Endophytic Entomopathogenic Fungi Research Articles

Plant–Entomopathogenic Fungi Interaction: Recent Progress and Future Prospects on Endophytism-Mediated Growth Promotion and Biocontrol

Entomopathogenic fungi, often acknowledged primarily for their insecticidal properties, fulfill diverse roles within ecosystems. These roles encompass endophytism, antagonism against plant diseases, promotion of the growth of plants, and inhabitation of the rhizosphere, occurring both naturally and upon artificial inoculation, as substantiated by a growing body of contemporary research. Numerous studies have highlighted the beneficial aspects of endophytic colonization. This review aims to systematically organize information concerning the direct (nutrient acquisition and production of phytohormones) and indirect (resistance induction, antibiotic and secondary metabolite production, siderophore production, and mitigation of abiotic and biotic stresses) implications of endophytic colonization. Furthermore, a thorough discussion of these mechanisms is provided. Several challenges, including isolation complexities, classification of novel strains, and the impact of terrestrial location, vegetation type, and anthropogenic reluctance to use fungal entomopathogens, have been recognized as hurdles. However, recent advancements in biotechnology within microbial research hold promising solutions to many of these challenges. Ultimately, the current constraints delineate potential future avenues for leveraging endophytic fungal entomopathogens as dual microbial control agents.

Endophytic entomopathogenic fungi isolates as growth promoters of the grass Urochloa brizantha

This study evaluated the growth-promoting action of 16 isolates of the entomopathogenic fungal genus Metarhizium spp., representing 14 from the native pastures and two commercial isolates, on the forage grass Urochloa brizantha, via drench application to seeds. Multivariate analysis of plant height, length of the longest leaf and root, and dry and fresh weight of leaves and roots indicated the most promising isolates, five from native pastures (CEPAF_ENT25, CEPAF_ENT26, CEPAF_ENT27, CEPAF_ENT42, and CEPAF_ENT59) and one commercial (IBCB 425), all isolates of Metarhizium anisopliae. Except for isolate CEPAF_ENT59, there was a positive correlation between growth parameters of U. brizantha with the contents of chlorophyll a and b and carotenoids and with the contents of N, P, and Zn in the leaves. Endophytic colonization tests indicated the presence of Metarhizium spp. in all plant parts, most frequently in the stems. Furthermore, the selected isolates of Metarhizium spp. were recovered from the cultivation substrate and positively affected the germination and initial growth of U. brizantha. Thus, the most promising isolates have potential for application to seeds of U. brizantha.

Population and attacks of Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) on corn inoculated with endophytic entomopathogenic fungi from South Sumatra, Indonesia

Population and attacks of Spodoptera frugiperda J.E. Smith (Lepidoptera: Noctuidae) on corn inoculated with endophytic entomopathogenic fungi from South Sumatra, Indonesia

Effect of endophytic entomopathogenic fungal conidia and blastospores induced in maize plants by seed inoculation on Spodoptera frugiperda immune response and mortality

Abstract. Sari JMP, Herlinda S, Suwandi S, Elfita. 2023. Effect of endophytic entomopathogenic fungal conidia and blastospores induced in maize plants by seed inoculation on Spodoptera frugiperda immune response and mortality. Biodiversitas 24: 5709-5717. Endophytic entomopathogenic fungi (EPF) can produce conidia and blastospores; however, the pathogenicity of conidia and blastospores inoculated in plants on Spodoptera frugiperda larvae is limited. This research aimed to detect the effect of the endophytic entomopathogenic fungal conidia and blastospores induced in maize plants by seed inoculation on S. frugiperda's immune response and mortality. A total of 10 isolates of endophytic EPF were used in this experiment. The study revealed that 9 days after treatments, S. frugiperda larvae consuming maize leaves inoculated with blastospores of endophytic entomopathogenic fungi; their hemocyte concentration did not show any significant differences between the fungal treatments and control. However, 1 up to 7 days after treatments, the concentration significantly differed from the control. Furthermore, B. bassiana JgSPK, JaGiP, and JaSpkPGA(2) isolates tended to be the most pathogenic compared to other isolates. Feeding on leaves colonized by endophytic EPF could reduce the larval and pupal weight of S. frugiperda. The percentage of S. frugiperda non-emergence pupae from larvae-eating maize leaves colonized with B. bassiana JgSPK and JaGiP isolates was significantly higher than other fungal treatments and the control. The endophytic entomopathogenic fungal conidia and blastospores inoculated in maize plants by seed inoculation have a lethal effect on S. frugiperda larvae. However, exposure to conidia and blastospores did not reduce or increase the hemocyte concentration in the larvae hemolymph of S. frugiperda.

