Special Issue "Fungal Endophytes and Their Interactions with Plants"

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Plant Microbe Interactions".

Deadline for manuscript submissions: closed (31 January 2020).

Special Issue Editor

Dr. Kathryn Guthridge
E-Mail
Guest Editor
Agriculture Victoria, AgriBio, Centre for AgriBioscience, Victoria 3083, Australia

Special Issue Information

Dear Colleagues,

This Special Issue, ‘Fungal Endophytes and Their Interactions with Plants’ is all about endophytes and their unique interactions with their host plant. Living within every plant are endophytic microorganisms that, being part of the plant microbiome, play a major role in the host plant’s wellbeing. As smaller organisms with short life cycles, they are involved in the evolution of the host plant by taking part in the host’s adaptation to environmental stresses. Consequently, endophytes are often associated with enhanced tolerance to abiotic stresses and resistance to pests and diseases and have been exploited for enhanced plant performance in a range of different industries.

This Special Issue will cover all aspects of the host–endophyte interaction, including discovery/characterization of novel fungi that are endophytic, genetics and genomics of endophyte, the role of endophytes in the plant microbiome, discovery/characterization of endophyte-derived secondary compounds, and application of endophytes for enhanced plant performance. This Special Edition will also include any new developments in the field.

Dr. Kathryn Guthridge
Guest Editor

Manuscript Submission Information

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Keywords

  • endophytic fungus
  • endophyte–host interactions
  • endophyte genomics
  • endophytes as the plant microbiome
  • endophyte-derived secondary products
  • application of endophytes in industry
  • endophyte transcriptomics
  • symbiotum performance

Published Papers (19 papers)

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Open AccessArticle
A Symbiotic Approach to Generating Stress Tolerant Crops
Microorganisms 2021, 9(5), 920; https://doi.org/10.3390/microorganisms9050920 - 25 Apr 2021
Viewed by 192
Abstract
Studies were undertaken to determine if fungal endophytes from plants in stressful habitats could be commercialized to generate climate resilient crop plants. Fungal endophytes were isolated from weedy rice plants and grasses from South Korea and the USA, respectively. Endophytes (Curvularia brachyspora [...] Read more.
Studies were undertaken to determine if fungal endophytes from plants in stressful habitats could be commercialized to generate climate resilient crop plants. Fungal endophytes were isolated from weedy rice plants and grasses from South Korea and the USA, respectively. Endophytes (Curvularia brachyspora and Fusarium asiaticum) from weedy rice plants from high salt or drought stressed habitats in South Korea conferred salt and drought stress tolerance to weedy rice and commercial varieties reflective of the habitats from which they were isolated. Fungal endophytes isolated from grasses in arid habitats of the USA were identified as Trichoderma harzianum and conferred drought and heat stress tolerance to monocots and eudicots. Two T. harzianum isolates were exposed to UV mutagenesis to derive strains resistant to fungicides in seed treatment plant protection packages. Three strains that collectively had resistance to commonly used fungicides were used for field testing. The three-strain mixture (ThSM3a) increased crop yields proportionally to the level of stress plants experienced with average yields up to 52% under high and 3–5% in low stress conditions. This study demonstrates fungal endophytes can be developed as viable commercial tools for rapidly generating climate resilient crops to enhance agricultural sustainability. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Effects of Lentil Genotype on the Colonization of Beneficial Trichoderma Species and Biocontrol of Aphanomyces Root Rot
Microorganisms 2020, 8(9), 1290; https://doi.org/10.3390/microorganisms8091290 - 24 Aug 2020
Viewed by 564
Abstract
Trichoderma species are opportunistic plant symbionts that are common in the root and rhizosphere ecosystems. Many Trichoderma species may enhance plant growth, nutrient acquisition, and disease resistance, and for these reasons, they are widely used in agriculture as biofertilizers or biocontrol agents. Host [...] Read more.
