Antifungal Activity of Beauveria bassiana Endophyte against Botrytis cinerea in Two Solanaceae Crops

Jaber L.R., Ownley B.H.

An increasing number of recent studies demonstrate that entomopathogenic fungi, often solely considered as insect pathogens, play additional roles in nature, including endophytism, plant disease antagonism, plant growth promotion, and rhizosphere colonization. These newly emerging, but not yet fully understood, ecological roles hint at the possibility that we have been overlooking important attributes in our quest to develop fungal entomopathogens exclusively as inundative biopesticides against insect and other arthropod pests. Such additional roles recently-discovered to be played by entomopathogenic fungi provide opportunities for the multiple use of these fungi in integrated pest management (IPM) strategies. Of particular interest is the ability displayed by various genera of entomopathogenic fungi to colonize a wide variety of plant species in different families, both naturally and artificially following inoculation, and confer protection against not only insect pests but also plant pathogens. This article reviews the literature currently available on the endophytic colonization of different host plants by fungal entomopathogens, and summarizes the negative effects of such colonization on insect pests and plant pathogens that have been reported to date. It also addresses the possible mechanisms of protection conferred by endophytic fungal entomopathogens and explores the potential use of these fungi as dual microbial control agents against both insect and pathogen pests. Moreover, interactions amongst endophytic fungal entomopathogens and other endophytes are discussed. Finally, current limitations and future research directions for the innovative use of endophytic fungal entomopathogens as dual microbial control agents are summarized.

Parsa S., Ortiz V., Gómez-Jiménez M.I., Kramer M., Vega F.E.

The common bean is the most important food legume in the world. We examined the potential of the fungal entomopathogens Beauveria bassiana and Metarhizium anisopliae applied as seed treatments for their endophytic establishment in the common bean. Endophytic colonization in sterile sand:peat averaged ca. 40% higher for fungus treatments and ca. six times higher for volunteer fungi (other fungal endophytes naturally occurring in our samples), relative to sterile vermiculite. Colonization by B. bassiana and M. anisopliae was least variable in sterile vermiculite and most variable in sterile soil:sand:peat. The impact of soil sterilization on endophytic colonization was assessed in a separate experiment using six different field-collected soils. Soil sterilization was the variable with the largest impact on colonization (70.8% of its total variance), while the fungal isolate used to inoculate seeds explained 8.4% of the variance. Under natural microbial soil conditions experienced by common bean farmers, seed inoculations with B. bassiana and M. anisopliae are unlikely to yield predictable levels of endophytic colonization.

Jaber L.R., Araj S.

Entomopathogenic fungi are typically applied as innundative sprays with the expectation of short-term pest control, but a growing number of studies demonstrate the potential of these fungi to endophytically colonize a wide variety of plants and confer longer-term protection. Endophytic colonization of plants by fungal entomopathogens can also enable these fungi to establish intricate interactions in a tritrophic context; thus affecting other groups of natural enemies such as parasitoids. Yet to date, effects of endophytic plant colonization on parasitoids have mostly been investigated using the grass-endophyte organism systems. The present study investigates the effects of the fungal entomopathogens Beauveria bassiana and Metarhizium brunneum , following their endophytic colonization of sweet pepper Capsicum annum , on the development and fecundity of two successive generations of the green peach aphid Myzus persicae in addition to parasitism by the aphid endoparasitoid Aphidius colemani in two replicate greenhouse experiments. Plant roots were drenched with the conidial suspension of each fungal strain or sterile water, and the endophytic colonization of different plant parts (root, stem, and leaf) was confirmed 7 (when 1st generation M. persicae started feeding on caged treatment plants) and 17 (when A. colemani started parasitizing 2nd generation M. persicae reared on caged treatment plants) days post-inoculation (dpi). Inoculation with the tested fungal entomopathogens enhanced several plant growth parameters that were sampled 7 dpi (before M. persicae infestation) and all plant growth parameters sampled 35 dpi (following infestation with two successive generations of M. persicae ). Fewer numbers of aphids were found when sampling plants inoculated with both fungal strains in comparison to the control during the development and reproduction of 1st and 2nd generations of M. persicae . The negative effects of plant colonization with the inoculated fungal strains on aphid development and fecundity also included prolonged development time, delayed onset of reproduction, and reduced birth rate. On the other hand, the percentage mummification and adult emergence of A. colemani progenies parasitizing 2nd generation aphid reared on inoculated or control plants were not affected by plant colonization with B. bassiana and M. brunneum. In addition, no differences were observed in development time, percentage female, and adult longevity of A. colemani progenies among inoculated and control plants. This study presents one of very few reports of the compatible use of endophytic fungal entomopathogens with other biological control agents, particularly parasitoids, for aphid suppression under controlled greenhouse conditions as part of an Integrated Pest Management (IPM) approach.

