Rhizosphere disturbance influences fungal colonization and community development on dead fine roots

Little is known about the community dynamics of fungi on decomposing fine roots, despite the importance of fine roots as a source of carbon to detrital systems in forests. We examined fungal communities on dead roots in a sugar-maple dominated northern hardwood forest to test the hypothesis that community development is sensitive to rhizosphere disruption. We generated cohorts of dead fine roots in root windows and disturbed the rhizosphere microbial community in half of the windows by moving roots into sieved bulk soil. We sampled root fragments repeatedly over time and cultured fungi from these fragments to explore temporal patterns of fungal species composition. Disturbing the root rhizosphere prior to initiating decomposition changed the dominant fungal taxa, the distribution of dominant species within the community, and the temporal development in the culturable fungal community. Dominance in control roots shifted from Neonectria in early decay to Umbelopsis in later decay. Disturbance roots were more evenly dominated over time by Trichoderma, Neonectria, another species of Umbelopsis, and Pochonia. Our results suggest that species interactions are important in the ecology of fine root decay fungi, with the rhizosphere community of the living root influencing development of the decay community.     

Preferential Colonization of Solanum tuberosum L. Roots by the Fungus Glomus intraradices in Arable Soil of a Potato Farming Area

The symbiosis between plant roots and arbuscular mycorrhizal (AM) fungi has been shown to affect both the diversity and productivity of agricultural communities. In this study, we characterized the AM fungal communities of Solanum tuberosum L. (potato) roots and of the bulk soil in two nearby areas of northern Italy, in order to verify if land use practices had selected any particular AM fungus with specificity to potato plants. The AM fungal large-subunit (LSU) rRNA genes were subjected to nested PCR, cloning, sequencing, and phylogenetic analyses. One hundred eighty-three LSU rRNA sequences were analyzed, and eight monophyletic ribotypes, belonging to Glomus groups A and B, were identified. AM fungal communities differed between bulk soil and potato roots, as one AM fungal ribotype, corresponding to Glomus intraradices, was much more frequent in potato roots than in soils (accounting for more than 90% of sequences from potato samples and less than 10% of sequences from soil samples). A semiquantitative heminested PCR with specific primers was used to confirm and quantify the AM fungal abundance observed by cloning. Overall results concerning the biodiversity of AM fungal communities in roots and in bulk soils from the two studied areas suggested that potato roots were preferentially colonized by one AM fungal species, G. intraradices.     

Diversity and Functionality of Arbuscular Mycorrhizal Fungi in Three Plant Communities in Semiarid Grasslands National Park, Canada

Septate endophytes proliferating in the roots of grasslands’ plants shed doubts on the importance of arbuscular mycorrhizal (AM) symbioses in dry soils. The functionality and diversity of the AM symbioses formed in four replicates of three adjacent plant communities (agricultural, native, and restored) in Grasslands National Park, Canada were assessed in periods of moisture sufficiency and deficiency typical of early and late summer in the region. The community structure of AM fungi, as determined by polymerase chain reaction-denaturing gradient gel electrophoresis, varied with sampling time and plant community. Soil properties other than soil moisture did not change significantly with sampling time. The DNA sequences dominating AM extraradical networks in dry soil apparently belonged to rare taxa unreported in GenBank. DNA sequences of Glomus viscosum, Glomus mosseae, and Glomus hoi were dominant under conditions of moisture sufficiency. In total, nine different AM fungal sequences were found suggesting a role for the AM symbioses in semiarid areas. Significant positive linear relationships between plant P and N concentrations and active extraradical AM fungal biomass, estimated by the abundance of the phospholipid fatty acid marker 16:1ω5, existed under conditions of moisture sufficiency, but not under dry conditions. Active extraradical AM fungal biomass had significantly positive linear relationship with the abundance of two early season grasses, Agropyron cristatum (L.) Gaertn. and Koeleria gracilis Pers., but no relationship was found under dry conditions. The AM symbioses formed under conditions of moisture sufficiency typical of early summer at this location appear to be important for the nutrition of grassland plant communities, but no evidence of mutualism was found under the dry conditions of late summer.     

