Root Endosphere Research Articles

Ecological niche selection shapes the assembly and diversity of microbial communities in Casuarina equisetifolia L.

The plant microbiome profoundly affects many aspects of host performance; however, the ecological processes by which plant hosts govern microbiome assembly, function, and dispersal remain largely unknown. Here, we investigated the bacterial and fungal communities in multiple compartment niches (bulk soil, rhizosphere soil, root endosphere, phylloplane, and leaf endosphere) of Casuarina equisetifolia L. at three developmental stages in Hainan Province, China. We found that microbiome assemblages along the soil-plant continuum were shaped by the compartment niches. Bacterial diversity and richness decreased from the soils to roots to leaves, with the highest network complexity found in the roots and the lowest found in the phylloplane. However, fungal diversity gradually increased from the soils to roots to phyllosphere, whereas fungal richness decreased from the soils to roots but increased from the roots to phyllosphere; the greatest network complexity was found in bulk soils and the lowest was found in the roots. Different biomarker taxa occurred in the different ecological niches. Bacterial and fungal communities exhibited distinct ecological functions; the former played important roles in maintaining plant growth and providing nutrients, whereas the latter predominantly decomposed organic matter. The bacterial community of C. equisetifolia mostly originated from bulk soil, whereas the fungal community was mainly derived from rhizosphere soil and air. Leaf endophytes were positively correlated with organic carbon, and root and soil microorganisms were positively correlated with total nitrogen, total phosphorus, and total potassium. Our findings provide empirical evidence for plant-microbiome interactions and contribute to future research on non-crop management and the manipulation of non-crop microbiomes.

Silicon fertilizer mediated structural variation and niche differentiation in the rhizosphere and endosphere bacterial microbiome and metabolites of sugarcane.

The microbiomes of plant are potential determinants of plant growth, productivity, and health. They provide plants with a plethora of functional capacities, namely, phytopathogens suppression, access to low-abundance nutrients, and resistance to environmental stressors. However, a comprehensive insight into the structural compositions of the bacterial abundance, diversity, richness, and function colonizing various microenvironments of plants, and specifically their association with bioactive compounds and soil edaphic factors under silicon (Si) amendment remains largely inconclusive. Here, high-throughput sequencing technology and nontargeted metabolite profiling method were adopted to test the hypotheses regarding microbiome niche abundance, diversity, richness, function, and their association with bioactive compounds and soil edaphic factors within different ecological niches (leaf, stem, root, rhizosphere, and bulk soils) under Si amendment during cane growth were we addressed. Our results demonstrated that Si correspondingly increased sugarcane theoretical production and yield, and remarkably enhanced soil nutrient status, especially Si, AP, and AK. It was also observed that bacterial diversity demonstrated tissue-dependent distribution patterns, with the bulk soil, rhizosphere soil, and root endosphere revealing the highest amount of bacterial diversity compared with the stem and leaf tissues. Moreover, Si exhibited the advantage of considerably promoting bacterial abundance in the various plant compartments. Co-occurrence interactions demonstrated that Si application has the potential to increase bacterial diversity maintenance, coexistence, and plant–soil systems bacteria connections, thereby increasing the functional diversity in the various plant tissues, which, in turn, could trigger positive growth effects in plants. Network analysis further revealed that metabolite profiles exhibited a strong association with bacterial community structures. It was also revealed that Si content had a considerable positive association with bacterial structures. Our findings suggest that the dynamic changes in microbe’s community composition in different plant and soil compartments were compartment-specific. Our study provides comprehensive empirical evidence of the significance of Si in agriculture and illuminated on differential metabolite profiles and soil microbe’s relationship.