Lozano-Tovar M.D., Garrido-Jurado I., Quesada-Moraga E., Raya-Ortega M.C., Trapero-Casas A.

The antifungal activity of the entomopathogenic fungi isolates Metarhizium brunneum EAMb 09/01-Su and Beauveria bassiana EABb 09/16-Su against the olive pathogens Verticillium dahliae and Phytophthora megasperma was evaluated. The crude extract and its partial purified fractions obtained from both isolates showed complete inhibition of the mycelial growth of V. dahliae. However, the same fractions obtained from B. bassiana EABb 09/16-Su were less effective against the mycelial growth of P. megasperma. Our results showed that M. brunneum EAMb 09/01-Su had the highest fungicidal activity, inhibiting the mycelial growth of both pathogens. Both fractions IV and VI from M. brunneum EAMb 09/01-Su were evaluated by the progress of the Verticillium wilt of the plant and showed clear antagonism against V. dahliae, reducing the severity of the symptoms between 38.9 and 58.9%. The active metabolite obtained from M. brunneum not only reduced the germination of V. dahliae microsclerotia but also inhibited hyphal formation, decreased the number of reproductive structures, and changed the conformation of the microsclerotial colony, preventing the formation of new microsclerotia. The evaluation of temperature, UV light and pH on the antifungal activity of the dialyzed fraction from M. brunneum showed that the antifungal activity was stable at 60 °C (2 h) and 120 °C (20 min) and to UV light radiation. However, the exposition to the dialyzed fraction at pH 7.5 and 8.5 affected the antifungal activity. The results of this study clearly showed that the entomopathogenic fungus M. brunneum EAMb 09/01-Su produces antifungal compounds that reduce the number of the pathogen propagules in the soil and the severity of Verticillium wilt. Therefore, this resource should be further studied as an alternative for the integrated management of Verticillium wilt and Phytophthora root rot, which is the most severe disease in all traditional olive-growing regions worldwide, and as a reliable and sustainable strategy for a reduced reliance on pesticides.

Kaonga C.C., Chidya R.C., Kosamu I.B., Abdel-dayem S.M., Mapoma H.W., Thole B., Mbewe R., Sakugawa H.

A review of Japan’s fungicide usage from the 1960s to recent times was conducted using data from the National Institute of Environmental Studies, Japan. A total of 16 commonly used fungicides were assessed and these are: captan, chlorothalonil, fenarimol, ferbam, fosetyl-Al, iprodione, isoprothiolane, mancozeb, mepronil, metalaxyl, myclobutanil, pencycuron, thiophanate-methyl, tolclofos-methyl, triadimefon and trifloxystrobin. The assessment revealed that the most used fungicide within the period (1962–2014) was chlorothalonil with a maximum usage amount of 1795 tons/year. The least used was found to be myclobutanil with a maximum usage amount of 8 tons/year within the same reporting period. Generally, the usage of most of the fungicides peaked between the 1980s to early 2000s. For most of these fungicides, their usage amounts have decreased in recent times. However, the continuous usage of these fungicides has a potential to cause problems in the environment ranging from mere irritations to being very toxic to human beings and organisms.

Feng N., Yu J., Zhao H., Cheng Y., Mo C., Cai Q., Li Y., Li H., Wong M.

Soil pollution with organic contaminants is one of the most intractable environmental problems today, posing serious threats to humans and the environment. Innovative strategies for remediating organic-contaminated soils are critically needed. Phytoremediation, based on the synergistic actions of plants and their associated microorganisms, has been recognized as a powerful in situ approach to soil remediation. Suitable combinations of plants and their associated endophytes can improve plant growth and enhance the biodegradation of organic contaminants in the rhizosphere and/or endosphere, dramatically expediting the removal of organic pollutants from soils. However, for phytoremediation to become a more widely accepted and predictable alternative, a thorough understanding of plant-endophyte interactions is needed. Many studies have recently been conducted on the mechanisms of endophyte-assisted phytoremediation of organic contaminants in soils. In this review, we highlight the superiority of organic pollutant-degrading endophytes for practical applications in phytoremediation, summarize alternative strategies for improving phytoremediation, discuss the fundamental mechanisms of endophyte-assisted phytoremediation, and present updated information regarding the advances, challenges, and new directions in the field of endophyte-assisted phytoremediation technology.