Trichoderma species are opportunistic plant symbionts that are common in the root and rhizosphere ecosystems. Many Trichoderma species may enhance plant growth, nutrient acquisition, and disease resistance, and for these reasons, they are widely used in agriculture as biofertilizers or biocontrol agents. Host plant genotype and other microorganisms, such as root pathogens, may influence the efficacy of Trichoderma inoculants. Aphanomyces euteiches is an important soil-borne oomycete in western Canada that causes root rot in legume crops such as lentil and pea, and there is not yet any significantly resistant varieties or effective treatments available to control the disease. In this study, the composition of root-associated fungal communities and the abundance of Trichoderma species, T. harzianum strain T-22 and T. virens strain G41, was determined in the roots of eight Lens genotypes based on internal transcribed spacer (ITS) Illumina MiSeq paired-end sequencing, both in the presence and the absence of the root rot pathogen Aphanomyces euteiches. Biocontrol effects of T. harzianum on A. euteiches was also examined. Significant genotypic variations were observed in the composition of root-associated fungal communities and the abundance of the different Trichoderma species in the lentil roots. The presence of A. euteiches altered the composition of Trichoderma found associated to the lentil genotypes. Biocontrol of A. euteiches by T. harzianum T22 species was observed in vitro and positive correlations between the abundance of Trichoderma and plant root and shoot biomass were observed in vivo. These findings revealed that lentil genotype and infection by the phytopathogen A. euteiches greatly influenced the colonization of root-associated fungi and the abundance of the Trichoderma species, as well as the effect on plant growth promotion. The multipartite interactions observed among lentil genotypes, Trichoderma species and A. euteiches suggest possibilities to select compatible host-beneficial microbe combinations in lentil breeding programs and to develop application strategies to harness the beneficial effects of Trichoderma inoculants in sustainable crop production systems. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Root Herbivory: Grass Species, Epichloë Endophytes and Moisture Status Make a Difference
Microorganisms 2020, 8(7), 997; https://doi.org/10.3390/microorganisms8070997 - 03 Jul 2020
Cited by 1 | Viewed by 696
Abstract
The root-feeding scarab insect Costelytra giveni causes severe damage to pasture ecosystems in New Zealand. Loline alkaloids produced by some Epichloë endophytes deter this insect. In two experiments, tall fescue infected with E. coenophiala, strain AR584, and endophyte-free (Nil) controls were subjected [...] Read more.
The root-feeding scarab insect Costelytra giveni causes severe damage to pasture ecosystems in New Zealand. Loline alkaloids produced by some Epichloë endophytes deter this insect. In two experiments, tall fescue infected with E. coenophiala, strain AR584, and endophyte-free (Nil) controls were subjected to pulse drought stress (DS) or well-watered conditions (WW). The second experiment also included meadow fescue infected with E. uncinata. After 4–6 weeks exposure to the different conditions, roots were excised and fed to C. giveni larvae for 7 days. Relative root consumption (RC), frass production, and relative weight change (RWC) of larvae were measured and the loline content of roots determined. RC and frass output were higher for larvae feeding on Nil DS tall fescue than WW and reduced by AR584. RWC was also greater on DS than on WW Nil plants but reduced by endophyte only in DS plants. RC, frass output, and RWC of larvae were reduced by endophyte in DS and WW meadow fescue, but the effect was greater for WW plants. Loline alkaloid concentration in roots was significantly higher in DS than WW tall fescue in Experiment I but higher in WW than DS meadow fescue in Experiment II. These experiments have demonstrated that moisture status interacts with endophyte to differentially affect root herbivory in tall fescue and meadow fescue. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Novel Antifungal Activity of Lolium-Associated Epichloë Endophytes
Microorganisms 2020, 8(6), 955; https://doi.org/10.3390/microorganisms8060955 - 24 Jun 2020
Cited by 1 | Viewed by 807
Abstract
Asexual Epichloë spp. fungal endophytes have been extensively studied for their functional secondary metabolite production. Historically, research mostly focused on understanding toxicity of endophyte-derived compounds on grazing livestock. However, endophyte-derived compounds also provide protection against invertebrate pests, disease, and other environmental stresses, which [...] Read more.
