Fungal endophytes: A potent biocontrol agent and a bioactive metabolites reservoir

Volatile Organic Compounds Produced by Trichoderma asperellum with Antifungal Properties against Colletotrichum acutatum

Managing plant diseases caused by phytopathogenic fungi, such as anthracnose caused by Colletotrichum species, is challenging. Different methods have been used to identify compounds with antibiotic properties. Trichoderma strains are a source of novel molecules with antifungal properties, including volatile organic compounds (VOCs), whose production is influenced by the nutrient content of the medium. In this study, we assessed the VOCs produced in dual confrontation systems performed in two culture media by Trichoderma strains (T. atroviride IMI206040, T. asperellum T1 and T3, and Trichoderma sp. T2) on Colletotrichum acutatum. We analysed the VOC profiles using gas chromatography coupled with mass spectrometry. The Luria Bertani (LB) medium stimulated the production of VOCs with antifungal properties in most systems. We identified 2-pentyl furan, dimethyl disulfide, and α-phellandrene and determined their antifungal activity in vitro. The equimolar mixture of those VOCs (250 µM ea.) resulted in 14% C. acutatum diametral growth inhibition. The infective ability and disease severity caused by the mycelia exposed to the VOCs mixture were notably diminished in strawberry leaves. Application of these VOCs as biofumigants may contribute to the management of anthracnose. LB represents a feasible strategy for identifying novel VOCs produced by Trichoderma strains with antifungal properties.

Endophytic fungi associated with Araucaria angustifolia (Bertol.) Kuntze

The diversity of endophytes and their ecological relationships with the endangered conifer Araucaria angustifolia (a critically endangered species) are unrevealed. This study aimed to characterize the diversity of endophytic fungi associated with A. angustifolia. To this end, we analyzed 90 fragments from five individuals collected from a mixed localized fragment in Guarapuava-PR, Brazil. The total DNA of 61 morphotypes was extracted and the Internal Transcribed Spacer (ITS) region was amplified and sequenced. The sequence analysis allowed the identification of 37 genera belonging to the phylum Ascomycota and the classes Eurotiomycetes, Dothideomycetes, and Sordariomycetes, divided into 11 orders and 13 families. Most of the isolated fungi belonged to the Sordariomycetes class (40%) and to the Xylaria genus (14%), while Eurotiomycetes was the minority class within the community. Our results reveal the high endophytic richness supporting the life cycle of A. angustifolia and reinforce the necessity for the conservation of this conifer, as many genetic resources can be lost owing to its irrational exploration.

Antagonistic potential of endophytic fungal isolates of tomato (Solanum lycopersicum L.) fruits against post-harvest disease-causing pathogens of tomatoes: An in vitro investigation

Post-harvest decay of fresh agricultural produce is a major threat to food security globally. Synthetic fungicides, commonly used in practice for managing the post-harvest losses, have negative impacts on consumers' health. Studies have reported the effectiveness of fungal isolates from plants as biocontrol agents of post-harvest diseases, although this is still poorly established in tomatoes (Solanum lycopersicum L. cv. Jasmine). In this study, 800 endophytic fungi were isolated from mature green and ripe untreated and fungicide-treated tomato fruits grown in open soil and hydroponics systems. Of these, five isolates (Aureobasidium pullulans SUG4.1, Coprinellus micaceus SUG4.3, Epicoccum nigrum SGT8.6, Fusarium oxysporum HTR8.4, Preussia africana SUG3.1) showed antagonistic properties against selected post-harvest pathogens of tomatoes (Alternaria alternata, Fusarium solani, Fusarium oxysporum, Geotrichum candidum, Rhizopus stolonifera, Rhizoctonia solani), with Lactiplantibacillus plantarum as a positive control. P. africana SUG3.1 and C. micaceus SUG4.3 significantly inhibited growth of all the pathogens, with antagonistic capabilities comparable to that exhibited by L. plantarum. Furthermore, the isolates produced an array of enzymes, including among others, amylase, cellulose and protease; and were able to utilize several carbohydrates (glucose, lactose, maltose, mannitol, sucrose). In conclusion, P. africana SUG3.1 and C. micaceus SUG4.3 may complement L. plantarum as biocontrol agents against post-harvest pathogens of tomatoes.

Fungal Endophytes as Mitigators against Biotic and Abiotic Stresses in Crop Plants

The escalating global food demand driven by a gradually expanding human population necessitates strategies to improve agricultural productivity favorably and mitigate crop yield loss caused by various stressors (biotic and abiotic). Biotic stresses are caused by phytopathogens, pests, and nematodes, along with abiotic stresses like salt, heat, drought, and heavy metals, which pose serious risks to food security and agricultural productivity. Presently, the traditional methods relying on synthetic chemicals have led to ecological damage through unintended impacts on non-target organisms and the emergence of microbes that are resistant to them. Therefore, addressing these challenges is essential for economic, environmental, and public health concerns. The present review supports sustainable alternatives, emphasizing the possible application of fungal endophytes as innovative and eco-friendly tools in plant stress management. Fungal endophytes demonstrate capabilities for managing plants against biotic and abiotic stresses via the direct or indirect enhancement of plants' innate immunity. Moreover, they contribute to elevated photosynthesis rates, stimulate plant growth, facilitate nutrient mineralization, and produce bioactive compounds, hormones, and enzymes, ultimately improving overall productivity and plant stress resistance. In conclusion, harnessing the potentiality of fungal endophytes represents a promising approach toward the sustainability of agricultural practices, offering effective alternative solutions to reduce reliance on chemical treatments and address the challenges posed by biotic and abiotic stresses. This approach ensures long-term food security and promotes environmental health and economic viability in agriculture.

Fungal Endophytes: Discovering What Lies within Some of Canada's Oldest and Most Resilient Grapevines

Plant diseases and pests reduce crop yields, accounting for global crop losses of 30% to 50%. In conventional agricultural production systems, these losses are typically controlled by applying chemical pesticides. However, public pressure is mounting to curtail agrochemical use. In this context, employing beneficial endophytic microorganisms is an increasingly attractive alternative to the use of conventional chemical pesticides in agriculture. A multitude of fungal endophytes are naturally present in plants, producing enzymes, small peptides, and secondary metabolites due to their bioactivity, which can protect hosts from pathogens, pests, and abiotic stresses. The use of beneficial endophytic microorganisms in agriculture is an increasingly attractive alternative to conventional pesticides. The aim of this study was to characterize fungal endophytes isolated from apparently healthy, feral wine grapes in eastern Canada that have grown without agrochemical inputs for decades. Host plants ranged from unknown seedlings to long-lost cultivars not widely propagated since the 1800s. HPLC-MS was used to identify unique endophyte-derived chemical compounds in the host plants, while dual-culture competition assays showed a range in endophytes' ability to suppress the mycelial growth of Botrytis, which is typically controlled in viticulture with pesticides. Twelve of the most promising fungal endophytes isolated were identified using multilocus sequencing and morphology, while DNA barcoding was employed to identify some of their host vines. These fungal endophyte isolates, which consisted of both known and putative novel strains, belonged to seven genera in six families and five orders of Ascomycota. Exploring the fungal endophytes in these specimens may yield clues to the vines' survival and lead to the discovery of novel biocontrol agents.