Effect of continuous cropping of konjac (Amorphophallus konjac) on soil bacterial communities as evaluated by Illumina high-throughput sequencing

ABSTRACT Illumina high-throughput sequencing was used to explore the diversity and composition of the soil and root endosphere bacterial communities in three replanted konjac sites in 1-, 3-, and 5-year cropping systems. Continuous cropping of konjac caused a substantial decrease in soil pH and the activities of soil sucrase, urease, catalase, and alkaline phosphatase, and led to a remarkable and persistent decrease in the soil and root endosphere bacterial species abundance and alpha-diversity. Among the nine dominant bacterial phyla, Proteobacteria and Actinobacteria had the highest relative abundance, with averages of 61.3% and 11.2%, respectively. Several potentially beneficial genera, including Acinetobacter, Arthrobacter, and Pseudomonas, were less abundant in soil (84.6%, 82.7%, and 83.3%) and root (98.6%, 71.4%, and 98.1%) samples under 5 years of continuous cropping compared with those under 1-year cropping. Conversely, the potentially harmful genus Haliangium exhibited higher relative abundance in 5-year soil and root samples than in 1-year samples. Continuous cropping altered the bacterial community composition in the soil and root endosphere of konjac by influencing soil variables, leading to a reduction in the alpha-diversity of bacteria and the relative abundance of potentially beneficial bacteria, which in turn resulted in konjac poor growth in the continuous cropping system.

Structural variability and niche differentiation of Paeonia lactiflora's root-associated microbiomes

Many microorganisms are found in the roots of plants, and are important for plant growth, nutrition uptake, and disease prevention. While the microorganisms of many crops such as soybean, rice, and maize have been studied, the root-associated microbial diversity of horticultural plants such as Paeonia lactiflora has been little studied. In this study, we investigated the composition, abundance, diversity and variability of microorganisms associated with different rhizospheric compartments (bulk soil, rhizosphere, rhizoplane, root endosphere) of different cultivars of P. lactiflora. We used the root and root-associated soil of a medicinal cultivar P. lactiflora cv ‘Hang Baishao’ (HS, 2n = 10) and an ornamental cultivar P. lactiflora cv ‘Zi Fengyu’ (ZFY, 2n = 10) as our study objectives. Based on Illumina Novaseq 6000 high-throughput sequencing, the 16S rRNA V4 amplicon of two cultivars of P. lactiflora root-associated bacterial communities and the ITS1-spanning amplicon of the fungal communities were sequenced, and the microbial communities were analyzed for relevant bioinformatics. Observed Species, Simpson, Shannon, and Chao1 indices showed that the microbial diversity of the rhizosphere was greater than that of the root, with the with the diversity decreasing from the bulk soil to the root endosphere. In addition, Cyanobacteria and Proteobacteria were the most abundant of the root-associated bacterial communities, accounting for 19.59 % and 31.23 %, respectively. On the other hand, Ascomycota (37.74 %) and Basidiomycota (11.15 %) were the most dominant fungal communities in the four root-associated compartments. Compared to ZFY, the root-associated compartments of HS were able to enrich more functional bacteria associated with bacterial inhibition, such as Kribbella, Actinophytocola and Actinoallomurus. This study explored the complex root microflora structure of P. lactiflora and provided a theoretical basis for future studies on the synthetic microbial community of soil.

Host genetic determinants drive compartment-specific assembly of tea plant microbiomes.

Diverse host factors drive microbial variation in plant-associated environments, whereas their genetic mechanisms remain largely unexplored. To address this, we coupled the analyses of plant genetics and microbiomes in this study. Using 100 tea plant (Camellia sinensis) cultivars, the microbiomes of rhizosphere, root endosphere and phyllosphere showed clear compartment-specific assembly, whereas the subpopulation differentiation of tea cultivars exhibited small effects on microbial variation in each compartment. Through microbiome genome-wide association studies, we examined the interactions between tea genetic loci and microbial variation. Notably, genes related to the cell wall and carbon catabolism were heavily linked to root endosphere microbial composition, whereas genes related to the metabolism of metal ions and small organic molecules were overrepresented in association with rhizosphere microbial composition. Moreover, a set of tea genetic variants, including the cytoskeleton-related formin homology interacting protein 1 gene, were strongly associated with the β-diversity of phyllosphere microbiomes, implying their interactions with the overall structure of microbial communities. Our results create a catalogue of tea genetic determinants interacting with microbiomes and reveal the compartment-specific microbiome assembly driven by host genetics.