Direct and indirect effects of two endophytic entomopathogenic fungi on survival and feeding behaviour of meadow spittlebug Philaenus spumarius

The most effective way to contain spread of the plant pathogen Xylella fastidiosa in Europe is to manage populations of its main insect vector, Philaenus spumarius L. (Hemiptera: Aphrophoridae). The action of some entomopathogenic endophytic fungi (EEF) on insect pests, directly through contact or indirectly by internal colonization of host plant tissues, may offer an excellent control option within integrated pest management (IPM) programmes. This study evaluated the impact of two EEF strains as control agents of P. spumarius (Metarhizium brunneum strain EAMa 01/58-Su and Beauveria bassiana strain EABb 01/33-Su [Hypocreales: Clavicipitaceae and Cordycipitaceae, respectively]); both strains were known to be excellent control agents of many other serious chewing and sap-sucking agricultural pests. First, the pathogenicity of strains applied directly to P. spumarius adults was evaluated, resulting in 50.0% and 32.0% mortality and a mean survival time of 4.7 and 6.2 days for M. brunneum and B. bassiana, respectively. Furthermore, colonization of Sonchus oleraceus by EEFs was observed after both soil and foliar applications. Greatest colonization (91.0%) was observed in plants treated with foliar applications of M. brunneum. Based on these results, we evaluated the feeding behaviour of P. spumarius on S. oleraceus plants previously colonized by M. brunneum using the ‘Electrical Penetration Graph’ technique. P. spumarius fed in a similar way on EEF-colonized and non-colonized S. oleraceus plants, with the exception that insects feeding on colonized plants reached xylem vessels faster than insects feeding on non-colonized plants. In addition, significantly higher mortality of P. spumarius was observed when feeding on plants treated by M. brunneum compared with the control. The duration of xylem ingestion events indicates that P. spumarius preferred to feed on basal leaves of the plant compared with apical leaves. Our results indicate strong potential for strain EAMa 01/58-Su of M. brunneum to be used as part of an X. fastidiosa IPM programme.

Dual role of endophytic entomopathogenic fungi: induce plant growth and control tomato leafminer Phthorimaea absoluta.

Entomopathogenic fungi (EPF) are multifunctional microorganisms acting not only as biopesticides against insect pests but also as endophytes which regulate plant growth. The tomato leafminer, Phthorimaea absoluta (Tuta absoluta) is a devastating invasive pest of tomatoes worldwide. However, effective alternatives are needed for a sustainable management of this invasive pest. In this study, the functional effects of five EPF isolates Metarhizium flavoviride, M. anisopliae, M. rileyi, Cordyceps fumosorosea and Beauveria bassiana were evaluated on tomato growth promotion and pest protection against P. absoluta. When directly sprayed with conidia, P. absoluta larvae showed high cumulative mortality of 100% to M. anisopliae under 1 × 108 conidia/mL, whereas M. flavoviride, B. bassiana, C. fumosorosea and M. rileyi caused cumulative mortality of 92.65%, 92.62%, 92.16% and 68.95%, respectively. Moreover, all five EPF isolates can successfully colonize tomato plants, whilst the colonization rate for each EPF depends on the inoculation method used. The most efficient inoculation method for M. flavoviride and M. rileyi was root dipping, for M. anisopliae and C. fumosorosea it was coating seed, and for B. bassiana it was foliage spraying. The highest plant colonization was obtained by M. flavoviride. Meanwhile, all these isolates promoted tomato plant growth upon inoculation. Furthermore, endophytic colonization of plants by the five EPF negatively affected the performance of P. absoluta, among them M. anisopliae and C. fumosorosea showed strong negative effects on the performance of P. absoluta. Our results highlight the potential of incorporating entomopathogenic fungi as endophytes in integrated pest management practices to protect tomatoes against P. absoluta. © 2023 Society of Chemical Industry.