Jaber L.R., Enkerli J.

The effect of increased duration of seed treatment with two fungal entomopathogens, Beauveria bassiana (NATURALIS) and Metarhizium brunneum (BIPESCO5), on the growth and colonization of broad bean ( Vicia faba ) was assessed in two replicate greenhouse experiments. The plants were inoculated by soaking seeds in a concentration of 1 × 10 7  conidia ml −1 of each of the two fungal strains or in sterile distilled water containing 0.1% Tween 80 for 2, 8, and 16 h. Percent seed germination and seedling emergence as well as primary root length were determined seven days post inoculation. Effects of fungal strain and seed treatment duration on plant height, number of leaf pair, fresh root and shoot weight were measured 14 and 28 days post inoculation. Seed treatment with either fungal strain significantly enhanced almost all measured plant growth parameters. Overall, plant growth was also significantly enhanced as seed treatment duration increased; irrespective of fungal strain. Percent colonization of different plant parts (root, leaf, and stem) sampled 14 and 28 days post inoculation increased as the duration of seed treatment increased as well. The increase in colonization rate due to increased seed treatment duration varied significantly among plant parts, but not among both sampling dates. Our study demonstrates that M. brunneum can systemically colonize different plant parts and improve plant growth when applied as a seed treatment. This was also confirmed for the well-known endophytic B. bassiana strain used in this study. Our results also provide the first report for the effect of increased duration of seed treatment with both endophytic fungal entomopathogens on plant growth enhancement.

Punja Z.K., Rodriguez G., Tirajoh A.

Tomato plants in two commercial greenhouses were treated with Rhapsody (Bacillus subtilis strain QST 713, rate of 1.45%) once every 4 weeks during 2012–2013 to determine effects on post-harvest fruit infection. Populations of Bacillus and disease incidence were monitored weekly from harvested fruit over an 18-week period. Population levels of Bacillus ranged from 75 to 110 × 104 colony forming units (cfu) cm−2 of fruit surface area one week after application to 25–30 × 104 cfu cm−2 of fruit surface area 4 weeks after application. Disease incidence on harvested fruit incubated at 21 °C for 7–10 days was variable, due to variation in inoculum levels within the greenhouse as well as variable environmental conditions. Both disease incidence and severity were significantly reduced on Rhapsody-treated fruit, especially in the 1–2 week period following application. Post-harvest storage temperature (13 °C vs. 21 °C) and incubation time (12 vs. 16 days) had a significant effect on final disease severity. Rhapsody-treated fruit incubated at 13 °C had an average of 1–2% fruit infection compared to up to 20% infection on untreated fruit at 21 °C. The most frequent pathogens affecting fruit quality were Penicillium sp. and Rhizopus stolonifer. Rhapsody applications made every 4 weeks maintained sufficiently high populations of Bacillus on the fruit surface to prevent spread of these fungi onto the fruit, resulting in significant post-harvest disease control on fresh market tomatoes. When combined with storage at 13 °C for no more than 12 days, disease was reduced to negligible levels.

Card S., Johnson L., Teasdale S., Caradus J.

Resquín-Romero G., Garrido-Jurado I., Delso C., Ríos-Moreno A., Quesada-Moraga E.

The current work reports how spray application of entomopathogenic fungi on alfalfa, tomato and melon plants may cause an additional Spodoptera littoralis larvae mortality due to a temporal colonization of the leaves and subsequent ingestion of those leaves by the larvae. Most entomopathogenic fungi (EF) (Ascomycota: Hypocreales) endophytes seem to colonize their host plants in a non-systemic pattern, in which case at least a transient endophytic establishment of the fungus should be expected in treated areas after spray application. In this work, all strains were able to endophytically colonize roots, stems and leaves during the first 96h after inoculation. Whilst the treatment of S. littoralis larvae with a 10(8)ml(-1) conidial suspension resulted in moderate to high mortality rates for the Metarhizium brunneum EAMb 09/01-Su (41.7-50.0%) and Beauveria bassiana EABb 01/33-Su (66.7-76.6%) strains, respectively, an additive effect was detected when these larvae were also fed endophytically colonized alfalfa, tomato, and melon leaves, with mortality rates varying from 25.0% to 46.7% as a function of the host plant and total mortality rates in the combined treatment of 75-80% and 33-60% for B. bassiana and M. brunneum, respectively. Fungal outgrowth was not detected in any of the dead larvae feeding on colonized leaves, whereas traces of destruxin A were detected in 11% of the insects fed tomato discs endophytically colonized by M. brunneum. The combined effects of the fungal spray with the mortality caused by the feeding of insects on transient EF-colonized leaves have to be considered to estimate the real acute impact of field sprays with entomopathogenic fungi on chewing insects.

