Inhibitory activity of bacterial lipopeptides against Fusarium oxysporum f.sp. Strigae.

This study investigated the influence of bacterial cyclic lipopeptides (LP; surfactins, iturins, fengycins) on microbial interactions. The objective was to investigate whether the presence of bacteria inhibits fungal growth and whether this inhibition is due to the release of bacterial metabolites, particularly LP. Selected endophytic bacterial strains with known plant-growth promoting potential were cultured in the presence of Fusarium oxysporum f.sp. strigae (Fos), which was applied as model fungal organism. The extracellular metabolome of tested bacteria, with a focus on LP, was characterized, and the inhibitory effect of bacterial LP on fungal growth was investigated. The results showed that Bacillus velezensis GB03 and FZB42, as well as B. subtilis BSn5 exhibited the strongest antagonism against Fos. Paraburkholderia phytofirmans PsJN, on the other hand, tended to have a slight, though non-significant growth promotion effect. Crude LP from strains GB03 and FZB42 had the strongest inhibitory effect on Fos, with a significant inhibition of spore germination and damage of the hyphal structure. Liquid chromatography tandem mass spectrometry revealed the production of several variants of iturin, fengycin, and surfactin LP families from strains GB03, FZB42, and BSn5, with varying intensity. Using plate cultures, bacillomycin D fractions were detected in higher abundance in strains GB03, FZB42, and BSn5 in the presence of Fos. Additionally, the presence of Fos in dual plate culture triggered an increase in bacillomycin D production from the Bacillus strains. The study demonstrated the potent antagonistic effect of certain Bacillus strains (i.e., GB03, FZB42, BSn5) on Fos development. Our findings emphasize the crucial role of microbial interactions in shaping the co-existence of microbial assemblages.

Membrane protein Bcsdr2 mediates biofilm integrity, hyphal growth and virulence of Botrytis cinerea.

Grey mould caused by Botrytis cinerea is a devastating disease responsible for large losses to agricultural production, and B. cinerea is a necrotrophic model fungal plant pathogen. Membrane proteins are important targets of fungicides and hotspots in the research and development of fungicide products. Wuyiencin affects the permeability and pathogenicity of B. cinerea, parallel reaction monitoring revealed the association of membrane protein Bcsdr2, and the bacteriostatic mechanism of wuyiencin was elucidated. In the present work, we generated and characterised ΔBcsdr2 deletion and complemented mutant B. cinerea strains. The ΔBcsdr2 deletion mutants exhibited biofilm loss and dissolution, and their functional activity was illustrated by reduced necrotic colonisation on strawberry and grape fruits. Targeted deletion of Bcsdr2 also blocked several phenotypic defects in aspects of mycelial growth, conidiation and virulence. All phenotypic defects were restored by targeted gene complementation. The roles of Bcsdr2 in biofilms and pathogenicity were also supported by quantitative real-time RT-PCR results showing that phosphatidylserine decarboxylase synthesis gene Bcpsd and chitin synthase gene BcCHSV II were downregulated in the early stages of infection for the ΔBcsdr2 strain. The results suggest that Bcsdr2 plays important roles in regulating various cellular processes in B. cinerea. KEY POINTS: • The mechanism of wuyiencin inhibits B. cinerea is closely associated with membrane proteins. • Wuyiencin can downregulate the expression of the membrane protein Bcsdr2 in B. cinerea. • Bcsdr2 is involved in regulating B. cinerea virulence, growth and development.

Berberine hydrochloride delays citrus sour rot mainly by disrupting carbohydrate and energy metabolism of Geotrichum citri-aurantii spores.