Effect of Beauveria bassiana and Metarhizium anisopliae on the growth of Spodoptera frugiperda by seed inoculation

Abstract. Sari JMP, Herlinda S, Suwandi S, Elfita. 2023. Effect of Beauveria bassiana and Metarhizium anisopliae on the growth of Spodoptera frugiperda by seed inoculation. Biodiversitas 24: 2350-2357. Spodoptera frugiperda J.E.Smith 1797 larvae are more difficult to control because they hide in the leaf sheaths. Therefore, it is necessary to use endophytic entomopathogenic fungi to control S. frugiperda larva. The aim of this research was to observe the effect of endophytic Beauveria bassiana (Bals.-Criv.) Vuill. and Metarhizium anisopliae (Metschn.) Sorok?n on the growth of S. frugiperda larvae by seed inoculation. A total of six isolates of B. bassiana (5 isolates) and M. anisopliae (1 isolate) were isolated from infected-host insect corpses and identified molecularly. The corn seeds were immersed using a fungal suspension of 1 x 1010 conidia mL-1. The results showed that feeding on maize leaves colonized with B. bassiana (JGTP240521A, WTTJC260521A, WTTJC290521A, WTTJC290521B, and JGNT300521 isolates) and M. anisopliae (WTTJC260521B isolate) significantly reduced the larval and pupal weight. The highest mortality (above 50%) of S. frugiperda larvae was recorded by B. bassiana (JGTP240521A isolate) . The treated larvae could produce abnormal and malformation pupae and adults, increasing mortality. Both fungi killed the larvae and induced disruption of normal growth larvae, pupae, and adults of S. frugiperda. B. bassiana was more pathogenic than M. anisopliae in killing the larvae of S. frugiperda. Results revealed that endophytic fungi B. bassiana and M. anisopliae inoculated through seed treatment had a negative impact on the growth of S. frugiperda larvae. Further studies are needed on the effect of B. bassiana and M. anisopliae by foliar spraying or seed treatment on maize plant to control S. frugiperda in the field.

Colonization and endophytic effect of Beauveria bassiana (Bals.-Criv.) Vuill. UHSB-END1 against Myzus persicae (Sulzer) and Plutella xylostella (L.) in cabbage

BackgroundFungal microbial biocontrol agent playing an important role in sustainable pest management with low cost. Conidial contact with cuticle is sufficient to cause disease in insects by entomopathogenic fungi (EPF) compared to bacteria and viruses which required ingestion of contaminated food. The field level application of fungi resulted inconsistent in their efficacy against insects as they withstand in the agroecosystem with adverse environmental conditions. To overcome this bottleneck, endophytic EPF, Beauveria bassiana (Bals.-Criv.) Vuill. (Cordycipitaceae: Hypocreales), is well-studied for the management of insects of cultivated crops and got promising results. The colonization of endophytic isolates varied from one host plant to another and virulence against insects too. Hence, the study was undertaken to know the colonization of indigenous B. bassiana UHSB-END1 isolate in cabbage plant and its efficacy against major insects of cabbage.ResultsThe indigenous isolate of B. bassiana UHSB-END1 was able to colonize cabbage in all the methods of inoculations (seed treatment, seedling root dip, soil drenching, foliar spray and combination treatment) at 30, 45 and 60 days of post-inoculation (dpi). However, the colonization of the fungus inside the cabbage was restricted to tissues of inoculation, and movement from the site of inoculation to other parts of the plant was poor. In the present study, colonization was the highest at 30 dpi in all methods of colonization with restricted colonization to the site of exposure of fungus. Further, in vivo and in planta assay confirmed the effectiveness of B. bassiana UHSB-END1 colonized cabbage against Myzus persicae (Sulzer) and Plutella xylostella (Linnaeus). Under in vivo conditions the maximum mortality of M. persicae and P. xylostella was recorded at 30 dpi. It was decreased slightly at 45 dpi, and the lowest morality was recorded at 60 dpi. In planta experiment also proved better efficacy against both the test insects. Wherein mortality of M. persicae ranged from 22 to 36% five days after release (DAR), it was increased to 48–68% at 10 DAR and reached highest mortality rate at 15DAR (72–96%). Similarly, mortality of P. xylostella ranged from 14 to 24% after five DAR, and it was 27–44% at 10 DAR, and maximum mortality rate of larvae were recorded at 15 DAR (64–96%).ConclusionThe present study reported 100% colonization of cabbage plant by indigenous B. bassiana UHSB-END1 at 30 dpi in combination of treatment and showed a maximum efficacy in managing the population of major insects of cabbage. Introducing this indigenous isolate will pave a ray of hope in managing the both key insects (P. xylostella and M. persicae) in cabbage agroecosystem without disturbing the environment and further helps in production of cabbage with minimum pesticide residue for consumers.