Seasonal differences in arbuscular mycorrhizal fungal communities in two woody species dominating semiarid caatinga forests

Tropical dry forests are strongly affected by seasonality, but its effects on belowground communities are poorly studied. Thus, the objective of this study was to reveal the effect of the season (dry versus wet) on the mycorrhizal status of roots and their potential colonization, and to determine the composition and abundance of spore-based communities of arbuscular mycorrhizal fungi (AMF) in rhizospheric soil of two dominant woody species in caatinga communities (tropical dry forest of the Brazilian Northeast). Soil and root samples were taken four times in each season (dry and wet). In the cases of the number of glomerospores and the number of infective propagules of AMF, there were significant differences between the hosts, with greater values observed in the rhizosphere of Commiphora leptophloeos than Mimosa tenuiflora. Mycorrhizal colonization and the number of infective propagules of AMF differed also between the seasons, being higher in the dry than the wet season. In total, fourteen AMF species were found in the rhizosphere of C. leptophloeos and twelve species were associated with M. tenuiflora. There was a predominance of the fungal genus Acaulospora, with seven species, followed by Gigaspora and Glomus. The species studied and the seasons differ in the composition and structure of the AMF community in the rhizosphere of the plants. The ecological significance of those differences needs to be examined further.     

Characterization of Arbuscular Mycorrhizal Fungus Communities of Aquilaria crassna and Tectona grandis Roots and Soils in Thailand Plantations

Aquilaria crassna Pierre ex Lec. and Tectona grandis Linn.f. are sources of resin-suffused agarwood and teak timber, respectively. This study investigated arbuscular mycorrhizal (AM) fungus community structure in roots and rhizosphere soils of A. crassna and T. grandis from plantations in Thailand to understand whether AM fungal communities present in roots and rhizosphere soils vary with host plant species and study sites. Terminal restriction fragment length polymorphism complemented with clone libraries revealed that AM fungal community composition in A. crassna and T. grandis were similar. A total of 38 distinct terminal restriction fragments (TRFs) were found, 31 of which were shared between A. crassna and T. grandis. AM fungal communities in T. grandis samples from different sites were similar, as were those in A. crassna. The estimated average minimum numbers of AM fungal taxa per sample in roots and soils of T. grandis were at least 1.89 vs. 2.55, respectively, and those of A. crassna were 2.85 vs. 2.33 respectively. The TRFs were attributed to Claroideoglomeraceae, Diversisporaceae, Gigasporaceae and Glomeraceae. The Glomeraceae were found to be common in all study sites. Specific AM taxa in roots and soils of T. grandis and A. crassna were not affected by host plant species and sample source (root vs. soil) but affected by collecting site. Future inoculum production and utilization efforts can be directed toward the identified symbiotic associates of these valuable tree species to enhance reforestation efforts.     

不同生境下川麦冬根围土壤丛枝菌根真菌多样性北大核心CSCD

采用高通量(Illumina Miseq)测序技术对栽培和野生2种生境下川麦冬根围的丛枝菌根(AM)真菌多样性和群落结构进行测定,并结合土壤理化因子进行相关性分析,以明确两种生境下川麦冬根围土壤AM真菌多样性和优势群落的分布特点,探讨AM真菌群落分布差异的驱动因子,为AM真菌应用于麦冬生产提供理论依据和技术支持。结果表明:(1)不同生境下川麦冬根围土壤中共鉴定出AM真菌3属10种,其中野生川麦冬根围土壤鉴定出的AM真菌3属7种,分别隶属于无梗囊霉属(Acaulospora)、多孢囊霉属(Diversispora)和球囊霉属(Glomus),而栽培环境下鉴定出AM真菌1属6种,隶属于球囊霉属。2个生境优势属均为球囊霉属。(2)不同生境下川麦冬根围AM真菌之间存在显著差异,野生生境下川麦冬根围土壤AM真菌多样性指数ACE和Shannon均显著高于人工栽培生境,而Simpson指数则相反。(3)相关性分析表明,AM真菌多样性指数及群落组成结构均与土壤理化因子存在相关性,其中全钾(TK)、全磷(TP)、全氮(TN)对AM真菌多样性指数和群落结构组成均存在显著影响。研究认为,不同生境下川麦冬根围AM真菌群落存在显著差异,球囊霉属为川麦冬互利共生的关键属,TK、TP、TN是不同生境川麦冬根围AM真菌群落差异的主要驱动因子。     