In Vitro Analysis of the Antagonistic Biological and Chemical Interactions between the Endophyte Sordaria tomento-alba and the Phytopathogen Botrytis cinerea

Plant pathogenic infections causing substantial global food losses are a persistent challenge. This study investigates a potential biocontrol strategy against the necrotrophic fungus Botrytis cinerea using the endophytic fungus Sordaria tomento-alba isolated from Gliricidia sepium in Colombia. Today, synthetic fungicides dominate B. cinerea control, raising environmental and health concerns. S. tomento-alba exhibits notable in vitro effects, inhibiting B. cinerea growth by approximately 60% during co-culture and 50% in double disc co-culture. Additionally, it suppresses botryanes production and produces the compound heptacyclosordariolone, which has proven effective in inhibiting B. cinerea mycelial growth and spore germination in vitro. This biocontrol agent could be a potential eco-friendly alternative to replace synthetic fungicides. Our study provides insights into the chemical and biological mechanisms underpinning the antagonistic activity of S. tomento-alba, emphasizing the need for further research to understand its biosynthesis pathways and optimize its biocontrol potential. It also contributes molecular evidence of fungal interactions with implications for advanced forums in molecular studies in biology and chemistry, particularly in addressing plant pathogenic infections and promoting sustainable agriculture.

Endophytic fungi: Unravelling plant-endophyte interaction and the multifaceted role of fungal endophytes in stress amelioration

Endophytic fungi colonize interior plant tissue and mostly form mutualistic associations with their host plant. Plant-endophyte interaction is a complex mechanism and is currently a focus of research to understand the underlying mechanism of endophyte asymptomatic colonization, the process of evading plant immune response, modulation of gene expression, and establishment of a balanced mutualistic relationship. Fungal endophytes rely on plant hosts for nutrients, shelter, and transmission and improve the host plant's tolerance against biotic stresses, including -herbivores, nematodes, bacterial, fungal, viral, nematode, and other phytopathogens. Endophytic fungi have been reported to improve plant health by reducing and eradicating the harmful effect of phytopathogens through competition for space or nutrients, mycoparasitism, and through direct or indirect defense systems by producing secondary metabolites as well as by induced systemic resistance (ISR). Additionally, for efficient crop improvement, practicing them would be a fruitful step for a sustainable approach. This review article summarizes the current research progress in plant-endophyte interaction and the fungal endophyte mechanism to overcome host defense responses, their subsequent colonization, and the establishment of a balanced mutualistic interaction with host plants. This review also highlighted the potential of fungal endophytes in the amelioration of biotic stress. We have also discussed the relevance of various bioactive compounds possessing antimicrobial potential against a variety of agricultural pathogens. Furthermore, endophyte-mediated ISR is also emphasized.

The seed microbiomes of staple food crops

The scientific community increasingly recognized that seed microbiomes are important for plant growth and nutrition. The versatile roles and modulating properties that microbiomes hold in the context of seeds seem to be an inherited approach to avert adverse conditions. These discoveries attracted extensive interest, especially in staple food crops (SFCs) where grain was consumed as food. Along with the rapid expansion of population and industrialization that posed a severe challenge to the yield of SFCs, microbiologists and botanists began to explore and engineer seed microbiomes, for safer and more fruitful grain production. To utilize seed microbiomes, we present an overall review of the most updated scientific literature on three representative SFCs (wheat, rice and maize) using the 5W1H (Which, Where, What, Why, When and How) method that provides a comprehensive understanding of the issue. These include which factors determine the composition of seed microbiomes? Where do seed microbiomes come from? What are these seed microbes? Why do these microbes choose seeds as their destination and when do microbes settle down and become seed communists? In addition, how do seed microbiomes work and can be manipulated effectively? Therefore, answering the aforementioned questions regarding SFCs seed microbiomes remain fundamental in bridging endophytic research gaps and harnessing their ecological services.

Fusarium solani PQF9 Isolated from Podocarpus pilgeri Growing in Vietnam as a New Producer of Paclitaxel

Endophytic fungi are known as an alternative promising source of anticancer drug, paclitaxel, however fungi inhabiting in medicinal plant Podocarpus pilgeri and their paclitaxel production have not been reported to date. In the present study, a total of 15 culturable fungi classified into 5 genera, were successfully recovered from P. pilgeri collected in Vietnam. Screening fungal dichloromethane extracts for anticancer activity revealed that only PQF9 extract displayed potent inhibitory effects on A549 and MCF7 cancer cell lines with IC50 values of 33.9 ± 2.3 µg/mL and 43.5 ± 1.7 µg/mL, respectively. Through PCR-based molecular screening, the isolate PQF9 was found to possess 3 key genes involved in paclitaxel biosynthesis. Importantly, high-performance liquid chromatography quantification showed that fungal isolate PQF9 was able to produce 18.2 µg/L paclitaxel. The paclitaxel-producing fungus was identified as Fusarium solani PQF9 based on morphological and molecular phylogenetic analysis. Intensive investigations by chromatographic methods and spectroscopic analyses confirmed the presence of paclitaxel along with tyrosol and uracil. The pure paclitaxel had an IC50 value of 80.8 ± 9.4 and 67.9 ± 7.0 nM by using cell viability assay on A549 lung and MCF7 breast cancer cells. In addition, tyrosol exhibited strong antioxidant activity by scavenging 2, 2-diphenyl-picrylhydrazyl (DPPH) (IC50 5.1 ± 0.2 mM) and hydroxyl radical (IC50 3.6 ± 0.1 mM). In contrast, no biological activity was observed for uracil. Thus, the paclitaxel-producing fungus F. solani PQF9 could serve as a new material for large-scale production and deciphering paclitaxel biosynthesis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01119-z.

Microbiome-Mediated Protection against Pathogens in Woody Plants

Pathogens, especially invasive species, have caused significant global ecological, economic, and social losses in forests. Plant disease research has traditionally focused on direct interactions between plants and pathogens in an appropriate environment. However, recent research indicates that the microbiome can interact with the plant host and pathogens to modulate plant resistance or pathogen pathogenicity, thereby altering the outcome of plant-pathogen interactions. Thus, this presents new opportunities for studying the microbial management of forest diseases. Compared to parallel studies on human and crop microbiomes, research into the forest tree microbiome and its critical role in forest disease progression has lagged. The rapid development of microbiome sequencing and analysis technologies has resulted in the rapid accumulation of a large body of evidence regarding the association between forest microbiomes and diseases. These data will aid the development of innovative, effective, and environmentally sustainable methods for the microbial management of forest diseases. Herein, we summarize the most recent findings on the dynamic structure and composition of forest tree microbiomes in belowground and aboveground plant tissues (i.e., rhizosphere, endosphere, and phyllosphere), as well as their pleiotropic impact on plant immunity and pathogen pathogenicity, highlighting representative examples of biological control agents used to modulate relevant tree microbiomes. Lastly, we discuss the potential application of forest tree microbiomes in disease control as well as their future prospects and challenges.

Plant-Disease-Suppressive and Growth-Promoting Activities of Endophytic and Rhizobacterial Isolates Associated with Citrullus colocynthis

This study was conducted to investigate the antagonistic potential of endophytic and rhizospheric bacterial isolates obtained from Citrullus colocynthis in suppressing Fusarium solani and Pythium aphanidermatum and promoting the growth of cucumber. Molecular identification of bacterial strains associated with C. colocynthis confirmed that these strains belong to the Achromobacter, Pantoea, Pseudomonas, Rhizobium, Sphingobacterium, Bacillus, Sinorhizobium, Staphylococcus, Cupriavidus, and Exiguobacterium genera. A dual culture assay showed that nine of the bacterial strains exhibited antifungal activity, four of which were effective against both pathogens. Strains B27 (Pantoea dispersa) and B28 (Exiguobacterium indicum) caused the highest percentage of inhibition towards F. solani (48.5% and 48.1%, respectively). P. aphanidermatum growth was impeded by the B21 (Bacillus cereus, 44.7%) and B28 (Exiguobacterium indicum, 51.1%) strains. Scanning electron microscopy showed that the strains caused abnormality in phytopathogens' mycelia. All of the selected bacterial strains showed good IAA production (>500 ppm). A paper towel experiment demonstrated that these strains improved the seed germination, root/shoot growth, and vigor index of cucumber seedlings. Our findings suggest that the bacterial strains from C. colocynthis are suppressive to F. solani and P. aphanidermatum and can promote cucumber growth. This appears to be the first study to report the efficacy of these bacterial strains from C. colocynthis against F. solani and P. aphanidermatum.

