Fungal Biocontrol Research Articles

Increased Phenoloxidase Activity Constitutes the Main Defense Strategy of Trichoplusia ni Larvae against Fungal Entomopathogenic Infections.

The cabbage looper Trichoplusia ni is an important agricultural pest worldwide and is frequently used as a model organism for assessing entomopathogenic fungi virulence, though few studies have measured the host response repertoire to fungal biocontrol agents. Here, we quantified the immune response of T. ni larvae following exposure to two entomopathogenic fungal species: Beauveria bassiana and Cordyceps javanica. Results from our study demonstrate that T. ni larvae exposed to fungal entomopathogens had higher total phenoloxidase activity compared to controls, indicating that the melanization cascade is one of the main immune components driving defense against fungal infection and contrasting observations from other insect-fungi interaction studies. We also observed differences in host response depending on the species of entomopathogenic fungi, with significantly higher induction observed during infections with B. bassiana than with C. javanica. Larvae exposed to B. bassiana had an increased expression of genes involved in prophenoloxidase response and the Imd, JNK, and Jak/STAT immune signaling pathways. Our results indicate a notable absence of Toll pathway-related responses, further contrasting results to other insect-fungi pathosystems. Important differences were also observed in the induction of antimicrobial effectors, with B. bassiana infections eliciting three antimicrobial effectors (lysozyme, gloverin, and cecropin), while C. javanica only induced cecropin expression. These results provide insight into the host response strategies employed by T. ni for protection against entomopathogenic fungi and increase our understanding of insect-fungal entomopathogen interactions, aiding in the design of more effective microbial control strategies for this important agricultural pest.

Assessing the Biosynthetic Inventory of the Biocontrol Fungus Trichoderma afroharzianum T22.

Natural products biosynthesized from biocontrol fungi in the rhizosphere can have both beneficial and deleterious effects on plants. Herein, we performed a comprehensive analysis of natural product biosynthetic gene clusters (BGCs) from the widely used biocontrol fungus Trichoderma afroharzianum T22 (ThT22). This fungus encodes at least 64 BGCs, yet only seven compounds and four BGCs were previously characterized or mined. We correlated 21 BGCs of ThT22 with known primary and secondary metabolites through homologous BGC comparison and characterized one unknown BGC involved in the biosynthesis of eujavanicol A using heterologous expression. In addition, we performed untargeted transcriptomics and metabolic analysis to demonstrate the activation of silent ThT22 BGCs via the "one strain many compound" (OSMAC) approach. Collectively, our analysis showcases the biosynthetic capacity of ThT22 and paves the way for fully exploring the roles of natural products of ThT22.

Prospects of Microbial Bio‐surfactants To Endorse Prolonged Conservation in the Pharmaceutical and Agriculture Industries

AbstractChemical surfactants have raised concerns due to their negative impact on ecosystems, prompting the search for eco‐friendly alternatives. Biosurfactants derived from microorganisms offer a promising solution. These biomolecules are less harmful and can replace toxic pesticide surfactants. Biosurfactants have shown potential in agriculture for food digestion, crop protection, soil fertility, disease management, antibacterial properties, and biofilm prevention. They eliminate plant‐pathogens and improve nutrient availability, supporting plant‐growth. Rhamnolipids, produced by Pseudomonas, reduce surface tension, are used as wetting agents and emulsifiers in agriculture, and antimicrobial and anti‐inflammatory medications. Surfactin, a biosurfactant from Bacillus subtilis, improves plant development, controls plant diseases, and fights pathogens and diseases. Candida bombicola yeast produces sophorolipids, biodegradable surfactants with antibacterial, anticancer, and anti‐inflammatory properties. Pseudozyma yeast produces mannosylerythritol lipids (MELs), which biocontrol fungus and have antibacterial, anticancer, and immunomodulatory activities. Biosurfactants also hold potential in pharmaceuticals, functioning as antioxidants, exhibiting antibacterial and anticancer activities, and acting as drug‐delivery systems. However, challenges in biosurfactant production include varying research methods, limited production organism sources, and cost implications for large‐scale manufacturing. This mini‐review explores microbiologically produced biosurfactants, their regulatory parameters, their applications in optimizing soil health and controlling plant infections, and their potential roles in the pharmaceutical sector.