Asexual Epichloë spp. fungal endophytes have been extensively studied for their functional secondary metabolite production. Historically, research mostly focused on understanding toxicity of endophyte-derived compounds on grazing livestock. However, endophyte-derived compounds also provide protection against invertebrate pests, disease, and other environmental stresses, which is important for ensuring yield and persistence of pastures. A preliminary screen of 30 strains using an in vitro dual culture bioassay identified 18 endophyte strains with antifungal activity. The novel strains NEA12, NEA21, and NEA23 were selected for further investigation as they are also known to produce alkaloids associated with protection against insect pests. Antifungal activity of selected endophyte strains was confirmed against three grass pathogens, Ceratobasidium sp., Dreschlera sp., and Fusarium sp., using independent isolates in an in vitro bioassay. NEA21 and NEA23 showed potent activity against Ceratobasidium sp. and NEA12 showed moderate inhibition against all three pathogens. Crude extracts from liquid cultures of NEA12 and NEA23 also inhibited growth of the phytopathogens Ceratobasidium sp. and Fusarium sp. and provided evidence that the compounds of interest are stable, constitutively expressed, and secreted. Comparative analysis of the in vitro and in planta metabolome of NEA12 and NEA23 using LCMS profile data revealed individual metabolites unique to each strain that are present in vitro and in planta. These compounds are the best candidates for the differential bioactivity observed for each strain. Novel endophyte strains show promise for endophyte-mediated control of phytopathogens impacting Lolium spp. pasture production and animal welfare. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Determination of Loline Alkaloids and Mycelial Biomass in Endophyte-Infected Schedonorus pratensis by Near-Infrared Spectroscopy and Chemometrics
Microorganisms 2020, 8(5), 776; https://doi.org/10.3390/microorganisms8050776 - 21 May 2020
Cited by 1 | Viewed by 1257
Abstract
Near infrared spectroscopy (NIRS) is an accurate, fast and nondestructive technique whose use in predicting forage quality has become increasingly relevant in recent decades. Epichloë-infected grass varieties are commonly used in areas with high pest pressure due to their better performances compared [...] Read more.
Near infrared spectroscopy (NIRS) is an accurate, fast and nondestructive technique whose use in predicting forage quality has become increasingly relevant in recent decades. Epichloë-infected grass varieties are commonly used in areas with high pest pressure due to their better performances compared to endophyte-free varieties. The insect resistance of Epichloë-infected grasses has been associated with four main groups of endophyte secondary metabolites: ergot alkaloids, indole-diterpenes, lolines and peramine. Concentrations of these alkaloids are usually measured with high performance liquid chromatography or gas chromatography analysis, which are accurate methods but relatively expensive and laborious. In this paper, we developed a rapid method based on NIRS to detect and quantify loline alkaloids in wild accessions of Schedonorus pratensis infected with the fungal endophyte Epichloë uncinata. The quantitative NIR equations obtained by modified partial least squares algorithm had coefficients of correlation of 0.90, 0.78, 0.85, 0.90 for N-acetylloline, N-acetylnorloline and N-formylloline and the sum of the three, respectively. The acquired NIR spectra were also used for developing an equation to predict in planta fungal biomass with a coefficient of correlation of 0.75. These results showed that the use of NIRS and chemometrics allows the quantification of loline alkaloids and mycelial biomass in a heterogeneous set of endophyte-infected meadow fescue samples. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Growth and Behavior of North American Microbes on Phragmites australis Leaves
Microorganisms 2020, 8(5), 690; https://doi.org/10.3390/microorganisms8050690 - 08 May 2020
Cited by 2 | Viewed by 820
Abstract
Phragmites australis subsp. australis is a cosmopolitan wetland grass that is invasive in many regions of the world, including North America, where it co-occurs with the closely related Phragmites australis subsp. americanus. Because the difference in invasive behavior is unlikely to be [...] Read more.
Phragmites australis subsp. australis is a cosmopolitan wetland grass that is invasive in many regions of the world, including North America, where it co-occurs with the closely related Phragmites australis subsp. americanus. Because the difference in invasive behavior is unlikely to be related to physiological differences, we hypothesize that interactions with unique members of their microbiomes may significantly affect the behavior of each subspecies. Therefore, we systematically inoculated both plant lineages with a diverse array of 162 fungal and bacterial isolates to determine which could (1) differentiate between Phragmites hosts, (2) infect leaves at various stages of development, or (3) obtain plant-based carbon saprophytically. We found that many of the microbes isolated from Phragmites leaves behave as saprophytes. Only 1% (two taxa) were determined to be strong pathogens, 12% (20 taxa) were weakly pathogenic, and the remaining 87% were nonpathogenic. None of the isolates clearly discriminated between host plant lineages, and the Phragmites cuticle was shown to be a strong nonspecific barrier to infection. These results largely agree with the broad body of literature on leaf-associated phyllosphere microbes in Phragmites. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Characterization of the Plant Growth-Promoting Activities of Endophytic Fungi Isolated from Sophora flavescens
Microorganisms 2020, 8(5), 683; https://doi.org/10.3390/microorganisms8050683 - 07 May 2020
Cited by 6 | Viewed by 1375
Abstract
Endophytic fungi in symbiotic association with their host plant are well known to improve plant growth and reduce the adverse effects of both biotic and abiotic stresses. Therefore, fungal endophytes are beginning to receive increased attention in an effort to find growth-promoting strains [...] Read more.