Kauppinen M., Saikkonen K., Helander M., Pirttilä A.M., Wäli P.R.

There is an urgent need to create new solutions for sustainable agricultural practices that circumvent the heavy use of fertilizers and pesticides and increase the resilience of agricultural systems to environmental change. Beneficial microbial symbionts of plants are expected to play an important role in integrated pest management schemes over the coming decades. Epichloë endophytes, symbiotic fungi of many grass species, can protect plants against several stressors, and could therefore help to increase the productivity of forage grasses and the hardiness of turf grasses while reducing the use of synthetic pesticides. Indeed, Epichloë endophytes have successfully been developed and commercialized for agricultural use in the USA, Australia and New Zealand. Many of the host grass species originate from Europe, which is a biodiversity hotspot for both grasses and endophytes. However, intentional use of endophyte-enhanced grasses in Europe is virtually non-existent. We suggest that the diversity of European Epichloë endophytes and their host grasses should be exploited for the development of sustainable agricultural, horticultural and landscaping practices, and potentially for bioremediation and bioenergy purposes, and for environmental improvement.

Klieber J., Reineke A.

The recent introduction and rapid spread of the tomato leaf miner Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) throughout Europe, Africa and the Middle East poses a severe threat to future cultivation of tomato and other Solanaceae. Among the best practicable means for effective and sustainable control of this invasive insect pest are entomopathogenic fungi, which can either prevent a further spread of this insect to new areas or keep population densities below an economic threshold level. Here, we report on the efficacy of a commercially available mycoinsecticide based on the entomopathogen Beauveria bassiana (Bals.) Vuill. (Ascomycota: Hypocreales) against all four larval stages of T. absoluta. In bioassays, high mortality rates and significantly reduced longevity of larvae were obvious when larvae had fed for a period of around 15 days on leaves with B. bassiana propagules present on the surface as an epiphyte with mortality values corrected for variance in control mortality of 90–100%. In addition, a second mode of action of B. bassiana against T. absoluta larvae was evident in bioassays in the form of an endophytic establishment of this fungus in treated tomato plants. Longevity of T. absoluta L4 larvae was significantly lower in individuals which had fed on surface-sterilized tomato leaves obtained from plants treated 18 days before the bioassay with a B. bassiana suspension compared to larvae feeding on control plants treated with water. Corrected mortality reached values between 30% and 50% for all larval instars. Growth of tomato plants was not inhibited due to colonization by endophytic B. bassiana and a weak systemic translocation of fungal propagules in non-treated leaves was evident in the assays. Accordingly, entomopathogenic fungi like B. bassiana express different modes of action again target insect pests, which is of particular relevance for the design of efficient management strategies for invasive pests like T. absoluta.

Barelli L., Moonjely S., Behie S.W., Bidochka M.J.

This review examines the symbiotic, evolutionary, proteomic and genetic basis for a group of fungi that occupy a specialized niche as insect pathogens as well as endophytes. We focus primarily on species in the genera Metarhizium and Beauveria, traditionally recognized as insect pathogenic fungi but are also found as plant symbionts. Phylogenetic evidence suggests that these fungi are more closely related to grass endophytes and diverged from that lineage ca. 100 MYA. We explore how the dual life cycles of these fungi as insect pathogens and endophytes are coupled. We discuss the evolution of insect pathogenesis while maintaining an endophytic lifestyle and provide examples of genes that may be involved in the transition toward insect pathogenicity. That is, some genes for insect pathogenesis may have been co-opted from genes involved in endophytic colonization. Other genes may be multifunctional and serve in both lifestyle capacities. We suggest that their evolution as insect pathogens allowed them to effectively barter a specialized nitrogen source (i.e. insects) with host plants for photosynthate. These ubiquitous fungi may play an important role as plant growth promoters and have a potential reservoir of secondary metabolites.

Feng P., Shang Y., Cen K., Wang C.

