Fumonisin B1 Production Research Articles

Regulation of Fumonisin B1 Production and Pathogenicity in Fusarium verticillioides by Histone Deacetylases

Transcriptional regulation mediated by the balance of histone acetylation and deacetylation is fundamental in responding to environmental cues by impacting chromatin remodeling. Histone deacetylases (HDACs) are enzymes that remove acetyl groups from histone and non-histone proteins, thus restoring a tight chromatin structure. In pathogenic fungi, HDACs have been implicated in growth, secondary metabolite biosynthesis, and virulence. However, the role of HDACs in the mycotoxin fumonisin B1 (FB1)-producing fungus Fusarium verticillioides is poorly understood. In this study, we systematically characterized six F. verticillioides HDACs. An increased level of H4K16ac was observed in the deletion mutant of FvHOS2, which was associated with vegetative growth, conidiation, and virulence when infecting sugarcane and maize. FvRpd3 appeared to be essential for vegetative growth, while FvHda1 promoted growth, and both contributed to conidiation and pathogenicity. In contrast, FvSirt4 displayed a negative correlation with these processes. Additionally, the FB1 production was positively affected by FvHos2 and FvRpd3, but negatively impacted by Fvhda1, FvSir2, FvHst2, and FvSirt4 through the regulation of different key fumonisin biosynthetic (FUM) genes. Further findings indicate an association between FvSirt4 and FvSkb1, which is a histone methylase that positively regulates FB1 and pathogenicity. Moreover, as a global transcriptional regulator, over 2365 genes (~15% of the genome) enriched in multiple metabolic pathways were significantly downregulated in the ΔFvhos2 mutants relative to the wild type. Overall, our results suggest distinct roles of HDACs in regulating the growth, virulence, mycotoxin FB1 production, and gene expression in F. verticillioides.

Unlocking the Potential of Lactococcus lactis subsp. lactis BIONCL17752 strain on Fumonisin B1 production by Fusarium verticillioides

Mycotoxins are the potent toxic chemical agent's linked to food safety, pose a serious risk to human and animal health globally. The management of toxigenic fungi is a challenging task in food and feed industries. The present investigation aimed to use probiotic potentials of lactic acid bacteria (LAB), and fermented cell-free broth as antifungal agents and neutralization of carcinogenic mycotoxin, fumonisin B1 (FB1) in food and feed considered as “turned waste into treasure”. We strived to investigate the probiotic potential of Lactococcus lactis subsp. lactis BIONCL17752 strain on prevention of growth and neutralization of FB1 produced by Fusarium verticillioides BIONCL4 strain to emulate as as a food grade bio-preservative. The BIONCL17752 strain exhibited excellent inhibitory activity against BIONCL4 strain. It was cultivated in MRS medium, and obtained cells pellet (CP) and cell-free supernatant (CFS) was lyophilized, and used for their antifungal activity against BIONCL4 strain. The minimum fungicidal concentration (MFC) determined as 12.5 μg/mL. Nevertheless, CFS assessed for neutralization of FB1 production which exhibited complete inhibition and downregulation of FB1 encoding FUM1 gene expression using quantitative real-time PCR (qPCR). Furthermore, CFS induced transcriptomic studies against BIONCL4 strain endorsed a significant downregulation of virulence, FB1, fusaric acid, fusarin, and chitin biosynthetic pathway genes. The CFS and cells reticent spore germination and FB1 production in the range of 40–61% and 74–85%, respectively under stored maize for 60 days. The current findings suggest BIONCL17752 strain apprehend the fungal growth and inhibit the FB1, and other toxigenic molecules biosynthesis, and can be employed as food grade preservative in the food industries to ensure the food safety and human health.