Correction for González-Guzmán et al., "Elucidating the Effect of Endophytic Entomopathogenic Fungi on Bread Wheat Growth through Signaling of Immune Response-Related Hormones".

Correction for González-Guzmán et al., "Elucidating the Effect of Endophytic Entomopathogenic Fungi on Bread Wheat Growth through Signaling of Immune Response-Related Hormones".

Combatting insects mediated biotic stress through plant associated endophytic entomopathogenic fungi in horticultural crops.

Horticultural production is a vital catalyst for economic growth, yet insect infestations reduce horticultural crop yield and quality. Pesticides and other pest control methods are used during planting to eliminate pests that cause direct and indirect losses. In such situations, endophytic entomo-pathogenic fungi (EEPF) can act as a potential tools for biological control. They protect plants by boosting growth, nutrition, morpho-physiology and salt or iron tolerance. Antixenosis, antibiosis and plant tolerance change insect performance and preferences. EEPF- plant colonisation slows herbivore development, food consumption, oviposition and larval survival. EEPF changes plant physio-chemical properties like volatile emission profile and secondary metabolite production to regulate insect pest defences. EEPF produces chitinases, laccases, amylases, and cellulases for plant defence. Recent studies focused on EEPF species' significance, isolation, identification and field application. Realizing their full potential is difficult due to insufficient mass production, storage stability and formulation. Genetic-molecular and bioinformatics can help to build EEPF-based biological control systems. Metagenomics helps study microbial EEPF taxonomy and function. Multi-omics and system biology can decode EEPF interactions with host plants and microorganisms. NGS (Next Generation Sequencing), comparative genomics, proteomics, transcriptomics, metabolomics, metatranscriptomics and microarrays are used to evaluate plant-EEPF relationships. IPM requires understanding the abiotic and biotic elements that influence plant-EEPF interaction and the physiological mechanisms of EEPF colonisation. Due to restricted research, there are hundreds of unexplored EEPFs, providing an urgent need to uncover and analyse them.

Impact of Beauveria bassiana and Metarhizium anisopliae on the Metabolic Interactions between Cucumber (Cucumis sativus L.) and Cucumber Mosaic Virus (CMV)