Significance Oosporein, a red 1,4-bibenzoquinone derivative, was first identified from fungi in the 1960s and exhibits antibiotic, antiviral, antifungal, and insecticidal activities. We report, to our knowledge, for the first time the novel pathway for oosporein biosynthesis in Beauveria bassiana that includes the polyketide synthase oosporein synthase 1 (OpS1) to produce the precursor orsellinic acid for OpS4 hydroxylation and then OpS7 oxidation to benzenetetrol, and the dimerization of the intermediate to oosporein is catalyzed by the catalase OpS5. The gene cluster is regulated by the transcription factor OpS3. We also found that oosporein is required for fungal virulence by inhibiting insect immunity. These results advance the knowledge of quinone biosynthetic machineries and demonstrate that a small molecule contributes to fungus–host interactions.

Behie S.W., Jones S.J., Bidochka M.J.

Endophytic fungi may display preferential tissue colonization within their plant hosts. Here we tested if the endophytic, insect pathogenic fungi (EIPF) Metarhizium and Beauveria showed preferential localization within plant tissues, in the field and under laboratory conditions. In the field, plants were sampled from three separate sites (Brock University, St. Catharines, Ontario; Pelham, Ontario; and Torngat Mountains National Park, Newfoundland, Canada) and EIPF were isolated from plant roots, the hypocotyl, and stem and leaves. Two genera of EIPF, Metarhizium spp. and Beauveria bassiana, were isolated from plants sampled, as well as the nematophagous fungus, Pochonia chlamydosporium. Metarhizium spp. were almost exclusively found in roots, whereas B. bassiana and P. chlamydosporium were found throughout the plant. The Metarhizium species were identified by RFLP and 95 % were Metarhizium robertsii, 4.3 % were M. brunneum, and 0.7 % were M. guizhouense. Lab studies with M. robertsii and B. bassiana reflected observations found in the field, that is, Metarhizium was restricted to the roots of plants while B. bassiana was found throughout the plant. Insect infection by these EIPF is preferential with respect to above and below ground insects, and the present study correlates above and below ground insect infections with endophytic colonization by these EIPF.

Liu L., Liu S., Meng Q., Chen B., Zhang J., Zhang X., Lin Z., Zou Z.

Certain entomopathogenic fungi, such as Beauveria bassiana, are highly pathogenic to arthropod pests and are able to colonize plant tissues, thereby enhancing both plant growth and disease resistance. This study assessed three B. bassiana strains (CBM1, CBM2, and CBM3) for their pathogenicity toward insect larvae and colonization potential in wheat. The insecticidal activity of the fungi against the larvae of the major lepidopteran pests Helicoverpa armigera, Spodoptera frugiperda, Mythimna separata, and Plutella xylostella was determined. The fungi were then applied to wheat plants using seed immersion and soil drench methods; their colonization rates were compared, and the impacts of fungal colonization on wheat growth and survival were evaluated. The results demonstrated that all three strains were effective in reducing insect damage, with B. bassiana CBM1 exhibiting the highest pathogenicity followed by CBM3 and CBM2. B. bassiana CBM1 was particularly effective, with a significantly higher colonization rate achieved through soil drenching compared to seed immersion. The soil inoculation of B. bassiana resulted in increased plant height at 30 days after sowing (DAS) and root length at 15 DAS compared to the control group. B. bassiana CBM1-colonized wheat increased the mortality of fall armyworm. This research has enriched the biological control microbial resource pool and highlights the potential of B. bassiana in integrated pest management strategies.

Saha N., Sharma A., Bora P.

Wang Y., Zou X., Zhu X., Qi J., Liu J., Zhang Z.

Nonribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) play crucial roles in the development and pathogenicity of the entomopathogenic fungus Beauveria bassiana. However, they are among the few biosynthetic gene clusters with unknown functions in B. bassiana. To investigate the role of the hybrid PKS–NRPS synthetase gene BBA_09856 in B. bassiana, we constructed a mutant strain, ∆BBA09856-WT, by deleting the BBA_09856 gene through Agrobacterium-mediated transformation. We then analyzed the biological characteristics of the mutant strain and the virulence of the mutant strain toward Ostrinia furnacalis larvae, as well as its antagonistic effects against the phytopathogen Botrytis cinerea. We found that the average growth rate of the three mutant strains, ∆BBA09856-WT, was significantly higher compared to the wild-type (WT) strain on the 15th day of culture on potato dextrose agar (PDA) plates (7.01 cm vs. 6.30 cm, p < 0.01). Additionally, the average spore production(3.16 × 107/cm2 vs. 9.95 × 106/cm2, p < 0.001) and germination rate (82.50% vs. 54.72%, 12 h, p < 0.001) were significantly different between the three mutant strains, ∆BBA09856-WT, and the WT strain. The average survival rates of O. furnacalis infected with the WT strain and the three mutant strains, ∆BBA09856-WT, after 8 days were 61.66%, and 30.00%, respectively, indicating that the pathogenicity of the tested mutant strains was significantly greater than that of the WT strain. The results of the dual culture test indicated that the inhibitory rates of the WT and ∆BBA09856-WT strains against B. cinerea were 40.25% and 47.65%, respectively (p < 0.001). Similarly, in the dual culture test, the WT strain reduced the growth of B. cinerea by 9.90%, while the ∆BBA09856-WT exhibited a significantly greater inhibition rate of 28.29% (p < 0.05). The diameters of disease spots, measured 6 d after inoculation with B. cinerea in the tomato treatment groups, revealed significant differences in endophytic colonization between the WT and ∆BBA09856-WT strains in the WT+Bc and ∆BBA09856-WT+Bc treatment groups (15.26 mm vs. 12.16 mm, p < 0.01). Notably, ∆BBA09856-WT exhibited enhanced virulence toward O. furnacalis larvae and increased antagonistic activity against B. cinerea. Our results indicate that the gene BBA_09856 may have a negative correlation with the development and virulence of B. bassiana toward the insect pest O. furnacalis larvae, as well as its antagonism against B. cinerea. These findings suggest that molecular techniques, such as gene editing, could be employed to develop superior strains of B. bassiana for the biological control of plant diseases and insect pests.

Sui L., Lu Y., Cheng K., Tian Y., Liu Z., Xie Z., Zhang Z., Li Q.

Alves V., Zamith-Miranda D., Frases S., Nosanchuk J.D.

Metabolomics has emerged as a transformative tool in the study of microbes, including pathogenic fungi, facilitating the identification of unique metabolic profiles that elucidate their pathogenic mechanisms, host interactions, and treatment resistance. This review highlights key applications of metabolomics in understanding fungal metabolites essential for human virulence, such as mycotoxins produced by various fungal species, including Aspergillus fumigatus (gliotoxin, fumagillins) and Candida species (phenylethyl alcohol, TCA cycle metabolites), and secondary metabolites that contribute to pathogenicity. It also explores the metabolic adaptations of fungi in relation to drug resistance and biofilm formation, revealing alterations in key metabolic pathways during infection, as seen in C. albicans and C. auris. Furthermore, metabolomics aids in deciphering host–pathogen interactions, showcasing how fungi like Cryptococcus neoformans and Candida modify host metabolism to promote survival and evade immune responses. The study of antifungal resistance mechanisms has also benefited from metabolomic approaches, identifying specific metabolite patterns that signify resistance, such as in Candida albicans and Candidozyma (Candida) auris, and informing new therapeutic strategies. The integration of metabolomics with other omics technologies is paving the way for a comprehensive understanding of fungal biology and pathogenesis. Such multi-omics approaches are crucial for discovering new therapeutic targets and developing innovative antifungal treatments. Thus, the purpose of this review is to provide an overview of how metabolomics is revolutionizing our understanding of fungal pathogenesis, drug resistance, and host interactions, and to highlight its potential for identifying new therapeutic targets and improving antifungal strategies.

Madlhophe S., Ogugua U.V., Makhubu F.N., Figlan S.

The growing global population has intensified concerns about food security, making it essential to produce crops sustainably to meet increasing demands without harming the environment. In this regard, biological control agents (BCAs) have recently gained more attention owing to their potential to manage fungal diseases of crops, particularly in the Solanaceae family. The proper use of selected BCAs such as Trichoderma spp., Bacillus spp., Pseudomonas fluorescens, Beauveria bassiana, and Gliocladium spp. has several benefits for Solanaceae crops. This review aims to summarize the effectiveness of various biological control strategies for fungal diseases in Solanaceae crops. We also provide basic knowledge on BCAs along with suggestions for further research to reduce the severity of these destructive diseases.

de Oliveira Filho V.A., Gubiani J.R., Borgonovi V.D., Hilário F., de Amorim M.R., Minori K., Bertolini V.K., Ferreira A.G., Biz A.R., Soares M.A., Teles H.L., Gadelha F.R., Berlinck R.G., Miguel D.C.

Kumari S., Gulia P., Choudhary P., Sharma N., Dahiya S., Punia A., Chhillar A.K.

