Search Results (51)

(1) Background: The larvae of Dioryctria sylvestrella typically bore into the shoots and cones of Pinus koraiensis, increasing tree breakage risk and reducing cone yield. (2) Methods: Five Beauveria bassiana strains were evaluated for virulence against fourth-instar larvae. And the levels of T-AOC and MDA in the larvae infected by each strain were measured. To assess larval responses to different strains, we measured the activities of six enzymes (SOD, CAT, POD, PPO, CarE, GST) and the levels of GSH and H₂O₂ in larvae treated with each strain. Additionally, the infection process of highly pathogenic B. bassiana in larvae was explored using scanning electron microscopy (SEM). (3) Results: Strain CGMCC3.2055 demonstrated the highest toxicity to larvae, achieving a cumulative corrected mortality of 80.56% on the 4th day and an LT₅₀ of 3.248 days. The T-AOC of larvae treated with strain CGMCC3.2055 was inhibited within 48 h. The relative MDA content in this group was significantly higher than that in other strain-treated groups at 6, 12, and 24 h. In Bb01-treated larvae, H₂O₂ accumulation at 6 and 24 h post-infection was influenced by POD activity rather than GSH levels; in BbZ1-treated larvae, the activities of CAT and POD were upregulated at 6 and 36 h, while the activity of SOD was downregulated, but the content of H₂O₂ increased significantly, resulting in accumulation; in CFCC81428-treated larvae, a decline in T-AOC coincided with substantial H₂O₂ accumulation over 48 h, while a concomitant increase in GSH content bolstered tolerance to lethal oxidative damage; in CGMCC3.2055-treated larvae, H₂O₂ only accumulated significantly at 24 and 48 h, yet upregulated CAT and POD were insufficient to effectively scavenge the excess H₂O₂; and in bio-21738-treated larvae, SOD-driven dismutation generated substantial H₂O₂ from 12 to 48 h, leading to pronounced accumulation from 6 to 48 h, yet limited upregulation of POD (only at 6 and 12 h) and CAT (only at 12 and 48 h) were insufficient to mitigate H₂O₂ buildup. PPO activity was upregulated within 48 h in all treatment groups except for BbZ1, where no upregulation was observed at 12 and 48 h. GST activity was upregulated in all treatment groups except for CGMCC3.2055, where a downregulation was observed at 12 h post-infection. CarE activity was significantly upregulated within 48 h in both CFCC81428 and CGMCC3.2055 groups; in the Bb01 group, CarE was upregulated only at 6 and 48 h; in the BbZ1 group, CarE was downregulated only at 48 h; and in the bio-21738 group, CarE showed no upregulation at 24 and 48 h. Through SEM, the infection process of the strain CGMCC3.2055 on the surface of the larvae was further determined, which mainly included adhesion, the appearance of bud-like protrusions, the growth of germ tubes along the epidermis and penetration of the epidermis, as well as the colonization of the strain and its emergence from the surface of the larvae. (4) Conclusions: This study first screened the highly pathogenic B. bassiana strain CGMCC3.2055 by evaluating its virulence to larvae and post-infection T-AOC and MDA levels. It also clarified the strain’s infection process and the larvae’s immune responses to various strains. Full article

Selenium nanoparticles (SeNPs) are currently receiving attention for controlling plant pathogenic microorganisms, are expected to be especially effective against the genus Phytophthora, and show high anti-oomycete activity. SeNPs synthesized with plant extracts have shown low toxicity, high bioavailability, and mechanisms of action that alter cellular integrity and damage key components of phytopathogen metabolism, causing denaturation and cell death. The aim of this study was to evaluate the inhibitory activity of SeNPs on mycelial growth and the development of reproductive structures in Phytophthora capsici in vitro. Different concentrations of SeNPs (0 to 400 µg/mL) in culture media were used to analyze mycelial growth, sporangium formation, zoospores, and germination of the germ tube. To explain the changes in morphology and development of P. capsici, increased relative conductance and activation of glycerol synthesis were related to osmotic stress and damage to membrane permeability. In addition, SeNPs inhibited the production of exopolysaccharides (EPSs), which are compounds associated with pathogen virulence. A lower accumulation of its biomass evidences alterations in the oomycete growth. The percentage of inhibition of mycelial growth increased with higher SeNP concentrations and incubation time, reaching 100% growth inhibition at 300 and 400 µg/mL. A concentration-dependent reduction in the number of spores, sporangia, and zoospore germination was observed. Concentrations of 50 and 100 µg/mL of SeNPs reduced biomass production by 30%. The increase in glycerol levels indicated an osmoregulatory response to SeNP-induced stress. Also, the increase in electrical conductivity suggested plasma membrane damage, which supports the potential of SeNPs as antifungal agents by inducing cell disruption and structural damage in P. capsici. These results provide new knowledge on the in vitro mechanism of action of SeNPs against P. capsici and offer a new biological alternative for the control of diseases caused by oomycetes. Full article