In natural systems, plant–endophyte interactions are important for reducing abiotic and biotic stresses in plants by producing a variety of metabolites that protect plants from pathogens and herbivores. Biocontrol strategies are increasingly being used as a viable alternative to chemical pesticides. Entomopathogenic fungi (EPF) are one of them, and they have been touted as a successful method for biological pest control in plants. Because EPF strains are sensitive to environmental conditions when sprayed, the recently discovered endophytic behavior of several EPF strains has improved their management. Cucumber mosaic virus (CMV) is one of the most common and serious plant viruses worldwide, infecting over 1200 plant species and being spread by more than 80 aphid species. CMV control is directed towards the use of chemical insecticides to eradicate its insect vectors. Endophytic EPF is currently being studied to control plant virus infection, and antagonistic effects have been reported. Metabolomics is an emerging research field for plant metabolite profiling and is employed to study plant–endophyte interactions. In the present research, metabolomics approaches were conducted to gain information into mechanisms involved in defense against CMV in endophytes Beauveria bassiana and Metarhizium anisopliae (EPF)-treated diseased cucumber plants. In addition, CMV-induced metabolic changes in cucumber plants were investigated. Our analysis indicated large differences in cucumber metabolites due to endophytes application. In total, six hundred and thirty-one metabolites were differentially expressed in endophyte-treated CMV diseased cucumber plants. Regulation of different kinds of amino acids, organic acids, and phenylpropanoids metabolites could provide insight about plant defense mechanism against CMV pathogen. Important metabolites were found to be regulated in diseased cucumber plants due to fungal endophytes treatment that could possibly confer tolerance to CMV disease.

Development of Spodoptera frugiperda fed on young maize plant’s fresh leaves inoculated with endophytic fungi from South Sumatra, Indonesia

Abstract. Lestari YA, Verawaty M, Herlinda S. 2022. Development of Spodoptera frugiperda fed on young maize plant’s fresh leaves inoculated with endophytic fungi from South Sumatra, Indonesia. Biodiversitas 23: 5056-5063. The endophytic entomopathogenic fungi are needed to control the Spodoptera frugiperda larvae hiding inside the maize plants. This research aimed to assess the effect of young maize inoculated with endophytic fungi on the development of S. frugiperda. The fungal isolates used for the bioassay were Beauveria bassiana JgSPK isolate (GenBank acc. no. MZ356494), B. bassiana JgCrJr isolate (GenBank acc. no. MZ356497), and Metarhizium anisopliae CaTpPga isolates (GenBank acc. no. MZ242073). Beauveria bassiana (JgSPK and JgCrJr isolates) and M. anisopliae (CaTpPga isolate) colonized young maize plant significantly reduced the pupae and adult emergence, adult longevity, eggs laid, and viable eggs of S. frugiperda. The fungi also significantly enhanced larval mortality compared to non-colonized ones. The larval mortality caused by M. anisopliae CaTpPga isolate (57.67%) was highest among other treatments but not significantly different from those treated with B. bassiana JgSPK isolate (51.33%). Furthermore, the developmental time (eggs, larvae, pupae stages, and lifespan) of S. frugiperda fed on leaves colonized with endophytic fungi significantly increased compared to non-colonized ones. So, B. bassiana and M. anisopliae inoculated as seed treatments caused negative effects on the development of S. frugiperda. These findings highlight the potential of endophytic B. bassiana and M. anisopliae from South Sumatra to protect maize against S. frugiperda.

Elucidating the Effect of Endophytic Entomopathogenic Fungi on Bread Wheat Growth through Signaling of Immune Response-Related Hormones.

ABSTRACTEntomopathogenic fungi (EF) provide a potent biocontrol tool; also, their endophytic behavior has broadened their contribution to integrated pest management (IPM) and crop production. In this work, Beauveria bassiana and Metarhizium brunneum were applied to bread wheat (Triticum aestivum) seedlings to elucidate how fungal colonization influences plant growth and the relative expression of 24 genes involved in hormonal syntheses and plant immune mechanisms. A preliminary assay was used to determine the time needed for fungal colonization and assess its effect on wheat growth. Then, plant material collected at various times after inoculation (viz., 2, 8, 20, and 36 h and 9 and 15 days) was used to investigate gene expression by quantitative reverse transcription PCR (RT-qPCR). During the colonization time, B. bassiana and M. brunneum caused strong downregulation of most genes associated with plant immunity and the synthesis of hormones like auxin, cytokinin, and gibberellin. This effect was concomitant with a slowdown of endophytic-colonization-related plant growth until 19 days postinoculation (dpi). However, the wheat started to recover at 15 dpi, simultaneously with upregulation of auxin- and gibberellin-related genes. The results suggest that the EF trigger induced systemic resistance rather than acquired systemic resistance during early plant-microbe cross talk in wheat. Also, they confirm that the hormone and immune responses of wheat triggered by EF inoculation influenced plant growth, which can be useful with a view to optimizing management of these microorganisms for sustainable agriculture.IMPORTANCE Microbial control of insect and mite pests is a key tool to develop integrated pest management (IPM) and sustainable agriculture. Entomopathogenic fungi (EF) may have associations with the plants, playing additional ecological roles in the rhizosphere, in the phylloplane, and as plant endophytes. Beauveria bassiana 04/01TIP and Metarhizium brunneum 01/58Su are two strains that showed very good results either in pest control or plant growth promotion and would be good candidates to develop mycoinsecticides as an alternative to pesticides. However, deep knowledge about their interaction with the plant would let farmers optimize their use and understand the plant response, enhancing and promoting their broader contribution to IPM and crop production.