Zanthoxylum bungeanum root-rot associated shifts in microbiomes of root endosphere, rhizosphere, and soil.

Root-rot disease has lead to serious reduction in yields and jeopardized the survival of the economically and ecologically important Zanthoxylum bungeanum trees cultured in Sichuan Province. In order to investigate the interaction between the microbiome and the root-rot disease, a metagenomic analysis was performed to characterize the microbial communities and functions in Z. bungeanum root endosphere, rhizosphere and bulk soil with/without root-rot disease. Soil physicochemical properties, microbial population size and enzyme activities were also analyzed for finding their interactions with the root-rot disease. As results, lower total nitrogen (TN) and available phosphorus (AP) contents but higher pH in rhizosphere and bulk soil, as well as lower substrate-induced respiration (SIR) and higher protease activity in bulk soil of diseased trees were found, in comparison with that of healthy trees. Microbial diversity and community composition were changed by root-rot disease in the endosphere, but not in rhizosphere and bulk soils. The endophytic microbiome of diseased trees presented higher Proteobacteria abundance and lower abundances of Bacteroidetes, Firmicutes and dominant fungal phyla. The relative abundances of nitrogen cycle- and carbon cycle-related genes in endophytic microbiomes were different between the diseased and healthy trees. Based on ANOSIM and PCoA, functional profiles (KEGG and CAZy) of microbiomes in rhizosphere and bulk soil shifted significantly between the diseased and healthy trees. In addition, soil pH, TN, AP, SIR, invertase and protease were estimated as the main factors influencing the shifts of taxonomic and functional groups in microbiomes of rhizosphere and bulk soil. Conclusively, the imbalance of root and soil microbial function groups might lead to shifts in the root endosphere-rhizosphere microenvironment, which in turn resulted in Z. bungeanum root-rot.

Diversity of fungal assemblages in rhizosphere and endosphere of blueberry (Vaccinium spp.) under field conditions revealed by culturing and culture-independent molecular methods.

Mycorrhizae are important to plants in improving nutrient absorption and stress resistance. To study mycorrhizal fungal diversity in blueberry, we combined culture method and culture-independent molecular method to analyze the root endosphere and rhizosphere fungi in three different cultivars. We obtained 212 isolates with a culture method and classified them into 40 types according to their morphological characteristics. Then, we amplified the internal transcribed spacer sequence and found rich species diversity. With high-throughput sequencing, 561 operational taxonomic units (OTUs) were annotated based on a 97% similarity level cutoff. The alpha diversity index revealed that the fungal abundance and diversity in the rhizosphere were higher than those in the endosphere. The dominant phyla were Ascomycota and Basidiomycota and the dominant genus was Oidiodendron. We also constructed the plant-fungus symbiotic system by inoculating in vitro stock shoots, which lays a theoretical foundation for further research to develop and utilize the dominant mycorrhizal fungi of blueberry.

Microbiome and pathobiome analyses reveal changes in community structure by foliar pathogen infection in rice.

Increasing evidence suggests that the plant rhizosphere may recruit beneficial microbes to suppress soil-borne pathogens, but microbiome assembly due to foliar pathogen infection and ecological mechanisms that govern microbiome assembly and functions in the diseased host are not fully understood. To provide a comprehensive view of the rice-associated microbiome, we compared bacterial and fungal communities of healthy rice and those infected with Magnaporthe oryzae, the causal agent of blast disease. We found that the soil had a greater diversity of bacterial and fungal communities than plant endospheric communities. There was no significant dysbiosis of bacterial and fungal microbiome diversity due to disease, but it caused a substantial alteration of bacterial community structure in the root and rhizosphere compartments. The pathobiome analysis showed that the microbiome community structure of leaf and grain tissues was changed markedly at the pathogen infection site, although the alpha diversity did not change. Correspondingly, the relative abundances of some bacteria and fungi were clearly altered in symptomatic tissues. We noted an increase in Rhizobium bacteria and a decline of Tylospora, Clohesyomyces, and Penicillium fungi in the symptomatic leaf and grain tissues from both locations. According to the inferred microbial network, several direct interactions between M. oryzae and other microbes were identified. The majority of edges in the interaction network were positive in diseased samples; contrastingly, the number of edges was much lower in the healthy samples. With source tracking analysis, we observed a sharp contrast in the source of root endosphere bacteria due to Magnaporthe infection. Whereas the majority (71%) of healthy root bacteria could be tracked from the soil, only a very small portion (17%) could be tracked from the soil for diseased samples. These results advanced our understanding and provided potential ideas and a theoretical basis for studying pathobiome and exploiting the microbiome for sustainable agriculture.