Functional analysis of cutinase transcription factors in Fusarium verticillioides

Fusarium verticillioides is an important pathogen of maize and causes serious yield losses and food safety issues worldwide. F. verticillioides produces highly toxic mycotoxin Fumonisin B1 (FB1) in infested commodities which makes these food and feeds unsafe for humans and animals. For pathogenic fungi to successfully penetrate its plant hosts, the pathogen secretes hydrolytic enzymes that can facilitate penetration into the plant cutin layer. However, there is limited information on how cutinases transcriptionally regulated to impact F. verticillioides pathogenicity. In this study, our aim is to functionally characterize cutinase transcription factors that regulate key cutinase activities that are directly associated with F. verticillioides pathogenicity and FB1 biosynthesis. Gene deletion of cutinase transcription factor FvCTF1α did not affect the growth and morphology of the fungal mycelia on CMII medium, whereas the conidiation, utilization of sodium acetate and sodium oleate, stress tolerance against cell wall interfering agent, and the cutinase and pectinase activities in the ΔFvctf1α mutant were negatively impacted. FvCtf1α regulates the expression of induced cutinase genes FvCUT1 and FvCUT4 by binding to their GC-rich promoters. In addition, FvCtf1α, containing a novel function in regulating FB1, interacts with the promoter of FvFUM1 and FvFUM6 to down-regulate the expression of FvFUM1 and FvFUM6, resulting in decreased production of FB1 in the ΔFvctf1α strain. ΔFvctf1α exhibited decreased pathogenicity in maize due to the down-regulation of pathogenicity-related genes as well as key downstream cutinase genes FvCUT3 and FvCUT4 in F. verticillioides. We also demonstrated that FvCtf1α regulated FvCUT3 and FvCUT4 differently; FvCUT4 via direct regulation while FvCUT3 via indirect regulation by interacting with FvFarB, a homologous protein of FvCtf1α. Moreover, RNA-seq analysis showed that FvCtf1α was associated with many pathways, such as fatty acid metabolism, carbon source utilization, cell wall integrity, oxidative stress, and fumonisin synthesis in F. verticillioides. Our study demonstrated that FvCtf1α was not only involved in the regulation of cutinases but also a broad spectrum of pathways that ultimately affect F. verticillioides virulence and mycotoxin biosynthesis.

Validamycin A Inhibited FB1 Biosynthesis by the Target FvNth in Fusarium verticillioides.

Validamycin A (VMA) is an antifungal antibiotic derived from Streptomyces hygroscopicus commonly used in plant disease management. Surprisingly, VMA was discovered to impede the production of fumonisin B1 (FB1) in agricultural settings. However, the specific target of VMA in Fusarium verticillioides remained unclear. To unravel the molecular mechanism of VMA, ultrastructural observations unveiled damage to mitochondrial membranes. Trehalase (FvNth) was pinpointed as the target of VMA by utilizing a 3D-printed surface plasmon resonance sensor. Molecular docking identified Trp285, Arg447, Asp452, and Phe665 as the binding sites between VMA and FvNth. A ΔFvnth mutant lacking amino acids 250-670 was engineered through homologous recombination. Transcriptome analysis indicated that samples treated with VMA and ΔFvnth displayed similar expression patterns, particularly in the suppression of the FUM gene cluster. VMA treatment resulted in reduced trehalase and ATPase activity as well as diminished production of glucose, pyruvic acid, and acetyl-CoA. Conversely, these effects were absent in samples treated with ΔFvnth. This research proposes that VMA hinders acetyl-CoA synthesis by trehalase, thereby suppressing the FB1 biosynthesis. These findings present a novel target for the development of mycotoxin control agents.

Evaluation of the efficacy of cinnamon oil on Aspergillus flavus and Fusarium proliferatum growth and mycotoxin production on paddy and polished rice: Towards a mitigation strategy

