Effects Of Endophytes Research Articles

The combination of nanoparticles and endophytes boosts Thyme (Thymus vulgaris L.) resistance to drought stress by elevating levels of phenolic compounds, flavonoids, and essential oils

BackgroundAs climate change and water scarcity increasingly threaten agricultural productivity, enhancing plant resilience to drought has attracted great attention. This study explored the potential of combining Fe2O3 nanoparticles (FeNPs), endophytic bacteria (EB), and endophytic fungi (EF) to boost drought tolerance in Thymus vulgaris. The research aimed to assess how these combined treatments affect the plant’s physiological responses and chemical composition under drought stress.ResultsA factorial experiment was designed using completely randomized design (CRD) method, incorporating four irrigation levels [100%, 75%, 50%, and 25% field capacity (FC)], four FeNPs concentrations (0, 0.5, 1, and 1.5 mg L−1), and three endophyte types (control, bacteria, and fungi). After extracting, purifying, identifying, and screening EB and EF from nine Lamiaceae species, the endophytes Azospirillum lipoferum and Aspergillus oryzae isolated from Salvia mirzayanii exhibited the highest drought resistance. The highest amounts of TFM (45.45 g) and TDM (21.56 g) were obtained using the combination of EB and FeNPs at 1 mg L−1 under irrigation with 100% FC. At 25% FC, EB treatment increased the activities of polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) by 62.12% and 18.23% compared to the control, respectively. In addition, under optimal humidity conditions, FeNP concentrations were higher than 0.5 mg L−1 leading to a decrease in PPO activity. At 25% FC, the highest content of total phenols was observed with a 37.5% increase under EB treatment using 1 mg L−1 of FeNPs, while the highest content of total flavonoids showed a 62.72% increase under EF treatment with 0.5 mg/L of FeNPs. The highest level of p-coumaric acid was obtained under EF (34.27% compared to control). At 25% FC, EB and FeNPs (1 mg L−1) increased the level of caffeic acid in thyme plants by 24.70% and 10.08%, respectively. In addition, inoculation with EB increased (11.9%) the content of ferulic acid in plants and the application of FeNPs as a foliar spray decreased the level of ferulic acid in thyme plants. The highest essential oil percentage at 25% FC was observed after inoculation with EF and FeNPs (0.5 mg L−1), resulting in significant increases of 14.7% and 82.12%, respectively, compared to the control. A decrease in irrigation level led to an increase in the percentage of essential oil in thyme plants while decreasing dominant essential oil compounds, thymol, and carvacrol. The levels of thymol and carvacrol in the essential oil were not affected by the interaction effects of drought stress, endophytes, and FeNPs. EF and FeNPs (1.5 mg L−1), respectively, caused significant increases of 17.44% and 29.87% compared to the control in the amount of thymol and significant increases of 13.75% and 31.01% in the amount of carvacrol. All FeNPs concentrations decreased the concentrations of ferulic acid, FeNPs (1.5 mg L−1) and PPO; these particles act as abiotic stressors at sub-toxic levels and become phytotoxic at higher concentrations.ConclusionsIt seems that combining endophytes with FeNPs showed promise in enhancing drought tolerance in T. vulgaris. These treatments have significantly contributed to the production of enzymatic antioxidants, flavonoids, and phenolic compounds, leading to a reduction in the amounts of oxidants. At the same time, they have improved both the quality and quantity of essential oils. This highlights the importance of establishing an effective antioxidant system in response to environmental stresses.Graphical

Endophytes infection increased the disease resistance of host Achnatherum sibiricum and non-symbiotic neighbours to pathogenic fungi