Influence of Soil Type,Cultivar and Verticillium dahliae on the Structure of the Root and Rhizosphere Soil Fungal Microbiome of Strawberry

Sustainable management of crop productivity and health necessitates improved understanding of the ways in which rhizosphere microbial populations interact with each other, with plant roots and their abiotic environment. In this study we examined the effects of different soils and cultivars, and the presence of a soil-borne fungal pathogen, Verticillium dahliae, on the fungal microbiome of the rhizosphere soil and roots of strawberry plants, using high-throughput pyrosequencing. Fungal communities of the roots of two cultivars, Honeoye and Florence, were statistically distinct from those in the rhizosphere soil of the same plants, with little overlap. Roots of plants growing in two contrasting field soils had high relative abundance of Leptodontidium sp. C2 BESC 319 g whereas rhizosphere soil was characterised by high relative abundance of Trichosporon dulcitum or Cryptococcus terreus, depending upon the soil type. Differences between different cultivars were not as clear. Inoculation with the pathogen V. dahliae had a significant influence on community structure, generally decreasing the number of rhizosphere soil- and root-inhabiting fungi. Leptodontidium sp. C2 BESC 319 g was the dominant fungus responding positively to inoculation with V. dahliae. The results suggest that 1) plant roots select microorganisms from the wider rhizosphere pool, 2) that both rhizosphere soil and root inhabiting fungal communities are influenced by V. dahliae and 3) that soil type has a stronger influence on both of these communities than cultivar.     

Arbuscular mycorrhizal fungi can shift plant-soil feedback of grass-endophyte symbiosis from negative to positive

Background and aims

Variations in root-associated fungal communities contribute to the so-called ‘crop rotation benefit’ on soil productivity. We assessed the effects of chickpea, lentil, and pea in wheat-based rotations, as compared to wheat monoculture, on the structure of root-associated fungal communities, and described the legacy of pulses on a following wheat crop.

Methods

The internal transcribed spacer (ITS) and 18S rRNA gene markers, and 454 amplicon pyrosequencing were used to describe the fungal communities of crop roots and rhizosphere soil in a field experiment and agronomic data were collected.

Results

Pulses influenced only the structure of the non-mycorrhizal fungal community of roots. Fusarium tricinctum, Clonostachys rosea, Fusarium redolens, and Cryptococcus sp. were specific to certain crops. Despite the absence of selective effects of pulses on their associated arbuscular mycorrhizal (AM) fungal community, pea had a legacy effect on the structure of the AM fungal community associated with the roots of the following wheat crop, in one of the two year/sites examined. Species of Mortierella, Cryptococcus, and Paraglomus in wheat rhizosphere soil may benefit yield, whereas species of Fusarium, Davidiella, Lachnum, Sistotrema and Podospora may reduce yield.

Conclusion

The effect of pulse crops on root fungal communities varied with rotation crop species. Pulses had various effects on the physiology of the following wheat crop, including increased productivity.