Bacterial Communities in the Endophyte and Rhizosphere of White Radish (Raphanus sativus) in Different Compartments and Growth Conditions.

Endophyte resources have important research value in multiresistance breeding, ecological protection, germicide development, and other fields. In this study, high-throughput sequencing (Illumina-MiSeq) technology was employed to analyse the diversity and community composition of white radish (Raphanus sativus) endophytes and rhizosphere bacteria in different compartments and cultivation conditions, including greenhouse and open field cultivation, at both the phylum and genus levels. Alpha diversity index analysis showed that the bacterial richness and diversity values of rhizosphere bacteria were higher than those of endophytes in different compartments. NMDS analysis and microbial co-occurrence network analysis showed that apart from the similarity in the endophytic bacterial composition of the leaf and root endosphere, the endophytic bacterial composition in flesh and epidermis of radish were also more similar. The dominant endophytic bacteria in white radish were Proteobacteria, Bacteroidetes, and Actinomycetes at the phylum level. We analyzed the effects of different ecological compartments and two cultivation environments on radish microorganisms, and found that ecological compartments played an important role, which was related to the mechanism of microbial assembly in plants. The same facility cultivation can also improve the diversity of radish microorganisms in different ecological compartments, and change the biomarkers that play a major role in rhizosphere microorganisms and endophytes of radish. Bacteria plays an important role in the process of plant growth, and the study of endophytes enriches the understanding of microbial diversity in white radish, which helps to provide insight into the ecological function and interaction mechanisms of plants and microorganisms.

Vineyard establishment under exacerbated summer stress: effects of mycorrhization on rootstock agronomical parameters, leaf element composition and root-associated bacterial microbiota

AimsClimate change imposes adaptation of viticulture in risk areas, such as the Mediterranean. Mycorrhization is a valid tool to reduce the impact of the expected temperature/drought increase. Aim of this work was to test the effects of mycorrhization on grapevine vegetative growth, element composition of soil/leaves, and microbiota of bulk soil/rhizosphere/endorhiza, in the field, under exacerbated summer stress conditions obtained by planting the rootstocks in June.Methods118 rooted cuttings of 1103-Paulsen (Vitis berlandieri × Vitis rupestris) were planted in Salento (Apulia, Southern Italy); about half of them were mycorrhized. Leaf Area Index, shoot growth and survival rate were monitored across two growing seasons. Leaf/shoot weight, chemical analysis of 25 elements, and 16S rRNA gene metabarcoding of bulk soil/rhizosphere/endorhiza were performed on subsamples.ResultsMycorrhized plants showed significantly higher survival rate and growth, and accumulated significantly higher amounts of 18 elements. 27 endorhizal OTUs (representing ~20% of total sequences) were differently distributed (20 OTUs more abundant in mycorrhized plants); in the rhizosphere, instead, 12 OTUs (~2.5% of total sequences) were differently distributed. A few Actinobacterial OTUs were enriched by mycorrhization in the root endosphere; the same OTUs were the most correlated with the chemical elements, suggesting a role in element dynamics. These OTUs were not hub taxa of the co-occurrence network.ConclusionsThis work shed light onto the interactions between mycorrhiza and microbiome, in the context of plant element dynamics, which is useful to identify potential target candidates for biotechnological applications, thus moving towards a more sustainable, ecosystem-based viticulture.