Epichloë infection can affect the fungal disease resistance of host grasses. However, few studies have been reported on the effects of endophyte infection on non-symbiotic neighbours. We surveyed the plant diseases in natural grassland, and compared differences of total disease index between neighboring and non-neighboring plants of Achnatherum sibiricum. Then laboratory experiments were conducted to investigate the effects of endophyte on the growth of four pathogen species as well as the brown patch of the host and its neighboring plants. The results of plant disease investigation in natural grassland showed that the major epidemic diseases of grasses were spot blight, rust disease and powdery mildew in Hulunbuir natural grassland. Among common herbages, the total disease index of endophyte-infected A. sibiricum was the lowest. Compared with non-neighboring plants, the brown patch disease index of Leymus chinensis, Stipa baicalensis and Agropyron cristatum was significantly reduced when neighbouring with A. sibiricum. The laboratory experiments results showed that the culture filtration of both Epichloë gansuensis and Epichloë sibiricum significantly restrained the growth of Curvularia lunata, Bipolaris sorokiniana, Sclerotinia sclerotiorum and Sclerotinia trifoliorum. The two species of endophytes could reduce lesion area of detached host leaves. In vivo plant experiments, the endophyte reduced the disease resistance of both the host and its neighbor grasses L. chinensis to C. lunata and B. sorokiniana. This study first verified that the endophytes in A. sibiricum have a positive effect on disease resistance of neighbor grasses to brown patch. The study contributes to the understanding of endophyte-host interactions and suggests potential applications of endophytes in biological control strategies for grassland management.

Effect of Bacterial Endophytes Isolated from Tropical Fruits against Listeria monocytogenes and Cronobacter sakazakii in Model Food Products

Listeria monocytogenes and Cronobacter sakazakii are two important foodborne bacterial pathogens. Bacterial endophytes, which reside in plant cells, can produce antimicrobial compounds to protect the host organism or inhibit pathogens. This study investigated the bacterial community of tropical fruits for their potential to inactivate L. monocytogenes or C. sakazakii in cantaloupe and liquid infant formula, respectively. Tropical fruits including papayas, dragon fruits, and sugar apples, were sourced from several countries. Candidate bacterial endophytes were recovered from these tropical fruits using blood agar and Reasoner’s 2A (R2A) agar and tested for potential inhibition against L. monocytogenes and C. sakazakii. A total of 196 bacterial endophytes were recovered from papayas, dragon fruits, and sugar apples. Among these bacterial endophytes, 33 (16.8%) and 13 (6.6%) of them demonstrated an inhibition zone against L. monocytogenes and C. sakazakii, respectively. The inhibitory strains were identified using 16S rRNA sequencing as Bacillus spp., Enterobacter spp., Klebsiella spp., Microbacterium spp., Pantoea spp., and Pseudomonas spp. A cocktail of Pantoea spp. and Enterobacter spp. was used in challenge studies with cantaloupe and significantly reduced the number of L. monocytogenes by approximately 2.5 log10 CFU/g. In addition, P. stewartii demonstrated antagonistic activity against C. sakazakii in liquid infant formula, i.e., it significantly decreased the number of C. sakazakii by at least 1 log10 CFU/mL. Thus, the use of bacterial endophytes recovered from fruits and vegetables could be a promising area of research. Their use as potential biocontrol agents to control bacterial pathogens in ready-to-eat foods warrants further investigation.

Role of Endophytic Entomopathogenic Fungi in Mediating Host Selection, Biology, Behavior, and Management of Tarnished Plant Bug, Lygus lineolaris (Hemiptera: Miridae).

