Temperature and water activity effects on production of T-2 and HT-2 by Fusarium langsethiae strains from north European countries

Impact of Environmental Conditions on the Concentrations of Trichothecenes, Their Glucosides, and Emerging Fusarium Toxins in Naturally Contaminated, Irradiated, and Fusarium langsethiae Inoculated Oats

Trichothecenes produced by Fusarium species are commonly detected in oats. However, the ratios of the concentrations of free trichothecenes and their conjugates and how they are impacted by different interacting environmental conditions are not well documented. This study aims to examine the effect of water activity (0.95 and 0.98 aw) and temperature (20 and 25 °C) stress on the production of T-2 and HT-2 toxins, deoxynivalenol and their conjugates, as well as diacetoxyscirpenol (DAS). Multiple mycotoxins were detected using liquid chromatography-tandem mass spectrometry from 64 contaminated oat samples. The highest concentrations of HT-2-glucoside (HT-2-Glc) were observed at 0.98 aw and 20 °C, and were higher than other type A trichothecenes in the natural oats' treatments. However, no statistical differences were found between the mean concentrations of HT-2-Glc and HT-2 toxins in all storage conditions analysed. DAS concentrations were generally low and highest at 0.95 aw and 20 °C, while deoxynivalenol-3-glucoside levels were highest at 0.98 aw and 20 °C in the naturally contaminated oats. Emerging mycotoxins such as beauvericin, moniliformin, and enniatins mostly increased with a rise in water activity and temperature in the naturally contaminated oats treatment. This study reinforces the importance of storage aw and temperature conditions in the high risk of free and modified toxin contamination of small cereal grains.

T-2 and HT-2 Toxins: Toxicity, Occurrence and Analysis: A Review

One of the major classes of mycotoxins posing serious hazards to humans and animals and potentially causing severe economic impact to the cereal industry are the trichothecenes, produced by many fungal genera. As such, indicative limits for the sum of T-2 and HT-2 were introduced in the European Union in 2013 and discussions are ongoing as to the establishment of maximum levels. This review provides a concise assessment of the existing understanding concerning the toxicological effects of T-2 and HT-2 in humans and animals, their biosynthetic pathways, occurrence, impact of climate change on their production and an evaluation of the analytical methods applied to their detection. This study highlights that the ecology of F. sporotrichioides and F. langsethiae as well as the influence of interacting environmental factors on their growth and activation of biosynthetic genes are still not fully understood. Predictive models of Fusarium growth and subsequent mycotoxin production would be beneficial in predicting the risk of contamination and thus aid early mitigation. With the likelihood of regulatory maximum limits being introduced, increased surveillance using rapid, on-site tests in addition to confirmatory methods will be required. allowing the industry to be proactive rather than reactive.

Iturin A Strongly Inhibits the Growth and T-2 Toxin Synthesis of Fusarium oxysporum: A Morphological, Cellular, and Transcriptomics Study

Fusarium oxysporum (F. oxysporum) is a common contaminant of dried fish, and the T-2 synthesis by this organism in dried fish products poses a serious public health risk. In this study, we investigated the effects of iturin A, a cyclic lipopeptide produced by Bacillus subtilis, on the growth and synthesis of the T-2 toxin of F. oxysporum, and transcriptomics was conducted. Results showed that the inhibitory effect of iturin A on F. oxysporum was significantly enhanced with an increase in iturin A concentrations. More specifically, compared with the control group, all indexes in the iturin A treatment group with 50 μg/mL were decreased to 24.84 mm, 0.33 × 106 cfu/mL, and 5.86 ng/mL for the colony diameter, number of spores, and concentration of T-2 toxin, respectively. Furthermore, iturin A was proven to destroy the integrity of cell membranes and cause a significant increase in ROS at 25 μg/mL or 50 μg/mL. Transcriptomic analysis revealed that with the treatment of iturin A, the genes of the oxidation-reduction process were up-regulated, while the gene expression of mycelial growth, cell integrity, transmembrane transport, energy metabolism, and others were down-regulated. More importantly, the Tri5 gene cluster was significantly inhibited. This study provided new insights into the mechanism for the inhibitory effect of iturin A on the growth and T-2 toxin synthesis of F. oxysporum and theoretical guidance for the application of iturin A in the preservation of dried aquatic products.

