Dark Septate Endophytic Fungi Research Articles

A novel growth-promoting dark septate endophytic fungus improved drought tolerance in blueberries by modulating phytohormones and non-structural carbohydrates.

Drought is a significant global issue affecting agricultural production, and the utilization of beneficial rhizosphere microorganisms is one of the effective ways to increase the productivity of crops and forest under drought. In this study, we characterized a novel growth-promoting dark septate endophytes (DSE) fungus R16 derived from the blueberry roots. Hyphae or microsclerotia were visible within the epidermal or cortical cells of R16-colonized blueberry roots, which was consistent with the typical characteristics of DSE fungi. Inoculation with R16 promoted the growth of blueberry seedlings and the advantage over the control group was more significant under PEG-induced drought. Comparison of physiological indicators related to drought resistance between the inoculated and control groups was performed on the potted blueberry plants, including the chlorophyll content, net photosynthetic rate, root activities, MDA and H2O2 content, which indicated that R16 colonization mitigated drought injury in blueberry plants. We further analyzed the effects of R16 on phytohormones and non-structural carbohydrates (NSCs) to explore the mechanism of increased drought tolerance by R16 in blueberry seedlings. The results showed that except for the GA content, IAA, ZT and ABA varied significantly between the inoculated and control groups. SPS and S6PDH activities in mature leaves, the key enzymes responsible for sucrose and sorbitol synthesis, respectively, as well as SDH, SuSy, CWINV, HXK and FRK in roots, the key enzymes involved in the NSCs metabolism, showed significant differences between the inoculated and control groups before and after drought treatment. These results suggested that the positive effects of R16 colonization on the drought tolerance of blueberry seedlings are partially attributable to the regulation of phytohormone and sugar metabolism. This study provided valuable information for the research on the interaction between DSE fungi and host plants as well as the application of DSE preparations in agriculture.

Intraspecific diploidization of a halophyte root fungus drives heterosis

How organisms respond to environmental stress is a key topic in evolutionary biology. This study focused on the genomic evolution of Laburnicola rhizohalophila, a dark-septate endophytic fungus from roots of a halophyte. Chromosome-level assemblies were generated from five representative isolates from structured subpopulations. The data revealed significant genomic plasticity resulting from chromosomal polymorphisms created by fusion and fission events, known as dysploidy. Analyses of genomic features, phylogenomics, and macrosynteny have provided clear evidence for the origin of intraspecific diploid-like hybrids. Notably, one diploid phenotype stood out as an outlier and exhibited a conditional fitness advantage when exposed to a range of abiotic stresses compared with its parents. By comparing the gene expression patterns in each hybrid parent triad under the four growth conditions, the mechanisms underlying growth vigor were corroborated through an analysis of transgressively upregulated genes enriched in membrane glycerolipid biosynthesis and transmembrane transporter activity. In vitro assays suggested increased membrane integrity and lipid accumulation, as well as decreased malondialdehyde production under optimal salt conditions (0.3 M NaCl) in the hybrid. These attributes have been implicated in salinity tolerance. This study supports the notion that hybridization-induced genome doubling leads to the emergence of phenotypic innovations in an extremophilic endophyte.

Azospirillum brasilense Inoculation in a Maize–Urochloa–Rice Cropping System Promotes Soil Chemical and Biological Changes and Increases Productivity

Large quantities of cover crop residues in the soil, combined, or not, with the inoculation of seeds with diazotrophic bacteria, can increase organic matter (OM) and protect soil microorganisms, such as arbuscular mycorrhizal fungi (AMF) and dark septate endophytic (DSE) fungi. Thus, the use of these sustainable biotechnologies can benefit microbial interactions, soil fertility and rice production in the Brazilian Cerrado region. In this study, we evaluated the effects of maize and Urochloa ruziziensis, intercropped or individually, as cover crops and an inoculation of Azospirillum brasilense on the chemical (fertility) and biological (C–microbial biomass and C–CO2 released) attributes of soil and the effects of root colonization by AMF and DSE on the yield of rice grown in succession in highlands. The experiment was conducted under field conditions, in a typical dystrophic Red Oxisol. The experimental design consisted of randomized blocks arranged in strips, incorporating a combination of eight residual cover crops: ((1) maize, (2) maize–I (I = inoculation of seeds with A. brasilense), (3) Urochloa (U. ruziziensis), (4) Urochloa–I, (5) maize + Urochloa–I, (6) maize + Urochloa–I, (7) maize–I + Urochloa and (8) maize–I + Urochloa–I). This was accompanied by two treatments of rice as a successor crop (inoculated or not with A. brasilense), with four replicates, totaling 64 experimental units. A cover crop and rice seed inoculation prompted increases in OM and AMF relative to DSE, while the inoculation of rice, regardless of the cover crop treatment, increased the soil’s P content. The combination of maize + Urochloa–I and inoculated rice as the next crop generated increases in its sum of bases (SBs) and cation exchange capacity (CEC). There was a 19% increase in rice grain yields when the seed was inoculated.