The Use of Some Animal Wastes in the Control of the Pathogenic Fungi Fusarium Solani And Rhizoctonia Solani on Tomato Plants

Background: This study was conducted to evaluate the efficiency of animal waste in controlling seedling death and root rot diseases in tomato caused by the pathogenic fungi Fusarium solani and Rhizoctonia solani In open field conditions, which were isolated from the soil of different locations. singly or in combination with the bio-control fungus Trichoderma harzianum.
 Materials and Methods: The fungal pathogens and fungi, Fusarium solani and Rhizoctonia solani, were tested and diagnosed, and the pathogenicity of the fungal isolates was tested. The resistance preparation was introduced, and the terrain ability was tested for it
 Results:The results of the pathogenicity test showed that the isolates taken from the greenhouses / Hilla R. solani and F. solani had the highest percentage of seedling mortality after emergence, reaching 97.500 and 95.00, respectively.The interaction showed the antagonistic ability of the fungus Trichoderma harzianum against the pathogenic fungi R. solani and F. solani, achieving an antibody score of 2.25
 Conclusion: The results of the aqueous extract of animal waste showed a significant reduction of the two pathogens R.solani and F.solani, where it reached the highest value at 4.100 when isolate F.solani for poultry extract and the smallest value was 8.300 when extracting cows, while all aqueous extracts did not affect the growth of the biofungus T. harzianum .It amounted to 8,900, 9,000, 8,925, and 8,925 (cows, sheep, horses, and poultry), respectively. The results of the laboratory isolation of animal waste showed the presence of (6) species of fungi.. Alternaria sp, Aspergillus niger, Penicillium sp, Trichoderma harzianum , macrohpomina sp , Cylindrocarpon sp

AfLaeA, a Global Regulator of Mycelial Growth, Chlamydospore Production, Pathogenicity, Secondary Metabolism, and Energy Metabolism in the Nematode-Trapping Fungus Arthrobotrys flagrans.

Arthrobotrys flagrans (Duddingtonia flagrans) is a typical nematode-trapping fungus which has been used for nematode biocontrol. The global regulator LaeA is widely distributed in filamentous fungi and plays a crucial role in secondary metabolism and development in addition to pathogenicity in fungal pathogens. In this study, the chromosome-level genome of A. flagrans CBS 565.50 was sequenced and homologous sequences of LaeA were identified in A. flagrans. A. flagrans LaeA (AfLaeA) knockout resulted in slower hyphal growth and a smoother hyphal surface. Importantly, deletion of AfLaeA resulted in the absence of chlamydospores and attenuated glycogen and lipid accumulation in hyphae. Similarly, disruption of the AfLaeA gene led to fewer traps and electron-dense bodies, lower protease activity, and a delay in capturing nematodes. The AfLaeA gene had a large effect on the secondary metabolism of A. flagrans, and both the deletion and overexpression of AfLaeA could yield new compounds, whereas some compounds were lost due to the absence of the AfLaeA. Protein-protein interactions between AfLaeA and another eight proteins were detected. Furthermore, transcriptome data analysis showed that 17.77% and 35.51% of the genes were influenced by the AfLaeA gene on days 3 and 7, respectively. AfLaeA gene deletion resulted in the higher expression level of the artA gene cluster, and multiple differentially expressed genes involved in glycogen and lipid synthesis and metabolism showed opposite expression patterns in wild-type and ΔAfLaeA strains. In summary, our results provide novel insights into the functions of AfLaeA in mycelial growth, chlamydospore production, pathogenicity, secondary metabolism, and energy metabolism in A. flagrans. IMPORTANCE The regulation of biological functions, such as the secondary metabolism, development, and pathogenicity of LaeA, has been reported in multiple fungi. But to date, no study on LaeA in nematode-trapping fungi has been reported. Moreover, it has not been investigated whether or not LaeA is involved in energy metabolism and chlamydospore formation has not been investigated. Especially in the formation mechanism of chlamydospores, several transcription factors and signaling pathways are involved in the production of chlamydospores, but the mechanism of chlamydospore formation from an epigenetic perspective has not been revealed. Concurrently, an understanding of protein-protein interactions will provide a broader perspective on the regulatory mechanism of AfLaeA in A. flagrans. This finding is critical for understanding the regulatory role of AfLaeA in the biocontrol fungus A. flagrans and establishes a foundation for developing high-efficiency nematode biocontrol agents.

