Phytopathogenic Fungi Research Articles

Gas chromatography-mass spectrometry comparative analysis of secondary metabolites produced by some Bacillus spp. as biocontrol agents against phytopathogenic fungi

Gas chromatography-mass spectrometry comparative analysis of secondary metabolites produced by some Bacillus spp. as biocontrol agents against phytopathogenic fungi

The sensor protein AaSho1 regulates infection structures differentiation, osmotic stress tolerance and virulence via MAPK module AaSte11-AaPbs2-AaHog1 in Alternaria alternata

The high-osmolarity-sensitive protein Sho1 functions as a key membrane receptor in phytopathogenic fungi, which can sense and respond to external stimuli or stresses, and synergistically regulate diverse fungal biological processes through cellular signaling pathways. In this study, we investigated the biological functions of AaSho1 in Alternaria alternata, the causal agent of pear black spot. Targeted gene deletion revealed that AaSho1 is essential for infection structure differentiation, response to external stresses and synthesis of secondary metabolites. Compared to the wild-type (WT), the ∆AaSho1 mutant strain showed no significant difference in colony growth, morphology, conidial production and biomass accumulation. However, the mutant strain exhibited significantly reduced levels of melanin production, cellulase (CL) and ploygalacturonase (PG) activities, virulence, resistance to various exogenous stresses. Moreover, the appressorium and infection hyphae formation rates of the ∆AaSho1 mutant strain were significantly inhibited. RNA-Seq results showed that there were four branches including pheromone, cell wall stress, high osmolarity and starvation in the Mitogen-activated Protein Kinase (MAPK) cascade pathway. Furthermore, yeast two-hybrid experiments showed that AaSho1 activates the MAPK pathway via AaSte11-AaPbs2-AaHog1. These results suggest that AaSho1 of A. alternata is essential for fungal development, pathogenesis and osmotic stress response by activating the MAPK cascade pathway via Sho1-Ste11-Pbs2-Hog1.

Antiphytopathogenic Diphenyl Ethers from the Marine-derived Fungus Aspergillus sydowii

Background: Natural products from the marine-derived Aspergillus sp. have great potential in agricultural usage due to their broad biological activities. Objective: This study was designed to investigate the antiphytopathogenic compounds from marinederived fungus Aspergillus sydowii LW09. Methods: The compounds were isolated and purified by chromatography methods, and their structures were elucidated by analysis of the NMR and MS spectroscopic data as well as comparison with those of literature. All compounds were evaluated for antibacterial activities against phytopathogenic bacteria Pseudomonas syringae and Ralstonia solanacarum, along with spore germination inhibition of phytopathogenic fungi Fusarium oxysporum and Alternaria alternata. Results: Two diphenyl ethers violaceols I (1) and II (2), along with two alkaloids acremolin (3) and WIN 64821 (4) were isolated from the fermentation extracts of A. sydowii LW09. Compound 1 showed significant antibacterial activity against P. syringae and R. solanacarum with the same MIC values of 4 μg/mL, while compound 2 showed obvious antibacterial activity against P. syringae and R. solanacarum with MIC values of 2 and 1 μg/mL, respectively. Moreover, both 1 and 2 could inhibit the spore germination of F. oxysporum in the concentration range of 64–128 μg/mL. In addition, violaceol I (1) also inhibited the spore germination of A. alternata at 128 μg/mL. Conclusion: This study provided the potential antiphytopathogenic drug candidate for further studies.

Combination of atmospheric and room temperature plasma and ribosome engineering techniques to enhance the antifungal activity of Bacillus megaterium L2 against Sclerotium rolfsii.