Early Physiological Response of Potato Plants to Entomopathogenic Fungi under Hydroponic Conditions

Endophytic entomopathogenic fungi are promising agents for the promotion of plant growth, the activation of immunity, and protection against phytopathogens. However, physiological changes in plants after treatment with fungi are insufficiently studied. We investigated the effect of potato inoculation with conidia from Metarhizium robertsii and Beauveria bassiana on the growth (fresh and dry weight, length of shoots and roots, counts of stolons and leaves, and total surface area of leaves) and physiological parameters (pigment contents, free proline and malondialdehyde content, and activity of antioxidant enzymes) at the initial stage of the plant–fungus interaction (seven days) under hydroponic conditions. The results showed that the fungi could act as an immune-modulating factor for plants based on the increase in malondialdehyde and proline contents. At the same time, we observed growth retardation and a decrease in the content of photosynthetic pigments, which may be caused by a tradeoff between plant growth and the immune response.

Effect of passage through the plant on virulence and endophytic behavioural adaptation in the entomopathogenic fungus Beauveria bassiana

Systemic crop protection using endophytic isolates of entomopathogenic fungi is at the forefront of IPM. Nonetheless, any potential trade-offs between virulence and endophytic behaviour must be elucidated if they are to be effectively used in pest management strategies. Here we investigated endophytic adaptation in an isolate of Beauveria bassiana following successive passage through melon, tomato and cotton tissues. Plants were sprayed with a suspension of B. bassiana endophytic isolate EABb 04/01-Tip to initiate endophytic colonization. Once colonization was established, the fungus was re-isolated from the plant, applied to another plant and re-isolated again; this was repeated to achieve three passages. After each passage, a conidial suspension of each isolate was used in bioassays to evaluate both virulence against 4th instar larvae of the model insect Galleria mellonella and to quantify the extent of endophytic activity in each respective host plant species. When sprayed leaves were inspected for fungal colonization, differences in percentage tissue colonization amongst the plant species were detected after the first re-isolation. Endophytic colonization rates in melon and tomato, which varied from 70 to 100%, were higher than those observed in cotton, which ranged from 40 to 50%; endophytic colonization in cotton increased to 75–100% after the third passage. This improvement in endophytic behaviour in cotton, an apparently suboptimal plant for fungal colonization, suggests an evolutionary adaptation to localized or transient endophytic colonization, while further assays are needed. Meanwhile, when endophytic colonization of non-sprayed leaves distant from the sprayed ones was investigated, endophytic activity was evident in all three crop species suggesting that movement within plants after successive passage increased the extent of endophytic colonization from transient to systemic. The present research highlights the potential for adaptation to endophytic behaviour in crops that are less suitable for endophytic colonization. Furthermore, we demonstrated stability in virulence after multiple passages through host plants. This is a key result for the development of IPM strategies based on endophytic entomopathogenic fungi.