Fungal endophyte bioinoculants as a green alternative towards sustainable agriculture

Over the past half century, limited use of synthetic fertilizers, pesticides, and conservation of the environment and natural resources have become the interdependent goals of sustainable agriculture. These practices support agriculture sustainability with less environmental and climatic impacts. Therefore, there is an upsurge in the need to introduce compatible booster methods for maximizing net production. The best straightforward strategy is to explore and utilize plant-associated beneficial microorganisms and their products. Bioinoculants are bioformulations consisting of selected microbial strains on a suitable carrier used in the enhancement of crop production. Fungal endophytes used as bioinoculants confer various benefits to the host, such as protection against pathogens by eliciting immune response, mineralization of essential nutrients, and promoting plant growth. Besides, they also produce various bioactive metabolites, phytohormones, and volatile organic compounds. To design various bioformulations, transdisciplinary approaches like genomics, transcriptomics, metabolomics, proteomics, and microbiome modulation strategies like gene editing and metabolic reconstruction have been explored. These studies will refine the existing knowledge on the diversity, phylogeny and beneficial traits of the microbes. This will also help in synthesizing microbial consortia by evaluating the role of structural and functional elements of communities in a controlled manner. The present review summarizes the beneficial aspects associated with fungal endophytes for capitalizing agricultural outputs, enlists various multi-omics techniques for understanding and modulating the mechanism involved in endophytism and the generation of new bioformulations for providing novel solutions for the enhancement of crop production.

New frontiers of soil fungal microbiome and its application for biotechnology in agriculture

The fungi-based technology provided encouraging scenarios in the transition from a conventionally based economic system to the potential security of sources closely associated with the agricultural sphere such as the agriculture. In recent years, the intensification of fungi-based processes has generated significant gains, additionally to the production of materials with significant benefits and strong environmental importance. Furthermore, the growing concern for human health, especially in the agriculture scenario, has fostered the investigation of organisms with high biological and beneficial potential for use in agricultural systems. Accordingly, this study offered a comprehensive review of the diversity of the soil fungal microbiome and its main applications in a biotechnological approach aimed at agriculture and food chain-related areas. Moreover, the spectrum of opportunities and the extensive optimization platform for obtaining fungi compounds and metabolites are discussed. Finally, future perspectives regarding the insurgency of innovations and challenges on the broad rise of visionary solutions applied to the biotechnology context are provided.

Evaluation of Trichoderma spp. on Fusarium oxysporum f. sp. asparagi and Fusarium wilt Control in Asparagus Crop

Among the key diseases affecting the asparagus crop (Asparagus officinalis L.), vascular wilting of asparagus caused by Fusarium oxysporum f. sp. asparagi stands out worldwide. This disease significantly shortens the longevity of the crop and limits economic production. Traditional control measures have been largely ineffective, and chemical control methods are difficult to apply, making biological control approaches, specifically the use of Trichoderma, an economical, effective, and risk-free alternative. This study aimed to identify the main factors that affect the efficacy of biopesticides studied as Biological Control Agents (BCAs) against Fusarium wilt in asparagus and to assess the efficacy of Trichoderma-based biopesticides under greenhouse and semi-field conditions. We evaluated the response of three Trichoderma spp. (T. atroviride, T. asperellum, and T. saturnisporum) to environmental variables, such as temperature and water activity, and their antagonistic capacity against Fusarium oxysporum f. sp. asparagi. All three Trichoderma species inhibited the growth of the pathogen in vitro. A decrease in water activity led to a greater reduction in the growth rate. The efficacy of the three biological control agents decreased with higher temperatures, resulting in minimal inhibition, particularly under conditions of restricted available water in the environment. The effect of the fungal inoculum density was also analyzed at two different temperatures. A direct correlation between the amount of inoculum and the score on the Disease Severity Index (DSI) was observed. A notable reduction in DSI was evident in treatments with high inoculum density (106 conidium/mL) for all three species of Trichoderma tested at both temperatures. In greenhouse and semi-field tests, we observed less disease control than expected, although T. asperellum and T. atroviride showed lower disease severity indices and increased the dry weight of seedlings and crowns, whereas T. saturnisporum resulted in the highest disease rate and lowest dry weight. This work highlights that the efficacy of Trichoderma as BCAs is influenced by various factors, including the quantity of soil inocula, and environmental conditions. The study findings have strong implications for selecting appropriate Trichoderma species for controlling specific pathogens under specific environmental conditions.

Biocontrol potential of the endophytic Epicoccum nigrum HE20 against stripe rust of wheat

Biological control using endophytic microorganisms represents an eco-friendly and effective alternative to the health-hazardous chemical fungicides used to control devastating plant diseases such as stripe rust in wheat. In this study, the inhibitory potential of the endophytic Epicoccum nigrum HE20, isolated from a healthy wheat plant, was screened against uredospores germination in vitro. A high suppression (96%) in the germination of the uredospores was recorded. GC-MS analysis of the culture filtrate of E. nigrum HE20 showed a production of various secondary metabolites with an antifungal background such as butyric acid, α-linolenic acid, hexanoic acid, lactic acid, 10,12-Tricosadiynoic acid, and pentadecanoic acid. Results from the greenhouse experiment revealed that the application of E. nigrum HE20 suspension led to a reduction in the disease severity by 87.5%, compared with the untreated-infected plants. Real-time PCR results exhibited an overexpression in three defensive genes (JERF3, GLU, and PR1) in the infected wheat plants, in response to the application of E. nigrum HE20, recorded 8-, 15.8-, and 3.5-fold, respectively. In addition, an increment in the phenolic content, activity of POD, PPO, and CAT, and a reduction in the lipid peroxidation were recorded due to the endophyte application. Transmission electron microscopic observations indicated mitigation of the pathogen in wheat cells after the treatment with E. nigrum HE20 metabolite. Furthermore, a growth-promoting effect was also observed due to E. nigrum HE20 application, as well as an increment in the total photosynthetic pigments in wheat leaves. Based on these results, it can be concluded that E. nigrum HE20 is a probable efficient bioagent against stripe rust in wheat. However, its field evaluation is highly necessary in the future studies.

Biochemical and Biotechnological Insights into Fungus-Plant Interactions for Enhanced Sustainable Agricultural and Industrial Processes

The literature is full of studies reporting environmental and health issues related to using traditional pesticides in food production and storage. Fortunately, alternatives have arisen in the last few decades, showing that organic agriculture is possible and economically feasible. And in this scenario, fungi may be helpful. In the natural environment, when associated with plants, these microorganisms offer plant-growth-promoting molecules, facilitate plant nutrient uptake, and antagonize phytopathogens. It is true that fungi can also be phytopathogenic, but even they can benefit agriculture in some way-since pathogenicity is species-specific, these fungi are shown to be useful against weeds (as bioherbicides). Finally, plant-associated yeasts and molds are natural biofactories, and the metabolites they produce while dwelling in leaves, flowers, roots, or the rhizosphere have the potential to be employed in different industrial activities. By addressing all these subjects, this manuscript comprehensively reviews the biotechnological uses of plant-associated fungi and, in addition, aims to sensitize academics, researchers, and investors to new alternatives for healthier and more environmentally friendly production processes.