Citrus sour rot is a common postharvest citrus disease caused by Geotrichum citri-aurantiiti, which has led to enormous economic losses, particularly during rainy seasons. In this study, we aimed to clarify the impact of berberine hydrochloride (BH), the hydrochloride form of an isoquinoline alkaloid, on the control efficiency of citrus sour rot and its antifungal mode against G. citri-aurantii. Results demonstrated that BH markedly impede the propagation of G. citri-aurantii by delaying the spores development from dormant stage into swollen and germinating stages, with the MIC and MFC value of 0.08 and 0.16 g L-1, respectively. When the artificially inoculated citrus fruit in control group were totally rotted, the disease incidence of BH-treated groups decreased by 35.00%-73.30%, which effectively delayed the disease progression and almost did not negatively affect fruit quality. SEM observation, CFW and PI staining images revealed that BH caused significant damage to both the cell membrane and cell wall of G. citri-aurantii spores, whereas only the cell membrane of the mycelium was affected. The impact of cell wall was related to the block of chitin and ß-1,3-glucan synthesis. Transcriptome results and further verification proved that 0.5 × MIC BH treatment affected the glycolysis pathway and TCA cycle mainly by inhibiting the production of acetyl-CoA and pyruvate. Subsequently, the activities of key enzymes declined, resulting in a further decrease in ATP levels, ultimately inhibiting the germination of spores. In conlusion, BH delays citrus sour rot mainly by disrupting carbohydrate and energy metabolism of G. citri-aurantii spores.

Physiological response of Metarhizium rileyi with linoleic acid supplementation.

Metarhizium rileyi has a broad biocontrol spectrum but is highly sensitive to abiotic factors. A Colombian isolate M. rileyi Nm017 has shown notorious potential against Helicoverpa zea. However, it has a loss of up to 22 % of its conidial germination after drying, which limits its potential as a biocontrol agent and further commercialization. Conidial desiccation resistance can be enhanced by nutritional supplements, which promotes field adaptability and facilitates technological development as a biopesticide. In this study, the effect of culture medium supplemented with linoleic acid on desiccation tolerance in Nm017 conidia was evaluated. Results showed that using a 2 % linoleic acid-supplemented medium increased the relative germination after drying by 41 % compared to the control treatment, without affecting insecticidal activity on H. zea. Also, the fungus increased the synthesis of trehalose, glucose, and erythritol during drying, independently of linoleic acid use. Ultrastructural analyses of the cell wall-membrane showed a loss of thickness by 22 % and 25 %, in samples obtained from 2 % linoleic acid supplementation and the control, respectively. Regarding its morphological characteristics, conidia inner area from both treatments did not change after drying. However, conidia from the control had a 24 % decrease in length/width ratio, whereas there was no alteration in conidia from acid linoleic. The average value of dry conidia elasticity coefficient from linoleic acid treatment was 200 % above the control. Medium supplementation with linoleic acid is a promising fermentation strategy for obtaining more tolerant conidia without affecting production and biocontrol parameters, compatible solutes synthesis, or modifying its cell configuration.

Functional analysis of the Aspergillus fumigatus kinome identifies a druggable DYRK kinase that regulates septal plugging.

More than 10 million people suffer from lung diseases caused by the pathogenic fungus Aspergillus fumigatus. Azole antifungals represent first-line therapeutics for most of these infections but resistance is rising, therefore the identification of antifungal targets whose inhibition synergises with the azoles could improve therapeutic outcomes. Here, we generate a library of 111 genetically barcoded null mutants of Aspergillus fumigatus in genes encoding protein kinases, and show that loss of function of kinase YakA results in hypersensitivity to the azoles and reduced pathogenicity. YakA is an orthologue of Candida albicans Yak1, a TOR signalling pathway kinase involved in modulation of stress responsive transcriptional regulators. We show that YakA has been repurposed in A. fumigatus to regulate blocking of the septal pore upon exposure to stress. Loss of YakA function reduces the ability of A. fumigatus to penetrate solid media and to grow in mouse lung tissue. We also show that 1-ethoxycarbonyl-beta-carboline (1-ECBC), a compound previously shown to inhibit C. albicans Yak1, prevents stress-mediated septal spore blocking and synergises with the azoles to inhibit A. fumigatus growth.