Poaceascoma zborayi sp. nov. and Agrorhizomyces patris gen. et spec. nov. – Two novel dark septate endophytes colonizing wheat (Triticum aestivum) roots from a cropland in Hungary

In this study, we investigated two distinct new phylogenetic lineages of root-colonizing dark septate endophytic fungi colonizing wheat (Triticum aestivum) roots from a long-term agricultural experimental site in Hungary. According to four-locus (internal transcribed spacer, partial large and small subunit regions of nuclear ribosomal DNA, and partial translation elongation factor 1-alpha) phylogenetic analyses, the isolates belong to the Lentitheciaceae and Didymosphaeriaceae of the Pleosporales (Dothideomycetes). We studied the morphology and culture characteristics of the strains. We carried out in vitro resynthesis pot experiments with their original hosts and found no overall negative effect of the inoculation with different isolates of the new taxa. One of the lineages belonged to the genus Poaceascoma (Lentitheciaceae) and represented a novel species described here as Poaceascoma zborayi. We could describe conidia-like structures from this species. Isolates of the other lineage represented a monotypic novel genus in the Didymosphaeriaceae. Accordingly, the new genus, Agrorhizomyces, represented by the species A. patris, is introduced. Sterile, globose structures resembling immature sporocarps were detected. Sequence similarity searches indicated that P. zborayi might be widely distributed, while no sequence similar to A. patris was found outside the sampling area.

The coexistence of arbuscular mycorrhizal fungi and dark septate endophytes synergistically enhanced the cadmium tolerance of maize

IntroductionArbuscular mycorrhizal fungi (AMF) and dark septate endophytic fungi (DSEs) generally coexist in the roots of plants. However, our understanding of the effects of their coexistence on plant growth and stress resistance is limited.MethodsIn the present study, the effects of single and dual inoculation of AMF and DSE on the growth, photosynthetic physiology, glutathione (GSH) metabolism, endogenous hormones, and cadmium (Cd) content of maize under 25 mg•kg-1 Cd stress were investigated.ResultsCompared with that after the non-inoculation treatment, AMF+DSE co-inoculation significantly increased the photosynthetic rate (Pn) of maize leaves; promoted root GSH metabolism; increased the root GSH concentration and activity of γ-glutamyl cysteine synthase (γ-GCS), ATP sulfatase (ATPS) and sulfite reductase (SIR) by 215%, 117%, 50%, and 36%, respectively; and increased the concentration of endogenous hormones in roots, with increases in zeatin (ZR), indole-3 acetic acid (IAA), and abscisic acid (ABA) by 81%, 209%, and 72%, respectively. AMF inoculation, DSE inoculation and AMF+DSE co-inoculation significantly increased maize biomass, and single inoculation with AMF or DSE increased the Cd concentration in roots by 104% or 120%, respectively. Moreover, significant or highly significant positive correlations were observed between the contents of ZR, IAA, and ABA and the activities of γ-GCS, ATPS, and SIR and the glutathione (GSH) content. There were significant or highly significant positive interactions between AMF and DSE on the Pn of leaves, root GSH metabolism, and endogenous hormone contents according to two-way analysis of variance. Therefore, the coexistence of AMF and DSE synergistically enhanced the Cd tolerance of maize.

Dark septate endophyte Anteaglonium sp. T010 promotes biomass accumulation in poplar by regulating sucrose metabolism and hormones.