Red grapes often suffer from postharvest diseases like blue mold and black mold caused by Penicillium expansum and Aspergillus niger. Biological control using beneficial yeasts and bacteria is an effective method to manage these diseases. Rhodotorula sp. and Bacillus sp. are effective microorganisms for the control of postharvest diseases of red grapes. This study combined two yeast strains (Rhodotorula graminis and Rhodotorula babjevae) and two bacterial strains (Bacillus licheniformis and Bacillus velezensis) to investigate their biological control effects on major postharvest diseases of red grapes and explore the underlying physiological mechanisms. Research showed that compound microorganism W3 outperformed the others; it reduced spore germination and germ tube growth of P. expansum and A. niger, while its volatiles further inhibited pathogen growth. Additionally, the treatment enhanced the antioxidant capacity of grapes and increased resistance to pathogens by boosting peroxidase activities, superoxide dismutase, catalase and ascorbate peroxidase, phenylalanine ammonolyase, and polyphenol oxidase. Furthermore, the combined treatment increased the activity and accumulation of antifungal compounds such as total phenols and flavonoids, thereby improving disease resistance and reducing decay. Therefore, composite microorganisms combining various antagonistic strains may offer a viable substitute for tackling postharvest diseases in red grapes. Full article

Background: The rapid development of mobile communication has caused an increase in electromagnetic field (EMF) emissions in the environment. However, there is a lack of research on the impact of EMFs on microorganisms. Thus, the aim of the study was the determine the effect of exposure to 900 and 1800 MHz electromagnetic fields on the entomopathogenic fungi (EPFs) Beauveria bassiana, Cordyceps fumosorosea, and Metarhizium anisopliae. Methods: The entomopathogenic fungi developed under exposure to an EMF for seven days. After the termination of exposure, the linear colony growth, sporulation, gemination, and pathogenicity of the EPFs were investigated. Results: The effect of EMFs on B. bassiana, C. fumosorosea, and M. anisopliae depended on the EMF frequency and the tested fungus species. Exposure to the 900 MHz frequency stimulated the growth of the mycelium and the pathogenicity of the entomopathogenic fungi, whereas the 1800 MHz electromagnetic field inhibited sporulation and spore germination. Conclusions: The exposure to the 900 MHz frequency stimulated the development of the mycelium of all tested species and the pathogenicity of C. fumosorosea. The sporulation and germ tube length of the entomopathogenic fungi were stimulated by the 900 MHz frequency. The 1800 MHz electromagnetic field inhibited the sporulation and spore germination of B. bassiana. Full article

In this work, liposomes loaded with the fungicide, Fludioxonil (FLUD), for the containment of fungal diseases in agriculture were developed. Three types of vesicles with different compositions were compared: (I) plain vesicles, composed of soy phosphatidylcholine and cholesterol; (II) PEG-coated vesicles, with an additional polyethylene glycol coating; and (III) cationic vesicles, containing didodecyldimethylammonium bromide. Nanometric-sized vesicles were obtained both by the micelle-to-vesicle transition method and by the extrusion technique, and encapsulation efficiency, drug loading content, and Zeta potential were determined for all the samples. The extruded and PEGylated liposomes were the most stable over time and together with the cationic ones showed a significant prolonged FLUD release capacity. The liposomes’ biological activity was evaluated on conidial germination, germ tube elongation and colony radial growth of the ascomycete Botrytis cinerea, a phytopathogenic fungus affecting worldwide many important agricultural crops in the field as well as in the postharvest phase. The extruded and PEGylated liposomes showed greater effectiveness in inhibiting germ tube elongation and colony radial growth of the fungal pathogen, even at 0.01 µg·mL⁻¹, the lowest concentration assessed. Full article