Microplastic influences the ménage à trois among the plant, a fungal pathogen, and a plant growth-promoting fungal species.

Microplastics (MP) can influence a plethora of fungal species within the rhizosphere. Nevertheless, there are few studies on the direct impacts of MPs on soil fungi and their intricate interplay with plants. Here, we investigated the impact of polyethylene microspheres (PEMS) on the ecological interactions between Fusarium solani, a plant pathogenic fungus, and Trichoderma viride, a fungal plant growth promotor, within the rhizosphere of Solanum lycopersicum (tomato). Spores of F. solani and T. viride were pre-incubated with PEMS at two concentrations, 100 and 1000 mg L-1. Mycelium growth, sporulation, spore germination, and elongation were evaluated. Tomato seeds were exposed to fungal spore suspensions treated with PEMS, and plant development was subsequently assessed after 4 days. The results showed that PEMS significantly enhanced the sporulation (106.0 % and 70.1 %) but compromised the spore germination (up to 27.3 % and 32.2 %) and radial growth (up to -5.2% and -21.7 %) of F. solani and T. viride, respectively. Furthermore, the 100 and 1000 mg L-1 concentrations of PEMS significantly (p<0.05) enhanced the mycelium density of T. viride (9.74 % and 22.30 %, respectively), and impaired the germ-tube elongation of F. solani after 4 h (16.16 % and 11.85 %, respectively) and 8 h (4 % and 17.10 %, respectively). In addition, PEMS amplified the pathogenicity of F. solani and boosted the bio-enhancement effect of T. viride on tomato root growth. Further, PEMS enhanced the bio-fungicidal effect of T. viride toward F. solani (p<0.05). In summary, PEMS had varying effects on F. solani and T. viride, impacting their interactions and influencing their relationship with tomato plants. It intensified the beneficial effects of T. viride and increased the aggressiveness of F. solani. This study highlights concerns regarding the effects of MPs on fungal interactions in the rhizosphere, which are essential for crop soil colonization and resource utilization.

Does sorghum phenolic extract have antifungal effect?

This study aimed to evaluate the antifungal effect of SC319 sorghum phenolic extract (SPE) on the Aspergillus, Fusarium, Penicillium, Stenocarpella, Colletotrichum, and Macrophomina genera. SPE was extracted by 20% ethanol and used in four assays: (1) against Fusarium verticillioides in solid (PDA) and liquid (PD) potato dextrose media; (2) Minimum Inhibitory Concentration (MIC) assay with 16 fungi isolates; (3) Conidial Germination Rate (CGR) with 14 fungi isolates and (4) Growth Curve (GC) with 11 fungi isolates. There was no reduction in the mycelial growth (colony diameter and dry weight) and in the number of Fusarium verticillioides spores in assay 1 (PDA and PD). The colony's dry weight was almost six times higher in the presence than in the absence of SPE. All SPE samples presented MIC (assay 1) above the maximum concentration tested (5000 µg.mL-1) for the 16 isolates. Also, there was no inhibitory effect of SPE on conidia germination rate (CGR). Oppositely, in GC assay, the control had a higher CFU count than the samples with SPE in 24 h. This result suggests that SPE can delay the fungal growth in the first hours of incubation, which is an important finding that may help reduce the severity of fungal diseases in plants. However, further studies are needed to confirm these results, including sorghum genotypes with different profiles of phenolic compounds. Although the SC319 SPE was not effective as an antifungal agent, it may have potential as a growth promoter of beneficial fungi in the food and pharmaceutical industries.

Suppression of anthracnose disease by orsellinaldehyde isolated from the mushroom Coprinus comatus.

