Pest management via endophytic colonization of tobacco seedlings by the insect fungal pathogen Beauveria bassiana

Metarhizium rileyi with broad-spectrum insecticidal ability confers resistance against phytopathogens and insect pests as a phytoendophyte

BACKGROUND

Entomophagous fungi (EPF) not only directly kill insect pests, but also colonize plants and improve their resistance against pests. However, most previous research has focused on Beauveria bassiana and Metarhizium anisopliae, and there are few reports on whether other EPF can enhance resistance against pests via endogenous colonization. Herein, an EPF strain was isolated from diseased larvae of Spodoptera litura in a soybean field, and subjected to genome-wide sequencing at the chromosomal level. The pathogenicity of the isolate toward various pest insects was evaluated, and the ability to colonize plants and induce resistance against phytopathogens and insect pests was tested.

RESULTS

The purified isolate was identified as M. rileyi and designated MrS1Gz1-1. Biological assays revealed its strong pathogenicity toward five insect pests belonging to Lepidoptera and Hemiptera. Furthermore, the strain inhibited the growth of soil-borne plant disease caused by Sclerotinia sclerotiorum in vitro. It colonized plants as an endophyte via soil application, thereby inducing plant resistance-related genes against phytopathogen infection, and it disrupted the feeding selectivity of S. litura larvae.

CONCLUSION

M. rileyi MrS1Gz1-1 has potential as a broad-spectrum microbial control agent that can induce resistance against phytopathogens and insect pests feeding as an endotype. The complete genome provides a valuable resource for exploring host interactions. © 2024 Society of Chemical Industry.

The Bbotf1 Zn(Ⅱ)2Cys6 transcription factor contributes to antioxidant response, fatty acid assimilation, peroxisome proliferation and infection cycles in insect pathogenic fungus Beauveria bassiana

The abilities to withstand oxidation and assimilate fatty acids are critical for successful infection by many pathogenic fungi. Here, we characterized a Zn(II)2Cys6 transcription factor Bbotf1 in the insect pathogenic fungus Beauveria bassiana, which links oxidative response and fatty acid assimilation via regulating peroxisome proliferation. The null mutant ΔBbotf1 showed impaired resistance to oxidants, accompanied by decreased activities of antioxidant enzymes including CATs, PODs and SODs, and down-regulated expression of many antioxidation-associated genes under oxidative stress condition. Meanwhile, Bbotf1 acts as an activator to regulate fatty acid assimilation, lipid and iron homeostasis as well as peroxisome proliferation and localization, and the expressions of some critical genes related to glyoxylate cycle and peroxins were down-regulated in ΔBbotf1 in presence of oleic acid. In addition, ΔBbotf1 was more sensitive to osmotic stressors, CFW, SDS and LDS. Insect bioassays revealed that insignificant changes in virulence were seen between the null mutant and parent strain when conidia produced on CZP plates were used for topical application. However, propagules recovered from cadavers killed by ΔBbotf1 exhibited impaired virulence as compared with counterparts of the parent strain. These data offer a novel insight into fine-tuned aspects of Bbotf1 concerning multi-stress responses, lipid catabolism and infection cycles.

Tripartite interactions of an endophytic entomopathogenic fungus, Asian corn borer, and host maize under elevated carbon dioxide

BACKGROUND

Biological control of insect pests is encountering an unprecedented challenge in agricultural systems due to the ongoing rise in carbon dioxide (CO2) level. The use of entomopathogenic fungi (EPF) in these systems is gaining increased attention, and EPF as crop endophytes hold the potential for combining insect pest control and yield enhancement of crops, but the effects of increased CO2 concentration on this interaction are poorly understood. Here, the introduction of endophytic EPF was explored as an alternative sustainable management strategy benefiting crops under elevated CO2, using maize (Zea mays), Asian corn borer (Ostrinia furnacalis), and EPF (Beauveria bassiana) to test changes in damage to maize plants from O. furnacalis, and the nutritional status (content of carbon, nitrogen, phosphorus, potassium), biomass, and yield of maize.

RESULTS

The results showed that endophytic B. bassiana could alleviate the damage caused by O. furnacalis larvae for maize plants under ambient CO2 concentration, and this effect was enhanced under higher CO2 concentration. Inoculation with B. bassiana effectively counteracted the adverse impact of elevated CO2 on maize plants by preserving the nitrogen content at its baseline level (comparable with ambient CO2 conditions without B. bassiana). Both simultaneous effects could explain the improvement of biomass and yield of maize under B. bassiana inoculation and elevated CO2.

