterilized in both Fm-inoculated and uninoculated treatments. Inoculation with Fm significantly increased the plant P uptake (p < 0.05) when compared to uninoculated treatments, but only in the plants gown in unsterile mycorrhizosphere. It can be concluded that inoculation of Fm increased root colonization and the uptake of P by sorghum plant in saline soil and native microbial community interactions were critical for increasing bioavailable P concentrations. These beneficial interactions between plants, mycorrhizae, and native microbes should be considered for soil fertility management in saline soils.

Arbuscular Mycorrhizal Fungal Communities of Native Plant Species under High Petroleum Hydrocarbon Contamination Highlights Rhizophagus as a Key Tolerant Genus

Arbuscular mycorrhizal fungi (AMF) have been shown to play an important role in increasing plant fitness in harsh conditions. Therefore, AMF are currently considered to be effective partners in phytoremediation. However, AMF communities in high levels of petroleum pollution are still poorly studied. We investigated the community structures of AMF in roots and rhizospheric soils of two plant species, Eleocharis elliptica and Populus tremuloides, growing spontaneously in high petroleum-contaminated sedimentation basins of a former petrochemical plant (91,000 μg/Kg of C10–C50 was recorded in a basin which is 26-fold higher than the threshold of polluted soil in Quebec, Canada). We used a PCR cloning, and sequencing approach, targeting the 18S rRNA gene to identify AMF taxa. The high concentration of petroleum-contamination largely influenced the AMF diversity, which resulted in less than five AMF operational taxonomical units (OTUs) per individual plant at all sites. The OTUs detected belong mainly to the Glomerales, with some from the Diversisporales and Paraglomerales, which were previously reported in high concentrations of metal contamination. Interestingly, we found a strong phylogenetic signal in OTU associations with host plant species identity, biotopes (roots or soils), and contamination concentrations (lowest, intermediate and highest). The genus Rhizophagus was the most dominant taxon representing 74.4% of all sequences analyzed in this study and showed clear association with the highest contamination level. The clear association of Rhizophagus with high contamination levels suggests the importance of the genus for the use of AMF in bioremediation, as well as for the survey of key AMF genes related to petroleum hydrocarbon resistance. By favoring plant fitness and mediating its soil microbial interactions, Rhizophagus spp. could enhance petroleum hydrocarbon pollutant degradation by both plants and their microbiota in contaminated sites.

Native Arbuscular Mycorrhizal Fungi Characterization from Saline Lands in Arid Oases, Northwest China

Arbuscular mycorrhizal fungi (AMF) colonize land plants in almost every ecosystem, even in extreme conditions, such as saline soils. In the present work, we report the mycorrhizal capacity of rhizosphere soils collected in the dry desert region of the Minqin Oasis, located in the northwest of China (Gansu province), which is characterized by several halophytes. Lycium spp. and Peganum nigellastrum were used as trap plants in a greenhouse experiment to identify autochthonous AMF associated with the halophytes’ rhizospheres. Morphological observations showed the typical AMF structures inside roots. Twenty-six molecularly distinct AMF taxa were recovered from soil and root DNA. The taxonomical diversity mirrors the several AMF adapted to extreme environmental conditions, such as the saline soil of central China. Knowledge of the AMF associated with halophytes may contribute to select specific fungal isolates to set up agriculture strategies for protecting non-halophyte crop plants in saline soils.

Environmental factors driving arbuscular mycorrhizal fungal communities associated with endemic woody plant Picconiaazorica on native forest of Azores

Abstract

Purpose

Arbuscular mycorrhizal fungi (AMF) play important key roles in the soil ecosystems as they link plants to the root-inaccessible part of soil. The aims of this study were to investigate which environmental factors influence the spatial and temporal structuring of AMF communities associated to Picconia azorica in two Azorean islands (Terceira and São Miguel islands), and investigate the seasonal variation in AMF communities between the two islands.

Methods

Communities of AMF associated with P. azorica in native forest of two Azorean islands (Terceira and São Miguel) were characterised by spore morphology or molecular analysis.

Results

Forty-five AMF spore morphotypes were detected from the four fragments of P. azorica forest representing nine families of AMF. Acaulosporaceae (14) and Glomeraceae (9) were the most abundant families. AMF density and root colonisation varied significantly between islands and sampling sites. Root colonisation and spore density exhibited temporal patterns, which peaked in spring and were higher in Terceira than in São Miguel. The relative contribution of environmental factors showed that factors such as elevation, relative air humidity, soil pH, and soil available P, K, and Mg influenced AMF spore production and root colonisation.

Conclusion

Different sporulation patterns exhibited by the members of the commonest families suggested different life strategies. Adaptation to a particular climatic and soil condition and host phenology may explain seasonal differences in sporulation patterns. Cohorts of AMF associated to P. azorica are shaped by regional processes including environmental filters such as soil properties and natural disturbance.