In the present investigation, the effect of cinnamon oil (CO) (10, 30, 50 and 70 %) on the growth rate (mm/day) and aflatoxin B1 (AFB1) and fumonisin B1 (FB1) production of Aspergillus flavus (AF01) and Fusarium proliferatum (FP01) isolates, respectively was determined at optimum water activities (0.95 and 0.99 aw) and temperatures (25, 30 and 35 °C) on paddy and polished rice grains. The results showed that the growth rate, AFB1 and FB1 production of all the fungal isolates decreased with an increase in CO concentrations on both matrices. AF01 and FP01 failed to grow under all conditions on paddy at 50 % of CO concentration whereas both fungi were completely inhibited (No Growth-NG) at 70 % of CO on polished rice. Regarding mycotoxin production, 30 % of CO concentrations could inhibit AFB1 and FB1 production in both matrices (No Detection-ND). In this study, the production of mycotoxins was significantly influenced by cinnamon oil compared to the growth of both fungi. These results indicated the promising potential of CO in improving the quality of rice preservation in post-harvest; however, further investigations should be evaluated on the effects on the qualitative characteristics of grains. Especially, the prospective application of CO in rice storage in industry scales to mitigate mycotoxin contamination need also to be further researched. Moreover, collaboration between researchers, agricultural experts, and food industry should be set up to achieve effective and sustainable strategies for preserving rice.

Genome-wide transcriptome analysis of toxigenic Fusarium verticillioides in response to variation of temperature and water activity on maize kernels

Fusarium verticillioides is one of the important mycotoxigenic pathogens of maize since it causes severe yield losses and produces fumonisins (FBs) to threaten human and animal health. Previous studies showed that temperature and water activity (aw) are two pivotal environmental factors affecting F. verticillioides growth and FBs production during maize storage. However, the genome-wide transcriptome analysis of differentially expressed genes (DEGs) in F. verticillioides under the stress combinations of temperature and aw has not been studied in detail. In this study, DEGs of F. verticillioides and their related regulatory pathways were analyzed in response to the stress of temperature and aw combinations using RNA-Seq. The results showed that the optimal growth conditions for F. verticillioides were 0.98 aw and 25 °C, whereas the highest per-unit yield of the fumonisin B1 (FB1) was observed at 0.98 aw and 15 °C. The RNA-seq analysis showed that 9648 DEGs were affected by temperature regardless of aw levels, whereas only 218 DEGs were affected by aw regardless of temperature variations. Gene Ontology (GO) analysis revealed that a decrease in temperature at both aw levels led to a significant upregulation of genes associated with 24 biological processes, while three biological processes were downregulated. Furthermore, when aw was decreased at both temperatures, seven biological processes were significantly upregulated and four were downregulated. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that the genes, whose expression was upregulated when the temperature decreased, were predominantly associated with the proteasome pathway, whereas the genes, whose expression was downregulated when the aw decreased, were mainly linked to amino acid metabolism. For the FB1, except for the FUM15 gene, the other 15 biosynthetic-related genes were highly expressed at 0.98 aw and 15 °C. In addition, the expression pattern analysis of other biosynthetic genes involved in secondary metabolite production and regulation of fumonisins production was conducted to explore how this fungus responds to the stress combinations of temperature and aw. Overall, this study primarily examines the impact of temperature and aw on the growth of F. verticillioides and its production of FB1 using transcriptome data. The findings presented here have the potential to contribute to the development of novel strategies for managing fungal diseases and offer valuable insights for preventing fumonisin contamination in food and feed storage.

Characterization of Fusarium verticillioides Med1 LxxLL Motif Involved in Fumonisin Biosynthesis.

The Med1 transcriptional coactivator is a crucial component of the Mediator middle complex, which regulates the expression of specific genes involved in cell development, differentiation, reproduction, and homeostasis. The Med1 LxxLL motif, a five-amino-acid peptide sequence, is essential for Med1-mediated gene expression. Our previous study revealed that the disruption of the Med1 subunit leads to a significant increase in fumonisin B1 (FB1) production in the maize pathogen Fusarium verticillioides. However, our understanding of how Med1 regulates FB1 biosynthesis in F. verticillioides, particularly through the Med1 LxxLL motifs, remains limited. To characterize the role of LxxLL motifs, we generated a series of Med1 LxxLL deletion and amino acid substitution mutants. These mutants exhibited impaired mycelial growth and conidia germination while demonstrating enhanced conidia production and virulence. Similar to the Med1 deletion mutant, Med1 LxxLL motif mutants also exhibited increased FB1 biosynthesis in F. verticillioides. Proteomic profiling revealed that the Med1 LxxLL motif regulated the biosynthesis of several key substances that affected FB1 production, including starch and carotenoid. Subsequent studies demonstrated that the production of amylopectin, which is strongly linked to FB1 biosynthesis, was significantly increased in Med1 LxxLL motif mutants. In addition, the disruption of carotenoid metabolic genes decreased carotenoid content, thus stimulating FB1 biosynthesis in F. verticillioides. Taken together, our results provide valuable insights into how the Med1 LxxLL motif regulates FB1 biosynthesis in the mycotoxigenic fungus F. verticillioides.