Non-insecticidal control strategies using entomopathogens, nematodes, and endophytes provide sustainable and safer alternatives for managing crop pests. This study investigated the potential of different fungal endophytes, specifically Beauveria bassiana strains, in colonizing cotton plants and their efficacy against tarnished plant bug, Lygus lineolaris. The effect of endophytes on plant growth parameters and cotton yield were measured during different plant growth stages. The entomopathogenicity of these fungi was studied in diet cup bioassays using L. lineolaris adults. The behavior of adult males and females toward endophytic cotton squares was analyzed using olfactometer assays. The experiments showed that the fungal endophytes colonized the plant structures of cotton plants, which resulted in an increase in the number of cotton squares, plant height, and weight compared to control plants. B. bassiana strains/isolates such as GHA, NI-8, and JG-1 caused significant mortality in Lygus adults compared to controls. Also, male and female Lygus adults exhibited repellence behavior towards endophytic cotton squares containing JG-1 isolate of B. bassiana and to other B. bassiana strains such as NI-8, GHA, and SPE-120. No differences were observed in the survival and development of L. lineolaris second-instar nymphs on endophytic cotton, and no yield differences were observed in the field experiments.

Effects of heading date and Epichloë endophyte on persistence of diploid perennial ryegrass (Lolium perenne). 2. Endophyte strain and interactions with heading date

Context Data are lacking on the effects of selected endophytes of perennial ryegrass (Lolium perenne L.) on ryegrass persistence. Aim We aimed to determine the impact of Epichloë endophyte on the persistence of mid- and late-heading perennial ryegrass cultivars. Method Two mid-heading (Samson, Bronsyn) and two late-heading (One50, Rohan) cultivars, infected with selected endophytes (AR37, nea2/6) or with standard toxic endophyte, were established in a replicated plot study grazed by cattle in a subtropical environment of the upper North Island of New Zealand. Persistence characteristics were quantified at least five times per annum, over 4 years. Key results Endophyte strain had an effect on persistence; infection with standard endophyte resulted in higher ryegrass ground cover percentage, ryegrass content in pasture dry matter and autumn yield than infection with nea2/6 on many occasions, and with AR37 on some occasions. There were negligible impacts on ryegrass tiller density or nutritive value. Trends were dominated by the main effect of endophyte; interactions with heading date were inconsistent. Conclusions Cultivars were more persistent when infected with standard endophyte than with selected endophytes, although persistence declined over 4 years for all cultivars and irrespective of heading date. Implications Reliance on selected endophyte is unlikely to prevent persistence decline of perennial ryegrass in a subtropical environment. Other strategies will be required to maintain the persistence of high-quality pastures based on perennial ryegrass.

Exploring the Potential of Endophytic Microorganisms and Nanoparticles for Enhanced Water Remediation.

Endophytic microorganisms contribute significantly to water bioremediation by enhancing pollutant degradation and supporting aquatic plant health and resilience by releasing bioactive compounds and enzymes. These microorganisms inhabit plant tissues without causing disease or any noticeable symptoms. Endophytes effectively aid in eliminating contaminants from water systems. Nanoparticles serve as potent enhancers in bioremediation processes, augmenting the efficiency of pollutant degradation by increasing surface area and bioavailability, thereby improving the efficacy and rate of remediation. Their controlled nutrient release and ability to stabilize endophytic colonization further contribute to the enhanced and sustainable elimination of contaminated environments. The synergistic effect of endophytes and nanoparticles in water remediation has been widely explored in recent studies, revealing compelling outcomes. Water pollution poses significant threats to human health, ecosystems, and economies; hence, the sixth global goal of the Sustainable Development Agenda 2030 of the United Nations aims to ensure the availability and sustainable management of water resources, recognizing their crucial importance for current and future generations. Conventional methods for addressing water pollution exhibit several limitations, including high costs, energy-intensive processes, the production of hazardous by-products, and insufficient effectiveness in mitigating emerging pollutants such as pharmaceuticals and microplastics. Noticeably, there is an inability to effectively remove various types of pollutants, thus resulting in incomplete purification cycles. Nanoparticle-enhanced water bioremediation offers an innovative, eco-friendly alternative for degrading contaminants. A growing body of research has shown that integrating endophytic microorganisms with nanoparticles for water bioremediation is a potent and viable alternative. This review examines the potential of using endophytic microorganisms and nanoparticles to enhance water remediation, exploring their combined effects and applications in water purification. The paper also provides an overview of synthetic methods for producing endophyte-nanoparticle composites to optimize their remediation capabilities in aqueous environments. The final section of the review highlights the constraints related to integrating endophytes with nanoparticles.