Diversity and Biocontrol Potential of Endophytic Fungi and Bacteria Associated with Healthy Welsh Onion Leaves in Taiwan

Foliar diseases caused by Stemphylium and Colletotrichum species are among the major biotic factors limiting Welsh onion production in Taiwan. Owing to concerns about the environment and the development of pathogen resistance to existing fungicides, biological control using endophytes is emerging as an eco-friendly alternative to chemical control. The aim of the present study was to isolate endophytes from healthy Welsh onion leaves and investigate their antagonistic potential against the major phytopathogenic fungi associated with Welsh onion plants in Taiwan. A total of 109 bacterial and 31 fungal strains were isolated from healthy Welsh onion leaves and assigned to 16 bacterial and nine fungal genera using morphological and molecular characterization based on DNA sequence data obtained from nuclear internal transcribed spacer (nrITS) (fungi) and 16S rRNA (bacteria). Evaluation of these endophytic isolates for biocontrol activity against leaf blight pathogens Colletotrichum spaethianum strain SX15-2 and Stemphylium vesicarium strain SX20-2 by dual culture assay and greenhouse experiments resulted in the identification of two bacterial isolates (GFB08 and LFB28) and two fungal isolates (GFF06 and GFF08) as promising antagonists to leaf blight pathogens. Among the four selected isolates, Bacillus strain GFB08 exhibited the highest disease control in the greenhouse study. Therefore, Bacillus strain GFB08 was further evaluated to understand the mechanism underlying its biocontrol efficacy. A phylogenetic analysis based on six genes identified Bacillus strain GFB08 as B. velezensis. The presence of antimicrobial peptide genes (baer, bamC, bmyB, dfnA, fenD, ituC, mlna, and srfAA) and the secretion of several cell wall degrading enzymes (CWDEs), including cellulase and protease, confirmed the antifungal nature of B. velezensis strain GFB08. Leaf blight disease suppression by preventive and curative assays indicated that B. velezensis strain GFB08 has preventive efficacy on C. spaethianum strain SX15-2 and both preventive and curative efficacy on S. vesicarium strain SX20-2. Overall, the current study revealed that healthy Welsh onion leaves harbour diverse bacterial and fungal endophytes, among which the endophytic bacterial strain, B. velezensis strain GFB08, could potentially be used as a biocontrol agent to manage the leaf blight diseases of Welsh onion in Taiwan.

Exploration and Evaluation of Secondary Metabolites from Trichoderma harzianum: GC-MS Analysis, Phytochemical Profiling, Antifungal and Antioxidant Activity Assessment

In this study, we investigated in vitro the potential of Trichoderma harzianum to produce bioactive secondary metabolites that can be used as alternatives to synthetic compounds. The study focused on analyzing two extracts of T. harzianum using ethyl acetate and n-butanol solvents with different polarities. The extracts were examined using phytochemical analysis to determine the content of polyphenols, flavonoids, tannins, and alkaloids. Thin-layer chromatography (TLC) and Gas chromatography-mass spectroscopy (GC-MS) analysis were used to profile volatile organic metabolites (VOCs) present in the extracts. Furthermore, the extracts were tested for their antifungal ability using the poison food technique. For measuring antioxidant activity, the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) test was used. Trichoderma harzianum was shown to have a significantly high content of tannins and alkaloids, with a noticeable difference between the two extracts. GC-MS analysis identified 33 potential compounds with numerous benefits that could be used in agriculture and the medicinal industry. Moreover, strong antifungal activity was identified against Sclerotinia sclerotiorum by 94.44%, Alternaria sp. by 77.04%, and Fusarium solani by 51.48; similarly, the IC₅₀ of antioxidant activity was estimated for ethyl acetate extract by 71.47% and n-butanol extract by 56.01%. This leads to the conclusion that Trichoderma harzianum VOCs play a significant role as an antifungal and antioxidant agent when taking into account the advantageous bioactive chemicals noted in the extracts. However, to our knowledge, this is the first study in Algeria presenting detailed phytochemical analysis and GC-MS profiling of Trichoderma harzianum for two extracts, ethyl acetate and n-butanol.

Exploration of non-phytopathogenic Aspergillus spp. isolates recovered from soil and compost as potential source of bioactive metabolites for potato Fusarium dry rot control

During storage, infected potato tubers by Fusarium species leads to significant losses. Searching natural-based alternatives to chemical fungicides for the control of tuber dry rot pathogens is becoming essential. Nine Aspergillus spp. (A. niger, A. terreus, A. flavus, and Aspergillus sp.) isolates, recovered from soil and compost samples, were explored and evaluated for their ability to suppress Fusarium sambucinum the main causal agent of potato tuber dry rot disease in Tunisia. All conidial suspensions of Aspergillus spp. tested and their cell-free culture filtrates had significantly inhibited the in vitro pathogen growth by 18.5 to 35.9% and by 9 to 69% compared to control, respectively. A. niger CH12 cell-free filtrate was the most active against F. sambucinum at the three concentration tested (10, 15, and 20% v v-1). Chloroform and ethyl acetate extracts from four Aspergillus spp., tested at 5% v v-1, had limited F. sambucinum mycelial growth by 34-60% and 38-66%, respectively, compared to control, with A. niger CH12 ethyl extract being the most active. Tested on potato tubers inoculated with F. sambucinum, all tested Aspergillus spp. isolates, their cell-free filtrates and organic extracts had significantly decreased the external diameter of dry rot lesion compared to pathogen-inoculated and untreated control tubers. For the rot penetration, all Aspergillus spp. isolates, their organic extracts and only filtrates from A. niger CH12 and MC2 isolates had significantly limited dry rot severity compared to pathogen-inoculated and untreated control. The highest reductions in the external diameter of dry rot lesion (76.6 and 64.1%) and the average rot penetration (77.1 and 65.1%) were achieved using chloroform and ethyl acetate extracts from A. niger CH12, respectively. These results clearly demonstrated the presence of bioactive compounds in Aspergillus spp. that can be extracted and explored as an eco-friendly alternative for the control of the target pathogen.

A Pipeline to Investigate Fungal-Fungal Interactions: Trichoderma Isolates against Plant-Associated Fungi

Soil fungi play essential roles in ecosystems, forming complex interaction networks with bacteria, yeasts, other fungi, or plants. In the framework of biocontrol strategies, Trichoderma-based fungicides are at the forefront of research as an alternative to synthetic ones. However, the impact of introducing new microbial strain(s) on the soil microbiome of a habitat is not well-explored. Aiming to identify a quantitative method to explore the complex fungal interactions, we isolated twelve fungi from three Italian vineyards and identified three strains of the Trichoderma genus in addition to nine more plant-associated fungi of different genera. Investigating in dual nucleation assay fungal-fungal interactions, we recognised two types of interaction: neutral or antagonistic. All three Trichoderma strains displayed a slight inhibitory behaviour against themselves. Trichoderma strains showed a mutually intermingling growth with Aspergillus aculeatus and Rhizopus arrhizus but antagonistic behaviour against the plant pathogens Alternaria sp., Fusarium ramigenum, and Botrytis caroliniana. Yet, in some cases, antagonistic behaviour by Trichoderma fungi was also observed against plant-promoting fungi (e.g., Aspergillus piperis and Penicillium oxalicum). Our study highlights the importance of studying the interactions between fungi, aiming to clarify better the impact of fungal-based biological fungicides in the soil communities, and offers a pipeline for further applications.