Antifungal activity of Lysinibacillus macroides against toxigenic Aspergillus flavus and Fusarium proliferatum and analysis of its mycotoxin minimization potential

BackgroundToxigenic fungi (Aspergillus and Fusarium) and their metabolites represent the major cause of corn and corn-based products contamination and consequently lead to severe economic and health issues.AimOur current study aimed to investigate the efficacy of using L. macroides Bac6 as a biological control agent against the toxigenic fungi; A. flavus f10 and F. proliferatum f30 and their mycotoxins.ResultsThe results illustrated that A. flavus f10 produced the aflatoxins AFB1 and AFG2 with concentrations of 21.239 and 13.593 ppb, respectively. While F. proliferatum f30 produced fumonisin B1 (9600 ppb). Furthermore, L. macroides showed a high potential for inhibition of toxigenic fungal growth using a dual culture method. F. proliferatum f30 and A. flavus f10 were found to be inhibited by a percentage of 80 and 62.5%, respectively. The results were confirmed using the scanning electron microscope. The antagonistic bacteria, L. macroides, showed chitinase productivity and activity of 26.45 U/L and 0.12 U/mL/min, respectively, which illustrates its potential application as a biocontrol agent. The GC-MS analysis revealed an abundance of Pyrrolo[1,2-a] pyrazine-1,4-dione, Hexahydro in the bacterial supernatant that exhibited antifungal characteristics. L. macroides had a significant reduction of AFB1 and AFG2 produced by A. flavus f10, recording 99.25% and 99% inhibition, respectively. It also showed strong inhibition of fumonisin B1 (90% inhibition) produced by F. proliferatum f30. Conclusion: Thus, the current study is a prospective study evaluating for the first time the potential impact of L. macroides Bac6 against the toxigenic fungi and their toxins.

Major Fusarium species and mycotoxins associated with freshly harvested maize grain in Uruguay.

Fusarium species are common fungal pathogens of maize. Fusarium graminearum and Fusarium verticillioides, among others, can cause maize ear rot, and they are also mycotoxin producers. The aims of this work were to determine the frequency and diversity of Fusarium species in Uruguayan maize kernels, evaluate the toxigenic potential of the isolates, determine toxin contamination levels on freshly harvested grain, and assess the sensitivity of main Fusarium species against fungicides. Fusarium verticillioides was the most frequent species isolated, followed by Fusarium graminearum sensu stricto. Of F. verticillioides isolates studied for fumonisin production, 72% produced fumonisin B1 and 32% fumonisin B2. Considering in vitro toxin production by F. graminearum sensu stricto isolates, deoxynivalenol was the main toxin produced, followed by zearalenone and nivalenol. Fumonisins were the most frequently found toxins on freshly harvested maize samples (98% in 2018 and 86% in 2019), and also, fumonisin B1 was the toxin with highest concentration in both years studied (4860µg/kg in 2018 and 1453µg/kg in 2019). Deoxynivalenol and zearalenone were also found as contaminants. Metconazole and epoxiconazole were the most effective fungicides tested on F. verticillioides isolates. Fusarium graminearum sensu stricto isolates also were more sensitive to metconazole compared to other fungicides; nevertheless, epoxiconazole was less efficient in controlling this species. This is the first study that reports Fusarium species and mycotoxin contamination levels associated with maize grain in Uruguay. Its detection is the main step to develop management strategies in order to minimize fungal infection in maize crops.

Fumonisin B1 Biosynthesis Is Associated with Oxidative Stress and Plays an Important Role in Fusarium proliferatum Infection on Banana Fruit.