Sclerotium rolfsii is an extremely destructive phytopathogenic fungus that causes significant economic losses. Biocontrol strategies utilizing antagonistic microorganisms present a promising alternative for controlling plant pathogens. Bacillus megaterium L2 has been identified as a potential microbial biocontrol agent in our previous study; however, its efficacy in controlling pathogens has yet to meet current demands. This study aims to enhance the antifungal activity of strain L2 against S. rolfsii R-67 through a two-round mutagenesis strategy and to preliminarily investigate the mutagenesis mechanism of the high antifungal activity mutant. We obtained mutant Dr-77 with the strongest antifungal activity against R-67, and its cell-free supernatant significantly reduced the infection potential of R-67 to Amorphophallus konjac corms, which may be attributed to the antimicrobial compound phenylacetic acid (PAA), and PAA content in Dr-77 (5.78 mg/mL) was 28.90 times higher than original strain L2. This compound exhibited strong antifungal ability against R-67, with a half maximal effective concentration (EC50) value of 0.475 mg/mL, significantly inhibiting mycelial growth and destroying the ultrastructure of R-67 at EC50 value. Notably, PAA also exhibited broad-spectrum antifungal activity against six phytopathogens at EC50 value. Moreover, genome analysis revealed nine different gene mutations, including those involved in PAA biosynthesis, and the activities of prephenate dehydratase (PheA) and phenylacetaldehyde dehydrogenase (ALDH) in PAA biosynthesis pathway were significantly increased. These results suggest that the elevated PAA content is a primary factor contributing to the enhanced antifungal activity of Dr-77, and that this mutagenesis strategy offers valuable guidance for the breeding of functional microbial resources. © 2024 Society of Chemical Industry.

A small antimicrobial peptide derived from a Burkholderia bacterium exhibits a broad-spectrum and high inhibiting activities against crop diseases.

Crop diseases cause significant quality and yield losses to global crop products each year and are heavily controlled by chemicals along with very limited antibiotics composed of small molecules. However, these methods often result in environmental pollution and pest resistance, necessitating the development of new bio-controlling products to mitigate these hazards. To identify effective antimicrobial peptides (AMPs) considered as potential sources of future antibiotics, AMPs were screened from five bacterial strains showing antagonism against a representative phytopathogenic fungus (Rhizoctonia Solani) through the Bacillus subtilis expression system, which has been developed for identifying bacterial AMPs by displaying autolysis morphologies. A total of 5000 colonies were screened, and five displaying autolysis morphologies showed antagonism against R. solani. A novel AMP with the strongest antagonism efficiency was determined and tentatively named HR2-7, which is composed of 24 amino acids with an alpha-helical structure. HR2-7 has strong and broad-spectrum antimicrobial activity, tested against 10 g-positive and -negative bacteria and four phytopathogenic fungi by contact culture in plates with minimal lethal concentrations of 4.0 μM. When applied as purified peptide or in fermented B. subtilis culture solution, HR2-7 showed strong controlling efficiency on plants against diverse fungal and bacterial pathogens. Based on current understanding, HR2-7 is recognized as the first AMP derived from an agricultural antagonistic bacterium. It exhibits wide-ranging and notable antimicrobial efficacy, offering a supplementary approach for managing plant diseases, in addition to conventional chemical pesticides and antibiotics.

Biological Activity of Essential Oil from Two Aromatic Species on the in vitro Control of Colletotrichum gloeosporioides (Penz.) Penz. & Sacc.

Objective: Essential oils (EO) from aromatic and medicinal plants (AMP) are considered a viable alternative for controlling phytopathogenic fungi of agronomic importance. This study evaluated the antifungal activity of thyme (Thymus vulgaris L.) and rue (Ruta graveolens L.) essential oils against Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. Design/Methodology/Approach: The antifungal activity was assessed using the agar disk diffusion method, with concentrations ranging from 10% to 100% of each EO. The phytochemical composition was analyzed using GC-MS. Morphological observations were conducted with a scanning electron microscope (SEM). Results: Significant antifungal activity was observed at concentrations of 50-100% of thyme EO. Rue EO exhibited a fungistatic effect for up to six days. Phytochemical analysis identified carvacrol (35.95%) and p-cymene (41.18%) as the major components in thyme EO, and 2-nonanone (24.24%) and 2-undecanone (68.69%) in rue EO. Findings/conclusions: The evaluated EOs significantly impacted fungal morphology at 60% concentration. The strong antifungal activity of thyme EO against C. gloeosporioides suggests its potential as an eco-friendly control alternative.