A series of hybrid compounds with triazole and thiazolidine nuclei connected by a linker has been synthesized and extensively studied. Various synthetic methods for the target compounds have been tested. A microbiological assessment of the obtained compounds was carried out on strains of pathogenic fungi C. albicans, C. non-albicans, multidrug-resistant C. auris, Rhizopus arrhizus, Aspergillus spp. and some dermatophytes and other yeasts. The lowest obtained MIC values for target compounds lie between 0.003 µg/mL and 0.5 µg/mL and therefore the compounds are not inferior or several times better than commercial azole drugs. The length of the acylpiperazine linker has a limited effect on antifungal activity. Some bioisosteric analogues were tested in microbiological analysis, but turned out to be weaker than the leader in activity. The highest activity was demonstrated by a compound with para-chlorobenzylidene substituent in the thiazolidine fragment. Molecular modelling was used to predict binding modes of synthesized molecules and rationalize experimentally observed SAR. The leader compound is twice more effective in inhibiting the formation of germ tubes by Candida albicans yeast cells compared to voriconazole. An increased level of Pdr5, an azoles drug efflux pump was observed, but the increase is lower than that caused by azoles. The results can be useful for further development of more powerful and safe antifungal agents. Full article

Penicillium digitatum is a major postharvest pathogen that threatens the global citrus fruit industry and causes great economic losses annually. In the present study, inhibitory properties of cinnamon bark oil (CBO) against P. digitatum in vitro were investigated. Results indicated that 0.03% CBO could efficiently inhibit the spore germination, germ tube elongation, mycelial growth, colonial expansion and conidial accumulation of P. digitatum. The results of fluorescein diacetate (FDA) and MitoTraker Orange (MTO) staining also proved the suppression effects of CBO against P. digitatum. Meanwhile, CBO could inhibit green mold rots induced by P. digitatum in citrus fruit when the working concentration of CBO exceeded 0.06%. In addition, the expressions of 12 genes critical for the growth and virulence of P. digitatum were also significantly regulated under CBO stress. Through a transcriptomic analysis, a total of 1802 common differentially expressed genes (DEGs) were detected in P. digitatum after 4 h and 8 h of CBO treatment. Most of the DEG products were associated with carbohydrate, amino acid and lipid metabolism. They directly or indirectly led to the disturbance of the membrane and the generation of reactive oxygen species (ROS). Our results may deepen the understanding of antifungal properties of CBO against P. digitatum and provide the theoretical foundation to uncover the antifungal mechanism of CBO at the molecular level. Full article

Rice blast, caused by the filamentous fungus Pyricularia oryzae, has long been one of the major threats to almost all rice-growing areas worldwide. Metconazole, 5-(4-chlorobenzyl)-2, 2-dimethyl-1-(1H-1, 2, 4-triazol-1-ylmethyl) cyclopentanol, is a lipophilic, highly active triazole fungicide that has been applied in the control of various fungal pathogens of crops (cereals, barley, wheat), such as the Fusarium and Alternaria species. However, the antifungal activity of metconazole against P. oryzae is unknown. In this study, metconazole exhibited broad spectrum antifungal activities against seven P. oryzae strains collected from rice paddy fields and the wild type strain P131. Scanning electron microscopic analysis and fluorescein diacetate staining assays revealed that metconazole treatment damaged the cell wall integrity, cell membrane permeability and even cell viability of P. oryzae, resulting in deformed and shrunken hyphae. The supplementation of metconazole in vitro increased fungal sensitivity to different stresses, such as sodium dodecyl sulfate, congo red, sodium chloride, sorbitol and oxidative stress (H₂O₂). Metconazole could inhibit key virulence processes of P. oryzae, including conidial germination, germ tube elongation and appressorium formation. Furthermore, this chemical prevented P. oryzae from infecting barley epidermal cells by disturbing appressorium penetration and subsequent invasive hyphae development. Pathogenicity assays indicated a reduction of over 75% in the length of blast lesions in both barley and rice leaves when 10 μg/mL of metconazole was applied. This study provides evidence to understand the antifungal effects of metconazole against P. oryzae and demonstrates its potential in rice blast management. Full article