AIMS: Anthracnose caused by Colletotrichum species is one of the most devastating diseases of fruits and crops. We isolated and identified an antifungal compound from the mushroom Coprinus comatus and investigated its inhibitory potential against anthracnose disease-causing fungi with the goal of discovering natural products that can suppress anthracnose-caused plant disease. METHODS AND RESULTS: The culture filtrate of C. comatus was subjected to a bioassay-guided isolation of antifungal compounds. The active compound was identified as orsellinaldehyde (2,4-dihydroxy-6-methylbenzaldehyde) based on mass spectroscopy and nuclear magnetic resonance analyses. Orsellinaldehyde displayed broad-spectrum inhibitory activity against different plant pathogenic fungi. Among the tested Colletotrichum species, it exhibited the lowest IC50 values on conidial germination and germ tube elongation of Colletotrichum orbiculare. The compound also showed remarkable inhibitory activity against Colletotrichum gloeosporiodes. The staining of Colletotrichum conidia with fluorescein diacetate and propidium iodide demonstrated that the compound is fungicidal. The postharvest in-vivo detached fruit assay indicated that orsellinaldehyde suppressed anthracnose lesion symptoms on mango and cucumber fruits caused by C. gloeosporioides and C. orbiculare, respectively. CONCLUSIONS: Orsellinaldehyde was identified as a potent antifungal compound from the culture filtrate of C. comatus. The inhibitory and fungicidal activities of orsellinaldehyde against different Colletotrichum species indicate its potential as a fungicide for protecting various fruits against anthracnose disease-causing fungi.

Formulation of essential oils-loaded solid lipid nanoparticles-based chitosan/PVA hydrogels to control the growth of Botrytis cinerea and Penicillium expansum.

Botrytis cinerea and Penicillium expansum are phytopathogenic fungi that produce the deterioration of fruits. Thus, essential oil (EO) has emerged as a sustainable strategy to minimize the use of synthetic fungicides, but their volatility and scarce solubility restrict their application. This study proposes the EO of Oreganum vulgare and Thymus vulgaris-loaded solid lipid nanoparticles (SLN) based chitosan/PVA hydrogels to reduce the infestation of fungi phytopathogen. EO of O. vulgare and T. vulgaris-loaded SLN had a good homogeneity (0.21-0.35) and stability (-28.8 to -33.0 mV) with a mean size of 180.4-188.4 nm. The optimization of EO-loaded SLN showed that the encapsulation of 800 and 1200 µL L-1 of EO of O vulgare and T. vulgaris had the best particle size. EO-loaded SLN significantly reduced the mycelial growth and spore germination of both fungi pathogen. EO-loaded SLN into hydrogels showed appropriate physicochemical characteristics to apply under environmental conditions. Furthermore, rheological analyses evidenced that hydrogels had solid-like characteristics and elastic behavior. EO-loaded SLN-based hydrogels inhibited the spore germination in B. cinerea (80.9 %) and P. expansum (55.7 %). These results show that SLN and hydrogels are eco-friendly strategies for applying EO with antifungal activity.

Exogenous Indole-3-Acetic Acid Suppresses Rice Infection of Magnaporthe oryzae by Affecting Plant Resistance and Fungal Growth.

Auxin is an important phytohormone that regulates diverse biologic processes, including plant growth and immunity. Indole-3-acetic acid (IAA), known as one of the main forms of auxin, is able to activate plant immunity. However, it is unknown whether IAA enhances plant resistance and/or suppresses the growth of the fungal pathogen Magnaporthe oryzae. Here, we found that IAA could induce expression levels of pathogenesis-related genes to enhance disease resistance and could control the development of blast disease through inhibiting M. oryzae infection. Exogenous IAA suppressed mycelial growth and delayed spore germination by inhibiting fungal endogenous IAA biosynthesis and impairing redox homeostasis, respectively. When applied to a field test, two IAA analogues, 1-naphthaleneacetic acid and 2,4-dichlorophenoxy acetic acid, can effectively control rice blast disease. Our study advances the understanding of IAA in controlling rice blast disease through suppressing pathogen growth and enhancing plant resistance.