     

The Effect of Sulfur on the Composition of Arbuscular Mycorrhizal Fungal Communities During the Pod-Setting Stage of Different Soybean Cultivars

This study sought to investigate the effect of sulfur levels on changes in the fungal community composition of arbuscular mycorrhizae (AM) at the pod-setting stage and the relationship between the amount of applied sulfur and AM fungal diversity in different soybean cultivars. The objective of the research was to determine the optimal sulfur application level for different soybean cultivars and to improve soybean yield and quality from the perspective of AM fungal diversity. Three soybean cultivars, Heinong 44, Heinong 48, and Heinong 37, were selected as study materials. In addition to 0.033?g each of N, P₂O₅ and K₂O per kg of soil, 0, 0.02, 0.04, or 0.06?g of elemental sulfur was applied to each kg of soil for the four treatment groups, S1, S2, S3, and S4, respectively. The AM fungal community structure was analyzed in the soil and root of different soybean cultivars using the PCR-DGGE technology. The results indicated a significant effect of sulfur on the AM fungal community structure in the roots and rhizospheric soil of different soybean cultivars. The three soybean cultivars in group S2 exhibited the highest diversity in AM fungus. Significant changes in the dominant fungal species were observed in the DGGE fingerprints of each sample, and Glomus, Funneliformis, Rhizophagus, and Claroideoglomus fungi were the dominant species of AM fungus in the roots and soil of soybean. The application of an appropriate amount of sulfur improved the diversity of AM fungi in roots and rhizospheric soil of different soybean cultivars.     

Effects of climatic and edaphic factors on arbuscular mycorrhizal fungi in the rhizosphere of Hippophae rhamnoides in the Loess Plateau, China

In order to investigate the effects of climatic and edaphic factors on arbuscular mycorrhizal (AM) fungi in the rhizosphere of Hippophae rhamnoides in the Loess Plateau, spore density, mycorrhizal colonization and gene diversity were analyzed by using the methods of microscopy and polymerase chain reactiondenaturing gradient gel electrophoresis (PCR-DGGE) respectively. The results showed that H. rhamnoides could form strong symbiotic relationships with AM fungi. There existed obvious differences in AM fungal colonization among five sampling sites in the Loess Plateau (P < 0.05). Correlation analysis showed that AM fungal colonization and spore density were closely related with climatic and edaphic factors. 42 different species (band types) were found in the DGGE gel. Based on analysing the position and intensity of AM fungal DGGE bands, the gene diversity indices, including species richness, evenness, Simpsom’s and Shannon-Weiner index, showed significant differences among five sampling sites (P < 0.05). All the AM species could be classified into four groups in the biplot of canonical correspondence analysis (CCA), and each group had various responses to climatic and edaphic factors. Monte Carlo random test indicated that soil available phosphorus (F = 2.26, P = 0.025) and spore density (F = 1.76, P = 0.006) were the dominating factors affecting AM fungal communities. In conclusion, AM fungal colonization and community diversity in the rhizosphere of H. rhamnoides showed obvious spatial heterogeneity among the different areas of the Loess Plateau, and climatic and edaphic conditions were important factors affecting the AM fungal communities. Therefore, screening and application of AM fungal strains in the Loess Plateau need to fully consider the local climatic and edaphic conditions.     

黑老虎内生真菌及根际土壤真菌的群落结构与生态功能分析

为探讨黑老虎(Kadsura coccinea)根际土壤和组织内生真菌菌群的组成及其生态功能，该研究采用ITS高通量测序技术对成熟黑老虎(根、茎、叶)内生真菌及根际土壤真菌群落结构、多样性和生态功能进行了分析。结果表明：(1)从12个样品中共获得2 241个可操作分类单元(OTU),涉及10门、41纲、95目、212科、367属，内生真菌(根、茎、叶)和根际土壤真菌OTU数分别为386、536、258、1 435个，其中共有的OTU为18个。在门水平上，黑老虎内生真菌及根际土壤真菌优势群落均为子囊菌门和担子菌门，其中子囊菌门在叶和茎中占比分别高达96.99%和95.37%;在属水平上，黑老虎根际土壤真菌中腐生真菌被孢霉属占比较高(为13.5%),叶和茎等生长旺盛的组织中子囊菌门未分类属和痂囊腔菌属占比较高。(2)α多样性分析结果显示，黑老虎根际土壤真菌群落的丰度和多样性明显高于内生真菌，茎中内生真菌丰度显著高于根和叶，而根、茎和叶组织间内生真菌多样性差异不显著；PCoA分析结果显示，叶和茎的真菌群落结构相似性更高。(3)利用FUNGuild数据库进行的功能预测分析结果显示，黑老虎根际土...     