Diversity, Ecological Characteristics and Identification of Some Problematic Phytopathogenic Fusarium in Soil: A Review

The genus Fusarium includes many pathogenic species causing a wide range of plant diseases that lead to high economic losses. In this review, we describe how the Fusarium taxonomy has changed with the development of microbiological methods. We specify the ecological traits of this genus and the methods of its identification in soils, particularly the detection of phytopathogenic representatives of Fusarium and the mycotoxins produced by them. The negative effects of soil-borne phytopathogenic Fusarium on agricultural plants and current methods for its control are discussed. Due to the high complexity and polymorphism of Fusarium species, integrated approaches for the risk assessment of Fusarium diseases are necessary.

T-2 and HT-2 toxins in harvested oat grains and their prevalence in whole grain flour during storage

Mycotoxin contamination of food is a constant global concern. There has been a scientific debate in Europe on the validation of accredited detection methods for type A trichothecenes T-2 and HT-2 and the restriction on dangerous concentrations. The issue is of great importance as this type of mycotoxin is frequently found in spring cereals grown in Lithuania. The aim of this study was to optimise and validate a method for the determination of T-2/HT-2 toxin concentrations in oats harvested in 2015-2018 and to observe the changes in the concentrations of both toxins in oat flour during 3- and 6-week storage at different temperatures and increased relative air humidity. All of the oat grain samples (100%) collected in 2015-2018 tested positive for contamination with type A trichothecenes. The highest mean co-contamination by T-2 + HT-2 (260.4 ± 140.9 µg/kg) and the highest concentration (594.6 µg/kg) were determined in 2018 when warm and wet weather conditions prevailed during oat flowering. The effect of long-term storage (6 weeks) on T-2 and HT-2 toxin production manifested itself only when the samples had been stored under cooler conditions (8 °C). The most important factors which impacted the variation of the concentrations of type A trichothecenes in flour were ambient temperature and storage time.

Mycotoxins in soil and environment

Mycotoxins are secondary metabolites produced by specific fungi that have harmful effects on animals and humans. Worldwide more than 300 different mycotoxins are already known, frequently with concentrations in harvest products exceeding acceptable limits. Nevertheless, although these compounds have extensively been studied in food and feed, only little is known about their occurrence and fate in soil and agro-environmental matrices, such as manure, sewage sludge, drainage water and sediments. Therefore, the aim of this review was to (i) resume available methods for quantifying mycotoxins in soil, (ii) describe the occurrence and quantities of mycotoxins in soil and related agro-environmental matrices, and (iii) discuss the environmental fate of these target compounds with specific focus on their leaching potential into groundwater. The safest and most reliable method for mycotoxin quantification relies on mass spectrometry, while the extraction method and solvent composition differ depending on the compound under investigation. Mycotoxin levels detected in soils to date were in the μg range, reaching maximum amounts of 72.1 μg kg^-1 for zearalenone, 32.1 μg kg^-1 for deoxynivalenol, 23.7 μg kg^-1 for ochratoxin A, 6.7 μg kg^-1 for nivalenol, and 5.5 μg kg^-1 for aflatoxin. Different compartments in the agroecosystem (cereals, corn, rice, water, manure, sewage sludge) each contained at least one mycotoxin. Mycotoxin retention in soils is controlled by texture, with significant adsorption of the compounds to clays but leaching potentials in sandy soils. We did not find any reports detecting mycotoxins in sediments, although there are increasing reports of mycotoxins in freshwater samples. Overall, it appears that soils and sediments are still underrepresented in research on potential environmental contamination with mycotoxins.