Plant biomass is a highly promising renewable feedstock for the production of biofuels, chemicals and materials. Enhancing the content of plant biomass through endophyte symbiosis can effectively reduce economic and technological barriers in industrial production. In this study, we found that symbiosis with the dark septate endophyte (DSE) Anteaglonium sp. T010 significantly promoted the growth of poplar trees and increased plant biomass, including cellulose, lignin and starch. To further investigate whether plant biomass was related to sucrose metabolism, we analyzed the levels of relevant sugars and enzyme activities. During the symbiosis of Anteaglonium sp. T010, sucrose, fructose and glucose levels in the stem of poplar decreased, while the content of intermediates such as glucose-6-phosphate (G6P), fructose-6-phosphate (F6P) and UDP-glucose (UDPG), and the activity of enzymes related to sucrose metabolism, including sucrose synthase (SUSY), cell wall invertase (CWINV), fructokinase (FRK) and hexokinase, increased. In addition, the contents of glucose, fructose, starch, and their intermediates G6P, F6P and UDPG, as well as the enzyme activities of SUSY, CWINV, neutral invertase and FRK in roots were increased, which ultimately led to the increase of root biomass. Besides that, during the symbiotic process of Anteaglonium sp. T010, there were significant changes in the expression levels of root-related hormones, which may promote changes in sucrose metabolism and consequently increase the plant biomass. Therefore, this study suggested that DSE fungi can increase the plant biomass synthesis capacity by regulating the carbohydrate allocation and sink strength in poplar.

Effects of root-colonizing fungi on pioneer Pinus thunbergii seedlings in primary successional volcanic mudflow on Kuchinoerabu Island, Japan.

Root-colonizing fungi, such as mycorrhizal fungi and dark septate endophyte fungi, are often found on pioneer plant species during early primary succession. However, little is known about which fungal species are responsible for the establishment of pioneer plants when these symbionts colonize simultaneously. We investigated the root-colonizing fungal communities of Pinus thunbergii that established prior to lichens, bryophytes, and short-lived herbaceous plants in a primary successional volcanic mudflow site on Kuchinoerabu Island, Japan. We collected a total of 54 current-year and 1- to 2-year-old seedlings. The colonization of root fungi was evaluated by direct observation of key structures (e.g., mantle, arbuscule, microsclerotia, and hyphae) and molecular analysis. Of the 34 current-year seedlings collected, only 12 individuals were colonized by ectomycorrhizal (ECM) fungi. By contrast, all 1- to 2-year-old seedlings were colonized by ECM fungi. Seedlings colonized by pine-specific ECM fungi, specifically Rhizopogon roseolus and Suillus granulatus, showed higher nitrogen and phosphorus contents in their needles compared to non-ECM seedlings. Arbuscular mycorrhizal fungi and dark septate endophyte fungi were found in only two and three individuals, respectively. The high density of mycophagous deer on Kuchinoerabu-jima may contribute to the favored dispersal of ECM fungi over other root-colonizing fungi. In conclusion, the seedling establishment of P. thunbergii at the volcanic mudflow may be largely supported by ECM fungi, with negligible effects of arbuscular mycorrhizal fungi and dark septate endophytes.

The potential of dark septate endhophyte fungus from white jabon (Neolamarckia cadamba (Roxb.) Bosser)

Endophytic fungi are one of the forest microbes that can be solutions for increasing the resistance of forest plants to environmental stress. Exploration and collection of endophytic fungi from the forest is important because the condition of the forest as a natural habitat for microbes has been disturbed due to degradation and deforestation. A potential plant species for forest and land rehabilitation is white jabon (Neolamarckia cadamba (Roxb.) Bosser). The research objective was to isolate and characterize endophytic fungi and to obtain the dark septate endhophyte from the roots of the white jabon which have the potential to increase plant growth. The fungus was isolated by surface sterilization method and then characterized and identified morphologically. Pathogenicity test was carried out to determine the pathogenicity of the fungus. The results of the study found ten isolates. Most of the isolated fungi showed sterile mycelia with septate hyphae, so they were not identified morphologically. The isolate of CPGS 3 isolates probably belonged to the genus Aureobasidium sp. CPGS 3, CPKR 6, and CPPS 11 isolates are candidates for dark septate endophyte fungi which have the potential to promote plant growth and not become pathogens in chinese cabbage (Brassica rapa).

Isolation, structural elucidation, and biological activity of a novel isocoumarin from the dark septate endophytic fungus Phialocephala fortinii.