Isolation and pathogenicity of endophytic fungi associated with some maize hybrids against certain Lepidoptera pests

The means of biological control methods in which entomopathogens are being applied to crops has been adopted for several years. However, endophytic entomopathogenic fungi could provide plants with longer protective effect compared to usual bio-control agents’ applications since they are being internally associated with plants and could grant them more sustainable protection. This study was an attempt to isolate the endophytic fungi from Hytech 2031, Pioneer 3444 and SC 132 maize hybrids and investigating their pathogenicity against Sesamia cretica, Pectinophora gossypiella and Spodoptera littoralis in different larval instars. Five fungi were isolated from the maize hybrids, i.e. Aspergillus flavus MRDS 301, Curvularia lunata MRDS 302, Chaetomium madrasense MRDS 303, Alternaria alternate MRDS 304 and Aspergillus flavus MRDS 305. C. lunata MRDS 302 and C. madrasense MRDS 303 treatments showed insecticidal effect (100 %) against S. cretica 1st instar larvae. All treatments against S. cretica significantly reduced the weight of the resulting full grown instar larvae. C. madrasense caused the highest mortality to P. gossipiella 1st instar larvae compared to other treatments. In general, A. flavus MRDS 305 was more effective than A. flavus MRDS 301 against all the tested pests. Soil infestation was a highly effective method of inoculation to introduce the fungus C. madrasense inside maize plants since the fungus was isolated from both roots and leaves.

Prospect of Endophytic Fungal Entomopathogens for Pest Management

Endophytic fungal entomopathogens could offer a number of benefits to their host plants, which include protection against the primary pests, resistance against microbial pathogens, stimulation of growth, or increase of heavy metal or drought tolerance. However, all reports, so far, indicate that colonization of some plants by entomopathogenic fungi seemly confer only certain benefits to their hosts or else only one parameter was examined. Our study underscores the practicability of introduction of specific insect fungal pathogen strains into host plants as endophytes that could simultaneously promote host plant growth and offer plant protection against microbial pathogens, and/or insect pests, which highlights the prospect of endophytic fungal entomopathogens for pest management. Here, we further commented on the study-involved issues and the factors that possibly affect colonization by fungal entomopathogens and the benefits to the host plant offered by the endophytes. Moreover, we put forward the possible link of some plant morphological changes and/or stimulation of some plant defense pathways with the resistance of the host plants against insect/ microbial pathogens, although the underlying mechanism remains somewhat of a mystery that should be uncovered in the future.

La inoculación con hongos endófitos entomopatógenos en semilla genera una respuesta fisiológica y promueve el crecimiento vegetal en plantas de chile poblano en invernadero

Introducción: Algunos hongos entomopatógenos actúan como endófitos y son promotores del crecimiento. Estos beneficios pueden ser explicados por mejoras en procesos fisiológicos. En esta investigación se evaluó el efecto de cepas comerciales de hongos endófitos entomopatógenos y de aislados de suelos agrícolas del estado de San Luis Potosí (HEE) sobre el crecimiento, fotosíntesis, intercambio de gases y producción en plantas de chile poblano, considerando el efecto del método de inoculación usado.Metodología: Se usó como modelo al chile poblano (Capsicum annuum L.) cultivado bajo condiciones de laboratorio y en invernadero. Se evaluaron siete cepas de HEE: tres aislados de suelo agrícola de San Luis Potosí, pertenecientes a los géneros Metarhizium. (aislado RV01), Paecilomyces. (RV05) y Penicillium (aislado SL14); dos cepas de los hongos entomopatógenos Beauveria bassiana [(Bals.-Criv.) Vuill. 1992] (aislado BB42) y Metarhizium anisopliae [(Metschn.) Sorokin 1883)] (aislado MA25) aisladas de insectos y dos cepas comerciales de B. bassiana (aislado BB09) y M. anisopliae (aislado MA28). Se preparó una solución de conidios y se probaron dos métodos: 1) inoculación en semilla; y 2) aspersión del sustrato y una segunda aplicación cuando emergió la primera hoja verdadera. Se incluyeron testigos en cada experimento (se inoculo agua y un agente surfactante). Se evaluaron parámetros fotosintéticos (eficiencia máxima y efectiva de PSII, disipación fotoquímica y no fotoquímica, tasa de transporte de electrones), intercambio de gases (tasa de asimilación neta, conductancia estomática y transpiración) y el porcentaje de colonización en hoja, tallo y raíces. Al final del experimento se midió la longitud de la raíz, biomasa seca total, de la parte aérea de la planta y de la raíz.Resultados: A los 33 días después de la inoculación se observó como la inoculación con RV01, MA25, BB09 y SL14 aumentaron la asimilación neta de CO2 y la conductancia estomática, respecto a los testigos, al ser inoculados por semilla o por aspersión. Inocular directamente las semillas con HEE mejoró significativamente la asimilación de CO2, la disipación fotoquímica y la eficiencia efectiva de PSII en comparación con plantas inoculadas por aspersión. El aislado RV05 sobresalió por los resultados observados en el invernadero, con mayor producción de biomasa total. Las plantas inoculadas por semilla mostraron un aumento en la producción de biomasa total, y en el peso seco de la parte aérea y de raíces con respecto a las plantas inoculadas por aspersión. Un mayor crecimiento en las plantas se asoció con la colonización endófita.Conclusiones: Los HEE aislados a partir de suelos agrícolas de San Luis Potosí pueden competir con cepas comerciales en la promoción del crecimiento de plantas de chile poblano en invernadero. La inoculación directa de HEE sobre la semilla genera mejores resultados, aunque con variaciones en función de la cepa.