CONCLUSION

This finding provides key information about the multifaceted benefits of B. bassiana as a maize endophyte. Our results highlight the promising potential of incorporating EPF as endophytes into integrated pest management strategies, particularly under elevated CO2 concentrations. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of root inoculation of entomopathogenic fungi on olfactory-mediated behavior and life-history traits of the parasitoid Aphidius ervi (Haliday) (Hymenoptera: Braconidae)

BACKGROUND

Although most biological control programs use multiple biological agents to manage pest species, to date only a few programs have combined the use of agents from different guilds. Using sweet pepper (Capsicum annuum L.), the entomopathogenic fungus Akanthomyces muscarius ARSEF 5128, the tobacco peach aphid Myzus persicae var. nicotianae and the aphid parasitoid Aphidius ervi as the experimental model, we explored whether root inoculation with an entomopathogenic fungus is compatible with parasitoid wasps for enhanced biocontrol of aphids.

RESULTS

In dual-choice behavior experiments, A. ervi was significantly attracted to the odor of M. persicae-infested C. annuum plants that had been inoculated with A. muscarius, compared to noninoculated infested plants. There was no significant difference in attraction to the odor of uninfested plants. Myzus persicae-infested plants inoculated with A. muscarius emitted significantly higher amounts of indole, (E)-nerolidol, (3E,7E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene and one unidentified terpene compared to noninoculated infested plants. Coupled gas chromatography-electroantennography, using the antennae of A. ervi, confirmed the physiological activity of these elevated compounds. Inoculation of plants with A. muscarius did not affect parasitism rate nor parasitoid longevity, but significantly increased the speed of mummy formation in parasitized aphids on fungus-inoculated plants.

CONCLUSION

Our data suggest that root inoculation of C. annuum with A. muscarius ARSEF 5128 alters the olfactory-mediated behavior of parasitoids, but has little effect on parasitism efficiency or life-history parameters. However, increased attraction of parasitoids towards M. persicae-infested plants when inoculated by entomopathogenic fungi can accelerate host localization and hence improve biocontrol efficacy. © 2023 Society of Chemical Industry.

Nicotiana benthamiana as a model plant host for Fusarium verticillioides to investigate RNA interference, cross-kingdom RNA exchange, and competitive endogenous RNA (ceRNA) network

BACKGROUND

Fusarium verticillioides is among the most devastating fungal pathogen of cereals. Therefore, it is crucial to employ effective and long-term strategies for managing F. verticillioides for sustainable agriculture. RNA interference (RNAi) being a natural defense mechanism of plants via regulation of gene expression, has emerged as a promising tool for eradicating pathogens. RNAi also operates between the host and pathogen through RNA exchange. RNAi interacts with competitive endogenous RNAs (ceRNAs) including long non-coding RNA (lncRNA), microRNA (miRNA), and mRNA. Due to the lack of an elaborate model to investigate all these mechanisms, this study aimed to establish a Nicotiana benthamiana (Nb)-F. verticillioides (Fv) phyto-pathosystem as an experimental model.

METHODS AND RESULTS

Nb seedlings were inoculated with Fv, and the pathogenicity was monitored morphologically, microscopically, biochemically, and transcriptionally. To observe the role of RNAi and RNA-exchange in pathogenicity, Nb-miR172 and Nb-miR399 targeting Nb-lncRNA-IPS (Induced by Phosphate Starvation1) and Nb-AP2 (Apetala2) and Nb-PHO2 (phosphate over-accumulator) ceRNA network and Fv-V-ATPase (Vesicle-fusing ATPase) targeted by Nb-miR172 were investigated. As a result, epidermal cell density, leaf area, petiole length, and chlorophyll content were reduced while the density of stomata and trichome and phenolic content and the activity of ascorbate peroxidase (APX) and glutathione reductase (GR) were increased in response to Fv infection in Nb. The expression of AP2 and PHO2 were downregulated against Fv but no significant changes were detected in IPS, miR172, and miR399 expression.

CONCLUSION

These findings suggested the Fv-Nb phyto-pathosystem as a useful experimental model to reveal genetic regulations.

Endophytic Beauveria bassiana promotes plant biomass growth and suppresses pathogen damage by directional recruitment

Introduction

Entomopathogenic fungi (EPF) can colonize and establish symbiotic relationships with plants as endophytes. Recently, EPF have been reported to suppress plant pathogens and induce plant resistance to diseases. However, the potential mechanisms via which EPF as endophytes control major plant diseases in situ remain largely unknown.