Effects of host phylogeny, habitat and spatial proximity on host specificity and diversity of pathogenic and mycorrhizal fungi in a subtropical forest

Soil plant-pathogenic (PF) and mycorrhizal fungi (MF) are both important in maintaining plant diversity, for example via host-specialized effects. However, empirical knowledge on the degree of host specificity and possible factors affecting the fungal assemblages is lacking. We identified PF and MF in fine roots of 519 individuals across 45 subtropical tree species in southern China in order to quantify the importance of host phylogeny (including via its effects on functional traits), habitat and space in determining fungal communities. We also compared host specificity in PF and MF at different host-phylogenetic scales. In both PF and MF, host phylogeny independently accounted for > 19% of the variation in fungal richness and composition, whereas environmental and spatial factors each explained no more than 4% of the variation. Over 77% of the variation explained by phylogeny was attributable to covariation in plant functional traits. Host specificity was phylogenetically scale-dependent, being stronger in PF than in MF at low host-phylogenetic scales (e.g. within genus) but similar at larger scales. Our study suggests that host-phylogenetic effects dominate the assembly of both PF and MF communities, resulting from phylogenetically clustered plant traits. The scale-dependent host specificity implies that PF were specialized at lower-level and MF at higher-level host taxa.

Effect of Soil Layer and Plant–Soil Interaction on Soil Microbial Diversity and Function after Canopy Gap Disturbance

Gaps by thinning can have different microclimatic environments compared to surrounding areas, depending on the size of the gap. In addition, gaps can play important roles in biological dynamics, nutrient cycling, and seedling regeneration. The impacts of gap size on soil microbial communities and enzyme activities in different soil layers in Chinese pine plantations are not well understood. Here, we created gaps of 45 m2 (small, G1), 100 m2 (medium, G2), and 190 m2 (large, G3) by thinning unhealthy trees in an aged (i.e., 50 years old) monoculture Chinese pine plantation in 2010. Soil samples were collected in 2015. The total, bacterial, Gram-positive (G+), and Gram-negative (G−) phospholipid fatty acid (PLFA) profiles were highest in medium gaps in both the organic and mineral layers. These indicesdecreased sharply as gap size increased to 190 m2, and each of the detected enzyme activities demonstrated the same trend. Under all the gap size managements, abundances of microbial PLFAs and enzyme activities in the organic layers were higher than in the mineral layers. The soil layer was found to have a stronger influence on soil microbial communities than gap size. Redundancy analysis (RDA) based on the three systems with different gap sizes showed that undergrowth coverage, diversity, soil total nitrogen (TN), total organic carbon (TOC), and available phosphorus (AT) significantly affected soil microbial communities. Our findings highlighted that the effect of gap size on soil microenvironment is valuable information for assessing soil fertility. Medium gaps (i.e., 100 m2) have higher microbial PLFAs, enzyme activity, and soil nutrient availability. These medium gaps are considered favorable for soil microbial communities and fertility studied in a Chinese pine plantation managed on the Loess Plateau.

Arbuscular mycorrhizal fungi in two vertical-flow wetlands constructed for heavy metal-contaminated wastewater bioremediation

Over the last three decades, the presence of arbuscular mycorrhizal fungi (AMF) in wetland habitats had been proven, and their roles played in wetland ecosystems and potential functions in wastewater bioremediation technical installations are interesting issues. To increase knowledge on the functions of AMF in the plant-based bioremediation of wastewater, we constructed two vertical-flow wetlands planting with Phragmites australis and investigated AMF distribution in plant roots and their roles played in purification of wastewater polluted by heavy metals (HMs), utilizing the Illumina sequencing technique. A total of 17 operational taxonomic units (OTUs) from 33,031 AMF sequences were obtained, with Glomus being the most dominant. P. australis living in the two vertical-flow constructed wetlands (CWs) harbored diverse AMF comparable with the AM fungal communities in upland habitats. The AMF composition profiles of CW1 (vegetated with non-inoculated plants) and CW2 (vegetated with mycorrhizal plants inoculated with Rhizophagus intraradices) were significantly different. CW1 (15 OTUs) harbored more diverse AMF than CW2 (7 OTUs); however, CW2 harbored much more OTU13 than CW1. In addition, a zipf species abundance distribution (SAD), which might due to the heavy overdominance of OTU13, was observed across AM fugal taxa in P. australis roots of the two CWs. CW1 and CW2 showed high (> 70%) removal capacity of HMs. CW2 exhibited significant higher Cd and Zn removal efficiencies than CW1 (CK) (p = 0.005 and p = 0.008, respectively). It was considered that AMF might play a role in HM removal in CWs.