A novel isocoumarin was isolated from the mycelia of the dark septate endophytic fungus Phialocephala fortinii. The chemical structure was determined to be 8-hydroxy-6-methoxy-3,7-dimethyl-1H-2-benzopyran-1-one based on mass spectrometry, 1H-nuclear magnetic resonance (NMR), and 13C-NMR spectroscopic analyses, including 2D-NMR experiments. The isolated compound inhibited root growth of Arabidopsis thaliana, suggesting its potential as a plant growth regulator.

The first report of dark septate endophytes from Indonesian Pinus merkusii and its symbiosis role as a plant growth promoter in nursery condition

Abstract. Akhir J, Herliyana EN, Surono, Budi SW. 2024. The first report of dark septate endophytes from Indonesian Pinus merkusii and its symbiosis role as a plant growth promoter in nursery condition. Biodiversitas 25: 312-321. To encourage the healthy growth of Pinus merkusii Jungh et de Vriese seedlings at the seedling stage, Dark Septate Endophytic (DSE) fungi were used as growth promoters. In this study, four DSE strains, i.e., Apls 1.5.3, Pls 32.1, Hs14.6a, and Hs14.6c isolated from P. merkusii roots, were tested for their ability to stimulate the growth of P. merkusii seedlings. After 14 weeks of incubation in nursery conditions, P. merkusii seedlings inoculated with four DSE strains experienced a higher increase in height and stem diameter when compared to the control treatment. Overall, the biomass results of P. merkusii seedlings treated with the DSE strains performed better than those of the control. Root colonization of P. merkusii seedlings showed that the 4 DSE strains significantly outperformed the control. The Hs14.6c strain outperformed the other strains and controls regarding nutrient (nitrogen) uptake. The findings of this study are the first to show that the DSE Apls 1.5.3 strain is similar to Cylindroccarpon, the Hs14.6a and Hs14.6c strains are similar to Cladophialophora sp., and the Pls 32.1 strain is similar to Oncopodiella trigonella based on identification results and phylogenetic trees and can be in symbiosis with seeds of P. merkusii, a pine species native to Indonesia.

Kemampuan Kapang Dark Septate Endophyte dari Akar Tanaman Aren dalam Menghambat Ganoderma sp.

Ganoderma is a fungal pathogen that can cause rot disease at the base of plant stems. This disease threatens oil palm production, especially in Southeast Asia. Trichoderma sp. fungi can control Basal Stem Rot disease in Ganoderma boninense but are ineffective. One solution that can be done to inhibit the growth of Ganoderma sp. is by using Dark Septate Endophyte (DSE) fungi. Research on DSE isolated from sugar palm (Arenga pinnata Merr.) has not been widely studied. The sugar palm plant is related to the oil palm plant in the Arecaceae family. This study aims to analyze the potential of DSE fungi from the roots of the sugar palm plant in inhibiting the pathogenic fungi Ganoderma sp. The stages of this research were isolation and purification of DSE fungi from sugar palm roots, DSE antagonists against Ganoderma sp., and DSE volatile compounds against Ganoderma sp. The results of isolation and purification showed that there were 18 DSE isolates grouped based on morphological similarities in the form of DSE fungi colony colors, where there were ten fungi isolates representing ten different colony colors, namely, isolate A.3.1 (1); A.3.2 (2); A.4.1 (2); A.4.1 (3); A.4.2; A.5.2; A.5.3; A.6.1(a); A.6.2(a); A.6.4(a). A total of 8 fungi isolates were tested for antagonists and volatile compound testing on Ganoderma sp. The results of the antagonist test showed that DSE A4.1(2) had the highest percentage of inhibition with a value of 36.12%, and isolated A6.2 had the highest percentage of inhibition and the lowest with a value of 15.65%. The testing results for volatile compounds showed that the isolate of DSE A4.2 had the highest percentage of inhibition against Ganoderma sp. at 18.25%. In comparison, the lowest inhibition percentage was obtained from DSE A5.2 fungi isolate with a value of 0.43%.
 
 Keywords: dark septate endophyte, ganoderma, sugar palm (Arenga pinnata Merr.)