Spatial variations of root-associated bacterial communities of alpine plants in the Qinghai-Tibet Plateau

Exploring the geospatial variation of root-associated microbiomes is critical for understanding plant-microbe-environment interactions and plant environmental adaptability. Root-associated bacterial communities from the three compartments [rhizosphere surrounding soil (RSS), rhizosphere soil (rhizosphere), and root endosphere (endophytic)] are influenced by multiple factors, including plant species and geographical locations. Nonetheless, these communities remain poorly understood under harsh conditions. In this study, we selected four dominant alpine plants on the Qinghai-Tibet Plateau (i.e., Elymus nutans, Festuca sinensis, Kobresia pygmaea, and Kobresia humilis) to investigate their root-associated bacterial communities across 11 geographical locations and determine the factors driving spatial variation. The results showed that the microbiota of the three compartments had significantly different community compositions, with more Pseudomonadaceae and Enterobacteriaceae present in the endosphere. Spatial variations in root endophytic microbiota were mainly governed by stochastic processes, which were different from the deterministic processes in the other two compartments. Meanwhile, the geographical location had greater effects on bacterial communities than plant species, and the spatial variation of α-diversity in the endosphere was much higher than that in the RSS and rhizosphere. We further found that the differentiation of bacterial diversity in the endosphere among sympatric plant species was enhanced by higher annual precipitation, lower soil nutrients (carbon and nitrogen), and pH. For example, the coefficient of variation of endosphere Pseudomonadaceae abundance was positively correlated with annual mean precipitation, whereas that of Enterobacteriaceae abundance was negatively correlated with soil pH. The co-occurrence network analysis identified a higher proportion of bacterial coexistence in the endosphere (70.9%) than in the RSS (49.5%) and rhizosphere soil (50.9%). Finally, we revealed the relative convergence of endophytic communities among sympatric plant species in the alpine grasslands.

Effect of endophytic bacterium, Stenotrophomonas maltophilia JVB5 on sunflowers

Identifiable endophytic bacteria with plant growth-promoting traits promise to ensure sustainable agriculture. However, information on the versatility and exploration of sunflower-associated bacteria as bioinoculants is less studied. Here, we present the whole-genome sequence and annotation of Stenotrophomonas maltophilia JVB5 isolated from the sunflower root endosphere from the North West province, South Africa. The whole-genome analysis revealed a genome size of 4 771 305 bp, a sequence read count of 8 764 890, a 66% guanine-cytosine content, 57 tRNAs, 268 contigs, and 4 160 protein-coding genes with functions in various metabolic pathways. Pathways involved in the indole acetic acid production were found in the S. maltophilia JVB5 genome. The whole-genome annotation predicted notable genes involved in bacterial colonisation, antibiosis, and plant growth promotion. The predicted genes are involved in the sulfur metabolism, and the oxidative stress may enhance the plant growth promotion and boost plant the resistance to stress. Upon inoculation, S. maltophilia JVB5 efficiently colonised the sunflower root under greenhouse conditions with a significant improvement on the wet plant weight of 437.20 g compared to the uninoculated control with a 331.04 g wet weight. The genomic analysis revealing specific functional genes in the bacteria genome suggests their bioprospecting in agriculture. Hence, understanding the mechanisms employed by S. maltophilia JVB5 based on the predicted multifunctional genes will help harness their bioresource in sustainable plant health.

Screening of plant growth-promoting bacteria isolated from sugarcane

Plant growth-promoting bacteria (PGPB) are known to establish positive relationships with plants. They act in favoring plant nutrition, production of phytohormones, control of pathogens and enhancement of stress tolerance. Thus, this study aimed to isolate bacteria from soil, rhizosphere, and root endosphere from sugarcane cultivated in the Southeastern of Brazil, to prospect strains with potential for plant growth promotion. The samples were plated in Nutrient Agar medium, and the morphologically distinct colonies were isolated and analyzed about indoleacetic acid production, phosphate solubilization and the growth control of the phytopathogenic fungus Fusarium verticillioides. A total of 219 isolates were obtained, of which 86 from soil, 67 from rhizosphere and 66 from sugarcane root endosphere. The strains that presented more than one mechanism of plant growth promotion were identified by the sequencing of 16S gene. Most species belonged to the genus Bacillus, which has strains already used in various biological products for the control of diseases in agriculture. Some Bacillus species isolated in our study have never been isolated from sugarcane, and others have been studied for the first time as plant growth promoters. The isolated strains constitute an important microbial bank to be explored to compose innovative products for agriculture.