[Temporal diversity dynamics of the arbuscular mycorrhizal fungi of Larrea tridentata (Sesse & Mocino ex DC) Coville in a semi-arid ecosystem]

Arbuscular mycorrhizal fungi (AMF) of arid and semiarid ecosystems are important for the development of plants that grow under biotic stress in wild or in agro-ecosystems. There is little information on the temporal diversity of these organisms in perennial plants from arid ecosystems in northern Mexico. On this study, the mycorrhizal colonization and the temporal diversity of AMF in the rhizosphere of Larrea tridentata, perennial plant abundant in the Chihuahuan Desert region were explored. Samples of the rhizosphere and roots of fifteen plants in each of the three sampling dates during the 2015 year were obtained. A total of 17 species of HMA belonging to 12 genera and 7 families within the phylum Glomeromycota in all three sampling dates were found. Funneliformis geosporum was the dominant species belonging to the family Glomeraceae which possess the highest genera number on L. tridentata. The highest mycorrhization percentage was in February with 83.22, followed by September and May with 75.27 and 65.27%, respectively. A maximum of 16 AM fungal species were isolated and identified from L. tridentata rhizosphere in February, 15 species in May and 12 species in September. Statistical analysis showed significant differences between sampling dates in the spores number.

Fungal community dynamics during a marine dinoflagellate (Noctiluca scintillans) bloom

Contamination and eutrophication have caused serious ecological events (such as algal bloom) in coastal area. During this ecological process, microbial community structure is critical for algal bloom succession. The diversity and composition of bacteria and archaea communities in algal blooms have been widely investigated; however, those of fungi are poorly understood. To fill this gap, we used pyrosequencing and correlation approaches to assess fungal patterns and associations during a dinoflagellate (Noctiluca scintillans) bloom. Phylum level fungal types were predominated by Ascomycota, Chytridiomycota, Mucoromycotina, and Basidiomycota. At the genus level drastic changes were observed with Hysteropatella, Malassezia and Saitoella dominating during the initial bloom stage, while Malassezia was most abundant (>50%) during onset and peak-bloom stages. Saitoella and Lipomyces gradually became more abundant and, in the decline stage, contributed almost 70% of sequences. In the terminal stage of the bloom, Rozella increased rapidly to a maximum of 50-60%. Fungal population structure was significantly influenced by temperature and substrate (N and P) availability (P < 0.05). Inter-specific network analyses demonstrated that Rozella and Saitoella fungi strongly impacted the ecological trajectory of N. scintillans. The functional prediction show that symbiotrophic fungi was dominated in the onset stage; saprotroph type was the primary member present during the exponential growth period; whereas pathogentroph type fungi enriched in decline phase. Overall, fungal communities and functions correlated significantly with N. scintillans processes, suggesting that they may regulate dinoflagellate bloom fates. Our results will facilitate deeper understanding of the ecological importance of marine fungi and their roles in algal bloom formation and collapse.

Homogenous stands of a wetland grass living in heavy metal polluted wetlands harbor diverse consortia of arbuscular mycorrhizal fungi

Over the last three decades, the presence of arbuscular mycorrhizal (AM) fungi in wetland habitats had received increased attention, however, their distribution and functions have not been studied intensively. Using Illumina sequencing technology, we examined the AM fungal communities in roots of Phragmites australis living in 3 heavy metals (HMs) polluted wetlands located in Hubei Province, China. A total of 258 operational taxonomic units (OTUs) from 235,213 sequences affiliated with 6 Glomeromycota families (Glomeraceae, Paraglomeraceae, Claroideoglomeraceae, Ambisporaceae, Archaeosporaceae, and Diversisporaceae) were obtained, with Glomeraceae and Paraglomeraceae being the most and second-most dominant family, respectively. P. australis living in the HMs polluted wetlands harbored diverse AM fungi, including many non-recorded species in upland habitats, and the OTU number which we obtained in this study was higher than most of the records of upland habitats. Dry and waterlogged samples had common OTUs, however, AM fungal communities at different levels in dry and corresponding waterlogged P. australis roots were significant different. In addition, results from this study suggested that a preemption (geometric model) species abundance distributions (SAD), which might due to the distinctive features, e.g. heavy overdominance and difference in the most dominant taxon of each sample, was observed across AM fugal taxa in P. australis roots of the 3 HMs polluted wetlands.

Arbuscular mycorrhizal fungal responses to abiotic stresses: A review

The majority of plants live in close collaboration with a diversity of soil organisms among which arbuscular mycorrhizal fungi (AMF) play an essential role. Mycorrhizal symbioses contribute to plant growth and plant protection against various environmental stresses. Whereas the resistance mechanisms induced in mycorrhizal plants after exposure to abiotic stresses, such as drought, salinity and pollution, are well documented, the knowledge about the stress tolerance mechanisms implemented by the AMF themselves is limited. This review provides an overview of the impacts of various abiotic stresses (pollution, salinity, drought, extreme temperatures, CO2, calcareous, acidity) on biodiversity, abundance and development of AMF and examines the morphological, biochemical and molecular mechanisms implemented by AMF to survive in the presence of these stresses.