Endophytic fungi in symbiotic association with their host plant are well known to improve plant growth and reduce the adverse effects of both biotic and abiotic stresses. Therefore, fungal endophytes are beginning to receive increased attention in an effort to find growth-promoting strains that could be applied to enhance crop yield and quality. In our study, the plant growth-promoting activities of endophytic fungi isolated from various parts of Sophora flavescens (a medicinally important plant in Mongolia and China) have been revealed and investigated. Fungal isolates were identified using molecular taxonomical methods, while their plant growth-promoting abilities were evaluated in plate assays. Altogether, 15 strains were isolated, representing the genera Alternaria, Didymella, Fusarium and Xylogone. Five of the isolates possessed phosphate solubilization activities and twelve secreted siderophores, while all of them were able to produce indoleacetic acid (IAA) in the presence or absence of tryptophan. The endogenous and exogenous accumulation of IAA were also monitored in liquid cultures using the HPLC-MS/MS technique to refine the plate assay results. Furthermore, for the highest IAA producer fungi, the effects of their extracts were also examined in plant bioassays. In these tests, the primary root lengths of the model Arabidopsis thaliana were increased in several cases, while the biomasses were significantly lower than the control IAA treatment. Significant alterations have also been detected in the photosynthetic pigment (chlorophyll-a, -b and carotenoids) content due to the fungal extract treatments, but these changes did not show any specific trends. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Unravelling the Role of Melanin in Cd and Zn Tolerance and Accumulation of Three Dark Septate Endophytic Species
Microorganisms 2020, 8(4), 537; https://doi.org/10.3390/microorganisms8040537 - 08 Apr 2020
Cited by 3 | Viewed by 1345
Abstract
Dark septate endophytes (DSEs) are often trace element (TE)-tolerant fungi and are abundant in TE-polluted environments. The production of melanin, a black polymer found in cell walls, was hypothesized by several authors to play a role in the TE tolerance of DSEs. To [...] Read more.
Dark septate endophytes (DSEs) are often trace element (TE)-tolerant fungi and are abundant in TE-polluted environments. The production of melanin, a black polymer found in cell walls, was hypothesized by several authors to play a role in the TE tolerance of DSEs. To test this hypothesis, we established a series of experiments using albino strains and melanin inhibitors and examined the responses to Cd and Zn. Six DSEs belonging to genera Cadophora sp., Leptodontidium sp. and Phialophora mustea, were evaluated. The strains mainly produced 1,8-dihydroxynaphthalene (DHN) melanin whereas 3,4-dihydroxyphenylalanin melanin was also synthetized. Cd and Zn decreased melanin synthesis in most of the strains. A reduction in melanin concentration in hyphae through the use of tricyclazole, an inhibitor of DHN-melanin synthesis, did not reduce the tolerance of the strains to Cd and Zn. Similarly, albino mutants of Leptodontidium sp. were not more sensitive to Cd and Zn than the WT strain. Moreover, tricyclazole-treated colonies accumulated less Cd but more Zn compared to untreated colonies. The Cd and Zn contents of Leptodontidium albino strains were variable and similar to that of the WT. The results suggest that melanin production is not an important functional trait that contributes to Cd and Zn tolerance, but might contribute to Cd accumulation. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Epichloë Endophyte Infection Rates and Alkaloid Content in Commercially Available Grass Seed Mixtures in Europe
Microorganisms 2020, 8(4), 498; https://doi.org/10.3390/microorganisms8040498 - 31 Mar 2020
Cited by 3 | Viewed by 2654
Abstract
Fungal endophytes of the genus Epichloë live symbiotically in cool season grass species and can produce alkaloids toxic to insects and vertebrates, yet reports of intoxication of grazing animals have been rare in Europe in contrast to overseas. However, due to the beneficial [...] Read more.