Metabolite Formation by Fungal Pathogens of Potatoes (Solanum tuberosum L.) in the Presence of Bioprotective Agents

The potato is a crop of global importance for the food industry. This is why effective protection against pathogens is so important. Fungi as potato pathogens are responsible for plant diseases and a significant reduction in yields, as well as for the formation of mycotoxins. This study focuses on the effect of three natural biocides, yeast Metschnikowia pulcherrima, lactic acid bacteria Lactiplantibacillus plantarum, and aqueous garlic extract, on the improvement of the physiology of planted potato tubers and the reduction in mycotoxin formation. The secondary metabolites produced by the fungal pathogens of genera Fusarium, Alternaria, Colletotrichum, Rhizoctonia, and Phoma in the presence of these biocontrol agents were compared to profiles obtained from contaminated potatoes. Analysis of liquid chromatography coupled with tandem mass spectrometry data showed the presence of 68 secondary metabolites, including the mycotoxins: alternariol, alternariol methyl ether, altertoxin-I, aurofusarin, beauvericin, diacetoxyscirpenol, enniatin B, and sterigmatocystin. The studies showed that the applied biocontrol agents had a positive effect on the physiological parameters of potatoes (including root growth, stem growth, gas exchange, and chlorophyll content index) and on the reduction in the production of mycotoxins and other secondary metabolites by Fusarium, Alternaria, and Phoma.

A systematic review on endophytic fungi and its role in the commercial applications

MAIN CONCLUSION

EF have been explored for its beneficial impact on environment and for its commercial applications. It has proved its worth in these sectors and showed an impact on biological properties of plants by producing various bioactive molecules and enzymes. Endophytes are plant mutualists that live asymptomatically within plant tissues and exist in almost every plant species. Endophytic fungi benefit from the host plant nutrition, and the host plant gains improved competitive abilities and tolerance against pathogens, herbivores, and various abiotic stresses. Endophytic fungi are one of the most inventive classes which produce secondary metabolites and play a crucial role in human health and other biotic aspects. This review is focused on systematic study on the biodiversity of endophytic fungi in plants, and their role in enhancing various properties of plants such as antimicrobial, antimycobacterial, antioxidant, cytotoxic, anticancer, and biological activity of secondary metabolites produced by various fungal endophytes in host plants reported from 1994 to 2021. This review emphasizes the endophytic fungal population shaped by host genotype, environment, and endophytic fungi genotype affecting host plant. The impact of endophytic fungi has been discussed in detail which influences the commercial properties of plants. Endophytes also have an influence on plant productivity by increasing parameters such as nutrient recycling and phytostimulation. Studies focusing on mechanisms that regulate attenuation of secondary metabolite production in EF would provide much needed impetus on ensuring continued production of bioactive molecules from a indubitable source. If this knowledge is further extensively explored regarding fungal endophytes in plants for production of potential phytochemicals, then it will help in exploring a keen area of interest for pharmacognosy.

Cellulase and chitinase activities and antagonism against Fusarium oxysporum f.sp. cubense race 1 of six Trichoderma strains isolated from Mexican maize cropping

OBJECTIVE

To evaluate the enzymatic and biocontrol capacity of native Trichoderma strains isolated from corn crops in Irapuato (state of Guanajuato) and Napízaro (state of Michoacán), Mexico.

RESULTS

Six native strains from Irapuato and Napízaro were tested, with five of them identified as T. harzianum and one as T. tomentosum. The six strains qualitatively and quantitatively showed enzyme activity for cellulase and chitinase. The best results were obtained for strains IrV6SIC7 and MichV6S2C2 with 878 IU L^-1 of chitinase and 1323 IU L^-1 of cellulase, respectively. All Trichoderma strains acted antagonistically toward Fusarium oxysporum f.sp. cubense race 1 (FocR1), with percentages of inhibition that ranged from 9 to 54%. In addition, the microscopic analysis allowed visualizing the mechanisms of mycoparasitism and antibiosis by either IrV6SIC7 or MichV6S2C2. The latter effects indicate that the tested native Trichoderma strains isolated from corn crops possessed enzymatic mechanisms as a strategy for biocontrolling FocR1 strains.

CONCLUSION

The enzyme production by the Trichoderma strains represents a potential biotechnological utilization for either agricultural or industrial purposes.

Biological Control Potential of Endophytic Fungi with Amelioration of Systemic Resistance in Sunflower and GC-MS Metabolic Profiling of Talaromyces assiutensis

Endophytic fungi live inside plant tissues but do not cause any disease. Several reports have now revealed that they have great influence on host. In this study, the beneficial role of endophytic fungi is highlighted and explored. Endophytic fungi isolated from healthy plants were identified as Aspergillus terreus, Curvularia lunata, C. hawaiiensis, Macrophomina phaseolina, Fusarium solani, Talaromyces assiutensis, and T. trachyspermus using 18S rRNA gene sequencing. In vitro, fungi evaluated for antimicrobial activity, showed significant activity. These fungi were tested in field application by exploring their broad spectrum. Talaromyces assiutensis and T. trachyspermus were applied in pots and field plot experiments using sunflower as test plants, along with endophytic Cephalosporium sp., and Chaetomium sp. Endophytic fungi showed significant activity against root rot pathogens affecting sunflower and improved plant biomass. They also improved production of plant defense biochemical markers (polyphenolic content and salicylic acid) with improvement in antioxidant potential. These fungi are used as biological control agents, so their culture filtrates are used to check the presence of metabolites by GC-MS. Several new compounds were isolated from T. assiutensis. The major bioactive compounds are Coumarin, 3,4-dihydro-6-methoxy-4,4-dimethyl, 1-Monolinoleoylglycerol trimethylsilyl ether, 1,2-Propanediol, 3-(octadecyloxy), Ethyl iso-allocholate, and 1H-Pyrazole, which possess antioxidant, antitumor, antibacterial, anticancer, and antimicrobial properties. These findings will lead to further in-depth research toward the potential use of these endophytic fungi for their possible use in agriculture and drug formation.

Endophytic Diaporthe as Promising Leads for the Development of Biopesticides and Biofertilizers for a Sustainable Agriculture

Plant pathogens are responsible for causing economic and production losses in several crops worldwide, thus reducing the quality and quantity of agricultural supplies. To reduce the usage of chemically synthesized pesticides, strategies and approaches using microorganisms are being used in plant disease management. Most of the studies concerning plant-growth promotion and biological agents to control plant diseases are mainly focused on bacteria. In addition, a great portion of registered and commercialized biopesticides are bacterial-based products. Despite fungal endophytes having been identified as promising candidates for their use in biological control, it is of the utmost importance to develop and improve the existing knowledge on this research field. The genus Diaporthe, encompasses plant pathogens, saprobes and endophytes that have been screened for secondary metabolite, mainly due to their production of polyketides and a variety of unique bioactive metabolites with agronomic importance. Some of these metabolites exhibit antifungal and antibacterial activity for controlling plant pathogens, and phytotoxic activity for the development of potential mycoherbicides. Moreover, species of Diaporthe are reported as promising agents in the development of biofertilizers. For this reason, in this review we summarize the potential of Diaporthe species to produce natural products with application in agriculture and describe the benefits of these fungi to promote their host plant's growth.