Inhibition of the Growth of Four Phytopathogenic Fungi by Eucalyptus Wood Vinegar

Purpose: The objective of this work aimed to assess the wood vinegar (WV) from the carbonization of Eucalyptus wood in the inhibition in vitro of Fusarium sp., Ganoderma sp., Macrophomina sp., and Sclerotium rolfsii. Method: WV was added to a culture medium and poured onto Petri dishes. After, the fungi were picked up in 1-mm disks and placed in the center of each Petri dish. The experimental design had five treatments, T1, T2, T3, T4, and T5, with crescent concentrations of WV, respectively, 0 (control), 5, 10, 15, and 20 mL L-1. The variables evaluated were fungal growth, mycelial growth rate index, and percentage of mycelial growth inhibition. Results and Discussion: A gradual decrease in the mycelial growth, in the mycelial growth rate index, and an increase in the percentage of mycelial growth inhibition were determined for all assessed fungi in the concentration of 20 mL L-1 of WV. Hence, the conclusion was that eucalyptus WV presented fungi-toxic properties over the assessed fungi and the product can be considered as an alternative for the chemical control of the incidence of these pathogens in crops and forest plantations. Research Implications: The use of natural products with fungi toxic properties is becoming important for the control of pathogens that attack crops and forest plantations due to the harmful effects of the conventional fungicides on living organisms and the environment. The search for efficient alternative products is therefore a goal to be reached in the field of phytopathology. Originality/ Value: The use of natural products with fungitoxic properties has been gaining ground in the control of pathogens affecting agricultural and forestry crops. This intensifies the search for natural products that are efficient in the biocontrol of phytopathologies.

Inhibitory effect of Eucalyptus globulus essential oil against Botryosphaeria dothidea and Fomitiporia mediterranea fungi causing wood diseases in viticulture

AbstractDieback diseases are caused by Fomitiporia and Botryosphaeria two genus of fungi that colonize wood tissue in grapevine. After the prohibition of sodium arsenite in 2001, no chemical treatments are available to control these diseases. Curettage is a possible substitute solution. The results depend on many factors. The use of essential oils can be an alternative and/or complementary way. This study aims to investigate the essential oil (EO) composition of Eucalyptus globulus (E. globulus) from leaves and flowers and to evaluate its antifungal activity against Botryosphaeria dothidae and Fomitiporia mediterranea fungi. GC–MS results show that 97.79% of oil composition was identified, of which the Eucalyptol is the major compound (76.33%). Other compounds were identified such as α-Pinene (9.81%); Allo-Aromadendrene (3.07%) and Limonene (2.55%). EO had a detrimental effect in vito on both developed Botryosphaeria dothidae and Fomitiporia mediterranea fungi. The effect is dose-dependent and increases with the duration of the treatment. Essential oil concentrations of 0.25% and 0.75% of E. globulus were efficient against Botryosphaeria dothidae and Fomitiporia mediterranea, respectively. This is the first report investigate the purpose of E. globulus EO to control this both phytopathogenic fungi. The results from the antifungal assays reveal that EO of E. globulus has an excellent inhibitory effect against both tested fungi.

A Novel Lactam and Two Rare Mycophenolic Acid Derivatives from the Fungus Penicillium Sclerotiorum JBHL321.

A novel lactam penicillactam (1), two rare mycophenolic acid (MPA) derivatives penimycophens A and B (2 and 3), together with two known biogenetically related MPA derivatives (4 and 5) and a known alkaloid (6) were isolated from the Penicillium sclerotiorum JBHL321. The structures of these compounds were determined by comprehensive spectroscopic analyses. The absolute configuration of 1 was confirmed by electronic circular dichroism (ECD) calculations. Compound 1 represent the rare example of a oxygen bridge-linked lactam from natural products. Structurally, compounds 2 and 3 were rare MPA derivatives featuring a methoxy group at C-3. The inhibitory activity of compounds 1-6 against two phytopathogenic fungi, three phytopathogenic bacteria and four cancer cell lines were evaluated. Compounds 2-5 exhibited significant cytotoxic activity against HeLa, MCF-7, A549 and MGC-803 cells with IC50 values in the low micromolar to nanomolar. Compound 3 exhibited especially cytotoxic activity against four different cell lines with IC50 values ranging from 0.06-0.14 μM, compared to IC50 values ranging from 0.62-2.51 μM for epirubicin.