Pervasive associations between dark septate endophytic fungi with tree root and soil microbiomes across Europe

Trees interact with a multitude of microbes through their roots and root symbionts such as mycorrhizal fungi and root endophytes. Here, we explore the role of fungal root symbionts as predictors of the soil and root-associated microbiomes of widespread broad-leaved trees across a European latitudinal gradient. Our results suggest that, alongside factors such as climate, soil, and vegetation properties, root colonization by ectomycorrhizal, arbuscular mycorrhizal, and dark septate endophytic fungi also shapes tree-associated microbiomes. Notably, the structure of root and soil microbiomes across our sites is more strongly and consistently associated with dark septate endophyte colonization than with mycorrhizal colonization and many abiotic factors. Root colonization by dark septate endophytes also has a consistent negative association with the relative abundance and diversity of nutrient cycling genes. Our study not only indicates that root-symbiotic interactions are an important factor structuring soil communities and functions in forest ecosystems, but also that the hitherto less studied dark septate endophytes are likely to be central players in these interactions.

Mineral fertilization impacts microbial activity and endophytic fungi but not microbial biomass in semiarid grasslands

Applications of mineral fertilizer to grasslands have become more frequent in recent decades to increase forage production. However, the impacts of mineral fertilizer on the soil microbiome is poorly understood in cold semiarid grassland ecosystems of Southern Patagonia, Argentina. Therefore, our objective was to analyze experimentally the influence of mineral nutrient fertilization (N, P, K, and NPK in combination) on soil microbial community attributes, such as microbial biomass carbon (MBC) and nitrogen (MBN), soil basal respiration (SBR), microbial metabolic coefficients, the colonization of endophytic fungi such as arbuscular mycorrhizal (AM) fungi, and dark septate endophytes (DSE), and aboveground plant productivity. Mineral fertilization with macronutrients (N, P, K, and NPK) decreased the SBR, qCO2, AM fungi and DSE fungi, but did not generate changes in MBC and MBN. The magnitude of these responses depends on years after fertilization. We found that soil microbiome was strongly dependent on a range of biotic and abiotic factors, such as growing season precipitation, aboveground plant biomass the relationship between the microbial biomass and microbial respiration, and between endophytic fungi and plants. This work improved our understanding of the soil microorganisms’ response to mineral fertilizer application and provides new insights into soil nutrient dynamics and ecosystem functioning.

The elusive bio-stimulatory function of Cladophialophora chaetospira SK51 to alleviate Fusarium wilt of strawberry

The highly virulent Fusarium oxysporum formae speciales (f.sp.) fragaria causes Fusarium wilt and significant losses in the strawberry agroindustry. The effective control strategies for this phytopathogen have yet to be developed. We aimed to evaluate the bioefficacy of root-colonizer dark septate endophytic fungi (DSEs) in controlling Fusarium wilt in simultaneous with biostimulation activities. Three out of nineteen tested isolates were selected because of their superior bioefficacy in regulating disease suppression and growth promotion. Notably, the highest level of disease suppression was marked at 90.48%, followed by 85.71% and 61.90% with the inoculation of these three selected isolates i.e., SK51, SK47, and SK48, respectively. The fungal isolates were identified based on partial SSU, LSU, and ITS as DSE fungus Cladophialophora chaetospira strain SK51, Exophiala sp. strain SK47, and E. pisciphila strain SK48. Our findings showed that C. chaetospira SK51 exhibited significant potential in promoting plant growth and suppressing diseases. It significantly enhanced various plant growth factors, such as the total plant biomass, the content of chlorophyll (SPAD), the formation of flower buds, and the development of fruits compared to both non-inoculated control and the other two DSE-inoculated plants. Our study provides new findings and perspectives on the use of the DSE, particularly C. chaetospira SK51 as a bioprotectant and biostimulant for enhancing the development, flower bud formation, and fruit development in strawberry plants.