Ecophysiology of Fusarium chaquense a Novel Type A Trichothecene Producer Species Isolated from Natural Grasses

Fusarium chaquense, a recently formally described novel species, has been identified as an T-2 toxin (T-2), HT-2 toxin (HT-2) and other toxins producer in natural grasses (Poaceae) from Argentina. The major objective of this study was to describe the effect of water activity (aW, 0.995, 0.98, 0.95, 0.93 and 0.91), temperature (15, 25 and 30 °C) and incubation time (5, 15 and 25 days) on growth and to evaluate the production of T-2, HT-2 toxins and beauvericin (BEA) by two F. chaquense strains in a grass-based media. The results showed a wide range of conditions for F. chaquense growth and mycotoxin production. Both strains had a maximum growth rate at the highest aW (0.995) and 25 °C. Regarding mycotoxin production, more T-2 than the other analysed mycotoxins were produced by the two strains. T-2 production was favoured at 0.995 aW and 30 °C, while HT-2 production at 0.98-0.95 aW and 15 °C. The maximum levels of BEA were produced at 0.995 aW and 25-30 °C. Two-dimensional profiles of aW by temperature interactions were obtained from these data in order to identify areas where conditions indicate a significant risk of mycotoxins accumulation on grass. For its versatility on growth and mycotoxin production in a wide range of aW and temperatures, F. chaquense would have an adaptive advantage over other Fusarium species, and this would explain its high frequency of isolation in natural grasses grown up in the Chaco wetlands.

T-2 Toxin-The Most Toxic Trichothecene Mycotoxin: Metabolism, Toxicity, and Decontamination Strategies

Among trichothecenes, T-2 toxin is the most toxic fungal secondary metabolite produced by different Fusarium species. Moreover, T-2 is the most common cause of poisoning that results from the consumption of contaminated cereal-based food and feed reported among humans and animals. The food and feed most contaminated with T-2 toxin is made from wheat, barley, rye, oats, and maize. After exposition or ingestion, T-2 is immediately absorbed from the alimentary tract or through the respiratory mucosal membranes and transported to the liver as a primary organ responsible for toxin's metabolism. Depending on the age, way of exposure, and dosage, intoxication manifests by vomiting, feed refusal, stomach necrosis, and skin irritation, which is rarely observed in case of mycotoxins intoxication. In order to eliminate T-2 toxin, various decontamination techniques have been found to mitigate the concentration of T-2 toxin in agricultural commodities. However, it is believed that 100% degradation of this toxin could be not possible. In this review, T-2 toxin toxicity, metabolism, and decontamination strategies are presented and discussed.

Intra-species variability in Fusarium langsethiae strains in growth and T-2/HT-2 mycotoxin production in response to climate change abiotic factors

The objective of this study was to evaluate the potential intra-species variability of 3 Fusarium langsethiae strains in response to extreme climate change (CC) conditions on an oat-based matrix. The impact of elevated temperature (25 vs 30-34 °C) coupled with increasing drought stress (0.98 vs 0.95 aw) and elevated CO2 (400 vs 1000 ppm) were examined on lag phases prior to growth, growth rate, and production of the mycotoxins T-2 and HT-2 and their ratio. In comparison to the control conditions (25 °C; 0.98; 400 ppm), exposure to increased temperature (30-34 °C), showed similar reductions in the lag phase and fungal growth rates of all 3 strains. However, with elevated CO2 a reduction in both lag phases prior to growth and growth rate occurred regardless of the aw examined. For T-2 and HT-2 mycotoxin production, T-2 showed the most intra-species variability in response to the interacting abiotic stress factors, with the 3 strains having different environmental conditions for triggering increases in T-2 production: Strain 1 produced higher T-2 toxin at 25 °C, while Strain 2 and the type strain (Fl201059) produced most at 0.98 aw/30 °C. Only Strain 2 showed a reduction in toxin production when exposed to elevated CO2. HT-2 production was higher at 25 °C for the type strain and higher at 30-34 °C for the other two strains, regardless of the aw or CO2 level examined. The HT-2/T-2 ratio showed no significant differences due to the imposed interacting CC abiotic conditions.