Phylogenetic analysis of nuclear small subunit rDNA sequences suggests that the endangered African Pencil Cedar,Juniperus procera,is associated with distinct members of Glomeraceae

The endangered indigenous tree species Juniperus procera, commonly known as African Pencil Cedar, is an important component of the dry Afromontane vegetation of Ethiopia and was shown to be AM in earlier studies. Here we describe the composition of AM fungi in colonized roots of J. procera from two dry Afromontane forests of Ethiopia. The nuSSU rDNA gene was amplified from colonized roots, cloned and sequenced using AM fungal specific primers that were partly developed for this study. Molecular phylogenetic analysis revealed that all the glomeralean sequences obtained belonged exclusively to the genus Glomus (Glomeraceae). Seven distinct Glomus sequence types were identified that all are new to science. The composition of the AM fungal communities between the sampled trees, and between the two study sites in general, differed significantly. Isolation and utilization of the indigenous AM fungal taxa from the respective sites might be required for successful enrichment plantation of this threatened Juniperus species.     

Distinct seasonal assemblages of arbuscular mycorrhizal fungi revealed by massively parallel pyrosequencing

? Understanding the dynamics of rhizosphere microbial communities is essential for predicting future ecosystem function, yet most research focuses on either spatial or temporal processes, ignoring combined spatio-temporal effects. ? Using pyrosequencing, we examined the spatio-temporal dynamics of a functionally important community of rhizosphere microbes, the arbuscular mycorrhizal (AM) fungi. We sampled AM fungi from plant roots growing in a temperate grassland in a spatially explicit manner throughout a year. ? Ordination analysis of the AM fungal assemblages revealed significant temporal changes in composition and structure. Alpha and beta diversity tended to be negatively correlated with the climate variables temperature and sunshine hours. Higher alpha diversity during colder periods probably reflects more even competitive interactions among AM fungal species under limited carbon availability, a conclusion supported by analysis of beta diversity which highlights how resource limitation may change localized spatial dynamics. ? Results reveal distinct AM fungal assemblages in winter and summer at this grassland site. A seasonally changing supply of host-plant carbon, reflecting changes in temperature and sunshine hours, may be the driving force in regulating the temporal dynamics of AM fungal communities. Climate change effects on seasonal temperatures may therefore substantially alter future AM fungal community dynamics and ecosystem functioning.     

Changes in arbuscular mycorrhizal fungal communities during invasion by an exotic invasive plant

Exotic invasive plants can show strong plant–soil feedback responses, but little is known about time scales for significant changes in soil microbial communities to occur after invasion. Previous work has suggested that plant invasions can modify arbuscular mycorrhizal (AM) fungal community structure. However, there is a lack of understanding about how long it takes for these changes to develop. To test this we investigated temporal changes in AM fungal communities colonising the invasive plant Vincetoxicum rossicum (Apocynaceae). We hypothesised that AM fungal community structure would change in a particular direction during the invasion process. We collected soil from two sites with a long history of invasion by this plant, with each site having paired invaded and uninvaded plots. Soil from these plots was used in a glasshouse experiment to characterise AM fungal community structure in the roots of V. rossicum at different times throughout a simulated growing season. AM fungal community structure differed between invaded and uninvaded plots. However, contrasting with our hypothesis, AM fungal communities colonising V. rossicum growing in soil from uninvaded plots did not change towards those in plants growing in previously invaded soil. Our data suggest that changes to AM fungal communities in the presence of V. rossicum require longer than the first growing season after establishment to develop.     