Dark septate endophytic fungi associated with pioneer grass inhabiting volcanic deposits and their functions in promoting plant growth

Abstract. Growth of the pioneer grass Miscanthus condensatus, one of the first vegetation types to be established on volcanic deposits, is promoted by root-associated fungi, particularly dark septate endophytes (DSEs). Fungal taxa within DSEs colonize the root of Miscanthus condensatus in oligotrophic Andosol, and their function in plant growth promotion remains largely unknown. We, therefore, comprehensively assessed the composition of the DSE community associated with Miscanthus condensatus root in volcanic ecosystems using the approaches of both metabarcoding (next-generation sequencing) and isolation (culturing). Also, the promotion effects of DSEs on plant growth (rice as a proxy) were evaluated by inoculation of core isolates to rice roots. Here, we found the following: (i) 70 % of culturable fungi that colonized Miscanthus condensatus phylogenetically belonged to DSEs; (ii) seven orders were identified by both sequencing and culturing methods; and (iii) inoculation of DSE isolates (Phialocephala fortinii, P. helvetica, and Phialocephala sp.) validated their effects on rice growth, particularly under an extremely low pH condition (compared to the control without inoculation, rice biomass was enhanced 7.6-fold after inoculation of P. fortinii). This study helps improve our understanding of the community of Miscanthus condensatus-associated DSE fungi and their functions in promoting plant growth.

Dark septate endophyte inoculation improved Pb phytoremediation of Jatropha curcas and Reutealis trisperma on gold mine tailings

This study investigated the symbiotic potential of Jatropha curcas and Reutealis trisperma with two isolates of dark septate endophyte (DSE) fungi (Cladosporium sp. and Rhyzopycnis vagum) grown on gold mine tailings media based on their ability to remediate Pb and their morphological, physiological, and anatomical changes. The targeted plants were grown for 12 weeks on different media contained mixed soil and compost, gold mine tailings, and tailing with additional charcoal. The result showed that DSE inoculation increased the height of J. curcas up to 24.1% in contaminated soil compared to control treatment without DSE. All DSE fungi were able to colonize both root plant even under gold mine tailing treatment. DSE inoculation increased chlorophyll content of both plants ranging from 11% to 33% compared to the plants without DSE. Jatropha curcas inoculated with DSE had the potential to be used as phytoremediation plant with a phytoextraction mechanism indicated by higher translocation factor (TF) value. Meanwhile, the R. trisperma was able to be used for phytoremediation categorized as phytostabilization due to lower TF values. The results of this study highlighted the possible role of the DSE symbiotic with J. curcas and R. trisperma to improve the efficiency of phytoremediation in contaminated lands.

Mycorrhizal fungal communities associated with three metal accumulator plants growing in an abandoned Pb smelting factory.

Plants associated with mycorrhizal fungi has the ability to establish on metal-contaminated soils playing an important role in phytoremediation programs. The objective of this study was to examine the presence of arbuscular mycorrhizal fungi (AMF) (spores density, diversity, indicator species, and root colonization) and dark septate endophytic fungi (DSE fungal root colonization) in three metal accumulator plants (Sorghum halepense, Bidens pilosa, and Tagetes minuta) growing in soils with high Pb content. The Pb content in AMF spores and plant biomass were also assessed. Rhizosphere soil samples were taken from the three dominant plant species at six study sites surrounding the abandoned Pb smelter and one uncontaminated site. The three studied plants were colonized by AMF and DSE fungi. A total of 24 AMF morphospecies were present in the Pb-contaminated areas. The AMF indicator species in the control site (non-contaminated area) was Funneliformis mosseae and in the most contaminated site were Gigaspora decipiens and Denticustata biornata. There was an increase in mycorrhizal variables such as the number of AMF vesicles, spore number, Pb content in AMF spores and plant biomass and DSE colonization (in Sorghum) with increasing soil Pb contamination, but a decrease in AMF diversity and richness was found. For upcoming soil restoration projects, it is crucial to understand the mycorrhizal fungi as well as the plant community that has adapted to the highly contaminated environment.

First report of inhibitory abilities of dark septate endophytic fungi against white root rot disease on Hevea brasiliensis seedlings in nursery conditions