Methods

Pot and field experiments were conducted to investigate the mechanisms via which an EPF, Beauveria bassiana, colonizes tomato, under Botrytis cinerea infection stress. B. bassiana blastospores were inoculated into tomato plants by root irrigation. Tomato resistance to tomato gray mold caused by B. cinerea was evaluated by artificial inoculation, and B. bassiana colonization in plants and rhizosphere soil under B. cinerea infection stress was evaluated by colony counting and quantitative PCR. Furthermore, the expression levels of three disease resistance-related genes (OXO, CHI, and atpA) in tomato leaves were determined to explore the effect of B. bassiana colonization on plant disease resistance performance in pot experiments.

Results

B. bassiana colonization could improve resistance of tomato plants to gray mold caused by B. cinerea. The incidence rate, lesion diameter, and disease index of gray mold decreased in both the pot and field experiments following B. bassiana colonization. B. bassiana was more likely to accumulate in the pathogen infected leaves, while decreasing in the rhizosphere soil, and induced the expression of plant resistance genes, which were up-regulated in leaves.

Discussion

The results indicated that plants could "recruit" B. bassiana from rhizosphere soil to diseased plants as directional effects, which then enhanced plant growth and resistance against pathogens, consequently inhibiting pathogen infection and multiplication in plants. Our findings provide novel insights that enhance our understanding of the roles of EPF during pathogen challenge.

Local Competition and Enhanced Defense: How Metarhizium brunneum Inhibits Verticillium longisporum in Oilseed Rape Plants

Metarhizium brunneum is a soil-borne fungal entomopathogen that can be associated with plant roots. Previous studies have demonstrated that root colonization by beneficial fungi can directly affect soil-borne pathogens through competition and antibiosis and can activate a systemic response in plants, resulting in a primed state for a faster and/or stronger response to stressors. However, the mechanisms by which Metarhizium inoculation ameliorates symptoms caused by plant pathogens are not well known. This study evaluated the ability of M. brunneum to protect oilseed rape (Brassica napus L.) plants against the soil-borne pathogen Verticillium longisporum and investigated whether the observed effects are a result of direct interaction and/or plant-mediated effects. In vitro and greenhouse experiments were conducted to measure fungal colonization of the rhizosphere and plant tissues, and targeted gene expression analysis was used to evaluate the plant response. The results show that M. brunneum delayed pathogen colonization of plant root tissues, resulting in decreased disease symptoms. Direct competition and antibiosis were found to be part of the mechanisms, as M. brunneum growth was stimulated by the pathogen and inhibited the in vitro growth of V. longisporum. Additionally, M. brunneum changed the plant response to the pathogen by locally activating key defense hormones in the salicylic acid (SA) and abscisic acid (ABA) pathways. Using a split-root setup, it was demonstrated that there is a plant-mediated effect, as improved plant growth and decreased disease symptoms were observed when M. brunneum was in the systemic compartment. Moreover, a stronger systemic induction of the gene PR1 suggested a priming effect, involving the SA pathway. Overall, this study sheds light on the mechanisms underlying the protective effects of M. brunneum against soil-borne pathogens in oilseed rape plants, highlighting the potential of this fungal entomopathogen as a biocontrol agent in sustainable agriculture.

Establishment of Beauveria bassiana as a fungal endophyte in potato plants and its virulence against potato tuber moth, Phthorimaea operculella (Lepidoptera: Gelechiidae)

The potato tuber moth, Phthorimaea operculella, is the most damaging potato pest in the world and is difficult to control as the larvae are internal feeders in the foliage and tubers. Entomopathogenic fungi that colonize plants as endophytes have lethal and sublethal pathological effects on insect pests. We show that Beauveria bassiana colonizes the aerial parts of potato plants endophytically after inoculation through soil drenching. Endophytic B. bassiana persisted in potato foliage for more than 50 days postinoculation. Bioassays indicated that foliage of B. bassiana-inoculated potato plants were pathogenic against larvae of P. operculella. Sublethal experiments indicated that B. bassiana negatively affected the growth, development, and reproduction of P. operculella. Development experiments showed that the weight of P. operculella pupae reared on B. bassiana-colonized potato plants (4.25 mg) was significantly less than that of those reared on uninoculated control plants (8.89 mg). Compared with newly eclosed larvae fed on control plants, those fed on B. bassiana-inoculated plants had significantly lower survivorship, with only 17.8% developing to the adult stage. Oviposition of P. operculella females reared on B. bassiana endophytically colonized plants was significantly lower (35 eggs/female) than of those reared on uninoculated plants (115 eggs/female). This study demonstrates that endophytic B. bassiana can be a potential biological control agent for the control and management of P. operculella. Comparing pupal weights of P. operculella reared on potato plants inoculated with the B. bassiana strain GZGY-1-3 and on untreated control plants, pupae from the control plants were significantly heavier than those from treated plants.