Unveiling of Swainsonine Biosynthesis via a Multibranched Pathway in Fungi.

The indolizidine alkaloid swainsonine (SW) is a deadly mycotoxin to livestock that can be produced by different plant-associated fungi, including the endophytic entomopathogenic fungi Metarhizium species. The SW biosynthetic gene cluster has been identified but the genetic mechanism of SW biosynthesis remains obscure. To unveil the SW biosynthetic pathway, we performed gene deletions in M. robertsii, heterologous expression of a core biosynthetic gene, substrate feedings, mass spectrometry, and bioassay analyses in this study. It was unveiled that SW is produced via a multibranched pathway by the hybrid nonribosomal peptide-polyketide synthase (NRPS-PKS) gene cluster in M. robertsii. The precursor pipecolic acid can be converted from lysine by both the SW biosynthetic cluster and the unclustered genes such as lysine cyclodeaminase. The hybrid NRPS-PKS enzyme produces three intermediates with and without domain skipping. Intriguingly, the biosynthetic process is coupled with the cis to trans nonenzymatic epimerization of C1-OH for both hydroxyl- and dihydroxyl-indolizidine intermediates. We also found that SW production was dispensable for fungal colonization of plants and infection of insect hosts. Functional characterization of the SW biosynthetic genes in this study may benefit the safe use of Metarhizium fungi as insect biocontrol agents and the management of livestock pastures from SW contamination by genetic manipulation of the toxin-producing fungi.

Does the Infectious Status of Aphids Influence Their Preference Towards Healthy, Virus-Infected and Endophytically Colonized Plants?

Aphids (Hemiptera: Aphididae) cause significant damage and transmit viruses to various crop plants. We aimed to evaluate how the infectious status of aphids influences their interaction with potential hosts. Two aphid (Myzus persicae and Rhopalosiphum padi) and plant (Nicotiana tabacum and Triticum aestivum) species were used. The preferences of aphids towards healthy, virus-infected (Potato Leafroll Virus (PLRV) and Barley Yellow Dwarf virus (BYDV)), and endophytic entomopathogenic fungi (EEPF)-inoculated (Beauveria bassiana and Metarhizium acridum) plants were investigated in dual-choice tests. The headspace volatiles of the different plant modalities were also sampled and analyzed. Viruliferous and non-viruliferous aphids were more attracted to EEPF-inoculated plants compared to uninoculated plants. However, viruliferous aphids were more attracted to EEPF-inoculated plants compared to virus-infected plants, while non-viruliferous insects exhibited no preference. Fungal-inoculated plants released higher amounts of aldehydes (i.e., heptanal, octanal, nonanal and decanal) compared to other plants, which might explain why viruliferous and non-viruliferous aphids were more abundant in EEPF-inoculated plants. Our study provides an interesting research perspective on how EEPF are involved in behavior of virus vector, depending on the infectious status of the latter.