Isolation and identification of phytopathogenic fungi from blueberry (Vaccinium corymbosum) and their biocontrol by Meyerozyma guilliermondii LMA-Cp01

Isolation and identification of phytopathogenic fungi from blueberry (Vaccinium corymbosum) and their biocontrol by Meyerozyma guilliermondii LMA-Cp01

Exploring the potential of bioactive compounds of Capparis spinosa L. from Morocco: Unveiling its antioxidant and antifungal powers against Alternaria alternata

Capparis spinosa L. is a Mediterranean shrub and one of the most important species of the gender Capparis due to its ecological, medicinal and economic importance. This species has strong adaptation characteristics to regions with fluctuating climates. This work aims to evaluate the effect of the locality’s climate and plant’s parts on the content of polyphenols, flavonoids and antioxidant and antifungal activities of caper leaves and seeds. The present study was carried out in 7 localities in 2 Moroccan regions, Oriental and Fez-Meknes, where we collected leaves and seeds samples. Phenolic compounds were determined by the Folin Ciocalteu method, antioxidant activity was studied by DPPH and ABTS tests and an in vitro test of antifungal activity was achieved using Alternaria alternata. The analysis of variance showed no significant effect of locality, plant’s parts and their interaction on the phenolic compounds, antioxidant and antifungal activities of C. spinosa. Methanolic leaves extracts demonstrated the most favorable outcomes, yielding a maximum polyphenol content of 124.48 ± 0.05 mg EAG/g DW. Additionally, the maximum flavonoid content was recorded at 24.51 ± 0.01 mg EQ/g DW. The evaluation of the antioxidant activity showed that the minimum inhibitory concentration at 50 % (IC50) is 2.06 ± 0.05 mg/mL and 2.05 ± 0.02 mg/mL using DPPH and ABTS tests respectively. These extracts exhibited the highest % of inhibition, 30.59 % at 1000 ppm against A. alternata. The richness of the caper plant in bioactive compounds reveals an interest in its therapeutic and pharmaceutical virtues. In addition, it could be an alternative to chemicals for the control of phytopathogenic fungi on fruits or vegetables.

The TOR signalling pathway in fungal phytopathogens: A target for plant disease control.

Plant diseases caused by fungal phytopathogens have led to significant economic losses in agriculture worldwide. The management of fungal diseases is mainly dependent on the application of fungicides, which are not suitable for sustainable agriculture, human health, and environmental safety. Thus, it is necessary to develop novel targets and green strategies to mitigate the losses caused by these pathogens. The target of rapamycin (TOR) complexes and key components of the TOR signalling pathway are evolutionally conserved in pathogens and closely related to the vegetative growth and pathogenicity. As indicated in recent systems, chemical, genetic, and genomic studies on the TOR signalling pathway, phytopathogens with TOR dysfunctions show severe growth defects and nonpathogenicity, which makes the TOR signalling pathway to be developed into an ideal candidate target for controlling plant disease. In this review, we comprehensively discuss the current knowledge on components of the TOR signalling pathway in microorganisms and the diverse roles of various plant TOR in response to plant pathogens. Furthermore, we analyse a range of disease management strategies that rely on the TOR signalling pathway, including genetic modification technologies and chemical controls. In the future, disease control strategies based on the TOR signalling network are expected to become a highly effective weapon for crop protection.

Antifungal activity of zinc oxide nanoparticles (ZnO NPs) on Fusarium equiseti phytopathogen isolated from tomato plant in Nepal

Fungal diseases pose a major threat to global agriculture, leading to reduced crop yields, health issues and significant economic impact. Application of nanoparticles are being explored in agriculture because of its ecofriendly as well as enhanced antimicrobial properties. In this study, using an aqueous extract of air-dried tea leaves, zinc oxide nanoparticles (ZnO NPs) are synthesized and it was characterized using various techniques such as X-ray diffraction, UV-Vis, FTIR spectroscopy and microscopic analysis. The growth inhibition activity of the ZnO-NPs was investigated against a phytopathogenic fungus, which was isolated and identified as Fusarium equiseti from tomato plant leaves. Our result showed that application of ZnO NPs at 750 ppm to 1200 ppm concentration range inhibited the growth of F. equiseti by 77.6% to 85.1% at 7 days of seeding the fungi in PDA media. Microscopic observation of the fungal strain treated with ZnO NPs showed that the presence of the nanoparticles agglomerates the normal hyphae of F. equiseti and formed curve tips and breakage of mycelia. Hence, our study shows that application ZnO NPs is promising approach for fungal growth inhibition and can be deployed to inhibit other plant diseases causing microbes in agriculture.