Endophytes Alleviate Drought-Derived Oxidative Damage in Achnatherum inebrians Plants Through Increasing Antioxidants and Regulating Host Stress Responses

Endophytes generally increase antioxidant contents of plants subjected to environmental stresses. However, the mechanisms by which endophytes alter the accumulation of antioxidants in plant tissues are not entirely clear. We hypothesized that, in stress situations, endophytes would simultaneously reduce oxidative damage and increase antioxidant contents of plants and that the accumulation of antioxidants would be a consequence of the endophyte ability to regulate the expression of plant antioxidant genes. We investigated the effects of the fungal endophyte Epichloë gansuensis (C.J. Li & Nan) on oxidative damage, antioxidant contents, and expression of representative genes associated with antioxidant pathways in Achnatherum inebrians (Hance) Keng plants subjected to low (15%) and high (60%) soil moisture conditions. Gene expression levels were measured using RNA-seq. As expected, the endophyte reduced the oxidative damage by 17.55% and increased the antioxidant contents by 53.14% (on average) in plants subjected to low soil moisture. In line with the accumulation of antioxidants in plant tissues, the endophyte increased the expression of most plant genes associated with the biosynthesis of antioxidants (e.g., MIOX, crtB, gpx) while it reduced the expression of plant genes related to the metabolization of antioxidants (e.g., GST, PRODH, ALDH). Our findings suggest that endophyte ability of increasing antioxidant contents in plants may reduce the oxidative damage caused by stresses and that the fungal regulation of plant antioxidants would partly explain the accumulation of these compounds in plant tissues.

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.

Regulation of mineral elements in Hordeum brevisubulatum by Epichloë bromicola under Cd stress

In this study, wild barley (Hordeum brevisubulatum) infected (E+) and uninfected (E-) by Epichloë bromicola were used for hydroponic experiments during the seedling stage. Various attributes, such as the effect of fungal endophyte on the growth and development of wild barley, the absorption of cadmium (Cd) and mineral elements (Ca, Mg, Fe, Mn, Cu, Zn), subcellular distribution, and chemical forms were investigated under CdCl2 stress. The results showed that the fungal endophy significantly reduced the Ca content and percentage of plant roots under Cd stress. The Fe and Mn content of roots, the mineral element content of soluble fractions, and the stems in the pectin acid or protein-chelated state increased significantly in response to fungal endophy. Epichloë endophyte helped Cd2+ to enter into plants; and reduced the positive correlation of Ca-Fe and Ca-Mn in roots. In addition, it also decreased the correlation of soluble components Cd-Cu, Cd-Ca, Cd-Mg in roots, and the negative correlation between pectin acid or protein-chelated Cd in stems and mineral elements, to increase the absorbance of host for mineral elements. In conclusion, fungal endophy regulated the concentration and distribution of mineral elements, while storing more Cd2+ to resist the damage caused by Cd stress. The study could provide a ground for revealing the Cd tolerance mechanism of endophytic fungal symbionts.

Divulgence into Mung Bean Growth Promotion Potential of Endophytes Isolated Across Different Geographical Regions of India

Background: Endophytic fungi in symbiotic association with their host plant are well known to improve plant growth and reduce the adverse effects of 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. Methods: In our study, the plant growth promoting activities of endophytic fungi isolated from various parts of India have been revealed and investigated. Fungal isolates were identified using molecular taxonomical methods, while their plant growth promoting abilities were evaluated in plate assays and in vitro studies. Altogether, seven strains were selected, representing the genera Fusarium, Chaetomium and Ulocladium. Result: Six of the isolates possessed phosphate solubilization activities, four secreted siderophores and four showed amylase activity, while all of them were able to produce indoleacetic acid (IAA). In order to investigate the effect of endophytes on plant growth, all seven fungi were selected concerning their potential ability to promote growth in mung bean. The results indicated that microbial endophytes selected from different geographical regions living originally in the plant host are able to influence the growth and fitness parameters of other plants through their promotion effects and could be used as inoculants to establish a sustainable crop production system.