In Vitro Detoxification of Aflatoxin B1, Deoxynivalenol, Fumonisins, T-2 Toxin and Zearalenone by Probiotic Bacteria from Genus Lactobacillus and Saccharomyces cerevisiae Yeast

The aim of the following research was to determine the detoxification properties of probiotic Lactobacillus sp. bacteria (12 strains) and S. cerevisiae yeast (6 strains) towards mycotoxins, such as aflatoxin B₁, deoxynivalenol, fumonisins, T-2 toxin and zearalenone, which pose as frequent feed contamination. The experiment involved analysing changes in concentration of mycotoxins in PBS solutions, after 6, 12 and 24 h of incubation with monocultures of tested microorganisms, measured by high-performance liquid chromatography (HPLC). We found that all strains detoxified the mycotoxins, with the highest reduction in concentration observed for the fumonisin B₁ and B₂ mixture, ranging between 62 and 77% for bacterial strains and 67–74% for yeast. By contrast, deoxynivalenol was the most resistant mycotoxin: its concentration was reduced by 19–39% by Lactobacillus sp. strains and 22–43% by yeast after 24 h of incubation. High detoxification rates for aflatoxin B₁, T-2 toxin and zearalenone were also observed, with concentration reduced on average by 60%, 61% and 57% by Lactobacillus, respectively, and 65%, 69% and 52% by yeast, respectively. The greatest extent of reduction in the concentration for all mycotoxins was observed after 6 h of incubation; however, a decrease in concentration was noted even after 24 h of incubation. Thus, the tested microorganisms can potentially be used as additives to decrease the concentrations of toxins in animal feed.

Water and temperature relations of Fusarium langsethiae strains and modelling of growth and T-2 and HT-2 mycotoxin production on oat-based matrices

In the UK and Northern Europe, ripening oats can become contaminated with T-2 and HT-2 mycotoxins, produced mainly by Fusarium langsethiae. There are indicative levels related to the maximum limits for oat grain for these toxins. The objectives of this study were to examine the effect of interacting conditions of temperature (10-30 °C) and water activity (a_w, 0.995-0.90) on (a) lag times prior to growth, (b) growth and (c) T-2 and HT-2 toxins by two strains of F. langsethiae isolated from oats in the UK and compare this with the type strain (Fl201059) which has been genomically sequenced, and (d) develop (and validated with published data) a probabilistic models for impacts of temperature × a_w on growth and toxin production. All three strains had an optimum a_w range and temperature of 0.995-0.98 and 25 °C for growth. For T-2 + HT-2 production these were 0.995 a_w and 20 °C. Overall, the type strain produced higher amounts of T-2 + HT-2 with a HT-2/T-2 ratio of up to 76. Using this study data sets and those from the literature, probabilistic models were developed and validated for growth and T-2 + HT-2 toxin production in relation to temperature × a_w conditions. These models, when applied in stored oats, will be beneficial in determining the conditions on the relative level of risk of contamination with these two toxins in the context of the EU indicative maximum levels.

Natural Co-Occurrence of Multiple Mycotoxins in Unprocessed Oats Grown in Ireland with Various Production Systems