The Glucanase Enzyme Activity from Rhizospheric Streptomyces spp. in Inhibiting Growth and Damaging the Cell Walls of the Mycelium of Fusarium oxysporum

Fusarium oxysporum, a phytopathogenic fungus responsible for fusarium wilt in more than 120 plant species, is primarily managed using synthetic fungicides, which pose environmental hazards. Therefore, alternative biological control methods are urgently needed. Actinomycetes isolated from maize rhizosphere, which produce β-1.3-glucanase enzymes that degrade fungal cell wall glucans, offer promising potential as biocontrol agents. This study aimed to evaluate glucanase activity, identify genes of actinomycetes, and assess their antifungal activity against F. oxysporum. Actinomycetes demonstrating glucanase production, Streptomyces sp. ARJ 22, Streptomyces tendae ARJ 42, Streptomyces sp. ARJ 44, and Streptomyces sp. ARJ 81, were selected. Streptomyces isolates exhibited activity values ranging from 10.38 to 24.08 U/mg of protein. The presence of the bglS gene, encoding endo-β-1.3-glucanase from glycoside hydrolase family 16, supports the production of glucanase. The amino acid sequence was constructed to 3D structural model. This model exhibited high similarity to endo-β-1.3-glucanase from Nocardiopsis sp. F96. In vitro assays demonstrated that all isolates inhibited hyphal growth of F. oxysporum. Direct inhibition assays showed an average inhibition of 26.18%, whereas the filtrate culture method showed 29.38% inhibition. Enzymes from Streptomyces sp. ARJ 44 was partially purified using acetone, resulting in a specific activity of 46.34 U/mg of protein and a purity increase of up to 1.92-fold. The purified enzyme inhibited the growth of F. oxysporum mycelia by 35.80%. This inhibition was confirmed by observing damage to F. oxysporum hyphae using scanning electron microscopy. The study concluded that the four Streptomyces sp. strains producing β-1.3-glucanase enzymes have potential as biocontrol agents against F. oxysporum.

Herbicides as fungicides: Targeting heme biosynthesis in the maize pathogen Ustilago maydis.

Pathogens must efficiently acquire nutrients from host tissue to proliferate, and strategies to block pathogen access therefore hold promise for disease control. In this study, we investigated whether heme biosynthesis is an effective target for ablating the virulence of the phytopathogenic fungus Ustilago maydis on maize plants. We first constructed conditional heme auxotrophs of the fungus by placing the heme biosynthesis gene hem12 encoding uroporphyrinogen decarboxylase (Urod) under the control of nitrogen or carbon source-regulated promoters. These strains were heme auxotrophs under non-permissive conditions and unable to cause disease in maize seedlings, thus demonstrating the inability of the fungus to acquire sufficient heme from host tissue to support proliferation. Subsequent experiments characterized the role of endocytosis in heme uptake, the susceptibility of the fungus to heme toxicity as well as the transcriptional response to exogenous heme. The latter RNA-seq experiments identified a candidate ABC transporter with a role in the response to heme and xenobiotics. Given the importance of heme biosynthesis for U. maydis pathogenesis, we tested the ability of the well-characterized herbicide BroadStar to influence disease. This herbicide contains the active ingredient flumioxazin, an inhibitor of Hem14 in the heme biosynthesis pathway, and we found that it was an effective antifungal agent for blocking disease in maize. Thus, repurposing herbicides for which resistant plants are available may be an effective strategy to control pathogens and achieve crop protection.