Natural variation in root exudation of GABA and DIMBOA impacts the maize root endosphere and rhizosphere microbiomes.

Root exudates are important for shaping root-associated microbiomes. However, studies on a wider range of metabolites in exudates are required for a comprehensive understanding about their influence on microbial communities. We identified maize inbred lines that differ in exudate concentrations of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA) and γ-aminobutyric acid (GABA) using a semi-hydroponic system. These lines were grown in the field to determine the changes in microbial diversity and gene expression due to varying concentrations of DIMBOA and GABA in exudates using 16S rRNA amplicon sequencing and metatranscriptomics. Results showed individual and interaction effects of DIMBOA and GABA on the rhizosphere and root endosphere β-diversity, most strongly at the V10 growth stage. The main bacterial families affected by both compounds were Ktedonobacteraceae and Xanthomonadaceae. Higher concentrations of DIMBOA in exudates affected the rhizosphere metatranscriptome, enriching for metabolic pathways associated with plant disease. This study validated the use of natural variation within plant species as a powerful approach for understanding the role of root exudates on microbiome selection. We also showed that a semi-hydroponic system can be used to identify maize genotypes that differ in GABA and DIMBOA exudate concentrations under field conditions. The impact of GABA exudation on root-associated microbiomes is shown for the first time.

Taxonomic and functional diversity of Dendrobium officinale microbiome in Danxia habitat.

Microbial communities that inhabit plants are crucial for plant survival and well-being including growth in stressful environments. The medicinal plant, Dendrobium officinale grows in the barren soils of the Danxia Habitat. However, the microbiome composition and functional potential for growth of this plant in this environment are still unexplored. In this study, we analysed the taxonomic and functional diversity of the D. officinale Microbiome by metagenomic sequencing of both rhizosphere and endosphere samples. A total of 155 phyla, 122 classes, 271 orders, 620 families and 2194 genera were identified from all samples. The rhizospheric microbes (DXRh) were mainly composed of Proteobacteria and Acidobacteria, while Basidiomycota and Ascomycota were the most dominant phyla in root endosphere (DXRo) and stem endosphere (DXS), respectively. Most of the dominant microbial communities had been reported to have diverse functional potentials that can help plant growth and development in stressful and nutrient-deprived ecological environmental. These include plant growth promoting rhizobacteria (PGPR) such as Massilia, Pseudomonas, Bradyrhizobium, Klebsiella, Streptomyces, Leclercia, Paenibacillus, Frankia and Enterobacter in the DXRh, Tulasnella and Serendipita in the DXRo, Colletotrichum and Burkholderia in the DXS and Paraburkholderia, Rhizophagus and Acetobacter in endosphere. Analysis using the KEGG, eggNOG and CAZy databases showed that metabolic pathways such as carbohydrate metabolism, amino acid metabolism, energy metabolism, genetic information processing and environmental information processing are significantly abundant, which may be related to the survival, growth and development of D. officinale in a stressful environment. We speculated that the microbial community with diverse taxonomic structures and metabolic functions inhabiting in different niches of plants supports the survival and growth of D. officinale in the stressful environment of Danxia Habitat. This study provided an important data resource for microbes associated with D. officinale and theoretical foundation for further studies.

Changes to the Bacterial Microbiome in the Rhizosphere and Root Endosphere of Persea americana (Avocado) Treated With Organic Mulch and a Silicate-Based Mulch or Phosphite, and Infested With Phytophthora cinnamomi.