Abstract: Screening for novel bioactive compounds has become more critical since drugresistant fungal infections have emerged and ethno-medicinal plants have been embarked as antifungal agents. The emphasis on medicinal plants has recently switched to the study of endophytes and their interactions with the host plant and screening of their antifungal activity. Endophytes are an endosymbiotic group of microorganisms that thrive within plant tissues without causing any symptoms or marking their presence. Endophytes have been looked into as potential resources for producing distinctive bioactive substances. The quest for bioactive natural compounds of endophytes isolated from higher plants is receiving a lot of interest from researchers worldwide, as seen by the recent surge in studies and publications on antifungal potential. This review aims to comprehend the role and applications of endophytes as a promising source of antifungal agents and enlighten on their most common mode of action.

Nischitha R.

Grass endophytic fungi have garnered increasing attention as a prolific source of bioactive metabolites with potential application across various fields, including pharmaceticals agriculture and industry. This review paper aims to synthesize knowledge on the diversity, isolation, and bioactivity of metabolites produced by grass endophytic fungi. Additionally, this approach aids in the conservation of rare and endangered plant species. Advanced analytical techniques such as high-performance liquid chromatography, liquid chromatograpy-mass spectrometry and gas chromatography are discussed as critical tools for metabolite identification and characterization. The review also highlights significant bioactive metabolites discovered to date, emphasizing their antimicrobial, antioxidant, and insecticidal activities and plant growth regulation properties. Besides address the challenges and future prospects in harnessing grass endophytic fungi for sustainable biotenological applications. By consolidating recent advancements and identifying agaps in the current research, this paper provides a comprehensive overview of the potential grass endophytic fungi as a valuable resource for novel bioactive compounds.

Vidal A., Castro P., Navarro F., Parada R., Mendoza L., Cotoras M.

Our research group isolated an endophyte yeast from the endemic plant Echinopsis chiloensis. This yeast, identified as Naganishia sp, produces volatile organic compounds (VOC) with antifungal activity against Botrytis cinerea. Due to the need for alternative control methods for this pathogen, the effect of VOC on B. cinerea was analyzed. On the fourth day of cultivation, in the presence of VOCs, the mycelial growth of B. cinerea stopped. VOCs inhibited 32.8% of the conidia germination and reduced sporulation by 70.6%. These compounds promoted the formation of infection cushions. VOCs caused damage to the cell wall and plasma membrane in B. cinerea. On the other hand, the volatile compounds induced oxidative stress, and led to membrane lipid peroxidation after 16 and 24 h of incubation in the presence of VOCs, because an increased level of malondialdehyde content was observed. These compounds exerted a fungistatic effect on B. cinerea. The volatile compounds emitted by Naganishia sp were identified by gas chromatography coupled with mass spectrometry as 3-methylbutyl acetate, ethylbenzene, 1-ethyl-3-methylbenzene, 2-phenylethanol, 2-heptanone and (5E)-6,10-dimethylundeca-5,9-dien-2-one. The most abundant volatile compound, 2-phenylethanol, inhibited the mycelial growth of B. cinerea with an IC50 value of 0.21 µL mL−1. The effect of this pure compound was also fungistatic. Finally, it was shown that volatile compounds decreased the severity of B. cinerea infection in tomatoes and grapes by 64.7 and 43,1%, respectively. This is the first report identifying volatile compounds emitted by a Naganishia sp. and describing their mode of action against B. cinerea.

Sui L., Lu Y., Xu M., Liu J., Zhao Y., Li Q., Zhang Z.

Sui L., Lu Y., Yang H., Liu Z., Wang L., Zou X., Li Q., Zhang Z.

Sunflower, a significant oleaginous crop with horticultural applications, faces challenges in yield and quality due to Sclerotinia sclerotiorum infection. As an endophyte, Beauveria bassiana demonstrated promise as a dual-purpose biocontrol agent, suppressing plant phytopathogens and inducing plant resistance against pests. While its role as an endophyte has been explored in leaf diseases, its efficacy against soil-borne diseases, especially sclerotinia disease, remains underexplored. In the present study, we evaluated the colonization ability of B. bassiana in sunflower plants through seed soaking and root irrigation methods. Additionally, we investigated its potential benefits in promoting plant growth and mitigating the negative effects of S. sclerotiorum infection. Our results showed that B. bassiana presented as an endophyte in sunflowers with both seed soaking and root irrigation treatments, leds to enhanced plant growth. Moreover, B. bassiana colonization significantly suppressed S. sclerotiorum infection in sunflower plants, even under conditions of artificial inoculation and infested soil. These findings indicate the promising ecological role of B. bassiana as a safe and effective strategy for biological control of sclerotinia disease in agroecosystems.