The natural co-occurrence of 42 mycotoxins was investigated in unprocessed oat grains grown in Ireland. The sample set included a total of 208 oat crops harvested during 2015–2016 and produced using conventional, organic, or gluten free farming systems. A range of different toxins was identified, including the major type A (neosolaniol, HT-2 and T-2 toxins, T-2 triol, and T-2-glucoside, co-occurring in 21 samples) and B trichothecenes (deoxynivalenol, nivalenol, and deoxynivalenol-3-glucoside), enniatins (B1, B, and A1, co-occurring in 12 samples), as well as beauvericin, alternariol, mycophenolic acid, and sterigmatocystin. The influences of sowing season, year, and production system were investigated, eventually indicating that the latter factor may have a higher impact than others on the production of certain mycotoxins in oats. The most frequently quantified compounds were HT-2 (51%) and T-2 (41%) toxins, with gluten free oats containing significantly lower concentrations of HT-2 compared to conventionally produced oats. Although the prevalence and concentrations of mycotoxin found in oat samples in this study should be substantially reduced by processing. However, as mycotoxin occurrence is clearly influenced by multiple factors, controlled field trials should be carried out to define optimal agronomic practices and mitigate mycotoxin production. Furthermore, this work highlights the need for regularly testing cereal-based foods with multi-residue analytical methods with wider specificities than the traditionally screened and regulated toxins, to generate knowledge on the occurrence of several mycotoxins that are, to date, rarely investigated.

A Two-Year Occurrence of Fusarium T-2 and HT-2 Toxin in Croatian Cereals Relative of the Regional Weather

To investigate into the T-2 and HT-2 toxin occurrence, 240 samples of unprocessed cereals (maize, wheat, barley, and oats) were sampled from different fields located in three Croatian regions during 2017-2018. In all samples, sum concentrations of T-2/HT-2 toxin were determined using the ELISA method, while the LC-MS/MS was used as a confirmatory method for both mycotoxins in positive samples (>LOD) and the establishment of T-2 over HT-2 toxin ratios. The results showed oats to be the most contaminated cereal, with T-2/HT-2 toxins detected in 70.0% of samples, followed by barley (40.9%), maize (26.8%) and wheat (19.2%), with the mean T-2/HT-2 ratio ranging from 1:2.7 in maize to 1:4.4 in oats. Sum T-2/HT-2 concentrations in two maize samples were higher than the indicative level recommended by the European Commission, necessitating subsequent investigations into the conditions under which these poorly investigated mycotoxins are produced. Statistically significantly (p < 0.05) higher concentrations of T-2/HT-2 toxin were determined in oats throughout study regions as compared to those found in wheat, but not maize and barley, while the concentrations of these mycotoxins were related to the regional weather in Croatia.

Effect of Selected Cooking Ingredients for Nixtamalization on the Reduction of Fusarium Mycotoxins in Maize and Sorghum

Although previous studies have reported the use of nixtamalization for mycotoxins reduction in maize, the efficacy of calcium hydroxide and other nixtamalization cooking ingredients for mycotoxin reduction/decontamination in sorghum and other cereals still need to be determined. The current study investigated the effect of five nixtamalization cooking ingredients (wood ashes, calcium hydroxide, sodium hydroxide, potassium hydroxide, and calcium chloride) on the reduction of Fusarium mycotoxins in artificially contaminated maize and sorghum using liquid chromatography-tandem mass spectrometry. All tested cooking ingredients effectively reduced levels of mycotoxins in the contaminated samples with reduction initiated immediately after the washing step. Except for the calcium chloride nixtamal, levels of fumonisin B₁, B_2, and B₃ in the processed sorghum nixtamal samples were below the limit of detection. Meanwhile, the lowest pH values were obtained from the maize (4.84; 4.99), as well as sorghum (4.83; 4.81) nejayote and nixtamal samples obtained via calcium chloride treatment. Overall, the results revealed that the tested cooking ingredients were effective in reducing the target mycotoxins. In addition, it pointed out the potential of calcium chloride, though with reduced effectiveness, as a possible greener alternative cooking ingredient (ecological nixtamalization) when there are environmental concerns caused by alkaline nejayote.