Effects of fungal endophytes and arbuscular mycorrhizal fungi on growth of Echium vulgare and alkannin/shikonin and their derivatives production in roots

Endophytic fungi as well as arbuscular mycorrhizal fungi (AMF) are known to stimulate plant growth and production of secondary metabolites in medicinal plants. Here, 10 endophytic fungi isolated from roots of wild Alkanna tinctoria plants and 5 AMF purchased from the Glomeromycota in vitro collection were evaluated, during two successive three-month greenhouse experiments, on the growth of Echium vulgare and alkannin/shikonin and their derivatives (A/Sd) production in the roots. Some of the endophytic fungi tested significantly increased plant growth parameters as compared to the control: Cladosporium allicinum, Cadophora sp., Clonostachys sp., Trichoderma hispanicum and Leptosphaeria ladina increased root volume, Plectosphaerella sp. And T. hispanicum root fresh weight and root water retention and T. hispanicum plant water retention. However, none of these fungi impacted A/Sd production. Conversely, none of the AMF strains tested impacted plant growth parameters, but those inoculated with Rhizophagus intraradices MUCL 49410 had a significantly higher concentration of alkannin/shikonin (A/S), acetyl-A/S, β,β– dimethylacryl-A/S, isovaleryl-A/S and total A/Sd, compared to the control plants. Further studies are needed to investigate the mechanisms involved in the production of A/Sd in plants associated to specific endophytic fungi/AMF and on the cultivation conditions required for optimal production of these compounds.

Effects of endophytes Trichoderma amazonicum and Acremonium strictum on fungal pathogens of Paspalum

AbstractIn natural ecosystems, many plants engage in symbiotic interactions with fungal endophytes which can have impacts on host plant communities. In South American grasslands, several endophytes have been isolated from different Paspalum species. The aim of this work was to evaluate the antagonistic effect of endophytes Trichoderma amazonicum and Acremonium strictum against Claviceps paspali through in vitro and in vivo assays. In addition, they were evaluated as biocontrol agents against fungal pathogens which produce leaf spots such as Alternaria alternata and Bipolaris sp. through in vitro experiments. The in vitro assessment was conducted by dual culture between the antagonists and the three pathogens. For the in vivo assay, plants of Paspalum notatum and Paspalum dilatatum were planted in the field in a completely randomized block design with six replications. Three treatments were applied: T1 = endophyte inoculum, T2 = fungicide, and T3 = control. Seed yield, seed set, healthy seed set, and weight of healthy seed set per kilogram of seeds were evaluated for three timepoints. Trichoderma amazonicum exhibited a high growth inhibition, while A. strictum a moderate to low effect in vitro. In the in vivo assay, significant differences were observed among treatments in both species. T1 increased the kilogram of healthy seed set per 100 kg of seed by increasing the seed set and weight of healthy seed set in at least one of the evaluated dates in P. notatum and P. dilatatum. Based on these results, T. amazonicum and A. strictum have antagonistic effects on the pathogens assessed.

Plant Protective and Growth Promoting Effects of Seed Endophytes in Soybean Plants.