Aspergillus flavus YRB2 from Thymelaea hirsuta (L.) Endl., a non-aflatoxigenic endophyte with ability to overexpress defense-related genes against Fusarium root rot of maize

Fusarium root rot, caused by Fusarium solani (Mart.) Sacc., represents one of the most damaging diseases of maize affecting plant growth and yield. In this study, the antagonistic potential of a non-aflatoxigenic endophytic Aspergillus flavus YRB2, isolated from Thymelaea hirsuta (L.) Endl., was tested against F. solani in vitro. In addition, its biocontrol activity against Fusarium root rot of maize was evaluated under greenhouse conditions. Its impacts on plant molecular, pathological, physiological, and growth levels were also studied. Results obtained revealed a potent antagonistic behavior for A. flavus YRB2 against F. solani in vitro, recording 80% growth inhibition. Seventeen secondary metabolites were detected in the n-hexane extract of A. flavus YRB2 filtered culture broth using GC-MS analysis. Among them, various antifungal secondary metabolites were produced, namely palmitic acid, α-linolenic acid, stearic acid, 2, 4-di-tert-butylphenol, diisobutyl phthalate, and heneicosane. In contrast, HPLC analysis showed that no aflatoxins (B1, B2, G1, and G2) were detected. Under greenhouse conditions, colonization of maize plants with A. flavus YRB2 exhibited a potential biocontrol activity against Fusarium root rot, recording 73.4% reduction in the disease severity. Triggering of transcriptional expression level of the defense-related genes JERF3 (7.2-fold), CHI II (8-fold), and POD (9.1-fold) was reported, indicating the inducing effect on the plant immunity. In addition, an increment in the antioxidant enzymes POD and PPO, and the total phenolic content in maize roots was also observed in response to this treatment. Moreover, a growth-promoting effect was also observed for colonization of maize plants with A. flavus YRB2. Based on the obtained data, we can conclude that A. flavus YRB2 may represent a promising biocontrol and growth-promoting agent for maize plants against Fusarium root rot. Nevertheless, field evaluation is highly requested before the use recommendation.

How to Completely Squeeze a Fungus-Advanced Genome Mining Tools for Novel Bioactive Substances

Fungal species have the capability of producing an overwhelming diversity of bioactive substances that can have beneficial but also detrimental effects on human health. These so-called secondary metabolites naturally serve as antimicrobial "weapon systems", signaling molecules or developmental effectors for fungi and hence are produced only under very specific environmental conditions or stages in their life cycle. However, as these complex conditions are difficult or even impossible to mimic in laboratory settings, only a small fraction of the true chemical diversity of fungi is known so far. This also implies that a large space for potentially new pharmaceuticals remains unexplored. We here present an overview on current developments in advanced methods that can be used to explore this chemical space. We focus on genetic and genomic methods, how to detect genes that harbor the blueprints for the production of these compounds (i.e., biosynthetic gene clusters, BGCs), and ways to activate these silent chromosomal regions. We provide an in-depth view of the chromatin-level regulation of BGCs and of the potential to use the CRISPR/Cas technology as an activation tool.

Production of Fungal Quinones: Problems and Prospects

Fungal quinones can be used for a variety of applications, such as pharmaceuticals, food colorants, textile dyes, and battery electrolytes. However, when producing quinones by fungal cultivation, many considerations arise regarding the feasibility of a production system, such as the quinone yield, purity, ease of extraction, and the co-production of mycotoxins. In this work, we display the initial screening of filamentous fungi for quinone production and evaluate their potential for future optimization. We investigated toluquinone (TQ) potentially produced by Penicillium cf. griseofulvum, terreic acid (TA) produced by Aspergillus parvulus and A. christenseniae, and anthraquinone (AQ) monomers and dimers produced by Talaromyces islandicus. The strains grew on various agar and/or liquid media and were analyzed by ultra-high-performance liquid chromatography–diode array detection–quadrupole time-of-flight mass spectrometry (UHPLC-DAD-QTOF MS). In the case of AQs, feature-based molecular networking (FBMN) was used for the identification of AQ analogs. TQ was not observed in the production strains. TA constituted one of the major chromatogram peaks and was secreted into the growth medium by A. parvulus. The AQs constituted many major chromatogram peaks in the mycelium extracts and endocrocin and citreorosein were observed extracellularly in small amounts.

Dynamics, phylogeny and phyto-stimulating potential of chitinase synthesizing bacterial root endosymbiosiome of North Western Himalayan Brassica rapa L

The less phytopathogen susceptibility in Himalayan Brassica rapa L. has made it an exceptional crop eluding synthetic pesticide inputs, thereby guarantying economically well-founded and ecologically sustainable agriculture. The relevance of niche microflora of this crop has not been deliberated in this context, as endosymbiosiome is more stable than their rhizosphere counterparts on account of their restricted acquaintance with altering environment; therefore, the present investigation was carried out to study the endophytic microfloral dynamics across the B. rapa germplasm in context to their ability to produce chitinase and to characterize the screened microflora for functional and biochemical comportments in relevance to plant growth stimulation. A total of 200 colonies of bacterial endophytes were isolated from the roots of B. rapa across the J&K UT, comprising 66 locations. After morphological, ARDRA, and sequence analysis, eighty-one isolates were selected for the study, among the isolated microflora Pseudomonas sp. Bacillus sp. dominated. Likewise, class γ-proteobacteria dominated, followed by Firmicutes. The diversity studies have exposed changing fallouts on all the critical diversity indices, and while screening the isolated microflora for chitinase production, twenty-two strains pertaining to different genera produced chitinase. After carbon source supplementation to the chitinase production media, the average chitinase activity was significantly highest in glycerol supplementation. These 22 strains were further studied, and upon screening them for their fungistatic behavior against six fungal species, wide diversity was observed in this context. The antibiotic sensitivity pattern of the isolated strains against chloramphenicol, rifampicin, amikacin, erythromycin, and polymyxin-B showed that the strains were primarily sensitive to chloramphenicol and erythromycin. Among all the strains, only eleven produced indole acetic acid, ten were able to solubilize tricalcium phosphate and eight produced siderophores. The hydrocyanic acid and ammonia production was observed in seven strains each. Thus, the present investigation revealed that these strains could be used as potential plant growth promoters in sustainable agriculture systems besides putative biocontrol agents.

The plant endosphere-hidden treasures: a review of fungal endophytes

The endosphere represents intracellular regions within plant tissues colonize by microbial endophytes without causing disease symptoms to host plants. Plants harbor one or two endophytic microbes capable of synthesizing metabolite compounds. Environmental factors determine the plant growth and survival as well as the kind of microorganisms associated with them. Some fungal endophytes that symbiotically colonize the endosphere of medicinal plants with the potential of producing biological products have been employed in traditional and modern medicine. The bioactive resources from endophytic fungi are promising; biotechnologically to produce cheap and affordable commercial bioactive products as alternatives to chemical drugs and other compounds. The exploration of bioactive metabolites from fungal endophytes has been found applicable in agriculture, pharmaceutical, and industries. Thus, fungal endophytes can be engineered to produce a substantive quantity of pharmacological drugs through the biotransformation process. Hence, this review shall provide an overview of fungal endophytes, ecology, their bioactive compounds, and exploration with the biosystematics approach.