The Role of Cytokinins and Abscisic Acid in the Growth, Development and Virulence of the Pathogenic Fungus Stagonospora nodorum (Berk.).

Cytokinins (CKs) and abscisic acid (ABA) play an important role in the life of both plants and pathogenic fungi. However, the role of CKs and ABA in the regulation of fungal growth, development and virulence has not been sufficiently studied. We compared the ability of two virulent isolates (SnB and Sn9MN-3A) and one avirulent isolate (Sn4VD) of the pathogenic fungus Stagonospora nodorum Berk. to synthesize three groups of hormones (CKs, ABA and auxins) and studied the effect of exogenous ABA and zeatin on the growth, sporulation and gene expression of necrotrophic effectors (NEs) and transcription factors (TFs) in them. Various isolates of S. nodorum synthesized different amounts of CKs, ABA and indoleacetic acid. Using exogenous ABA and zeatin, we proved that the effect of these hormones on the growth and sporulation of S. nodorum isolates can be opposite, depends on both the genotype of the isolate and on the concentration of the hormone and is carried out through the regulation of carbohydrate metabolism. ABA and zeatin regulated the expression of fungal TF and NE genes, but correlation analysis of these parameters showed that this effect depended on the genotype of the isolate. This study will contribute to our understanding of the role of the hormones ABA and CKs in the biology of the fungal pathogen S. nodorum.

Use of Ozone as a Substrate Treatment for the Control of Trichoderma in the Production of Pleurotus ostreatus.

Pleurotus ostreatus is one of the most widely cultivated species in the world. It can be produced in many lignocellulosic substrates after carrying out a treatment to eliminate competing microorganisms. The most commonly used is pasteurization by steam or by immersion in hot water. The aim of this work is to evaluate if ozone can be employed as treatment for decontamination of the substrate used for the production of the edible mushroom P. ostreatus to control of green mold Trichoderma. Wheat straw was employed as a substrate. We used two different methodologies: bubbling ozone into a tank with water and the substrate, and injecting ozone into a closed tank with the substrate inside. Ten treatments were carried out including two treatments with inoculation by a spray of conidia of Trichoderma. The effect of ozone on the conidia was also evaluated. We found that the treatment of the substrate with ozone in immersed water resulted more effective (lower growth of Trichoderma) than injecting ozone into a closed tank. Anyway, we found that the contaminant fungi could grow on the substrate in both treatments with ozone. We observed that although ozone affected the conidia when it was bubbled into water, some of them still managed to survive and could germinate 72 h later. P. ostreatus could grow and produce fruiting bodies on a substrate that was previously treated with ozone and yields were not affected. Based on the results obtained, we conclude that ozone may not be an effective agent to control Trichoderma in highly contaminated substrates, at least in the experimental conditions that we used, for the production of P. ostreatus.

The CsPbs2-interacting protein oxalate decarboxylase CsOxdC3 modulates morphosporogenesis, virulence, and fungicide resistance in Colletotrichum siamense.

The HOG MAPK pathway mediates diverse cellular and physiological processes, including osmoregulation and fungicide sensitivity, in phytopathogenic fungi. However, the molecular mechanisms underlying HOG MAPK pathway-associated stress homeostasis and pathophysiological developmental events are poorly understood. Here, we demonstrated that the oxalate decarboxylase CsOxdC3 in Colletotrichum siamense interacts with the protein kinase kinase CsPbs2, a component of the HOG MAPK pathway. The expression of the CsOxdC3 gene was significantly suppressed in response to phenylpyrrole and tebuconazole fungicide treatments, while that of CsPbs2 was upregulated by phenylpyrrole and not affected by tebuconazole. We showed that targeted gene deletion of CsOxdC3 suppressed mycelial growth, reduced conidial length, and triggered a marginal reduction in the sporulation characteristics of the ΔCsOxdC3 strains. Interestingly, the ΔCsOxdC3 strain was significantly sensitive to fungicides, including phenylpyrrole and tebuconazole, while the CsPbs2-defective strain was sensitive to tebuconazole but resistant to phenylpyrrole. Additionally, infection assessment revealed a significant reduction in the virulence of the ΔCsOxdC3 strains when inoculated on the leaves of rubber tree (Hevea brasiliensis). From these observations, we inferred that CsOxdC3 crucially modulates HOG MAPK pathway-dependent processes, including morphogenesis, stress homeostasis, fungicide resistance, and virulence, in C. siamense by facilitating direct physical interactions with CsPbs2. This study provides insights into the molecular regulators of the HOG MAPK pathway and underscores the potential of deploying OxdCs as potent targets for developing fungicides.