Fungal endophytes of the genus Epichloë live symbiotically in cool season grass species and can produce alkaloids toxic to insects and vertebrates, yet reports of intoxication of grazing animals have been rare in Europe in contrast to overseas. However, due to the beneficial resistance traits observed in Epichloë infected grasses, the inclusion of Epichloë in seed mixtures might become increasingly advantageous. Despite the toxicity of fungal alkaloids, European seed mixtures are rarely tested for Epichloë infection and their infection status is unknown for consumers. In this study, we tested 24 commercially available seed mixtures for their infection rates with Epichloë endophytes and measured the concentrations of the alkaloids ergovaline, lolitrem B, paxilline, and peramine. We detected Epichloë infections in six seed mixtures, and four contained vertebrate and insect toxic alkaloids typical for Epichloë festucae var. lolii infecting Lolium perenne. As Epichloë infected seed mixtures can harm livestock, when infected grasses become dominant in the seeded grasslands, we recommend seed producers to test and communicate Epichloë infection status or avoiding Epichloë infected seed mixtures. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
Open AccessArticle
Agroforestry Management Systems Drive the Composition, Diversity, and Function of Fungal and Bacterial Endophyte Communities in Theobroma Cacao Leaves
Microorganisms 2020, 8(3), 405; https://doi.org/10.3390/microorganisms8030405 - 13 Mar 2020
Cited by 5 | Viewed by 1373
Abstract
Cacao (Theobroma cacao L.) is one of the most economically important crops worldwide. Despite the important role of endophytes for plant growth and health, very little is known about the effect of agroforestry management systems on the endophyte communities of T. cacao [...] Read more.
Cacao (Theobroma cacao L.) is one of the most economically important crops worldwide. Despite the important role of endophytes for plant growth and health, very little is known about the effect of agroforestry management systems on the endophyte communities of T. cacao. To close this knowledge gap, we investigated the diversity, community composition, and function of bacterial and fungal endophytes in the leaves of T. cacao trees growing in five major cacao-growing regions in the central region of Cameroon using DNA metabarcoding. Fungal but not bacterial alpha diversity measures differed significantly between the agroforestry management systems. Interestingly, less managed home-garden cacao forests harbored the lowest fungal richness and diversity. Our results suggest that the composition of bacterial and fungal endophyte communities is predominantly affected by agroforestry management systems and, to a lesser extent, by environmental properties. The core microbiome detected comprised important fungal phytopathogens, such as Lasiodiplodia species. Several predicted pathways of bacterial endophytes and functional guilds of fungal endophytes differed between the agroforest systems which might be attributed to bacteria and fungi specifically associated with a single agroforest. Our results provide the basis for future studies on foliar fungal and bacterial endophytes of T. cacao and their responsiveness towards agroforestry management systems. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Characterization of Fungal Endophytes Isolated from the Metal Hyperaccumulator Plant Vachellia farnesiana Growing in Mine Tailings
Microorganisms 2020, 8(2), 226; https://doi.org/10.3390/microorganisms8020226 - 08 Feb 2020
Cited by 2 | Viewed by 1068
Abstract
Heavy metal pollution has become an environmental and health problem worldwide. With the aim of finding novel strategies for metal bioremediation, endophytic fungi from the heavy metal hyperaccumulator plant Vachellia farnesiana were isolated and characterized. The plants were growing in mine tailings, rich [...] Read more.
Heavy metal pollution has become an environmental and health problem worldwide. With the aim of finding novel strategies for metal bioremediation, endophytic fungi from the heavy metal hyperaccumulator plant Vachellia farnesiana were isolated and characterized. The plants were growing in mine tailings, rich in Zn, Pb, and Cu. Morphological and phylogenetic analyses indicated that the fungal strains belonged to Neocosmospora and Aspergillus genera. The Neocosmospora isolate belongs to the Fusarium solani species complex (FSSC) that groups phytopathogen species. However, in this case the plants from which it was isolated did not show any signs of disease. Both fungal strains were able to remove significant amounts of heavy metals from liquid cultures, either in a mixture of the three metals or each metal in a single culture. In response to lead exposure, the Neocosmospora sp. strain secreted specific novel phenolic compounds other than anthraquinones or naphtoquinones, which have been described in similar situations. The Aspergillus sp. dropped the pH in the medium. High-performance liquid chromatography determinations indicated that this strain secreted mainly glutamic acid in response to lead, a novel mechanism, which has not been reported elsewhere. Malic and succinic acids were also produced in response to lead exposure. Possibly, glutamic and succinic acids (synthesized in the Krebs cycle) can be used to cope with metal toxicity due to the plant providing photosynthates to the fungus. These fungi showed the potential to be used for bioremediation or restoration of metal-polluted environments. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Removal of Soil Microbes Alters Interspecific Competitiveness of Epichloë Endophyte-Infected over Endophyte-Free Leymus chinensis
Microorganisms 2020, 8(2), 219; https://doi.org/10.3390/microorganisms8020219 - 06 Feb 2020
Viewed by 613
Abstract
Epichloë endophytes may not only affect the growth and resistances of host grasses, but may also affect soil environment including soil microbes. Can Epichloë endophyte-mediated modification of soil microbes affect the competitive ability of host grasses? In this study, we tested whether Epichloë [...] Read more.