The AreA Nitrogen Catabolite Repression Activator Balances Fungal Nutrient Utilization and Virulence in the Insect Fungal Pathogen Beauveria bassiana

In many fungi, the AreA GATA-type transcription factor mediates nitrogen catabolite repression affecting fungal development and, where applicable, virulence. Here, we investigated the functions of AreA in the fungal entomopathogen and plant endophyte Beauveria bassiana using knockdown of gene expression. The antiAreA mutants were impaired in nitrogen utilization and showed increased sensitivities to osmotic stressors but increased tolerances to oxidative/hypoxia stresses. Repression of BbAreA caused overall minimal effects on fungal virulence. The minor effects on virulence appeared to be due in part to competing secondary effects where host defense phenoloxidase activity was significantly decreased, but production of the fungal metabolite oosporein was increased and hyphal body development was impaired. Knockdown of BbAreA expression also resulted in impairment in ability of the fungus to associate with host plants. These data implicate that BbAreA likely acts as a regulator to balance fungal nutrient utilization, pathogenicity, and mutualism, facilitating the fungal occupation of host niches.

Dual Action of Beauveria bassiana (Hypocreales; Cordycipitaceae) Endophytic Stains as Biocontrol Agents against Sucking Pests and Plant Growth Biostimulants on Melon and Strawberry Field Plants

Entomopathogenic fungi (EPF) can colonize plant tissues and serve crops not only as biopesticides but also as biostimulants that promote plant growth and trigger defense mechanisms. In this context, field trials were conducted evaluating two commercial strains of the entomopathogen Beauveria bassiana (Hypocreales: Cordycipitaceae), GHA (Botanigard) and PPRI 5339 (Velifer® ES) and a wild strain (AP0101) isolated from Achaia, Greece. The three strains were investigated in the field for their endophytic effects on melon Cucumis melo (Cucurbitales: Cucurbitaceae) and strawberry Fragaria sp. (Rosales: Rosaceae) plants and in particular for their ability to colonize plant tissues, control infestations of sucking insects Aphis gossypii (Hemiptera: Aphididae), Chaetosiphon fragaefolii (Hemiptera: Aphididae) and Frankliniella occidentalis (Thysanoptera: Thripidae), and improve plant growth parameters (plant height, number of flowers and fruits). All experimental fungal strains successfully colonized both plants. A significant decrease in the aphid and thrip populations was observed in the treated plants compared to the untreated control. As for plant growth, the number of flowers and fruits was significantly increased in plants treated with B. bassiana strains AP0101 and PPRI 5339. Our results clearly indicate that fungal endophytes can efficiently act as dual action agents demonstrating both insecticidal and growth-promoting effects.

Root Colonization by Fungal Entomopathogen Systemically Primes Belowground Plant Defense against Cabbage Root Fly

Entomopathogenic fungi infect insects via spores but also live inside plant tissues as endophytes. Frequently, colonization by entomopathogens provides plants with increased resistance against insects, but the mechanisms are little understood. This study investigated direct, local, and systemic root-mediated interactions between isolates of the fungus Metarhizium brunneum and larvae of the cabbage root fly (CRF) Delia radicum attacking Brassica napus plants. All fungal isolates infected CRF when conidia were present in the soil, leading to 43–93% mortality. Locally, root-associated M. brunneum isolates reduced herbivore damage by 10–20% and in three out of five isolates caused significant insect mortality due to plant-mediated and/or direct effects. A split-root experiment with isolate Gd12 also demonstrated systemic plant resistance with significantly reduced root collar damage by CRF. LC-MS analyses showed that fungal root colonization did not induce changes in phytohormones, while herbivory increased jasmonic acid (JA) and glucosinolate concentrations. Proteinase inhibitor gene expression was also increased. Fungal colonization, however, primed herbivore-induced JA and the expression of the JA-responsive plant defensin 1.2 (PDF1.2) gene. We conclude that root-associated M. brunneum benefits plant health through multiple mechanisms, such as the direct infection of insects, as well as the local and systemic priming of the JA pathway.