Fungal response to oxidative stress during infection on postharvest fruit is largely unknown. Here, we found that hydrogen peroxide (H2O2) treatment inhibited the growth of Fusarium proliferatum causing crown rot of banana fruit, confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation. H2O2 exposure increased endogenous reactive oxygen species (ROS) and fumonisin B1 (FB1) production in F. proliferatum, possibly by modulating FUM or ROS-related gene expression. Importantly, H2O2 treatment inhibited F. proliferatum growth in vivo but induced FB1 accumulation in banana peel. Finally, we constructed the FpFUM21 deletion mutant (ΔFpfum21) of F. proliferatum that was attenuated in FB1 biosynthesis and less tolerant to oxidative stress. Moreover, the ΔFpfum21 strain was less virulent compared to the wild type (WT) due to the inability to induce FB1 production in the banana host. These results suggested that FB1 biosynthesis is associated with oxidative stress in F. proliferatum and contributes to fungal infection on banana fruit.

Detection of the Enzymes and Toxins Produced by the Pathogenic Fungi that Cause Chias Pollen Disease on Different Date Palm Cultivars in Iraq

Mohamed, Kh.A. and M.A. Alfahd. 2023. Detection of the Enzymes and Toxins Produced by the Pathogenic Fungi that Cause Chias Pollen Disease on Different Date Palm Cultivars in Iraq. Arab Journal of Plant Protection, 41(1): 65-70. https://doi.org/10.22268/AJPP-41.1.065070 This study aimed to determine the exo-enzyme activity of some inflorescence-rot causing fungi that were isolated from different date palm cultivars such as Mauginiella scaettae, Fusarium solani, Fusarium oxysporium and Alternaria radicina and their ability to produce protease and cellulase enzymes on Czapek dox (CD) liquid media supplemented with carboxy methyl cellulose (CMC), as well as their ability to produce Fumonisin B1 toxin using the enzyme linked immunoassay assay (ELISA). The results obtained showed a discrepancy in the amount of enzymes and toxins produced by these pathogens. The fungus F. oxysporum produced the highest cellulase enzyme activity, which amounted to 1.1933 units/ml, whereas Alternaria radicina produced the highest protease enzyme activity which amounted to 50,964 units/ml. The pathogen M. scaettae produced the highest toxin concentration of 38.465 µg/kg, whereas the pathogen Fusarium solani did not produce this toxin. Keywords: Mauginiella. Scaettae, enzymes, fumonisin B1, toxins.

Genetic diversity of toxigenic Fusarium verticillioides associated with maize grains, India.

In the present investigation, prevalence, genetic diversity, and mycotoxin producing potential of Fusarium species associated with maize grain samples were studied from different geographical regions of India. The highest prevalence of Fusarium verticillioides was recorded as 88.52%, followed by F. coffeatum, F. foetens, and F. euwallaceae, 6.55%, 3.27%, and 1.63%, respectively. We isolated 54 strains of F. verticillioides, and their genetic diversity was studied by inter simple sequence repeats (ISSR). The ISSR fingerprints (AG) 8C and (AG) 8G showed 252 and 368 microsatellite sites in the genome of F. verticillioides and resulted in 99-100% repeatability and reproducibility. The Simpson (SID) and Shannon (H) indices (0.78 and 2.36) suggest that F. verticillioides strains exhibit moderate to high diversity. Molecular detection of fumonisin B1 (FB1) biosynthetic genes (FUM1 and FUM13) involved in FB1 production in F. verticillioides was confirmed by polymerase chain reaction (PCR). Furthermore, 91% of the strains were positive for FB1 production, which was affirmed by liquid chromatography with tandem mass spectrometry (LC-MS-MS). In-vitro appurtenance of F. verticillioides spores exhibited a high to moderate effect on the growth and development of the maize. The current finding demonstrated that most F. verticillioides strains showed a wide range of genetic diversity with varied toxigenic and pathogenic potentials. In conclusion, for the first time, F. coffeatum, F. foetens, and F. euwallaceae species were reported from maize grain samples in India. They were positive for FB1 and negatively affecting grain quality, which is a major concern in food safety.