Identification of potential fungal biocontrol agents for the management of ripgut brome

Ripgut brome (Bromus diandrus) is a significant weed in arable systems with cereals being negatively impacted through yield reduction and contamination of harvested grain. There are limited herbicide options for its control, and reduction of the weed seed bank is a key part of its management. Ripgut brome seeds were incubated in three soils known to harbour a range of plant pathogens, and a range of fungi were subsequently isolated from ungerminated seeds. The most prevalent putative fungal pathogens isolated were Fusarium spp. and Marasmius sp. Selected isolates were cultured on artificial media and tested for their ability to inhibit germination of ripgut brome seeds in a series of in vitro assays, with many isolates completely inhibiting germination. When isolates were tested for their activity against non-target arable species in plant assays, three of five Fusarium spp. isolates significantly inhibited germination of oats and barley while a Marasmius sp. isolate had no effect on germination of these species. Further plant assays using four Marasmius sp. isolates against a wider range of plant species (oats, barley, ryegrass, brome, cocksfoot, and prairie grass) indicated some variability between Marasmius sp. isolates, with two isolates slightly inhibiting germination of some plant species, while two isolates (W14, W17) had no adverse effects. Sequencing of the ITS region of the Marasmius sp. isolates indicated that they were closely related but distinct from M. graminum, which is known to have some phytopathogenic activity and M. oreades which has not yet been reported as a plant pathogen. Further investigation of the Marasmius isolates as potential biocontrol agents for ripgut brome seed is warranted.

Metarhizium anisopliae E6 secretome reveals molecular players in host specificity and toxicity linked to cattle tick infection

Although Metarhizium anisopliae is one of the most studied fungal biocontrol agents, its infection mechanism is far from being completely understood. Using multidimensional protein identification technology (MudPIT), we evaluated the differential secretome of M. anisopliae E6 induced by the host Rhipicephalus microplus cuticle. The proteomic result showed changes in the expression of 194 proteins after exposure to host cuticle, such as proteins involved in adhesion, penetration, stress and fungal defense. Further, we performed a comparative genomic distribution of differentially expressed proteins of the M. anisopliae secretome against another arthropod pathogen, using the Beauveria bassiana ARSEF2860 protein repertory. Among 47 analyzed protein families, thirty were overexpressed in the M. anisopliae E6 predicted genome compared to B. bassiana. An in vivo toxicity assay using a Galleria mellonella model confirmed that the M. anisopliae E6 secretome was more toxic in cattle tick infections compared to other secretomes, including B. bassiana with cattle ticks and M. anisopliae E6 with the insect Dysdereus peruvianus, which our proteomic results had also suggested. These results help explain molecular aspects associated with host infection specificity due to genetic differences and gene expression control at the protein level in arthropod-pathogenic fungi.

Biocontrol-based strategies for improving soil health and managing plant-parasitic nematodes in coffee production.

Coffee is an important commodity for Kenya, where production is steadily declining, despite a global rise in demand. Of the various constraints affecting production, plant-parasitic nematodes are a significant, but often overlooked, threat. As a perennial crop, treating plantations once infected with nematodes becomes difficult. The current study evaluated the drenching application of two biocontrol agents, Trichoderma asperellum and Purpureocillium lilacinum, for their nematode control efficacy, as well as their impact on the soil nematode community structure on mature, established coffee trees in Kenya. Seven Arabica coffee field trials were conducted over two years on trees of various ages. All the fields were heavily infested with Meloidogyne hapla, the first report of the species on coffee in Kenya. Both fungal biocontrol agents were detected endophytically infecting roots and recovered from soil but not until six months after initial applications. The population densities of M. hapla had significantly declined in roots of treated trees 12 months after the initial application, although soil nematode density data were similar across treatments. Based upon the maturity index and the Shannon index, treatment with T. asperellum led to improved soil health conditions and enrichment of diversity in the microbial community. Application of P. lilacinum, in particular, led to an increased abundance of fungivorous nematodes, especially Aphelenchus spp., for which P. lilacinum would appear to be a preferred food source. The soils in the trials were all stressed and denuded, however, which likely delayed the impact of such treatments or detection of any differences between treatments using indices, such as the functional metabolic footprint, over the period of study. A longer period of study would therefore likely provide a better indication of treatment benefits. The current study positively demonstrates, however, the potential for using biologically based options for the environmentally and climate-smart management of nematode threats in a sustainable manner on established, mature coffee plantations.