Ranesi M., Vitale S., Staropoli A., Di Lelio I., Izzo L.G., De Luca M.G., Becchimanzi A., Pennacchio F., Lorito M., Woo S.L., Vinale F., Turrà D.

Beauveria bassiana (Bb) is a widespread entomopathogenic fungus widely used in agriculture for crop protection. Other than pest control, fungi belonging to the B. bassiana complex represent an important microbial resource in agroecosystems, considering their multiple interactions with other microorganisms as antagonists of phytopathogens, or with plants as endophytic colonizers and growth promoters. Here, we characterised field collected or commercial isolates of B. bassiana relative to the environmental factors that affect their growth. We further compared the metabolome, the entomopathogenic potential and biocontrol activity of the tested isolates respectively on the insect pest Spodoptera littoralis or against the fungal plant pathogen Fusarium oxysporum. Our analysis revealed that the B. bassiana complex is characterised by a high level of inter-isolate heterogeneity in terms of nutritional requirements, establishment of intra- or inter-kingdom interactions, and the nature of metabolites produced. Interestingly, certain B. bassiana isolates demonstrated a preference for low nutrient plant-derived media, which hints at their adaptation towards an endophytic lifestyle over a saprophytic one. In addition, there was a noticeable variation among different B. bassiana isolates in their capacity to kill S. littoralis larvae in a contact infection test, but not in an intrahaemocoelic injection experiment, suggesting a unique level of adaptability specific to the host. On the other hand, most B. bassiana isolates exhibited similar biocontrol efficacy against the soil-dwelling ascomycete F. oxysporum f. sp. lycopersici, a pathogen responsible for vascular wilt disease in tomato plants, effectively averting wilting. Overall, we show that the effectiveness of B. bassiana isolates can greatly vary, emphasising the importance of isolate selection and nutritional adaptability consideration for their use in sustainable agriculture.

Harsonowati W., Latifah E., Nurrahma A.H., Purwani J., Iqbal R., Parray J.A., Patel A.D.

Chili pepper, widely recognized as a popular spice and an important cash crop worldwide, faces significant threats from climate change-related stress, particularly plant disease outbreaks. Emerging global diseases like Phytophthora blight, anthracnose fruit rot, and Ralstonia bacterial wilt threaten chili-producing countries, causing substantial annual yield losses. These major threatening diseases are difficult to control due to their widespread, extensive, and long-lived survival structures. Disease management practices rely on agrochemicals, leading to resistance to phytopathogens and environmental issues. Current research focuses on developing innovative, effective, chemical-free, and sustainable biosecurity strategies to address these challenges. Endophytes are plant endosymbionts that provide new insights for scientists due to their remarkable genome regulation to host plants. This review highlights the current state of emerging global diseases affecting chili pepper crops based on bibliometric analysis. We also focus on endophytes-mediated plant defense response as a sustainable solution for chemical pesticides. This review discusses the importance of omics-based technologies in deciphering the biochemical and molecular mechanisms of endophytes-mediated chili plant tolerance to various pathogens. A holistic approach of plant endophytes and multi-omics technologies can help develop effective mitigation strategies to prevent disease outbreaks for sustainable crop production and environmental restoration in the modern era of Agriculture 4.0 ‒ a green agricultural revolution.

Naimuzzaman M., Rahman F., Alvi A.T., Yeasmin L., Mittra P.K., Roy S.K.

This extensive book chapter examines the intricate correlation between plant stress and agriculture, emphasizing the diverse challenges presented by both abiotic and biotic stressors on crop productivity, quality, and global food security. The growing population and climate change-induced adversities have led to an urgent need for sustainable stress-tolerant crops. The integration of advanced biotechnological techniques, precision breeding, and ecological insights has facilitated the development of crops equipped to withstand various stressors, thereby transforming the landscape of stress-tolerant agriculture. Moreover, the investigation of plant growth–promoting fungi (PGPF) as a solution presents a promising avenue for enhancing plant growth, nutrient acquisition, and stress resilience through symbiotic interactions. PGPF have the potential to revolutionize agricultural practices, reduce reliance on agrochemicals, and bolster crop resilience in the face of environmental fluctuations, thus offering a sustainable pathway to address the challenges posed by changing climates and limited resources. This review illuminates the complex interplay between plants, microorganisms, and their environment, highlighting the significance of innovative strategies to ensure sustainable agricultural development in the future.