CHARACTERIZATION AND MYCOTOXIN ANALYSIS OF Fusarium spp. FROM HIGHLAND AREAS IN MALAYSIA

Fusarium isolates from highland areas in Malaysia were mostly recovered from two species of grasses, Elyhordeum montanense and Paspalum conjugatum. The isolates were grouped into four morphological groups. Based on TEF-1α sequences, morphotype 1 isolates were molecularly identified as F. graminearum species complex, morphotype 2 as F. venenatum, morphotype 3 as F. avenaceum and morphotype 4 as F. kyushuense. Restriction analysis of the Intergenic Spacer region showed high levels of genetic diversity of isolates in F. graminearum species complex and F. venenatum. For mycotoxin analysis, only F. avenaceum and F. kyushuense produced beauvericin and moniliformin (0.869 & 0.321 µg/kg, respectively). Zearalenone was produced by 32 isolates of F. graminearum species complex (0.002 – 0.437 µg/kg), two isolates of F. venenatum (0.006 - 0.014 µg/kg) and F. kyushuense (0.006 µg/kg). Only F. avenaceum isolate produced fumonisin B1 (0.001 µg/kg). The present study indicates the occurrence of Fusarium species commonly reported in highland areas in Malaysia where the weather is cooler and the temperature is lower than in the lowland areas. To our knowledge, this is the first report on the occurrence of phylogenetic species within F. graminearum species complex, F. venenatum, F. avenaceum and F. kyushuense in Malaysia.

Genomic footprints related with adaptation and fumonisins production in Fusarium proliferatum.

Fusarium proliferatum is the principal etiological agent of rice spikelet rot disease (RSRD) in China, causing yield losses and fumonisins contamination in rice. The intraspecific variability and evolution pattern of the pathogen is poorly understood. Here, we performed whole-genome resequencing of 67 F. proliferatum strains collected from major rice-growing regions in China. Population structure indicated that eastern population of F. proliferatum located in Yangtze River with the high genetic diversity and recombinant mode that was predicted as the putative center of origin. Southern population and northeast population were likely been introduced into local populations through gene flow, and genetic differentiation between them might be shaped by rice-driven domestication. A total of 121 distinct genomic loci implicated 85 candidate genes were suggestively associated with variation of fumonisin B1 (FB1) production by genome-wide association study (GWAS). We subsequently tested the function of five candidate genes (gabap, chsD, palA, hxk1, and isw2) mapped in our association study by FB1 quantification of deletion strains, and mutants showed the impact on FB1 production as compared to the wide-type strain. Together, this is the first study to provide insights into the evolution and adaptation in natural populations of F. proliferatum on rice, as well as the complex genetic architecture for fumonisins biosynthesis.

Distinct Function of Mediator Subunits in Fungal Development, Stress Response, and Secondary Metabolism in Maize Pathogen Fusarium verticillioides.

Mediator is a nucleus-localized, multisubunit protein complex highly conserved across eukaryotes. It interacts with RNA polymerase II transcription machinery as well as various transcription factors to regulate gene expression. However, systematic characterization of the Mediator complex has not been performed in filamentous fungi. In our study, the goal was to investigate key biological functions of Mediator subunits in a mycotoxigenic plant pathogen Fusarium verticillioides. Although there is some level of divergence in the constituent subunits, the overall structure was conserved between Saccharomyces cerevisiae and F. verticillioides. We generated 11 Mediator subunit deletion mutants and characterized vegetative growth, conidia formation, environmental stress response, carbon and fatty acid use, virulence, and fumonisin B1 (FB1) biosynthesis. Each Mediator subunit deletion mutant showed deficiencies in at least three of the phenotypes tested, suggesting that each subunit has different principal functions in F. verticillioides development, metabolism, and virulence. The deletion of FvMed1 led to increased FB1 production, and we confirmed that FvMed1 is transported from the nucleus to the cytoplasm under fumonisin-producing conditions. Taken together, our study characterized various important functional roles for Mediator subunits in F. verticillioides and suggests that select subunits can perform unique cytoplasmic functions independent of the core Mediator in fungal nucleus.