Fungal Endophytes: An Alternative Biocontrol Agent against Phytopathogenic Fungi

There has been renewed interest in the application of endophytic fungi to control phytopathogenic fungi, which cause significant damage to crop health, ultimately leading to losses in agricultural productivity. Endophytic fungi inhibit pathogens via different modes of action—mycoparasitism, competition (for nutrients and ecological niches), antibiosis, and induction of plant defense—thus demonstrating the ability to control a wide range of phytopathogenic fungi in different growth phases and habitats. However, many studies have been conducted under laboratory conditions, and there is a huge lack of studies in which real field testing was performed. Aspergillus, Clonostachys, Coniothyrium, Trichoderma, and Verticillium have been proven to be the most effective fungal biocontrol agents. Trichoderma is regarded as the most promising group in commercial formulations. In this study, we attempted to emphasize the significance of fungal endophytes in controlling phytopathogenic fungi, while reporting recent advances in endophytic biology and application.

The effect of Trichoderma longibrachiatum Against Damping-off Pathogens on Different Varieties of Cucumber in Vitro

The study was carried out to evaluate the effect of Trichoderma longibrachiatum against damping-off pathogens on four commercial cultivars of cucumber in vitro. Various sites of Najaf province including (Abasia, Quzwenia, Haydaria, Manathera and Meshkab) were surveyed to detect the spread of studied disease. Pathogenic fungi were isolated from roots and stem parts of infected cucumber plants that collected from studied sites then diagnosed morphologically. The pathogenicity test was conducted on fungal isolates and the susceptibility of four different cucumber varieties (Superina F1, Beit alpha F1, Cucumber short and Hybrid cucumber) to these isolates was tested in laboratory with the presence of the fungal bio-control T. longibrachiatum. One isolate of Fusarium sp. and another isolate of R. solani found to be very virulence which increase the percentage of damping off on seedlings up to 90and 100% respectively compare to control treatment of the four studied varieties that recorded 100, 95, 90 and 85 respectively and reduced vegetative and root growth indicators of cucumber plants (the weight and the length of plumule, the weight and the length of radicale) and these isolates were chosen to complete the later studies. The diagnosis of these two isolate then confirmed by (PCR) to F. solani and R. solani as both isolates were registered in National Center for Biotechnology Information (NCBI) under ON394603 and ON398997 accession numbers respectively. Results showed that T. longibrachiatum treatment was increased studied indicators when it was added alone or with other treatments to the soil of plastic pots and provided a protection for cucumber plants from the infection by the disease. The susceptibility of the four studied different cucumber varieties to F. solani and R. solani showed that Cucumber short and Beit alpha F1 varieties were more susceptible to the infection by damping off pathogens compare to moderate susceptibility in Hybrid cucumber, while Superina F1 showed less susceptibility which clearly indicated in the studied vegetative and root growth indicators of cucumber plants.

Purpureocillium lilacinum strain AUMC 10620 as a biocontrol agent against the citrus nematode Tylenchulus semipenetrans under laboratory and field conditions