Antifungal and Antivirulence Activity of Vanillin and Tannic Acid Against Aspergillus fumigatus and Fusarium solani.

Aspergillus fumigatus and Fusarium solani infections have become severe health threat; both pathogens are considered a priority due to the increasing emergence of antifungal-resistant strains and high mortality rates. Therefore, the discovery of new therapeutic strategies has become crucial. In this study, we evaluated the antifungal and antivirulence effects of vanillin and tannic acid against Aspergillus fumigatus and Fusarium solani. The minimum inhibitory concentrations of the compounds were determined by the microdilution method in RPMI broth in 96-well microplates according to CLSI. Conidial germination, protease production, biofilm formation, and in vivo therapeutic efficacy assays were performed. The results demonstrated that vanillin and tannic acid had antifungal activity against Aspergillus fumigatus, while tannic acid only exhibited antifungal activity against Fusarium solani. We found that vanillin and tannic acid inhibited conidial germination and secreted protease production and biofilm formation of the fungal pathogens using sub-inhibitory concentrations. Besides, vanillin and tannic acid altered the fungal membrane permeability, and both compounds showed therapeutic effect against aspergillosis and fusariosis in an infection model in Galleria mellonella larvae. Our results highlight the antivirulence effect of vanillin and tannic acid against priority pathogenic fungi as a possible therapeutic alternative for human fungal infections.

Synthesis, Characterization, and Antifungal Activity of Benzimidazole-Grafted Chitosan against Aspergillus flavus.

Aspergillus flavus contamination in agriculture and food industries poses threats to human health, leading to a requirement of a safe and effective method to control fungal contamination. Chitosan-based nitrogen-containing derivatives have attracted much attention due to their safety and enhanced antimicrobial applications. Herein, a new benzimidazole-grafted chitosan (BAC) was synthesized by linking the chitosan (CS) with a simple benzimidazole compound, 2-benzimidazolepropionic acid (BA). The characterization of BAC was confirmed by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance spectroscopy (1H and 13C NMR). Then, the efficiency of BAC against A. flavus ACCC 32656 was investigated in terms of spore germination, mycelial growth, and aflatoxin production. BAC showed a much better antifungal effect than CS and BA. The minimum inhibitory concentration (MIC) value was 1.25 mg/mL for BAC, while the highest solubility of CS (16.0 mg/mL) or BA (4.0 mg/mL) could not completely inhibit the growth of A. flavus. Furthermore, results showed that BAC inhibited spore germination and elongation by affecting ergosterol biosynthesis and the cell membrane integrity, leading to the permeabilization of the plasma membrane and leakage of intracellular content. The production of aflatoxin was also inhibited when treated with BAC. These findings indicate that benzimidazole-derived natural CS has the potential to be used as an ideal antifungal agent for food preservation.

Nitric oxide-mediated regulation of Aspergillus flavus asexual development by targeting TCA cycle and mitochondrial function.