BackgroundThe dark septate endophytes (DSE) are endophytic and non-mycorrhizal fungi with the ability to impact and control some plant pathogens and promote plant growth. The aim of this study was to investigate the effectiveness of five different DSE fungal isolates in controlling white root rot disease (WRRD) caused by the plant pathogen, Rigidoporus microporus in Hevea brasiliensis in a nursery system. There are no previous reports on the role of DSE in controlling WRRD. In this study, the efficacy of five DSE isolates, including Acrocalymma vagum SBTBMDS 1, Clonostachys chloroleuca TMDS 2.1, Lasiodiplodia theobromae APDS 3.2, Penicillium oxalicum TMDS 3.2, and Fusarium falciforme TBMDS 2.4b, was tested for their ability to reduce the severity of WRRD in vivo.ResultsThe results showed that all the DSE isolates were able to inhibit R. microporus, leading to a decrease in the disease severity of WRRD, with percentages ranging from 7.50 to 17.5% and percentage of disease inhibition from 57.67 to 83.33% than the controls, which had a severity percentage of 45%. The TMDS3.2 isolate showed high efficacy in increasing the girth (137%) and height (63.3%) of H. brasiliensis seedlings, while the isolates of P. oxalicum TMDS 3.2 and F. falciforme TMDS 2.4b enhanced the dry weight (123 and 122%, respectively) than the control. Two isolates of P. oxacilum TMDS 3.2 and C. chloroleuca TMDS 2.1 increased the root volume (120 and 107%, respectively) than the control. Gas chromatography–mass spectrometry (GC–MS) analysis showed the ability of three selected DSE isolates, L. theobromae APDS 3.2, F. falciforme TBMDS 2.4b, and P. oxacilum TMDS 3.2, to produce acetic acid butyl methyl-phosphinoylmethyl ester and ethanone, 1-(4-methyl-1H(imidazol-2-yl)—that previously reported as antimicrobials.ConclusionThis study demonstrated that DSE fungal isolates had the potential to act as a biocontrol agent against R. microporus in H. Brasiliensis seedlings. In the future, the findings of this study could be utilized to prevent WRRD, one of the most serious problems in rubber plantations, in an environmentally friendly way by reducing the usage of fungicides.

Occurrence of dark septate endophytes in Phragmites australis in the Baiyang Lake and their resistance to Cd stress

Heavy metal pollution poses a serious hazard to human health, and microbial remediation of heavy metals in soil has been widely studied. A group of ascomycetes classified as dark septate endophytes (DSEs) colonize plant roots and benefit host plants under abiotic stress conditions. In this study, Phragmites australis, a common remediation plant in Baiyang Lake, was investigated. The root system and soil of P. australis were collected in typical heavy metal-contaminated sites, and the species diversity and community structure of DSEs in P. australis roots were studied. In addition, DSE strains were isolated, cultured, and tested for their tolerance to Cd stress. The results showed that DSEs occur extensively in P. australis roots, forming typical dark septate hyphae, with a total colonization rate of 19.7–83.1%. Morphological and ITS sequencing analyses were used to identify 10 DSE fungi in 9 genera. Among these fungi, 6 strains with considerable resistance to Cd stress were identified. The biomass values of Poaceascoma helicoides, Alternaria doliconidium, and Acrocalymma vagum strains increased as the Cd concentration increased. These results can not only help to understand plant-DSE interactions in wetland environments, but also provide a theoretical basis for making full use of DSE fungi to alleviate heavy metals in soil.

First Report of Tripartite Symbiosis Potential among Soybean, Bradyrhizobium japonicum, and Dark Septate Endophytes

Successful soybean and rhizobium interaction is characterized by the formation of root nodules. This symbiosis significantly affects the growth and yield of soybeans and has long been recognized as a key factor in sustainable agricultural systems. Naturally, soybeans could form a tripartite symbiotic relationship with rhizobium and arbuscular mycorrhizal fungi (AMF). However, there is no information regarding the symbiotic potential of soybean, nodulating bacteria, and dark septate endophytic (DSE) fungi. This study aims to delve into new tripartite symbiosis potential, shedding light on its efficacy in improving soybean growth while reducing environmental impacts. We examined the effect of incorporating two DSEs: Cladophialophora chaetospira SK51 (Cc) and Veronaeopsis simplex Y34 (Vs), into the classic soybean-rhizobium symbiosis. Under sterile conditions, the co-inoculation of DSEs with Bradyrhizobium japonicum IncB6 (Bj) significantly increased the nodule number and dry weight, leading to the acceleration of soybean vegetative growth. Soybean nodule numbers under co-inoculation treatments-CcBj and VsBj-were significantly increased by 77.6 and 43.6%, respectively, compared to the Bj treatment. Furthermore, under the CcBj and VsBj treatments, the soybean nodule dry mass was significantly increased by 455 and 363%, respectively, compared to Bj. This finding represents the first report of new beneficial tripartite symbiosis potential for soybean nodulation and vegetative growth.