Plant growth and responses of the microbial profile of the rhizosphere soil and root endosphere were investigated for avocado plants infested or not infested with Phytophthora cinnamomi and the changes were compared in plants grown with various soil additives or by spraying plants with phosphite. Soil treatments were organic mulches or silica-based mineral mulch. Reduction of root growth and visible root damage was least in the infested plants treated with phosphite or mineral mulch applied to the soil. Rhizosphere soils and root endospheres were analyzed for bacterial communities using metabarcoding. Bacterial abundance and diversity were reduced in infested rhizospheres and root endospheres. The presence or absence of mineral mulch resulted in greater diversity and larger differences in rhizosphere community composition between infested and non-infested pots than any other treatment. Some rhizosphere bacterial groups, especially Actinobacteria and Proteobacteria, had significantly higher relative abundance in the presence of Phytophthora. The bacterial communities of root endospheres were lower in abundance than rhizosphere communities and not affected by soil treatments or phosphite but increased in abundance after infection with P. cinnamomi. These findings suggested that the addition of silicate-based mineral mulch protects against Phytophthora root rot, which may be partly mediated through changes in rhizosphere bacterial community composition. However, the changes to the microbiome induced by spraying plants with phosphite are different from those resulting from the application of mineral mulch to the soil.

Phosphorus and Zinc Are Strongly Associated with Belowground Fungal Communities in Wheat Field under Long-Term Fertilization.

ABSTRACTBelowground fungi are closely related to crop growth, and agricultural fertilization is widely known to affect soil fungal communities. Yet it remains unclear whether fungal communities in differing belowground habitats—root endosphere, rhizosphere soil, and bulk soil—respond differently to long-term fertilization. Here we investigated the variation in fungal communities of root endosphere, rhizosphere soil, and bulk soil under 35 years of fertilization in wheat fields. Specifically, the fertilization regimes were applied as five treatments: soils receiving NPK fertilizer, NPK and cow manure (NPK+CM), NPK and pig manure (NPK+PM), NPK and wheat straw (NPK+WS), and no fertilizer (Control). Long-term fertilization significantly impacted fungal community composition in all three habitats, and these effects were stronger in the rhizosphere and bulk soils than root endosphere. Mantel test results showed that fungal community composition was significantly correlated with phosphorus and zinc contents. Further, fungal alpha diversity was lowest in the NPK+PM treatment and was negatively correlated with both phosphorus and zinc contents. Moreover, NPK+PM treatment had the lowest complexity of fungal co-occurrence network, and in general network complexity was significantly negatively correlated with the zinc and phosphorus contents. Taken together, these results suggest that long-term fertilization can impact fungal communities not only in soils but in root endosphere, and this is strongly associated with the contents of phosphorus and zinc there, a finding important for guiding fertilization management practices and supporting sustainable agriculture.IMPORTANCE Fungi, an essential component in nutrient cycling and plant growth, are highly sensitive to fertilization. However, there are limited studies on fungi in root endosphere under long-term fertilization management. Our research extended the study on the endophytic fungal community of crop roots under agricultural management and found that its responses were similar to the communities in soil habitats. In addition, the type of organic materials was reported as the main driver affecting soil fungal community under long-term fertilization. Our research further revealed that the underlying mechanism of affecting the fungal communities in the soils and roots was the differences in phosphorus and zinc contents caused by the application of different organic materials. Therefore, our results highlight that except for phosphorus, zinc content of the organic materials should be considered in long-term organic fertilization systems.

Organic fertilization regimes suppress fungal plant pathogens through modulating the resident bacterial and protistan communities