Nitric oxide (NO) is a signaling molecule with diverse roles in various organisms. However, its role in the opportunistic pathogen Aspergillus flavus remains unclear. This study investigates the potential of NO, mediated by metabolites from A. oryzae (AO), as an antifungal strategy against A. flavus. We demonstrated that AO metabolites effectively suppressed A. flavus asexual development, a critical stage in its lifecycle. Transcriptomic analysis revealed that AO metabolites induced NO synthesis genes, leading to increased intracellular NO levels. Reducing intracellular NO content rescued A. flavus spores from germination inhibition caused by AO metabolites. Furthermore, exogenous NO treatment and dysfunction of flavohemoglobin Fhb1, a key NO detoxification enzyme, significantly impaired A. flavus asexual development. RNA-sequencing and metabolomic analyses revealed significant metabolic disruptions within tricarboxylic acid (TCA) cycle upon AO treatment. NO treatment significantly reduced mitochondrial membrane potential (Δψm) and ATP generation. Additionally, aberrant metabolic flux within the TCA cycle was observed upon NO treatment. Further analysis revealed that NO induced S-nitrosylation of five key TCA cycle enzymes. Genetic analysis demonstrated that the S-nitrosylated Aconitase Acon and one subunit of succinate dehydrogenase Sdh2 played crucial roles in A. flavus development by regulating ATP production. This study highlights the potential of NO as a novel antifungal strategy to control A. flavus by compromising its mitochondrial function and energy metabolism.

Cd pollution in agroforestry ecosystems: An abiotic factor affecting the passive and active lethal efficiency of Beauveria bassiana to Lymantria dispar larvae.

This study evaluated the effects of cadmium (Cd) exposure on the passive and active lethal efficiency of Beauveria bassiana (Bb) to Lymantria dispar larvae and analyzed the corresponding mechanism from mycelial vegetative growth, fungal and host nutrient competition, and fungal spore performance. The results showed that the passive lethal efficiency of Bb to Cd-exposed L. dispar larvae was significantly higher than that of larvae not exposed to Cd. After Bb infection, the fungal biomass in living larvae and the mycelium encapsulation index of dead larvae were significantly decreased under Cd exposure. Cd exposure damaged the mycelial structure, as well as inhibited the mycelial growth and sporulation quantity. A total of 15 and 39 differentially accumulated mycotoxin metabolites were identified in Bb mycelia treated with low Cd and high Cd, respectively, and the contents of these differentially accumulated mycotoxins in the low Cd and high Cd treatment groups were overall lower than those in the control group. Nutrient content and energy metabolism-related gene expression were significantly decreased in Cd-exposed larvae, both before and after Bb infection. Trehalose supplementation alleviated the nutritional deficiency of larvae under the combined treatment of Cd and Bb and decreased the larval susceptibility to Bb. Compared with untreated Bb, the lethal efficiency of low Cd-exposed Bb to larvae increased significantly, while high Cd-exposed Bb was significantly less lethal to larvae. Cd exposure promoted at low concentrations but inhibited the hydrophobicity and adhesion of spores at higher concentrations. Spore germination rate and stress resistance of Bb decreased significantly under the treatment of both Cd concentrations. Taken together, heavy metals can be regarded as an abiotic environmental factor that directly affects the lethal efficiency of Bb to insect pests.

Use of natural-based commercial products as an alternative for providing bioprotection against verticillium wilt of olive.

BACKGROUND: As a result of the ineffectiveness of existing control methods against Verticillium dahliae, the causal agent of verticillium wilt of olive (Olea europaea; VWO), it is necessary to search for sustainable and environmentally friendly alternatives, such as bioprotection by products based on plant extracts and other naturally synthesized compounds. Therefore, present study aimed to evaluate the effects of seven natural-based commercial products on the inhibition of mycelial growth, the germination of V. dahliae conidia and microsclerotia, and disease progression in olive plants (cv. Picual). Aluminium lignosulfonate and a copper phosphonate salt (copper phosphite) were included for comparative purposes. RESULTS: The seaweed and willow extracts and copper phosphite inhibited V. dahliae mycelial growth by more than 50% at the high doses tested. Most of the products inhibited conidial germination by up to 90% compared to the control at the high doses tested. However, none of the products showed efficacy above 50% in inhibiting microsclerotia germination. The willow extract was the most effective at reducing disease severity and progression in olive plants, with no significant differences compared to the non-inoculated negative control. CONCLUSION: The results of the present study suggest that the use of natural-based products (i.e. seaweed and willow extracts) is a potential sustainable alternative in an integrated VWO control strategy. © 2024 Society of Chemical Industry.