Seed-borne diseases reduce not only the seed germination and seedling growth but also seed quality, resulting in the significant yield loss in crop production. Plant seed harbors diverse microbes termed endophytes other than pathogens inside it. However, their roles and application to agricultures were rarely understood and explored to date. Recently, we had isolated from soybean seeds culturable endophytes exhibiting in-vitro antagonistic activities against common bacterial and fungal seed-borne pathogens. In this study, we evaluated effects of seed treatment with endophytes on plant growth and protection against the common seed-borne pathogens: four fungal pathogens (Cercospora sojina, C. kikuchii, Septoria glycines, Diaporthe eres) and two bacterial pathogens (Xanthomonas axonopodis pv. glycines, Pseudomonas syringae pv. tabaci). Our experiments showed that treatment of soybean seeds with seed endophytes clearly offer protection against seed-borne pathogens. We also found that some of the endophytes promote plant growth in addition to the disease suppression. Taken together, our results demonstrate agricultural potential of seed endophytes in crop protection.

The “Trojan horse” strategy: Seed fungal endophyte symbiosis helps to explain the invasion success of the grass, Poa annua, in Maritime Antarctica

AbstractAimPoa annua L. (annual bluegrass) is presently the sole invasive vascular plant species to have successfully established in Maritime Antarctica, where it poses a significant conservation threat to native plant species. However, the reasons for its success in the region have yet to be established. Here, we determined whether the invasiveness of P. annua, and its competitiveness with the native Antarctic hairgrass Deschampsia antarctica, is influenced by symbioses formed with seed fungal endophytes, and whether plants derived from seeds from four global regions differ in their performance.LocationsFour regions (Maritime Antarctica, sub‐Antarctica, South America and Europe).MethodsEndophyte frequency was measured in P. annua seeds collected from the four regions. The germination, survival, biomass accumulation, flowering and competitiveness with D. antarctica of P. annua plants grown from endophyte‐uncolonised and uncolonised seeds was determined in the laboratory. The effects of endophytes on P. annua seed germination and survival and seedling osmoprotection were also assessed in the Maritime Antarctic natural environment using locally‐sourced seeds.ResultsEndophytes were at least twice as frequent in seeds from Maritime Antarctica than in those from other regions. A higher proportion of endophyte‐colonized seeds germinated and survived than did uncolonised seeds, but only when they originated from Maritime Antarctica. Seed endophytes increased the competitiveness of P. annua with D. antarctica, but only for plants grown from Maritime Antarctic seeds. In the field, endophyte‐colonized seeds from Maritime Antarctica germinated and survived more frequently than uncolonised seeds, and osmoprotection was higher in seedlings grown from colonized seed.Main ConclusionsThe findings indicate beneficial effects of seed endophytes on invasion‐related traits of P. annua, such as survival, germination success and flowering. Together with vegetative and reproductive traits facilitating the colonization process, the seed‐fungal endophyte symbiosis can be invoked as an important factor explaining the invasiveness of P. annua in Maritime Antarctica.

Effects of Phosphorus-dissolving Dark Septate Endophytes on the Growth of Blueberry.

Dark septate endophytes (DSEs) are widely distributed and improve plant growth. DSEs secrete large amounts of enzymes to mineralize insoluble phosphorus in soil and convert it into soluble phosphorus, promoting plant uptake of phosphorus. However, the effects of DSEs with phosphate-solubilizing ability on host plants need further study. In this study, phosphorus-dissolving DSEs were screened for growth-promoting effects. We isolated, identified and characterized three DSE species (Thozetella neonivea, Pezicula ericae and Hyaloscyphaceae sp.) showing phosphate-solubilizing ability. The impact of single, dual or triple inoculation of DSEs on blueberry plant characteristics was studied. Their effects on colonization intensity, seedling biomass, nutrients in plants and soil, and activities of plant resistance enzymes and soil enzymes were markedly upregulated relative to the control (P < 0.05). The available phosphorus and acid phosphatase levels in different combinations were significantly increased. These findings indicate that the application of the three DSEs may be valuable in facilitating the cultivation of blueberry with a higher biomass and improved plant quality.

The composition characteristics of endophytic communities and their relationship with metabolites profile in Ephedra sinica under wild and cultivated conditions.