Colletotrichum gloeosporioides is widely distributed and causes anthracnose on many crops, resulting in serious economic losses. Common fungal extracellular membrane (CFEM) domain proteins have been implicated in virulence and their interaction with the host plant, but their roles in C. gloeosporioides are still unknown. In this study, a CFEM-containing protein of C. gloeosporioides was identified and named as CgCFEM1. The expression levels of CgCFEM1 were found to be markedly higher in appressoria, and this elevated expression was particularly pronounced during the initial stages of infection in the rubber tree. Absence of CgCFEM1 resulted in impaired pathogenicity, accompanied by notable perturbations in spore morphogenesis, conidiation, appressorium development and primary invasion. During the process of appressorium development, the absence of CgCFEM1 enhanced the mitotic activity in both conidia and germ tubes, as well as compromised conidia autophagy. Rapamycin was found to basically restore the appressorium formation, and the activity of target of rapamycin (TOR) kinase was significantly induced in the CgCFEM1 knockout mutant (∆CgCFEM1). Furthermore, CgCFEM1 was proved to suppress chitin-triggered reactive oxygen species (ROS) accumulation and change the expression patterns of defense-related genes. Collectively, we identified a fungal effector CgCFEM1 that contributed to pathogenicity by regulating TOR-mediated conidia and appressorium morphogenesis of C. gloeosporioides and inhibiting the defense responses of the rubber tree. Full article

Infection biology and defence responses of watermelon attacked by Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae) were studied in two genotypes, accessions PI189225 (moderately resistant) and 232-0125/B (susceptible). On intact leaf surfaces, spores started to germinate 14 h after inoculation (hai) with one to three germ tubes, which subsequently developed and formed appressoria. Invasion of the host tissue started at 20 hai by direct penetration from appressoria or occasionally indirectly through stomata. In the susceptible accession, a significantly higher number of direct penetrations were observed than in the moderately resistant. After invasion, hyphal colonisation was restricted in the intercellular spaces in the moderately resistant accession, whereas they developed extensively, causing tissue decay, in the susceptible accession. Macroscopic symptoms were seen in leaves of the moderately resistant accession as small and dry lesions, whereas big, water-soaked lesions developed on the susceptible accession within 48 hai. Investigations of the defence responses of the two accessions showed accumulation of H₂O₂ at penetration sites beneath appressoria in the moderately resistant, but to a lesser extent in the susceptible accession. Such H₂O₂ accumulation correlated with a reduction in penetration frequency and a lower level of hyphal growth after infection in the moderately resistant accession. There was a rapid and early increase in total peroxidase as well as β-1,3-glucanase activity in the moderately resistant compared to the susceptible accession. These results indicate that fungal penetration and development in watermelon are inhibited by a consorted action of different responses including accumulation of H₂O₂, peroxidase and β-1,3-glucanase. Full article

Alternaria alternata is the main pathogenic fungus of postharvest black spots in fruits and vegetables. This study aimed to explore the antifungal activity of methionine on A. alternata in vitro and to reveal related antifungal mechanisms through a metabolomics analysis. The results showed that the inhibitory effects of L-methionine (Met) treatment on mycelium growth, spore germination, and the germ tube elongation of A. alternata were enhanced with an increase in the Met concentration, but the inhibitory effects decreased when the Met concentration was higher than 50 mmolL⁻¹. The results of propidium iodide staining and scanning electron microscopy showed that the Met treatment damaged the plasma membrane integrity of the A. alternata spores and caused an irreversible deformation of mycelium. In addition, after the Met treatment, the leakage of electrolytes, nucleic acid, and proteins in the A. alternata cells was significantly higher than that in the control group, indicating that the Met treatment increased the permeability of the cell membranes. Eighty-one different metabolites, divided into seven categories, were identified through the metabolomics analysis, including forty-three downregulated metabolites and thirty-eight upregulated metabolites. Among them, these differential metabolites were mainly involved in amino acid synthesis and metabolism, the pentose phosphate pathway, and the TCA cycle. Therefore, the antifungal effect of the Met treatment on A. alternata was mainly to damage the integrity of the cell membranes, make nucleic acid and protein contents leak, and affect the TCA cycle, carbohydrate metabolism, amino acid synthesis metabolism, and the metabolic pathways associated with cell membrane biosynthesis. Thus, the growth and development of A. alternata were inhibited. The research enriched the investigation of the effect of the antifungal mechanism of Met treatment on A. alternata and provided a theoretical basis for the application of Met to prevent and treat postharvest black spots in fruits and vegetables. Full article