Three concentrations (1.25, 2.5, and 5 × 107 spores ml−1) (of the biocontrol fungus Purpureocillium lilacinum (strain AUMC 10620) were tested on citrus nematode Tylenchulus semipenetrans under in vitro and field conditions. Larvae and eggs were exposed to the fungal spores in vitro for 24, 48, and 72 h, and the findings were recorded at each time point. These results were compared with the application of the nematicide abamectin. Strain AUMC 10620 effectively reduced larval activity and egg hatching of T. semipenetrans under laboratory conditions. The highest concentration (5× 107 spores ml−1) of P. lilacinum, resulted in 89.01% immobility in the larvae, compared to abamectin, which resulted in 65.93% immobility after 48 h of exposure. These percentages of immobility were increased after 72 h of exposure (100 and 85.09%) when P. lilacinum at a concentration of 5 × 107 spores ml−1 and abamectin were used, respectively. On the other hand, the two other P. lilacinum concentrations (1.25, and 2.5 × 107 spores ml−1) affected the T. semipenetrans larvae to a lesser extent. The highest fungal concentration 5× 107 spores ml−1 inhibited the hatching of T. semipenetrans eggs in vitro with 71.34, 80, and 86.67% after 24, 48 and 72 h of treatment compared to the abamectin treatment which showed 76.67, 78, and 87% after the abovementioned periods, respectively. In addition, the application of P. lilacinum (5 × 107 spores ml−1) or abamectin under field conditions significantly (P < 0.05) reduced the population of the major nematode species (T. semipenetrans, Tylenchorhynchus spp., Helicotylenchus spp., and Pratylenchus spp.) infesting citrus after one, two, and three weeks of treatment compared to the control treatment but with no significant (P > 0.05) differences between the two treatments. Three weeks after the field application, the percentage of nematode reduction was significantly (P < 0.05) smaller than the control treatment at concentrations of 5, 2.5, and 1.25 × 107 spores ml−1, respectively, by 78.42, 64.03, and 58.35%. It is evident from these results that the application of P. lilacinum strain (AUMC 10620) can be used in integrated pest management programs to control nematodes infesting citrus trees.Graphical abstract

Bioponics—An Organic Closed-Loop Soilless Cultivation System: Yields and Characteristics Compared to Hydroponics and Soil Cultivation

Sustainable food production has become increasingly important. Soilless cultivation systems offer several advantages, such as water and nutrient use efficiency, and can be implemented where traditional agriculture is impossible. Bioponic systems use locally or regionally available nutrient sources from organic waste streams (either fluid or solid) and can thus contribute to closing nutrient cycles locally. Bioponics harnesses the metabolic processes of microorganisms which release nutrients from organic matter. This study aimed to set up a bioponic system, by using biogas digestate concentrate and biochar as nutrient sources, and promoting nutrient release from the organic sources by including a biofilter in the system. The development of water quality, plant growth, and quality was monitored extensively. In addition, the influence of either the fungal biocontrol agent Trichoderma atrobrunneum or UV-C treatment of the nutrient solution on plant health and growth was investigated. Three cultivation cycles with Lactuca sativa (“HAWKING” Salanova®) in bioponic (BP), hydroponic (HP), and soil (SO) cultivation were performed. The study showed that healthy lettuces could be produced in BP systems, using a biogas digestate concentrate and biochar as nutrient sources, despite salt accumulation in the nutrient solution. In plant sap analyses, lettuces cultivated in BP systems contained less nitrate but more ammonium and chloride. The yield of the lettuces grown in the BP systems was intermediate, compared to the HP and the SO. The fungus, T. atrobrunneum, strain, T720, survived in soil and soilless cultivation systems. Compared to the HP and the SO systems, the shoot height of lettuces grown in the BP system, with the application of Trichoderma, was significantly increased. In SO systems with Trichoderma application, a significantly higher chlorophyll and flavonoid content, but significantly lower shoot height was observed. The fresh weight of lettuce roots was significantly higher in HP systems with Trichoderma treatment. Cultivating plants by using organic waste streams requires commitment and experience from producers. In BP systems, a biofilter (either within the system or externally, to increase nutrient levels) can help to rapidly convert the ammonium-rich fertilizer to plant-available nutrients. Unlike conventional HP systems, in BP systems, nutrients are released slowly over time, requiring close monitoring and adjustments. In conclusion, healthy lettuces for human consumption can be produced in BP systems, and the application of the biocontrol agent used has some beneficial influence on plant growth.

Antifungal activity of volatile and non-volatile metabolites of endophytes of Chloranthus elatior Sw.