Cover Picture: Synthesis and Antifungal Activities of Glucosamine Aromatic Derivatives Against Four Phytopathogenic Fungi of Crops (Chem. Biodiversity 11/2024)

Cover Picture: Synthesis and Antifungal Activities of Glucosamine Aromatic Derivatives Against Four Phytopathogenic Fungi of Crops (Chem. Biodiversity 11/2024)

Bidirectional interactions between Grosmannia abietina and hybrid white spruce: Pathogenicity, monoterpene defense responses, and fungal growth and reproduction

Bark beetle-vectored phytopathogenic fungi can play critical roles in how beetle outbreaks affect the health of forest trees. However, trees can defend themselves against fungal infection. How Grosmannia abietina, a symbiotic fungus of spruce beetle (Dendroctonus rufipennis), affects the health of mature hybrid white spruce (Picea engelmannii x glauca) and is in turn affected by the tree's defenses are unknown. We conducted field inoculations of this spruce to study the degree of pathogenicity of G. abietina, characterized the trees' resulting defensive monoterpene responses, and assessed monoterpene effects on fungal growth and reproduction in laboratory bioassays. Our results indicated that G. abietina is phytopathogenic to hybrid white spruce, which induced monoterpenes in response to infection. Dominant induced monoterpenes generally inhibited fungal growth but stimulated spore production. These findings provide insights into the bidirectional effects between spruce beetle-vectored fungi and host trees, highlighting the complex role of monoterpenes in modulating fungal activities.

A botanical nanoemulsion against phytopathogenic fungi Colletotrichum sp. and Fusarium oxysporum: Preparation, in vitro and in vivo bioassay

A botanical nanoemulsion against phytopathogenic fungi Colletotrichum sp. and Fusarium oxysporum: Preparation, in vitro and in vivo bioassay

Green Synthesis of Pleurotus Eryngii-Derived Nanomaterials for Phytopathogen Control.

Growing concerns over the human health and environmental impacts of conventional fungicides, coupled with the escalating challenge of microbial resistance, have fueled the search for sustainable biocontrol strategies against plant pathogens. This study reports, for the first time, the green synthesis and characterization of a novel, eco-friendly nanomaterial, designated Pleurotus eryngii-Lecithin-Chitosan Nanomaterial (PEELCN), derived from P. eryngii extract (PEE), lecithin (L), and chitosan (C). The structural attributes of PEELCN were elucidated using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), and zeta potential measurements, confirming the successful formation of a stable and uniform nanostructure. The antifungal activity of PEELCN, and PEE, was assessed against five economically important phytopathogenic fungi: Neoscytalidium dimidiatum, Alternaria alternata, Verticillium dahliae, Bipolaris sorokiniana, and Fusarium oxysporum. Both PEE and PEELCN exhibited significant inhibitory effects on the mycelial growth of V. dahliae, B. sorokiniana, and N. dimidiatum, with varying degrees of efficacy. The differential antifungal activity suggests a species-specific mode of action. The findings highlight the promising potential of PEELCN as a sustainable, biocompatible, and cost-effective nanofungicide for the management of plant diseases, with the potential for development into a commercially viable biofungicide for sustainable agriculture.

Synthesis and Antifungal Evaluation of Cinnamic Acid-Geraniol Hybrids as Potential Fungicides.

Cinnamic acid and geraniol are two well-known antifungal natural products and widely applied in food and cosmetics industries. To discover novel natural product-based fungicide candidates with more potent activity and good ecological compatibility for the management of plant diseases, a series of cinnamic acid-geraniol hybrids were prepared by means of molecular hybridization and their chemical structures were well confirmed by spectral analysis. The antifungal activities of the target compounds against three phytopathogenic fungi Fusarium graminearum, Gaeumannomyces graminis (Sacc.) Arx et Oliver var. tritici (Sacc.) Walker, and Valsa mali were evaluated. Among them, compounds 5 e and 5 f showed the remarkable antifungal activity against G. graminis with the EC50 values of 82.719 and 91.828 μg/mL, respectively; while compounds 5 f and 6 b exhibited the obvious antifungal activity against V. mali. It suggested that compound 5 f can be further optimized for the design of novel broad-spectrum fungicide molecules as the secondary lead compound. In addition, some interesting structure-antifungal activity relationships were obtained. This work will provide some reference and guidance for the further discovery of novel fungicide candidates based on cinnamic acid and geraniol.