Sensitivity of Botrytis cinerea from Vineyards to Boscalid, Isofetamid, and Pydiflumetofen in Shandong Province, China.

Succinate dehydrogenase inhibitor (SDHI) fungicides are the most commonly and effectively used class of fungicides for controlling gray mold. Among them, only boscalid has been registered in China for controlling grape gray mold, whereas isofetamid and pydiflumetofen are two new SDHI fungicides that have demonstrated high efficacy against various fungal diseases. However, the sensitivity of Botrytis cinerea isolates from vineyards in China to these three fungicides is currently unknown. In this study, the sensitivity of 55 B. cinerea isolates from vineyards to boscalid, isofetamid, and pydiflumetofen was determined, with the effective concentrations for inhibiting 50% of spore germination (EC50) values ranging from 1.10 to 393, 0.0300 to 42.0, and 0.0990 to 25.5 µg ml-1, respectively. The resistance frequencies for boscalid, isofetamid, and pydiflumetofen were 60.0, 7.2, and 12.8%, respectively. Three mutations (H272R, H272Y, and P225F) were detected in the SdhB subunit, with H272R being the most prevalent (75.7%), followed by H272Y (16.2%) and P225F (8.1%). All three mutations are associated with resistance to boscalid, and of them, H272R mutants exhibited high resistance. Only P225F and H272Y mutants exhibited resistance to isofetamid and pydiflumetofen, respectively. A weakly positive cross-resistance relationship was observed between boscalid and pydiflumetofen (r = 0.38, P < 0.05). Additionally, the H272R mutants showed no significant fitness costs, whereas the remaining mutants exhibited reduced mycelial growth (P225F) and sporulation (H272Y and P225F). These results suggest that isofetamid and pydiflumetofen are effective fungicides against B. cinerea in vineyards, but appropriate rotation strategies must be implemented to reduce the selection of existing SDHI-resistant isolates.

Efficacy of antifungal agents against fungal spores: An in vitro study using microplate laser nephelometry and an artificially infected 3D skin model.

Dermal fungal infections seem to have increased over recent years. There is further a shift from anthropophilic dermatophytes to a growing prevalence of zoophilic species and the emergence of resistant strains. New antifungals are needed to combat these fungi and their resting spores. This study aimed to investigate the sporicidal effects of sertaconazole nitrate using microplate laser nephelometry against the microconidia of Trichophyton, chlamydospores of Epidermophyton, blastospores of Candida, and conidia of the mold Scopulariopsis brevicaulis. The results obtained were compared with those from ciclopirox olamine and terbinafine. The sporicidal activity was further determined using infected three-dimensional full skin models to determine the antifungal effects in the presence of human cells. Sertaconazole nitrate inhibited the growth of dermatophytes, molds, and yeasts. Ciclopirox olamine also had good antifungal activity, although higher concentrations were needed compared to sertaconazole nitrate. Terbinafine was highly effective against most dermatophytes, but higher concentrations were required to kill the resistant strain Trichophyton indotineae. Sertaconazole nitrate, ciclopirox olamine, and terbinafine had no negative effects on full skin models. Sertaconazole nitrate reduced the growth of fungal and yeast spores over 72 h. Ciclopirox olamine and terbinafine also inhibited the growth of dermatophytes and molds but had significantly lower effects on the yeast. Sertaconazole nitrate might have advantages over the commonly used antifungals ciclopirox olamine and terbinafine in combating resting spores, which persist in the tissues, and thus in the therapy of recurring dermatomycoses.