内生真菌发酵提取物和植物生长调节剂对大豆根际细菌多样性的影响

为了研究内生真菌发酵提取物和植物生长调节剂对大豆根际细菌多样性的影响,采用PCR-DGGE技术分析了各处理中不同发育期的大豆根际细菌群落变化。结果发现发酵提取液和植物生长调节剂能增加部分优势菌群的数量,但对根际细菌类群结构影响并不明显;生育周期也是影响根际细菌数量的重要因素。另外割胶测序发现优势菌群主要是Proteobacteria(变形菌门)、Acidobacteria(酸杆菌纲)、Nitrospira(硝化螺旋菌属)、Bradyrhizobium(慢生根瘤菌属)等,这些也都是大豆根际比较常见的细菌类群。     

生姜根系不同生态位细菌群落多样性特征、组成及结构差异

生姜作为常见的调味品和传统中药材,是我国重要的经济作物之一。作为取食部分的生姜块茎与根系直接相连,其产量、品质与根相关细菌群落密切相关。然而,关于生姜根系微环境中细菌群落的特点仍鲜有报道,土壤环境能否衍生出宿主特异性内生菌群落尚不清楚。以生姜根系不同生态位细菌群落为研究对象,采用高通量测序技术,对非根际、根际及根内细菌进行16S rRNA基因测序。结果表明,不同生态位细菌群落多样性存在显著差异,其中非根际及根际细菌群落多样性(Shannon index, Observed species, Faith′s PD)显著高于内生菌群落。同时,各生态位共现网络稳定性和复杂度表现为非根际>根际>根内细菌群落。而在组成上,细菌群落在不同生态位差异显著(R²=0.57,P=0.001)。其中变形菌门(Proteobacteria)是根内的优势门,该门类下假单胞菌属(Pseudomonas)、短波单胞菌属(Brevundimonas)、寡养单胞菌属(Stenotrophomonas)及泛菌属(Pantoea)在根内显著富集。在根际细菌中,拟杆菌门(Bacteroid...     

Effects of phenolic acids from ginseng rhizosphere on soil fungi structure,richness and diversity in consecutive monoculturing of ginseng

Ginseng yield and quality are seriously compromised by consecutive monoculturing in northeastern China. The imbalance of soil fungi communities and autotoxicity of ginseng are the major factors in consecutive monoculturing ginseng crops. Soil fungal communities were identified using Illumina MiSeq sequencing, applied to soils that consecutively cultured ginseng (CCG) for six years and new forest soil (NFS), or receiving application of phenolic acids (PAs). The CCG field received five treatments with five different phenolic acids, including gallic acid (GA), salicylic acid (SA), 3-phenylpropionic acid (3-PA), benzoic acid (BA) and cinnamic acid (CA), which were detected from ginseng rhizosphere in consecutive cropping soil. Fungal richness, fungi diversity, community composition, relative taxon abundances, root rot disease, and growth rate were compared among the different treatments. 579 fungal operational taxonomic units at 97% ITS sequence identity were found among 201,617 sequence reads derived from 18 separate soil samples. Members of the phylum Ascomycota dominated the soil fungal communities, and putative pathogens, such as Fusarium, Gibberella and Nectriaceae_unclassified which may include the abundant sexual morph of Cylindrocarpon destructans, showed higher relative abundances in the CCG fields. Compared to the CCG and NFS fields, PAs (except CA) enhanced the fungi richness and decreased fungi diversity. Cluster analysis indicated that the PAs (except CA) changed the fungi structure in a uniform way. PAs stimulate root rot disease and enhance disease severity, restricting plant growth. The results suggest that the PAs (except CA) may enhance the fungi richness, decrease the fungi diversity and changed the fungi structure to increase fungal pathogen loads, which could explain the declined yield and quality of ginseng in consecutively monocultured ginseng crops.     