AbstractIntroductionFungal plant pathogens are an emerging threat to economically important crop production worldwide and a significant risk to global food security. However, we have limited knowledge of how agricultural management practices drive the emergence and spread of pathogens within crop microbiomes and the underlying ecological mechanisms.Materials and MethodsWe characterized the profiles of potential fungal plant pathogens, as well as bacterial and protistan communities, in sorghum phyllosphere, root endosphere, and rhizosphere and bulk soils collected from a long‐term experiment with multiple inorganic and organic fertilization regimes.ResultsWe found contrasting patterns of fungal plant pathogens across the four sorghum–soil compartments and that organic fertilization regime significantly reduced the diversity and proportions of fungal plant pathogens in rhizosphere and bulk soils. We further found that the changes in fungal plant pathogens were driven more by resident bacterial and protistan communities than by soil physicochemical parameters. There was a significantly negative relationship between the diversity of fungal plant pathogens in the rhizosphere and bulk soils with sorghum yield and protein contents. Structural equation modeling revealed that long‐term organic fertilization regimes contributed to the suppression of fungal plant pathogens mainly through modulating the resident bacterial and protistan communities.ConclusionThese findings advance our understanding of the responses of fungal plant pathogens in crop microbiomes to fertilization regimes, with implications for more targeted strategies to manage the impacts of fungal pathogens on plant health and economic losses.

Amplicon sequencing reveals the arbuscular mycorrhizal fungal community composition in Cryptomeria japonica at one local site

ABSTRACT Arbuscular mycorrhizal fungi (AMF) colonize the plant root endosphere and extend the host’s resource network. However, little is known about the method to characterize the intraradical AMF communities of a specific tree species in forests. Therefore, we aimed at testing a method for characterizing and comparing the extra- and intraradical AMF communities of Cryptomeria japonica (Cupressaceae). In February 2020, we tracked and sampled roots from 5 target trees and the surrounding soil and confirmed their identity using plan DNA barcoding methods. After a microscopic analysis of mycorrhizal root colonization, we used Illumina amplicon sequencing to characterize the corresponding AMF communities. The C. japonica roots were colonized by AMF, displaying the Paris- and Arum-types of mycorrhizae. At 100% sequence identity, amplicon sequences of the small-subunit nuclear ribosomal RNA gene clustered into 155 operational taxonomic units (OTUs), 33 and 139 in the intra- and extraradical AMF communities, respectively, corresponding to three families and five genera. Nevertheless, only Acaulospora, Glomus, and Rhizophagus were detected in the root samples. The AMF communities did not significantly differ between the root and the surrounding soil, but we observed a significant nestedness pattern in the community. To avoid erroneous conclusions, combining plant DNA barcoding with amplicon sequencing is a reliable approach, which we recommend for future studies to describe the intraradical AMF community of a specific tree species in forests.

Epichloë Endophyte Infection Changes the Root Endosphere Microbial Community Composition of Leymus Chinensis Under Both Potted and Field Growth Conditions.

Epichloë endophytes can not only affect the growth and resistance of the host plant but also change the biotic and abiotic properties of the soil where the host is situated. Here, we used endophyte-infected (EI) and endophyte-free (EF) Leymus chinensis as plant materials, to study the microbial diversity and composition in the host root endosphere and rhizosphere soil under both pot and field conditions. The results showed that endophyte infection did not affect the diversity of either bacteria or fungi in the root zone. There were significant differences in both bacterial and fungal communities between the root endosphere and the rhizosphere, and between the field and the pot, while endophytes only affected root endosphere microbial communities. The bacterial families affected by endophyte infection changed from 29.07% under field conditions to 40% under pot conditions. In contrast, the fungal families affected by endophyte infection were maintained at nearly 50% under both field and pot conditions. That is to say, bacterial communities in the root endosphere were more strongly affected by environmental conditions, and in comparison, the fungal communities were more strongly affected by species specificity. Endophytes significantly affected the fungal community composition of the host root endosphere in both potted and field plants, only the effect was more obvious in potted plants. Endophyte infection increased the abundance of three fungal families (Thelebolaceae, Herpotrichiellaceae and Trimorphomycetaceae) under both field and potted conditions. In potted plants, endophytes also altered the dominant fungi from pathogenic Pleosporales to saprophytic Chaetomiaceae. Endophyte infection increased the relative abundance of arbuscular mycorrhizal fungi and saprophytic fungi, especially under potted conditions.Overall, endophytes significantly affected the fungal community composition of the host root endosphere in both potted and field plants. Endophytes had a greater impact on root endosphere microorganisms than the rhizosphere, a greater impact on fungal communities than bacteria, and a greater impact on root endosphere microorganisms under potted conditions than at field sites.