Toxigenic Fungi and Mycotoxins in a Climate Change Scenario: Ecology, Genomics, Distribution, Prediction and Prevention of the Risk

Toxigenic fungi and mycotoxins are very common in food crops, with noticeable differences in their host specificity in terms of pathogenicity and toxin contamination. In addition, such crops may be infected with mixtures of mycotoxigenic fungi, resulting in multi-mycotoxin contamination. Climate represents the key factor in driving the fungal community structure and mycotoxin contamination levels pre- and post-harvest. Thus, there is significant interest in understanding the impact of interacting climate change-related abiotic factors (especially increased temperature, elevated CO2 and extremes in water availability) on the relative risks of mycotoxin contamination and impacts on food safety and security. We have thus examined the available information from the last decade on relative risks of mycotoxin contamination under future climate change scenarios and identified the gaps in knowledge. This has included the available scientific information on the ecology, genomics, distribution of toxigenic fungi and intervention strategies for mycotoxin control worldwide. In addition, some suggestions for prediction and prevention of mycotoxin risks are summarized together with future perspectives and research needs for a better understanding of the impacts of climate change scenarios.

Genome-wide association mapping of Fusarium langsethiae infection and mycotoxin accumulation in oat (Avena sativa L.)

Fusarium langsethiae is a symptomless pathogen of oat panicles that produces T-2 and HT-2 mycotoxins, two of the most potent trichothecenes produced by Fusarium fungi in cereals. In the last few years, the levels of these mycotoxin in oat grain has increased and the European commission have already recommended a maximum level for of 1000 μg kg^-1 for unprocessed oat for human consumption. The optimal and most sustainable way of combating infection and mycotoxin contamination is by releasing resistant oat varieties. Here the objective was to determine if we could identify any genomic loci associated with either the accumulation of F. langsethiae DNA or mycotoxins in the grain. In each of two years, field trials were conducted wherein 190 spring oat varieties were inoculated with a mixture of three isolate of the pathogen. Mycotoxins were quantified using liquid chromatography-tandem mass spectrometry. Varieties were genotyped using 16,863 genotyping by sequencing markers. Genome-wide association studies associated 5 SNPs in the linkage group Mr06 with T-2 + HT-2 mycotoxin accumulation. Markers were highly correlated, and a single QTL was identified. The marker avgbs_6K_95238.1 mapped within genes showing similarity to lipase, lipase-like or lipase precursor mRNA sequences and zinc-finger proteins. These regions have previously been shown to confer a significant increase in resistance to Fusarium species.

Influence of Two Garlic-Derived Compounds, Propyl Propane Thiosulfonate (PTS) and Propyl Propane Thiosulfinate (PTSO), on Growth and Mycotoxin Production by Fusarium Species In Vitro and in Stored Cereals

Two garlic-derived compounds, Propyl Propane Thiosulfonate (PTS) and Propyl Propane Thiosulfinate (PTSO), were examined for their efficacy against mycotoxigenic Fusarium species (F. graminearum, F. langsethiae, F. verticillioides). The objectives were to assess the inhibitory effect of these compounds on growth and mycotoxin production in vitro, and in situ in artificially inoculated wheat, oats and maize with one isolate of each respectively, at different water activity (a_w) conditions when stored for up to 20 days at 25 °C. In vitro, 200 ppm of either PTS or PTSO reduced fungal growth by 50-100% and mycotoxin production by >90% depending on species, mycotoxin and a_w conditions on milled wheat, oats and maize respectively. PTS was generally more effective than PTSO. Deoxynivalenol (DON) and zearalenone (ZEN) were decreased by 50% with 80 ppm PTSO. One-hundred ppm of PTS reduced DON and ZEN production in wheat stored at 0.93 a_w for 20 days, although contamination was still above the legislative limits. Contrasting effects on T-2/HT-2 toxin contamination of oats was found depending on a_w, with PTS stimulating production under marginal conditions (0.93 a_w), but at 0.95 a_w effective control was achieved with 100 ppm. Treatment of stored maize inoculated with F. verticilliodies resulted in a stimulation of total fumonsins in most treatments. The potential use of such compounds for mycotoxin control in stored commodities is discussed.