Changes in mycorrhizal colonization and overall fungal communities across upland and wetland <Emphasis Type="Italic">Acer</Emphasis> forests of the Virginia Coastal Plain

Arbuscular mycorrhiza (AM) are common in the roots of most plants and provide benefits such as enhanced uptake of soil nutrients and water when the environment limits these resources. Two primary factors proposed in the literature as limiting the extent of mycorrhizal colonization of wetland plants are: (1) the low oxygen environment; and (2) the level of available phosphorus. The present study evaluated AM colonization of maple (Acer) roots and the fungal community structure in paired upland/wetland locations in the Virginia Coastal Plain to determine if wetland conditions affected the root fungal community. The range of observed AM colonization, based on 60 samples collected on 11 dates covering 3 years, was from 4 to 55%. Overall, soil redox potential and available phosphorus concentration were not significant in explaining the difference in AM colonization of Acer roots. In fact, the site with the greatest percent colonization in this study was a wetland site. A comparison of fungal diversity between the pooled wetland site communities and the pooled upland site communities was conducted and the difference was significant (p = 0.003), but the upland sites exhibited the lower diversity. Communities from all sites were dissimilar. Geographic location exerted a greater effect over community structure than did upland versus wetland status. This study concludes that the forested wetland environments studied here neither limited AM colonization nor reduced the overall fungal community and in fact may present a more favorable environment for fungal diversity.     

Analogous wheat root rhizosphere microbial successions in field and greenhouse trials in the presence of biocontrol agents Paenibacillus peoriae SP9 and Streptomyces fulvissimus FU14

Two Pythium-infested soils were used to compare the wheat root and rhizosphere soil microbial communities from plants grown in the field or in greenhouse trials and their stability in the presence of biocontrol agents. Bacteria showed the highest diversity at early stages of wheat growth in both field and greenhouse trials, while fungal diversity increased later on, at 12 weeks of the crop cycle. The microbial communities were stable in roots and rhizosphere samples across both soil types used in this study. Such stability was also observed irrespective of the cultivation system (field or greenhouse) or addition of biocontrol coatings to wheat seeds to control Pythium disease (in this study soil infected with Pythium sp. clade F was tested). In greenhouse plant roots, Archaeorhizomyces, Debaryomyces, Delftia, and unclassified Pseudeurotiaceae were significantly reduced when compared to plant roots obtained from the field trials. Some operational taxonomic units (OTUs) represented genetic determinants clearly transmitted vertically by seed endophytes (specific OTUs were found in plant roots) and the plant microbiota was enriched over time by OTUs from the rhizosphere soil. This study provided key information regarding the microbial communities associated with wheat roots and rhizosphere soils at different stages of plant growth and the role that Paenibacillus and Streptomyces strains play as biocontrol agents in supporting plant growth in infested soils.     

Relative Importance of Deterministic and Stochastic Processes in Driving Arbuscular Mycorrhizal Fungal Assemblage during the Spreading of a Toxic Plant

Both deterministic and stochastic processes are expected to drive the assemblages of arbuscular mycorrhizal (AM) fungi, but little is known about the relative importance of these processes during the spreading of toxic plants. Here, the species composition and phylogenetic structure of AM fungal communities colonizing the roots of a toxic plant, Ligularia virgaurea, and its neighborhood plants, were analyzed in patches with different individual densities of L. virgaurea (represents the spreading degree). Community compositions of AM fungi in both root systems were changed significantly by the L. virgaurea spreading, and also these communities fitted the neutral model very well. AM fungal communities in patches with absence and presence of L. virgaurea were phylogenetically random and clustered, respectively, suggesting that the principal ecological process determining AM fungal assemblage shifted from stochastic process to environmental filtering when this toxic plant was present. Our results indicate that deterministic and stochastic processes together determine the assemblage of AM fungi, but the dominant process would be changed by the spreading of toxic plants, and suggest that the spreading of toxic plants in alpine meadow ecosystems might be involving the mycorrhizal symbionts.