Epichloë endophytes may not only affect the growth and resistances of host grasses, but may also affect soil environment including soil microbes. Can Epichloë endophyte-mediated modification of soil microbes affect the competitive ability of host grasses? In this study, we tested whether Epichloë endophytes and soil microbes alter intraspecific competition between Epichloë endophyte-colonized (EI) and endophyte-free (EF) Leymus chinensis and interspecific competition between L. chinensis and Stipa krylovii. The results demonstrated that Epichloë endophyte colonization significantly enhanced the intraspecific competitive ability of L. chinensis and that this beneficial effect was not affected by soil microbes. Under interspecific competition, however, significant interactions between Epichloë endophytes and soil microbes were observed. The effect of Epichloë endophytes on interspecific competitiveness of the host changed from positive to neutral with soil microbe removal. Here higher mycorrhizal colonization rates probably contributed to interspecific competitive advantages of EI over EF L. chinensis. Our result suggests that Epichloë endophytes can influence the competitive ability of the host through plant soil feedbacks from the currently competing plant species. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Antifungal Activity of Beauveria bassiana Endophyte against Botrytis cinerea in Two Solanaceae Crops
Microorganisms 2020, 8(1), 65; https://doi.org/10.3390/microorganisms8010065 - 31 Dec 2019
Cited by 8 | Viewed by 1481
Abstract
Botrytis cinerea causes substantial losses in tomato and chili pepper crops worldwide. Endophytes have shown the potential for the biological control of diseases. The colonization ability of native endophyte strains of Beauveria bassiana and their antifungal effect against B. cinerea were evaluated in [...] Read more.
Botrytis cinerea causes substantial losses in tomato and chili pepper crops worldwide. Endophytes have shown the potential for the biological control of diseases. The colonization ability of native endophyte strains of Beauveria bassiana and their antifungal effect against B. cinerea were evaluated in Solanaceae crops. Root drenching with B. bassiana was applied, and endophytic colonization capacity in roots, stems, and leaves was determined. The antagonistic activity was evaluated using in vitro dual culture and also plants by drenching the endophyte on the root and by pathogen inoculation in the leaves. Ten native strains were endophytes of tomato, and eight were endophytes of chili pepper. All strains showed significant in vitro antagonism against B. cinerea (30–36%). A high antifungal effect was observed, and strains RGM547 and RGM644 showed the lowest percentage of the surface affected by the pathogen. Native strains of B. bassiana colonized tomato and chili pepper tissues and provided important levels of antagonism against B. cinerea. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Generation of Epichloë Strains Expressing Fluorescent Proteins Suitable for Studying Host-Endophyte Interactions and Characterisation of a T-DNA Integration Event
Microorganisms 2020, 8(1), 54; https://doi.org/10.3390/microorganisms8010054 - 27 Dec 2019
Cited by 1 | Viewed by 777
Abstract
Methods for the identification and localisation of endophytic fungi are required to study the establishment, development, and progression of host-symbiont interactions, as visible reactions or disease symptoms are generally absent from host plants. Fluorescent proteins have proved valuable as reporter gene products, allowing [...] Read more.