Fungal quinones: diversity, producers, and applications of quinones from Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium

Quinones represent an important group of highly structurally diverse, mainly polyketide-derived secondary metabolites widely distributed among filamentous fungi. Many quinones have been reported to have important biological functions such as inhibition of bacteria or repression of the immune response in insects. Other quinones, such as ubiquinones are known to be essential molecules in cellular respiration, and many quinones are known to protect their producing organisms from exposure to sunlight. Most recently, quinones have also attracted a lot of industrial interest since their electron-donating and -accepting properties make them good candidates as electrolytes in redox flow batteries, like their often highly conjugated double bond systems make them attractive as pigments. On an industrial level, quinones are mainly synthesized from raw components in coal tar. However, the possibility of producing quinones by fungal cultivation has great prospects since fungi can often be grown in industrially scaled bioreactors, producing valuable metabolites on cheap substrates. In order to give a better overview of the secondary metabolite quinones produced by and shared between various fungi, mainly belonging to the genera Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium, this review categorizes quinones into families such as emodins, fumigatins, sorbicillinoids, yanuthones, and xanthomegnins, depending on structural similarities and information about the biosynthetic pathway from which they are derived, whenever applicable. The production of these quinone families is compared between the different genera, based on recently revised taxonomy. KEY POINTS: • Quinones represent an important group of secondary metabolites widely distributed in important fungal genera such as Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium. • Quinones are of industrial interest and can be used in pharmacology, as colorants and pigments, and as electrolytes in redox flow batteries. • Quinones are grouped into families and compared between genera according to the revised taxonomy.

Selection of Endophytic Beauveria bassiana as a Dual Biocontrol Agent of Tomato Pathogens and Pests

Endophytic fungi (EF) can enhance both plant growth and defense barriers against pests and pathogens, contributing to the reduction of chemical pesticides and fertilizers use in agriculture. Beauveria bassiana is an entomopathogenic fungus showing endophytism in several crops, often associated with a good capacity to limit the development of pests and disease agents. However, the diversity of the protective efficacy and plant response to different strains can be remarkable and needs to be carefully assessed for the successful and predictable use of these beneficial microorganisms. This study aims to select B. bassiana strains able to colonize tomato plants as endophytes as well as to control two important disease agents, Botrytis cinerea and Alternaria alternata, and the pest aphid, Macrosiphum euphorbiae. Nine wild-type isolates and one commercial strain were screened for endophytism, then further characterized for plant-growth promotion plus inhibition of disease development and pest infestation. Four isolates proved to have a good control activity against the biotic stressors tested, but only Bb716 was also able to promote plant growth. This work provides a simple workflow for the selection of beneficial EF, paving the way towards more effective use of B. bassiana in Integrate Pest Management (IPM) of tomato.

Microbial Biocontrol Strategies for Ambrosia Beetles and Their Associated Phytopathogenic Fungi

Ambrosia beetles and their symbiotic fungi are causing severe damage in natural and agro-ecosystems worldwide, threatening the productivity of several important tree crops such as avocado. Strategies aiming at mitigating their impact include the application of broad-spectrum agrochemicals and the incineration of diseased trees, but the increasing demand for environment-friendly strategies call for exploring biological control for the management of ambrosia beetles and their phytopathogenic fungal symbionts. The aim of this review is to examine the existing knowledge on biocontrol approaches using beneficial microorganisms and microbial natural products with entomopathogenic and antifungal activity against ambrosia beetles and fungi. We show that biocontrol has been mainly focused on the insect, using entomopathogenic fungi (EPF) such as Beauveria spp. or Metarhizium spp. However, recent studies have been integrating EPF with mycoparasitic fungi such as Trichoderma spp. to simultaneously challenge the vector and its fungal symbionts. Novel approaches also include the use of microbial natural products as insect lures or antifungal agents. Contrastingly, the potential of bacteria, including actinobacteria (actinomycetes), as biocontrol agents of ambrosia fungi has been little investigated. We thus suggest that future research should further examine the antifungal activity of bacterial strains, with an emphasis on harsh environments. We also suggest pursuing the isolation of more effective microbial strains with dual biocontrol effect, i.e., exhibiting fungicidal/insecticidal activities. Moreover, additional efforts should aim at determining the best application methods of biocontrol agents in the field to ensure that the positive effects detected in vitro are sustained. Finally, we propose the integration of microbiome studies in pest and disease management strategies as they could provide us with tools to steer the beneficial host plant microbiome and to manipulate the beetle microbiome in order to reduce insect fitness.

Lignocellulolytic Enzyme Production from Wood Rot Fungi Collected in Chiapas, Mexico, and Their Growth on Lignocellulosic Material

Wood-decay fungi are characterized by ligninolytic and hydrolytic enzymes that act through non-specific oxidation and hydrolytic reactions. The objective of this work was to evaluate the production of lignocellulolytic enzymes from collected fungi and to analyze their growth on lignocellulosic material. The study considered 18 species isolated from collections made in the state of Chiapas, Mexico, identified by taxonomic and molecular techniques, finding 11 different families. The growth rates of each isolate were obtained in culture media with African palm husk (PH), coffee husk (CH), pine sawdust (PS), and glucose as control, measuring daily growth with images analyzed in ImageJ software, finding the highest growth rate in the CH medium. The potency index (PI) of cellulase, xylanase, and manganese peroxidase (MnP) activities was determined, as well as the quantification of lignin peroxidase (LiP), with the strains Phlebiopsis flavidoalba TecNM-ITTG L20-19 and Phanerochaete sordida TecNM-ITTG L32-1-19 being the ones with the highest PI of hydrolase activities with 2.01 and 1.83 cellulase PI and 1.95 and 2.24 xylanase PI, respectively, while Phlebiopsis flavidoalba TecNM-ITTG L20-19 and Trametes sanguinea TecNM-ITTG L14-19 with 7115 U/L LiP activity had the highest oxidase activities, indicating their ability to oxidize complex molecules such as lignin.

Fungal Endophytes of Tahiti Lime (Citrus citrus × latifolia) and Their Potential for Control of Colletotrichum acutatum J. H. Simmonds Causing Anthracnose

Colletotrichum acutatum is one of the causal agents of anthracnose in several crops, and of post-flowering fruit drop (PFD) in citrus and key lime anthracnose (KLA). The pathogen normally attacks flowers, causing lesions only in open flowers. Under very favorable conditions, however, it can also affect flower buds and small fruits, causing complete rotting of the fruit and a premature fall, resulting in major economic crop losses. We isolated endophytic fungi from Tahiti lime to evaluate its diversity, verify its antagonistic capacity against the phytopathogen Colletotrichum acutatum C-100 in dual tests, and evaluate the ability of various endophytic agents to control flowers with induced anthracnose. 138 fungal isolates were obtained from 486 fragments of branches, leaves, and fruit; from which 15 species were identified morphologically. A higher isolation frequency was found in branches and leaves, with a normal level of diversity compared to other citrus species. Of the 15 morphospecies, 5 were trialed against C. acutatum in antagonism tests, resulting in a finding of positive inhibition. 2 endophytic fungi from the antagonism tests demonstrated high inhibition of the phytopathogen, and were thus used in in vivo tests with Tahiti lime flowers, applied in a spore solution. Spore solutions of two molecularly identified species, Xylaria adscendens, and Trichoderma atroviride, reduced the lesions caused by the phytopathogen in these in vivo tests. The finding that these endophytes react antagonistically against C. acutatum may make them good candidates for further biological control research in an agroindustry that requires environmental sustainability.