Agriculture crops that have fungal infections suffer significant economic losses and reduced crop output. Chemical fungicides are used to tackle the problem, although this has additional detrimental side effects. There is an urgent need for safe and novel antifungals. Volatiles from plant-beneficial endophytic fungi are considered promising alternatives for the biological control of fungal pathogens as a sustainable approach in an agroecosystem. In the present investigation, a volatile-emitting sterile endophytic fungus, Diaporthe sp. CEL3 with bio-fumigation activity, was isolated from leaves of the ethnomedicinal plant Chloranthus elatior Sw., collected from the Passighat forest of North-East India. The camphor odor volatiles of CEL3 showed an inhibitory effect against eight fungal pathogens in vitro and minimized the infections of Monilinia fructicola, a causal agent of cherry fruit rot, in VOC-exposed cherry fruits. Rhizoctonia solani, Botrytis cinerea, Pythium ultimum, and M. fructicola were maximally inhibited up to 51.5%, 55.8%, 61.9%, and 78.5%, respectively, in comparison to control by the volatiles. Another isolate, CEL7, identified as Curvularia sp., synthesized non-volatile, soluble antifungal metabolites in its cell-free extracts and exhibited antifungal action. Bioassay-guided fractionation revealed the presence of imidazole compounds- (2-aminoethyl)-1H-imidazole-2-carbaldehyde, Pyrazole 4, 5 imidazole, 1-formyl 3-ethyl, phenol compounds-Phenol, 4-[2-(methylamino) ethyl]-, 6-Nitro-3-chlorophenol, Phenol, 2,4,6-tri-tert-butyl-, etc., in the cell-free extracts, with a MIC value of 250-2,000 µg ml-1. Optimum VOC emission was achieved in a modified PDA medium with instantly smashed potato (150 g L-1), dextrose (20 g L-1), wheat husk (20 g L-1), and yeast extract (20 g L-1), with additional salts. Interestingly, endophytic CEL3 emitted different types of volatiles, and trans-verbenol (32.25%), geraniol (30.32%), trans-ocimenol (12.90%), and mentha-4,8-diene (5.16%) were the prime ones. These VOCs cause lethal leakage of protein and necessary intracellular molecules from the fungal pathogens. Thus, CEL3 could potentially be used as a bio-fumigating agent to control post-harvest infections caused by fungal pathogens. This study opens a new approach to the use of endophytic fungi in biocontrol.

Preventing mycelial spread of Heterobasidion annosum in young Scots pine stands using fungal and viral biocontrol agents

Heterobasidion annosum is one of the most important causal agents of root rot of pines in Europe. The timing of cuttings to wintertime or stump treatment by control agents in summertime are used to prevent the spread of the fungus to new forest sites via aerial spores. However, there are no efficient control treatments for an already established infection except for changing the tree species to a resistant one, which often is not possible. In this study, we tested whether treating stumps around Heterobasidion disease centres by the biocontrol fungus Phlebiopsis gigantea could reduce the spread of the pathogen. In addition, we tested whether the infection of H. annosum by a debilitating mycovirus, HetPV13-an1, would affect the control efficacy. The results showed that the enlargement of disease centres was reduced by P. gigantea, and that this biocontrol effect was enhanced by the virus application. Furthermore, the results showed that the growth rate of P. gigantea varies not only between root systems, but also among different roots of a single stump.

Dual RNA-Seq Profiling Unveils Mycoparasitic Activities of Trichoderma atroviride against Haploid Armillaria ostoyae in Antagonistic Interaction Assays.

Armillaria ostoyae, a species among the destructive forest pathogens from the genus Armillaria, causes root rot disease on woody plants worldwide. Efficient control measures to limit the growth and impact of this severe underground pathogen are under investigation. In a previous study, a new soilborne fungal isolate, Trichoderma atroviride SZMC 24276 (TA), exhibited high antagonistic efficacy, which suggested that it could be utilized as a biocontrol agent. The dual culture assay results indicated that the haploid A. ostoyae-derivative SZMC 23085 (AO) (C18/9) is highly susceptible to the mycelial invasion of TA. In the present study, we analyzed the transcriptome of AO and that of TA in in vitro dual culture assays to test the molecular arsenal of Trichoderma antagonism and the defense mechanisms of Armillaria. We conducted time-course analysis and functional annotation and analyzed enriched pathways and differentially expressed genes including biocontrol-related candidate genes from TA and defense-related candidate genes from AO. The results indicated that TA deployed several biocontrol mechanisms when confronted with AO. In response, AO initiated multiple defense mechanisms to protect against the fungal attack. To our knowledge, the present study offers the first transcriptome analysis of a biocontrol fungus attacking AO. Overall, this study provides insights that aid the further exploration of plant pathogen-biocontrol agent interaction mechanisms. IMPORTANCE Armillaria species can survive for decades in the soil on dead woody debris, develop rapidly under favorable conditions, and harmfully infect newly planted forests. Our previous study found Trichoderma atroviride to be highly effective in controlling Armillaria growth; therefore, our current work explored the molecular mechanisms that might play a key role in Trichoderma-Armillaria interactions. Direct confrontation assays combined with time course-based dual transcriptome analysis provided a reliable system for uncovering the interactive molecular dynamics between the fungal plant pathogen and its mycoparasitic partner. Furthermore, using a haploid Armillaria isolate allowed us to survey the deadly prey-invading activities of the mycoparasite and the ultimate defensive strategies of its prey. Our current study provides detailed insights into the essential genes and mechanisms involved in Armillaria defense against Trichoderma and the genes potentially involved in the efficiency of Trichoderma to control Armillaria. In addition, using a sensitive haploid Armillaria strain (C18/9), with its complete genome data already available, also offers the opportunity to test possible variable molecular responses of Armillaria ostoyae toward diverse Trichoderma isolates with various biocontrol abilities. Initial molecular tests of the dual interactions may soon help to develop a targeted biocontrol intervention with mycoparasites against plant pathogens.