Methods for the identification and localisation of endophytic fungi are required to study the establishment, development, and progression of host-symbiont interactions, as visible reactions or disease symptoms are generally absent from host plants. Fluorescent proteins have proved valuable as reporter gene products, allowing non-invasive detection in living cells. This study reports the introduction of genes for two fluorescent proteins, green fluorescent protein (GFP) and red fluorescent protein, DsRed, into the genomes of two distinct perennial ryegrass (Lolium perenne L.)-associated Epichloë endophyte strains using A. tumefaciens-mediated transformation. Comprehensive characterisation of reporter gene-containing endophyte strains was performed using molecular genetic, phenotypic, and bioinformatic tools. A combination of long read and short read sequencing of a selected transformant identified a single complex T-DNA insert of 35,530 bp containing multiple T-DNAs linked together. This approach allowed for comprehensive characterisation of T-DNA integration to single-base resolution, while revealing the unanticipated nature of T-DNA integration in the transformant analysed. These reporter gene endophyte strains were able to establish and maintain stable symbiotum with the host. In addition, the same endophyte strain labelled with two different fluorescent proteins were able to cohabit the same plant. This knowledge can be used to provide the basis to develop strategies to gain new insights into the host-endophyte interaction through independent and simultaneous monitoring in planta throughout its life cycle in greater detail. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Transcriptome Analysis of Choke Stroma and Asymptomatic Inflorescence Tissues Reveals Changes in Gene Expression in Both Epichloë festucae and Its Host Plant Festuca rubra subsp. rubra
Microorganisms 2019, 7(11), 567; https://doi.org/10.3390/microorganisms7110567 - 16 Nov 2019
Cited by 1 | Viewed by 866
Abstract
Many cool-season grasses have symbiotic relationships with Epichloë (Ascomycota, Clavicipitaceae) fungal endophytes that inhabit the intercellular spaces of the above-ground parts of the host plants. The presence of the Epichloë endophytes is generally beneficial to the hosts due to enhanced tolerance to biotic [...] Read more.
Many cool-season grasses have symbiotic relationships with Epichloë (Ascomycota, Clavicipitaceae) fungal endophytes that inhabit the intercellular spaces of the above-ground parts of the host plants. The presence of the Epichloë endophytes is generally beneficial to the hosts due to enhanced tolerance to biotic and abiotic stresses conferred by the endophytes. Many Epichloë spp. are asexual, and those infections always remain asymptomatic. However, some Epichloë spp. have a sexual stage and produce a macroscopic fruiting body, a stroma, that envelops the developing inflorescence causing a syndrome termed “choke disease”. Here, we report a fungal and plant gene expression analysis of choke stroma tissue and asymptomatic inflorescence tissue of Epichloë festucae-infected strong creeping red fescue (Festuca rubra subsp. rubra). Hundreds of fungal genes and over 10% of the plant genes were differentially expressed when comparing the two tissue types. The differentially expressed fungal genes in the choke stroma tissue indicated a change in carbohydrate and lipid metabolism, as well as a change in expression of numerous genes for candidate effector proteins. Plant stress-related genes were up-regulated in the stroma tissue, suggesting the plant host was responding to the epiphytic stage of E. festucae as a pathogen. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessArticle
Analysis of the Indole Diterpene Gene Cluster for Biosynthesis of the Epoxy-Janthitrems in Epichloë Endophytes
Microorganisms 2019, 7(11), 560; https://doi.org/10.3390/microorganisms7110560 - 13 Nov 2019
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Abstract
Epoxy-janthitrems are a class of indole diterpenes with structural similarity to lolitrem B. Two taxa of asexual Epichloë endophytes have been reported to produce epoxy-janthitrems, LpTG-3 (Lolium perenne Taxonomic Group 3; e.g., NEA12) and LpTG-4 (e.g., E1). Epichloë epoxy-janthitrems are [...] Read more.