Isolation and identification of two Beauveria bassiana strains from silkworm, Bombyx mori

Silkworm diseases caused by fungi infection occur frequently in sericulture and brought huge economic loss to sericulture. However, on the other hand, some fungi such as Beauveria bassiana, as an important entomological fungus, play an important role in biological control of insect pests. Here, two fungal pathogens causing yellow muscardine were isolated from the silkworm and named as SZY1 and SZY2. These two strains showed almost the same conidial morphology which were smooth, near-spherical, spherical, or ovoid and 2.7 ± 0.6 µm × 2.5 ± 0.9 µm in size, and the hyphal growth rate was also similar. However, the conidia production of SZY2 was almost twice as many as that of SZY1. The complete ribosomal RNA gene was sequenced and analyzed. As a result, the gene sequences of internal transcript space 1 (ITS1)-5.8S rRNA-internal transcript space 2 (ITS2) of SZY1 and SZY2 were identical in sequence and size, and for 18S rRNA, 28S rRNA, and intergenic spacer (IGS), the gene identity of SZY1 to SZY2 was 99%, 99%, and 98%, respectively. Results of phylogenetic analysis based on either ITS1-5.8S rRNA-ITS2 or 18S rRNA showed that both SZY1 and SZY2 were closely related to Beauveria bassiana. These results revealed that the pathogens of yellow muscardine SZY1 and SZY2 were identified as two different strains of Beauveria bassiana, which could provide diagnostic evidence for silkworm muscardine and was helpful for the research and development of novel Bombyx batryticatus and fungal biological insecticide.

The Entomopathogenic Fungi Metarhizium brunneum and Beauveria bassiana Promote Systemic Immunity and Confer Resistance to a Broad Range of Pests and Pathogens in Tomato

Biocontrol agents can control pathogens by reenforcing systemic plant resistance through systemic acquired resistance (SAR) or induced systemic resistance (ISR). Trichoderma spp. can activate the plant immune system through ISR, priming molecular mechanisms of defense against pathogens. Entomopathogenic fungi (EPF) can infect a wide range of arthropod pests and play an important role in reducing pests' population. Here, we investigated the mechanisms by which EPF control plant diseases. We tested two well studied EPF, Metarhizium brunneum isolate Mb7 and Beauveria bassiana as the commercial product Velifer, for their ability to induce systemic immunity and disease resistance against several fungal and bacterial phytopathogens, and their ability to promote plant growth. We compared the activity of these EPF to an established biocontrol agent, Trichoderma harzianum T39, a known inducer of systemic plant immunity and broad disease resistance. The three fungal agents were effective against several fungal and bacterial plant pathogens and arthropod pests. Our results indicate that EPF induce systemic plant immunity and disease resistance by activating the plant host defense machinery, as evidenced by increases in reactive oxygen species production and defense gene expression, and that EPF promote plant growth. EPF should be considered as control means for Tuta absoluta. We demonstrate that, with some exceptions, biocontrol in tomato can be equally potent by the tested EPF and T. harzianum T39, against both insect pests and plant pathogens. Taken together, our findings suggest that EPF may find use in broad-spectrum pest and disease management and as plant growth promoting agents.

Fungal Endophytes and Their Role in Agricultural Plant Protection against Pests and Pathogens

Virtually all examined plant species harbour fungal endophytes which asymptomatically infect or colonize living plant tissues, including leaves, branches, stems and roots. Endophyte-host interactions are complex and span the mutualist-pathogen continuum. Notably, mutualist endophytes can confer increased fitness to their host plants compared with uncolonized plants, which has attracted interest in their potential application in integrated plant health management strategies. In this review, we report on the many benefits that fungal endophytes provide to agricultural plants against common non-insect pests such as fungi, bacteria, nematodes, viruses, and mites. We report endophytic modes of action against the aforementioned pests and describe why this broad group of fungi is vitally important to current and future agricultural practices. We also list an extensive number of plant-friendly endophytes and detail where they are most commonly found or applied in different studies. This review acts as a general resource for understanding endophytes as they relate to potential large-scale agricultural applications.