Ephedra sinica is one of the most famous Chinese medicinal plants. The insufficient supply of wild resources has led to the increased use of cultivated products. However, the related medicinal quality differs significantly. Although the influence of external environment on the quality of E. sinica has been studied, the impact of endophytic microbes on it remains vague. This study characterized differential metabolites and microbial community compositions in wild and cultivated E. sinica by combining metabolomics with microbiomics, and explored the effect of endophytes on the formation of differential metabolites further. The results showed that the difference in quality between wild and cultivated E. sinica was mainly in the productions of alkaloids, flavonoids, and terpenoids. The associated endophytes had special compositional characteristics. For instance, the distribution and abundance of dominant endophytes varied between wild and cultivated E. sinica. Several endophytes had significant or highly significant correlations with the formations of ephedrine, pseudoephedrine, D-cathinone, methcathinone, coumarin, kaempferol, rhamnetin, or phenylacetic acid. This study will deepen our understanding of the plant-endophyte interactions and provide a strategy for the quality control of E. sinica products.

The synergy of dark septate endophytes and organic residue on Isatis indigotica growth and active ingredients accumulation under drought stress

Drought is a major abiotic stress factor affecting plant growth and production, while utilizing beneficial endophytic fungi is one of the most promising strategies for enhancing plant growth and drought tolerance. In the present study, a pot experiment was conducted to investigate the beneficial effects of dark septate endophytes (DSE) (Acrocalymma aquatica and Alternaria alstroemeriae) combine with organic residues from sterilized or non-sterilized fermented corn straw by Trichoderma afroharzianum on the growth and drought resistance of Isatis indigotica. Drought stress (30% field water capacity) reduced the shoot biomass, root biomass, and epigoitrin content of I. indigotica by 34.30%, 80.85%, and 16.51%, respectively. The DSE inoculation alone increased shoot biomass and epigoitrin content under well-watered condition (70% field water capacity) by 13.75%− 65.98% and 52.33%− 67.59%, respectively, and shoot biomass under drought stress by 37.27%− 84.91%. The organic residues application alone increased root biomass under well-watered condition and drought stress by 71.88%− 107.06% and 463.61%− 678.69%, respectively. The mixed application of DSE and organic residues increased root biomass and epigoitrin content under well-watered condition by 66.79%− 144.66% and 89.02%− 136.63%, respectively, and under drought stress by 410.66%− 580.49% and 28.26%− 88.37%, respectively. Structural equation modeling demonstrated that DSE inoculation, organic residue application, and the mixed application improved the growth of I. indigotica under drought stress through different direct and indirect pathways. Variation partitioning showed that DSE was the primary factor improving the epigoitrin content, and organic residue was the primary factor influencing plant biomass and morphological parameters. The mixed application of DSE and organic residue had further synergistic effects on soil enzyme activities, soil organic matter, root biomass, and epigoitrin content, especially the mixed application of A. aquatica and sterilized organic residue. These results contribute to a further understanding of the ecological function of DSE in dryland soils and reveal the synergistic application value of DSE and organic residue for medicinal plant cultivation.

Endophytic infection increases the belowground over-yielding effects of the host grass community mainly by increasing the complementary effects.