Anti-toxicogenic fungi and toxin-reducing effects of bacillomycin D in combination with fungicides

Mycotoxins are toxic secondary metabolites produced by fungus including Aspergillus and Fusarium. They can contaminate food and cause major health issues. Bacillomycin D (BD) is a natural antimicrobial lipopeptide generated by Bacillus that has excellent antifungal capabilities, but its high price prevents it from being widely used. Chemically produced and essential oil-based fungicides are also currently the most frequent types. In the study, the effects of combining BD with two types of fungicides on the growth of toxicogenic fungi as well as the generation of deoxynivalenol (DON) and fumonisin B1 (FB1) were examined. It was discovered that BD was more effective in suppressing molds than the other two types of fungicides, and it could be combined with synthetic or essential oil-based fungicides to provide a synergistic or additive effect. BD 31.25 μg/mL + Thymol (Thy) 7.81 μg/mL and BD 11.45 μg/mL + Cinnamon oil (Cin) 3.90 μg/mL inhibited F. graminearum, respectively. The combination of BD+Thy and BD+Cin at this concentration considerably reduced 60%–80% spore germination, when DON dropped below 300 ng/L. Furthermore, both combinations suppressed F. moniliforme growth and FB1 synthesis in a dose-dependent manner at lower concentrations. At an action dose of 2 MIC, FB1 production might be reduced to less than 100 ng/L. Our findings indicated that BD might interact synergistically with various fungicides, suggesting that it could be useful in the field of antifungal and toxicity reduction in food.

In Search of Resistance Against Fusarium Ear Rot: Ferulic Acid Contents in Maize Pericarp Are Associated With Antifungal Activity and Inhibition of Fumonisin Production.

Fusarium verticillioides is a fungal pathogen of maize that causes seedling blight, stem rot, and Fusarium ear rot. Fungal infestation of maize kernels and ears affects grain quality from the ensuing mycotoxin buildup. Among the mycotoxins produced by F. verticillioides, fumonisins accumulate to high levels in Fusarium-infected maize kernels, fumonisin B1 (FB1) being the most abundant in naturally infected maize. Achieving resistance to Fusarium ear rot has been challenging, as various environmental factors facilitate fungal infection. Among the maize grain components that contribute to resistance to F. verticillioides infection, the pericarp is the first barrier faced by the fungus and thus plays a key role. Phenolic acids are major constituents of maize pericarp, of which ferulic acid (FA) is the predominant molecular species. In this work, we explored the relationship between FA levels, fungal infection, and FB1 production in 51 maize genotypes and whether the antioxidant activity of FA might play a role. We confirmed that FA is a major component of the seed pericarp, whose levels as bound FA varied between 4.5 and 26.3 mg/g across maize genotypes. We selected two pools of five maize varieties, with contrasting FA contents: low FA (LFA; 6.14 ± 0.40 mg/g) and high FA (HFA; 15.49 ± 1.31 mg/g). In vitro, HFA extracts inhibited fungal growth with effects comparable to FA concentrations in the 0.25–0.50 mM range. We also established a kernel assay to study F. verticillioides colonization and FB1 production in the LFA and HFA genotypes. Fungal colonization was significantly lower in HFA genotypes relative to LFA genotypes, based on ergosterol levels. Moreover, FB1 production was also inhibited in the HFA genotypes. Importantly, the antioxidant activity of maize pericarp extracts was associated with FA contents, with HFA extracts exhibiting a greater antioxidant activity than LFA extracts. Overall, our results highlight the role of FA and its antioxidant activity on resistance to Fusarium ear rot and provide the basis of a phenotypic trait that can be deployed for breeding selection.