Chemical Identification of Secondary Metabolites from Rhizospheric Actinomycetes Using LC-MS Analysis: In Silico Antifungal Evaluation and Growth-Promoting Effects.

The rhizosphere is a rich source of actinomycetes which can produce several potential biologically active secondary metabolites. The principal goal for this research is to extract, purify, and characterize the bioactive secondary metabolites produced by three different strains of actinomycetes isolated from the rhizosphere of rosemary, black locust, and olive. The plant growth-promoting effect (PGPE) of the studied strains of actinomycetes on Ocimum basilicum L. (basil) and the disease-control effect on necrotic stem lesions of "black leg" caused by Fusarium tabacinum on basil were evaluated in silico. The cell-free culture filtrates from the studied actinomycetes isolates were evaluated in vitro for their antimicrobial activity against some common phytopathogens. The secondary metabolites obtained from the cell-free culture filtrates have been chemically characterized using high-resolution electrospray ionization of liquid-chromatography/mass-spectrometric detection (ESI-(HR)Orbitrap-MS). Results of the in silico trial showed that all studied isolates demonstrated PGPE on basil seedlings, improved some eco-physiological characteristics, and reduced the disease incidence of F. tabacinum. The extracted metabolites from the studied actinomycetes demonstrated antimicrobial activity in a Petri-plates assay. The chemical analysis revealed the presence of 20 different components. This research emphasizes how valuable the examined isolates are for producing bioactive compounds, indicating their putative antimicrobial activity and their potential employment as fungal biocontrol agents. In particular, the obtained results revealed the possibility of green synthesis of some important secondary metabolites, such as N-Acetyl-l-histidinol, Rhizocticin A, and Eponemycin, from actinomycetes. The bioactive metabolites may be successively used to develop novel bio-formulations for both crop protection and/or PGPE.

Fungal Community Associated with the Leaf-Cutting Ant Acromyrmex crassispinus (Hymenoptera: Formicidae) Colonies: a Search for Potential Biocontrol Agents.

The leaf-cutting ant Acromyrmex crassispinus is considered an important pest in forest plantations in southern Brazil. This work aimed to study the fungal community associated with A. crassispinus colonies, subjected to treatments with subdoses of granulated baits (sulfluramid), which might reduce the ability of the ants to care for their symbiotic fungus and other fungi (maybe biocontrol fungi) would take over, to prospect for potential biological control agents. Samplings of fungus gardens and dead ants allowed the identification of 195 fungal isolates, distributed in 29 families, 36 genera, and 53 species. The most frequent genera were Trichoderma (49.2%), Penicillium (13.8%), Chaetomium (6.2%), and Fusarium (3.6%). This is the first study that conducted a survey of antagonistic and entomopathogenic fungi to A. crassispinus and its symbiotic fungus, reporting for the first time the occurrence of potential biological control agents. Escovopsis weberi, Fusarium oxysporum, Rhizomucor variabilis, Trichoderma atroviride, Trichoderma harzianum, Trichoderma koningiopsis, and Trichoderma spirale are considered some of the potential biocontrol organisms.

Metabolomic profiling and its association with the bio-efficacy of Aspergillus niger strain against Fusarium wilt of guava.