Increases in plant species diversity may increase the community diversity effect and produce community over-yielding. Epichloë endophytes, as symbiotic microorganisms, are also capable of regulating plant communities, but their effects on community diversity effects are often overlooked. In this experiment, we investigated the effects of endophytes on the diversity effects of host plant community biomass by constructing artificial communities with 1-species monocultures and 2- and 4-species mixtures of endophyte-infected (E+) and endophyte-free (E-) Achnatherum sibiricum and three common plants in its native habitat, which were potted in live and sterilized soil. The results showed that endophyte infection significantly increased the belowground biomass and abundance of Cleistogenes squarrosa, marginally significantly increased the abundance of Stipa grandis and significantly increased the community diversity (evenness) of the 4-species mixtures. Endophyte infection also significantly increased the over-yielding effects on belowground biomass of the 4-species mixtures in the live soil, and the increase in diversity effects on belowground biomass was mainly due to the endophyte significantly increasing the complementary effects on belowground biomass. The effects of soil microorganisms on the diversity effects on belowground biomass of the 4-species mixtures were mainly derived from their influences on the complementary effects. The effects of endophytes and soil microorganisms on the diversity effects on belowground biomass of the 4-species communities were independent, and both contributed similarly to the complementary effects on belowground biomass. The finding that endophyte infection promotes belowground over-yielding in live soil at higher levels of species diversity suggests that endophytes may be one of the factors contributing to the positive relationship between species diversity and productivity and explains the stable co-existence of endophyte-infected Achnatherum sibiricum with a variety of plants in the Inner Mongolian grasslands.

Biocontrol Impacts on Wheat Physiology and Fusarium Head Blight Outcomes Are Bacterial Endophyte Strain and Cultivar Specific

Fusarium head blight (FHB) is an economically important disease of small grains globally and is primarily caused by Fusarium graminearum in North America. Recently, microbial biocontrols have risen in importance as sustainable agents of disease control. However, the path to implementation of microbial biocontrols in agriculture will require an understanding of how microbiota both affect plant performance overall and vary with inherent host disease resistance. Using a full-factorial, controlled greenhouse experiment, we tested how seven bacterial endophyte seed soak treatments affected both plant physiology prior to pathogen infection and FHB disease progression in Triticum aestivum (wheat). Bacterial endophyte treatments strongly affected the light-dependent reactions of photosynthesis, with changes in plant traits regulating light energy allocation and the build-up of electrochemical energy storage across the thylakoid membrane. Physiological responses were contingent on host variety. The direct effects of bacterial endophytes on wheat response to infection were weak and dependent on the inherent disease resistance of the host variety. However, disease outcomes were indirectly mediated by bacterial impacts on plant traits, with proton motive force traits emerging as common predictors of disease response across both host varieties and other traits indicating potential trade-offs in host response to bacterial inoculants and F. graminearum infection. Our results provide an alternate mechanism for microbial biocontrol efficacy other than direct antagonism with the pathogen inside the host. Furthermore, the chlorophyll-fluorescence and absorbance-based markers assessed here may have translational potential as a phenotyping tool for FHB susceptibility in wheat and other small grains.

Identification, Characterization, and Growth-Promoting Effects of Bacterial Endophytes Isolated from Okra (Abelmoschus esculentus L.)

Microorganisms colonize plant roots and exhibit plant growth promotion properties, therefore functioning as biofertilizers. To effectively use plant growth-promoting rhizobacteria, understanding their colonizing behavior and ability to compete with co-existing bacteria is essential. In this study, 12 endophytic bacterial strains belonging to seven genera in four classes with 99–100% homology were isolated from the roots of okra plants (Abelmoschus esculentus L.). Four isolates (Okhm3, Okhm5-4, Okhm10, and Okhm11) were inoculated on okra seeds and their effects on plant growth and colonization with single and mixed inoculations were evaluated. Okra was cultivated using sterilized vermiculite, and the growth parameters and colonization were measured 30 d after seed inoculation. All strains exhibited plant growth promotion traits that could improve okra plant growth in pot culture experiments. Notably, Okhm5-4 and Okhm10 strains (belonging to the Ensifer and Pseudomonas genera) revealed the highest growth-promoting effects on okra plants. Both strains were detected in the endosphere and rhizosphere of okra plants. Okhm10 and Okhm5-4, with lower colonization than Okhm3, showed better growth than Okhm3. Therefore, the colonization potential does not determine the growth-promoting effects. While Okhm3 populations remained stable in both inoculation conditions, the population level of other strains decreased in the mixed inoculation. This study showed bacterial endophytes isolated from Okra can be exploited as bio-fertilizers for sustainable agriculture systems.