Stress responses on the growth and mycotoxin biosynthesis of Fusarium proliferatum associated with stored poultry feeds

Animal and poultry feeds majorly constitutes of cereal grains and their by-products representing an excellent substrate for fungal colonization and mycotoxin contamination. Additionally, ecological factors play a crucial role in the process of fungal colonization in stored food/feed material. Here, we propose the physiological behavior of Fusarium proliferatum MYS9 in response to the combinational effects of different abiotic factors such as light, temperature, solutes and relative humidity. Red and blue spectral lights had stimulating effect on the growth and biomass and also Fumonisin B1 production recording 141.60 µg and 69.77 µg/g feed, respectively. The radial growth and biomass formation of F. proliferatum declined with the increasing ionic solute potential while the non-ionic solute potential showed an irregular pattern of growth and biomass. The room temperature (28 °C) showed maximum colony diameter (7.78 cm), biomass (1.32 g per 50 mL medium) and FB1 biosynthesis (913.25 µg/g feed). A significant radial growth was observed at 96% relative humidity and a high biomass of 0.82 g per 50 mL medium was observed at 98% humidity. A maximum growth of the fungus was observed at 28 °C in combination of -51.02 bars of osmotic pressure while the lower and higher temperature ranges with high osmotic pressures restricted the growth. The present study provides useful data facilitating a better understanding of the influence of ecological factors on fungal growth and toxin production in feeds and help to optimize storage measures and prevention strategies.

Toxicity, bioactivity of triazole fungicide metconazole and its effect on mycotoxin production by Fusarium verticillioides: New perspective from an enantiomeric level

The chiral triazole fungicide metconazole has four stereoisomers, is a broad-spectrum fungicide and is widely used for controlling Fusarium head blight caused by Fusarium species. In this study, systemic assessments of metconazole stereoisomers were performed, including stereoselective toxicity toward the aquatic organism Daphnia magna, fungicidal activity and effects on fumonisin production by the pathogen Fusarium verticillioides (F. verticillioides) in relation to different conditions. The toxicity of metconazole was enantioselective, and there was a 2.1–2.9-fold difference. The activities of superoxide dismutase (SOD) and catalase (CAT) increased and decreased, respectively, after treatment with metconazole stereoisomers, and the differences were observed among the stereoisomers. Among the four stereoisomers, (1S,5R)-metconazole showed the highest fungicidal activity under all assayed conditions, and the differences ranged from 4.4 to 45.2 times. Moreover, metconazole stereoisomers can stereoselectively affect on fumonisin B1 production by F. verticillioides and abiotic factors, such as water activity and temperature, play an important role. Our study provides new insight into metconazole at the stereoisomeric level, including its toxicity, bioactivity, and effect on Fusarium species producing mycotoxins.

Use of Mustard Extracts Fermented by Lactic Acid Bacteria to Mitigate the Production of Fumonisin B1 and B2 by Fusarium verticillioides in Corn Ears.

Corn (Zea mays) is a worldwide crop subjected to infection by toxigenic fungi such as Fusarium verticillioides during the pre-harvest stage. Fusarium contamination can lead to the synthesis of highly toxic mycotoxins, such as Fumonisin B1 (FB1) and Fumonisin B2 (FB2), which compromises human and animal health. The work aimed to study the antifungal properties of fermented yellow and oriental mustard extracts using nine lactic acid bacteria (LAB) in vitro. Moreover, a chemical characterization of the main phenolic compounds and organic acids were carried out in the extracts. The results highlighted that the yellow mustard, fermented by Lactiplantibacillus plantarum strains, avoided the growth of Fusarium spp. in vitro, showing Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC) values, ranging from 7.8 to 15.6 g/L and 15.6 to 31.3 g/L, respectively. Then, the lyophilized yellow mustard fermented extract by L. plantarum TR71 was applied through spray-on corn ears contaminated with F. verticillioides to study the antimycotoxigenic activity. After 14 days of incubation, the control contained 14.71 mg/kg of FB1, while the treatment reduced the content to 1.09 mg/kg (92.6% reduction). Moreover, no FB2 was observed in the treated samples. The chemical characterization showed that lactic acid, 3-phenyllactic acid, and benzoic acid were the antifungal metabolites quantified in higher concentrations in the yellow mustard fermented extract with L. plantarum TR71. The results obtained confirmed the potential application of fermented mustard extracts as a solution to reduce the incidence of mycotoxins in corn ears.