Ecological and Molecular Interactions between Insects and Fungi

Insects and fungi represent two of the most widespread groupings of organisms in nature, occurring in every kind of ecological context and impacting agriculture and other human activities in various ways. Moreover, they can be observed to reciprocally interact, establishing a wide range of symbiotic relationships, from mutualism to antagonism. The outcome of these relationships can in turn affect the extent at which species of both organisms can exert their noxious effects, as well as the management practices which are to be adopted to counter them. In conjunction with the launch of a Special Issue of Microorganisms with the same title, this article offers a general overview of the manifold aspects related to such interactions from the perspective of implementing our capacity to regulate them in a direction more favorable for the environment, crop production and human health.

The endophytic bacterial entomopathogen Serratia marcescens promotes plant growth and improves resistance against Nilaparvata lugens in rice

Entomopathogenic bacteria are commonly used as biological agents to control different insect pests. However, little is known about the role of bacterial entomopathogens as endophytes in regulating both plant growth and resistance against insect pests. Here, we applied the entomopathogenic bacterium Serratia marcescens S-JS1 via rice seed inoculation and evaluated its effects on host plant growth and resistance against the rice pest Nilaparvata lugens. Furthermore, the induction of defense-related secondary metabolites by the bacterium was assessed by GC-MS/MS. We showed that S-JS1 was able to endophytically colonize the roots and shoots of rice seedlings following seed inoculation. Colonized plants showed increased seed germination (9.4-13.3 %), root (8.2-36.4 %) and shoot lengths (4.1-22.3 %), and root (26.7-69.3 %) and shoot fresh weights (19.0-49.0 %) compared to plants without inoculation. We also identified the production of indole-3-acetic acid by S-JS1, which is likely involved in enhancing rice plant growth. In a two-choice test, N. lugens adults preferred to feed on untreated control plants than on plants treated with S-JS1. In the no-choice feeding tests, the survival of N. lugens nymphs that fed on S-JS1-treated plants was significantly lower than that of nymphs that fed on untreated plants. Additionally, seeds treated with 10⁹ cfu/mL S-JS1 resulted in elevated levels of secondary metabolites, which may be associated with N. lugens resistance in rice plants. Therefore, we suggest that the entomopathogenic bacterium S. marcescens be considered a potentially promising endophyte for use in an innovative strategy for the integrated management of insect pests.

Testing Virulence of Different Species of Insect Associated Fungi against Yellow Mealworm (Coleoptera: Tenebrionidae) and Their Potential Growth Stimulation to Maize

This paper investigates 71 isolates of two genera of entomopathogens, Metarhizium and Beauveria, and a biostimulative genus Trichoderma, for their ability to infect yellow mealworms (Tenebrio molitor) and to stimulate maize (Zea mays) growth. Fungal origin, host, and isolation methods were taken into account in virulence analysis as well. Isolates Metarhizium brunneum (1154) and Beauveria bassiana (2121) showed the highest mortality (100%) against T. molitor. High virulence seems to be associated with fungi isolated from wild adult mycosed insects, meadow habitats, and Lepidopteran hosts, but due to uneven sample distribution, we cannot draw firm conclusions. Trichoderma atroviride (2882) and Trichoderma gamsii (2883) increased shoot length, three Metarhizium robertsii isolates (2691, 2693, and 2688) increased root length and two M. robertsii isolates (2146 and 2794) increased plant dry weight. Considering both criteria, the isolate M. robertsii (2693) was the best as it caused the death of 73% T. molitor larvae and also significantly increased maize root length by 24.4%. The results warrant further studies with this isolate in a tri-trophic system.

Endophytic colonization of entomopathogenic fungi increases plant disease resistance by changing the endophytic bacterial community

Various mechanisms are involved in plant disease resistance mediated by entomopathogenic fungi; however, the role of plant endophytic microbes in disease resistance is unknown. In the present study, we showed that the disease incidence of northern corn leaf blight caused by Exserohilum turcicum (Et) on maize was reduced significantly by soil inoculation with Beauveria bassiana (Bb). Meanwhile, B. bassiana colonization and E. turcicum infection increased the diversity and abundance and diversity of endophytic bacteria and fungi, respectively, while the abundance of endophytic bacterial of the Bb + Et treatment decreased significantly compared with that of Et treatment alone. However, Bb + Et treatment increased the relative abundance of plant beneficial bacteria significantly, for example, Burkholderia and Pseudomonas. Network analyses showed that the microbiome complexity increased after soil inoculation with B. bassiana. Taken together, these results revealed the potential mechanism by which entomopathogenic fungi exert biological control of maize leaf spot disease.