Epoxy-janthitrems are a class of indole diterpenes with structural similarity to lolitrem B. Two taxa of asexual Epichloë endophytes have been reported to produce epoxy-janthitrems, LpTG-3 (Lolium perenne Taxonomic Group 3; e.g., NEA12) and LpTG-4 (e.g., E1). Epichloë epoxy-janthitrems are not well understood, the biosynthetic pathway and associated gene complement have not been described and while the literature suggests they are associated with superior protection against pasture insect pests and are tremorgenic in grazing mammals, these properties have not been confirmed using isolated and purified compounds. Whole genome sequence analysis was used to identify candidate genes for epoxy-janthitrem biosynthesis that are unique to epoxy-janthitrem producing strains of Epichloë. A gene, jtmD, was identified with homology to aromatic prenyl transferases involved in synthesis of indole diterpenes. The location of the epoxy-janthitrem biosynthesis gene cluster (JTM locus) was determined in the assembled nuclear genomes of NEA12 and E1. The JTM locus contains cluster 1 and cluster 2 of the lolitrem B biosynthesis gene cluster (LTM locus), as well as four genes jtmD, jtmO, jtm01, and jtm02 that are unique to Epichloë spp. that produce epoxy-janthitrems. Expression of each of the genes identified was confirmed using transcriptome analysis of perennial ryegrass-NEA12 and perennial ryegrass-E1 symbiota. Sequence analysis confirmed the genes are functionally similar to those involved in biosynthesis of related indole diterpene compounds. RNAi silencing of jtmD and in planta assessment in host-endophyte associations confirms the role of jtmD in epoxy-janthitrem production. Using LCMS/MS technologies, a biosynthetic pathway for the production of epoxy-janthitrems I–IV in Epichloë endophytes is proposed. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessReview
Do Foliar Endophytes Matter in Litter Decomposition?
Microorganisms 2020, 8(3), 446; https://doi.org/10.3390/microorganisms8030446 - 21 Mar 2020
Cited by 3 | Viewed by 1147
Abstract
Litter decomposition rates are affected by a variety of abiotic and biotic factors, including the presence of fungal endophytes in host plant tissues. This review broadly analyzes the findings of 67 studies on the roles of foliar endophytes in litter decomposition, and their [...] Read more.
Litter decomposition rates are affected by a variety of abiotic and biotic factors, including the presence of fungal endophytes in host plant tissues. This review broadly analyzes the findings of 67 studies on the roles of foliar endophytes in litter decomposition, and their effects on decomposition rates. From 29 studies and 1 review, we compiled a comprehensive table of 710 leaf-associated fungal taxa, including the type of tissue these taxa were associated with and isolated from, whether they were reported as endo- or epiphytic, and whether they had reported saprophytic abilities. Aquatic (i.e., in-stream) decomposition studies of endophyte-affected litter were significantly under-represented in the search results (p < 0.0001). Indicator species analyses revealed that different groups of fungal endophytes were significantly associated with cool or tropical climates, as well as specific plant host genera (p < 0.05). Finally, we argue that host plant and endophyte interactions can significantly influence litter decomposition rates and should be considered when interpreting results from both terrestrial and in-stream litter decomposition experiments. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessReview
Cannabis Microbiome and the Role of Endophytes in Modulating the Production of Secondary Metabolites: An Overview
Microorganisms 2020, 8(3), 355; https://doi.org/10.3390/microorganisms8030355 - 02 Mar 2020
Cited by 8 | Viewed by 2840
Abstract
Plants, including cannabis (Cannabis sativa subsp. sativa), host distinct beneficial microbial communities on and inside their tissues and organs, including seeds. They contribute to plant growth, facilitating mineral nutrient uptake, inducing defence resistance against pathogens, and modulating the production of plant [...] Read more.
Plants, including cannabis (Cannabis sativa subsp. sativa), host distinct beneficial microbial communities on and inside their tissues and organs, including seeds. They contribute to plant growth, facilitating mineral nutrient uptake, inducing defence resistance against pathogens, and modulating the production of plant secondary metabolites. Understanding the microbial partnerships with cannabis has the potential to affect the agricultural practices by improving plant fitness and the yield of cannabinoids. Little is known about this beneficial cannabis-microbe partnership, and the complex relationship between the endogenous microbes associated with various tissues of the plant, and the role that cannabis may play in supporting or enhancing them. This review will consider cannabis microbiota studies and the effects of endophytes on the elicitation of secondary metabolite production in cannabis plants. The review aims to shed light on the importance of the cannabis microbiome and how cannabinoid compound concentrations can be stimulated through symbiotic and/or mutualistic relationships with endophytes. Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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Open AccessCorrection
Correction: Krauss, J., et al. Epichloë Endophyte Infection Rates and Alkaloid Content in Commercially Available Grass Seed Mixtures in Europe. Microorganisms 2020, 8, 498
Microorganisms 2020, 8(10), 1616; https://doi.org/10.3390/microorganisms8101616 - 21 Oct 2020
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The authors wish to make the following correction to this paper [...] Full article
(This article belongs to the Special Issue Fungal Endophytes and Their Interactions with Plants)
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