Bio-control agents are the best alternative to chemicals for the successful management of plant diseases. The fungus Aspergillus niger is known to produce diverse metabolites with antifungal activity, attracting researchers to exploit it as a bio-control agent for plant disease control. In the present study, 11 A. niger strains were isolated and screened for their antagonism against the guava wilt pathogen under in vitro and in planta conditions. Strains were identified morphologically and molecularly by sequencing the internal transcribed spacer (ITS), β-tubulin, and calmodulin genes. The strains were evaluated through dual culture, volatile, and non-volatile methods under an in vitro study. AN-11, AN-6, and AN-2 inhibited the test pathogen Fusarium oxysporum f. sp. psidii (FOP) at 67.16%, 64.01%, and 60.48%, respectively. An in planta study was conducted under greenhouse conditions with 6 months old air-layered guava plants (var. Allahabad Safeda) by pre- and post-inoculation of FOP. The AN-11 strain was found to be effective under both pre- and post-inoculation trials. Furthermore, gas chromatography-mass spectrometry (GC-MS) analysis was carried out to characterize the volatile compounds of the most potential strain, A. niger. The hexane soluble fraction showed the appearance of characteristic peaks of hexadecenoic acid methyl ester (4.41%), 10-octadecanoic acid methyl ester (3.79%), dodecane (3.21%), undecane (3.19%), gibepyrone A (0.15%), 3-methylundecane (0.36%), and citroflex A (0.38%). The ethyl acetate fraction of the bio-control fungi revealed the occurrence of major antifungal compounds, such as acetic acid ethyl ester (17.32%), benzopyron-4-ol (12.17%), 1,2,6-hexanetriol (7.16%), 2-propenoic acid ethanediyl ester (2.95%), 1-(3-ethyloxiranyl)-ethenone (0.98%), 6-acetyl-8-methoxy dimethyl chromene (0.96%), 4-hexyl-2,5-dihydro dioxo furan acetic acid (0.19%), and octadecanoic acid (1.11%). Furthermore, bio-control abilities could be due to hyper-parasitism, the production of secondary metabolites, and competition for sites and nutrients. Indeed, the results will enrich the existing knowledge of metabolomic information and support perspectives on the bio-control mechanism of A. niger.

The nematicidal potential of novel fungus, Trichoderma asperellum FbMi6 against Meloidogyne incognita

One of the most damaging pests in vegetable crops is the root-knot nematode (Meloidogyne incognita) worldwide. The continuous use of nematicide is costly and has unintended consequences for human and environmental health. To minimize nematicides, eco-friendly integrated nematode management is required. Trichoderma, an antagonistic fungus has been explored to control root-knot nematode. The fungal bio-control strain FbMi6 was identified as Trichoderma asperellum (accession no. MT529846.1). T. asperellum FbMi6 showed substantial nematicidal activity in the laboratory, with egg hatch suppression (96.6%) and juvenile mortality (90.3%) of M. incognita. T. asperellum FbMi6 was examined under pot and field conditions (after neem cake enrichment), both alone and in combination, and compared with controls. Application of T. asperellum FbMi6 enriched neem cake (1-ton ha-1) increased (28.3%) the okra yield and decreased (57.1%) nematode population as compared with control. T. asperellum FbMi6 enriched neem cake had higher polyphenol content (resistance enhancer) in okra compared with inoculated check.

The Exploitation of Microbial Antagonists against Postharvest Plant Pathogens.

Postharvest disease management is vital to increase the quality and productivity of crops. As part of crop disease protection, people used different agrochemicals and agricultural practices to manage postharvest diseases. However, the widespread use of agrochemicals in pest and disease control has detrimental effects on consumer health, the environment, and fruit quality. To date, different approaches are being used to manage postharvest diseases. The use of microorganisms to control postharvest disease is becoming an eco-friendly and environmentally sounds approach. There are many known and reported biocontrol agents, including bacteria, fungi, and actinomycetes. Nevertheless, despite the abundance of publications on biocontrol agents, the use of biocontrol in sustainable agriculture requires substantial research, effective adoption, and comprehension of the interactions between plants, pathogens, and the environment. To accomplish this, this review made an effort to locate and summarize earlier publications on the function of microbial biocontrol agents against postharvest crop diseases. Additionally, this review aims to investigate biocontrol mechanisms, their modes of operation, potential future applications for bioagents, as well as difficulties encountered during the commercialization process.