Potential of microbial endophytes to enhance the resistance to postharvest diseases of fruit and vegetables

Food loss of fruit and vegetables caused by postharvest diseases is a major issue worldwide. The method used to prevent and control postharvest diseases is usually to use chemical fungicides, but long-term and large-scale use will make the pathogens resistant and potentially have a negative impact on human health and the ecological environment. Therefore, finding a safe and effective biological control method instead of chemical control is a hot research topic in recent years. Endophytes, colonizing plants asymptomatically, can promote the growth of the hosts and enhance their resistance. The use of endophytes as biological control agents for postharvest diseases of fruit and vegetables has attracted increasing attention in the last 20 years. Compared with chemical control, endophytes have the advantages of being more environmentally friendly, sustainable, and safer. However, there are relatively few relevant studies, so herein we summarize the available literature. This review focuses mainly on the recent progress of using endophytes to enhance the resistance of postharvest fruit and vegetables to diseases, with the emphasis on the possible mechanisms and the potential applications. Furthermore, this article suggests future areas for study using antagonistic endophytes to prevent and control fruit and vegetable postharvest diseases: (i) screening more potential broad-spectrum anti-pathogen endophytes and their metabolic active substances by the method of macrogenomics; (ii) elucidating the underlining molecular mechanism among endophytes, harvested vegetables and fruit, pathogens, and microbial communities; (iii) needing more application research to overcome the difficulties of commercialization practice. © 2020 Society of Chemical Industry.

Antifungal meroterpenes and dioxolanone derivatives from plant-associated endophytic fungus Phyllosticta sp. WGHL2

Four new meroterpenes named as guignardones U-X (1-4), along with eleven known meroterpenes (5-15) and three known dioxolanone derivatives (16-18), were obtained from the endophytic fungus Phyllosticta sp. WGHL2. The structural elucidation was conducted by HRESIMS, NMR, single crystal X-ray diffraction, along with ECD calculations and comparison. In antifungal tests, compound 16 possessed broad-spectrum antifungal activities against Rhizoctonia solani, Fusarium graminearum and Botrytis cinerea with inhibition ratio of 48.43%, 40.98%, and 49.53% at 50 μg/mL, respectively. Moreover, compound 16 showed moderate protective effect against B. cinerea in vivo at 200 μg/mL and exhibited effective inhibition on the spore germination of B. cinerea.

Implications of endophytic microbiota in Camellia sinensis: a review on current understanding and future insights

Endophytic fungi and bacteria are the most ubiquitous and representative commensal members that have been studied so far in various higher plants. Within colonization and interaction with their host plants, endophytic microbiota are reportedly to modulate not only the host's growth but also holobiont resilience to abiotic and biotic stresses, providing a natural reservoir and a promising solution for sustainable agricultural development challenged by global climate change. Moreover, possessing the talent to produce a wide array of high-value natural products, plant endophytic microbiota also serve as an alternative way for novel drug discovery. In this review, tea, one of the world's three largest nonalcoholic beverages and a worldwide economic woody crop, was highlighted in the context of endophytic microbiota. We explore the recent studies regarding isolation approaches, distribution characteristics and diversity, and also biological functions of endophytic microbiota in Camellia sinensis (L.) O. Kuntze. Profoundly, the future insight into interaction mechanism between endophytic microbiota and tea plants will shed light on in-depth exploration of tea microbial resources.

Fungal communities decline with urbanization-more in air than in soil

Increasing evidence suggests that degradation of biodiversity in human populated areas is a threat for the ecosystem processes that are relevant for human well-being. Fungi are a megadiverse kingdom that plays a key role in ecosystem processes and affects human well-being. How urbanization influences fungi has remained poorly understood, partially due to the methodological difficulties in comprehensively surveying fungi. Here we show that both aerial and soil fungal communities are greatly poorer in urban than in natural areas. Strikingly, a fivefold reduction in fungal DNA abundance took place in both air and soil samples already at 1 km scale when crossing the edge from natural to urban habitats. Furthermore, in the air, fungal diversity decreased with urbanization even more than in the soil. This result is counterintuitive as fungal spores are known to disperse over large distances. A large proportion of the fungi detectable in the air are specialized to natural habitats, whereas soil fungal communities comprise a large proportion of habitat generalists. The sensitivity of the aerial fungal community to anthropogenic disturbance makes this method a reliable and efficient bioindicator of ecosystem health in urban areas.

Antagonistic Activity of Endophytic and Rhizosphere Fungi Isolated From Sea Purslane (Sesuvium portulacastrum) Against Pythium Damping off of Cucumber

This study was conducted to investigate the antagonistic activity of endophytic and rhizosphere fungi isolated from a medicinal plant, Sesuvium portulacastrum, against Pythium aphanidermatum, the cause of damping off of cucumber. A total of 40 endophytic and 19 rhizosphere fungi were isolated from S. portulacastrum. Three endophytic isolates and two rhizosphere isolates gave >50% suppression of P. aphanidermatum in the in vitro dual-culture tests. Scanning electron microscopic studies at the inhibition zone showed hyphae wall damage and abnormal mycelial growth of the genus Pythium. Molecular analysis identified the antagonistic endophytes as Aspergillus insulicola (isolate A435), A. insulicola (A419), and Aspergillus melleus (A412) and the rhizosphere antagonists as Aspergillus terreus (A213) and Aspergillus luchuensis (A116). Except for A116, the culture filtrates of the other antagonists significantly increased the electrolyte leakage from Pythium mycelia, whereas ethyl acetate extracts of A435, A412, and A213 showed significant growth suppression. All five antagonists were able to produce varying amounts of cellulase and β-glucanase enzymes. However, A435, A412, and A213 showed significantly higher cellulase activity, whereas A435 and A116 showed the highest β-glucanase activity. Controlled glasshouse growth experiments showed that isolates A435 and A116 resulted in up to 70% control of damping off, whereas isolates A412 and A213 showed 30 to 40% damping-off control. The antagonists A435, A116, and A213 also contributed to increased cucumber shoot length as well as shoot and root dry mass. The synergetic effects of metabolites and hydrolytic enzymes could be the reason for the variation between isolates in the antagonistic activity and cucumber growth promotion. This study reports for the first time A. insulicola, A. melleus, and A. luchuensis as potential biocontrol agents against P. aphanidermatum-induced damping off of cucumber.

The endosphere microbial communities, a great promise in agriculture

Agricultural food production and sustainability need intensification to address the current global food supply to meet human demand. The continuous human population increase and other anthropogenic activities threaten food security. Agrochemical inputs have long been used in conventional agricultural systems to boost crop productivity, but they are disadvantageous to a safe environment. Towards developing environmentally friendly agriculture, efforts are being directed in exploring biological resources from soil and plant microbes. The survival of the rhizosphere and endosphere microbiota is influenced by biotic and abiotic factors. Plant microbiota live interdependently with the host plants. Endophytes are regarded as colonizer microbes inhabiting and establishing microbial communities within the plant tissue. Their activities are varied and include fixing atmospheric nitrogen, solubilizing phosphate, synthesis of siderophores, secretion of metabolite-like compounds containing active biocontrol agents in the control of phytopathogens, and induced systemic resistance that stimulates plant response to withstand stress. Exploring beneficial endophyte resources in the formulation of bio-inoculants, such as biofertilizers, as an alternative to agrochemicals (fertilizers and pesticides) in developing environmentally friendly agriculture and for incorporation into crop breeding and disease control program is promising. Therefore, in this review, endosphere microbial ecology, associating environmental factors, and their roles that contribute to their effectiveness in promoting plant growth for maximum agricultural crop productivity were highlighted.