Fusarium heading blight (FHB) is a devastating disease in wheat, primarily caused by field invasion of Fusarium graminearum. Due to the scarcity of resistant wheat varieties, the agricultural sector resorts to chemical fungicides to control FHB incidence. On the other hand, biocontrol represents a promising, eco-friendly approach aligned with sustainable and green agriculture concepts. In the present study, a bacterial endophyte, Pseudescherichia sp. (GSE25), was isolated from wheat seeds and identified through complete genome sequencing and phylogenetic analysis. In vitro testing of this endophytic strain demonstrated strong antifungal activity against F. graminearum PH-1 by inhibiting spore germination, suppressing germ tube growth, and causing cell membrane damage. Under field conditions, the strain GSE25 significantly reduced the FHB incidence and the associated deoxynivalenol mycotoxin accumulation by over 60% and 80%, respectively. These findings highlight the potential of the isolated bacterial endophyte Pseudescherichia sp. GSE25 strain as a biocontrol agent in protecting wheat from FHB-caused F. graminearum. This is the first report showing a biocontrol effect of Pseudescherichia sp. a strain against phytopathogens. Full article

With the prevalence of systemic fungal infections caused by Candida albicans and non-albicans species and their resistance to classical antifungals, there is an urgent need to explore alternatives. Herein, we evaluate the impact of the monoterpene carvacrol, a major component of oregano and thyme oils, on clinical and laboratory strains of C. albicans and Nakaseomyces glabratus. Carvacrol induces a wide range of antifungal effects, including the inhibition of growth and hyphal and biofilm formation. Using biochemical and microscopic approaches, we elucidate carvacrol-induced hyphal inhibition. The significantly reduced survival rates following exposure to carvacrol were accompanied by dose-dependent vacuolar acidification, disrupted membrane integrity, and aberrant morphology. Germ tube assays, used to elucidate the relationship between vacuolar dysfunction and hyphal inhibition, showed that carvacrol significantly reduced hyphal formation, which was accompanied by a defective C. albicans morphology. Thus, we show a link between vacuolar acidification/disrupted vacuole membrane integrity and compromised candidal morphology/morphogenesis, demonstrating that carvacrol exerts its anti-hyphal activity by altering vacuole integrity. Full article

In order to optimize crop production and mitigate the adverse impacts associated with the utilization of chemical agents, it is necessary to explore new biocontrol agents. Bacillus velezensis has been widely studied as a biocontrol agent because of its efficient and ecofriendly plant disease control mechanisms. This study shows that the strain ZN-S10 effectively reduces the area of leaf spots caused by the pathogen Colletotrichum changpingense ZAFU0163-1, which affects conidia production and germination, inhibits mycelium growth, and induces mycelium deformation. In antifungal experiments with crude extracts, we observed a delay in the cell cycle of conidia, which may be responsible for the inhibition of conidial germination. Among the bioactive metabolites detected through integrated LC-MS- and GC-MS-based untargeted metabolomics, 7-O-Succinyl macrolactin A, telocinobufagin, and surfactin A may be the main antifungal metabolites of strain ZN-S10. The presence of 7-O-Succinyl macrolactin A could explain the cell damage in germ tubes. This is the first report of telocinobufagin detected in B. velezensis. These results are significant for understanding the inhibitory mechanisms employed by B. velezensis and should serve as a reference in the production of biocontrol agents. Full article

Some endophyte bacteria can improve plant growth and suppress plant diseases. However, little is known about the potential of endophytes bacteria to promote wheat growth and suppress the Fusarium seedling blight pathogen Fusarium graminearum. This study was conducted to isolate and identify endophytic bacteria and evaluate their efficacy for the plant growth promotion and disease suppression of Fusarium seedling blight (FSB) in wheat. The Pseudomonas poae strain CO showed strong antifungal activity in vitro and under greenhouse conditions against F. graminearum strain PH-1. The cell-free supernatants (CFSs) of P. poae strain CO were able to inhibit the mycelium growth, the number of colonies forming, spore germination, germ tube length, and the mycotoxin production of FSB with an inhibition rate of 87.00, 62.25, 51.33, 69.29, and 71.08%, respectively, with the highest concentration of CFSs. The results indicated that P. poae exhibited multifarious antifungal properties, such as the production of hydrolytic enzymes, siderophores, and lipopeptides. In addition, compared to untreated seeds, wheat plants treated with the strain showed significant growth rates, where root and shoot length increased by about 33% and the weight of fresh roots, fresh shoots, dry roots, and dry shoots by 50%. In addition, the strain produced high levels of indole-3-acetic acid, phosphate solubilization, and nitrogen fixation. Finally, the strain demonstrated strong antagonistic properties as well as a variety of plant growth-promoting properties. Thus, this result suggest that this strain could be used as an alternate to synthetic chemicals, which can serve as an effective method of protecting wheat from fungal infection. Full article