Analysis of Toxigenic Fusarium Species Associated with Wheat Grain from Three Regions of Russia: Volga, Ural, and West Siberia

Wheat grains collected in three regions of Russia—Volga, Ural, and West Siberia—were analyzed for triangulation of methods in analysis of toxigenic Fusarium species. The presence of fungi and quantitative content of their biomass were detected by using various analytical methods, including a mycological and immunochemical methods, and quantitative PCR. Additionally, an enzyme-linked immunosorbent assay and high-performance liquid chromatography with tandem mass spectrometry were applied for determination of mycotoxins. Regional differences were found regarding the contamination of wheat grain by Fusarium fungi and their toxins. The most important observation was the detection of F. graminearum in the Ural and West Siberian regions, where this pathogen had not been found previously. A maximum damaged grains by F. graminearum and F. sporotrichioides was found in the grain samples from West Siberia. The DNA of F. graminearum was detected in 19.2% and DNA of F. sporotrichioides was found in 84.1% of the analyzed grain samples. The amount of Fusarium antigens in the grain samples from the West Siberian region was 7–8 times higher than in the grain samples from the other two regions. Significant contamination of the grain with deoxynivalenol and T-2/HT-2 toxins (maximum contents were 2239 ppb and 199 ppb, respectively) was detected in the West Siberian region.

Modified Fusarium Mycotoxins in Cereals and Their Products-Metabolism, Occurrence, and Toxicity: An Updated Review

Mycotoxins are secondary fungal metabolites, toxic to humans, animals and plants. Under the influence of various factors, mycotoxins may undergo modifications of their chemical structure. One of the methods of mycotoxin modification is a transformation occurring in plant cells or under the influence of fungal enzymes. This paper reviews the current knowledge on the natural occurrence of the most important trichothecenes and zearalenone in cereals/cereal products, their metabolism, and the potential toxicity of the metabolites. Only very limited data are available for the majority of the identified mycotoxins. Most studies concern biologically modified trichothecenes, mainly deoxynivalenol-3-glucoside, which is less toxic than its parent compound (deoxynivalenol). It is resistant to the digestion processes within the gastrointestinal tract and is not absorbed by the intestinal epithelium; however, it may be hydrolysed to free deoxynivalenol or deepoxy-deoxynivalenol by the intestinal microflora. Only one zearalenone derivative, zearalenone-14-glucoside, has been extensively studied. It appears to be more reactive than deoxynivalenol-3-glucoside. It may be readily hydrolysed to free zearalenone, and the carbonyl group in its molecule may be easily reduced to α/β-zearalenol and/or other unspecified metabolites. Other derivatives of deoxynivalenol and zearalenone are poorly characterised. Moreover, other derivatives such as glycosides of T-2 and HT-2 toxins have only recently been investigated; thus, the data related to their toxicological profile and occurrence are sporadic. The topics described in this study are crucial to ensure food and feed safety, which will be assisted by the provision of widespread access to such studies and obtained results.

Identification and Characterization of Spontaneous Auxotrophic Mutants in Fusarium langsethiae

Analysis of 49 strains of Fusarium langsethiae originating from northern Europe (Russia, Finland, Sweden, UK, Norway, and Latvia) revealed the presence of spontaneous auxotrophic mutants that reflect natural intraspecific diversity. Our investigations detected that 49.0% of F. langsethiae strains were auxotrophic mutants for biotin, and 8.2% of the strains required thiamine as a growth factor. They failed to grow on vitamin-free media. For both prototrophic and auxotrophic strains, no growth defect was observed in rich organic media. Without essential vitamins, a significant reduction in the growth of the auxotrophic strains results in a decrease of the formation of T-2 toxin and diacetoxyscirpenol. In addition, all analysed F. langsethiae strains were distinguished into two subgroups based on PCR product sizes. According to our results, 26 and 23 strains of F. langsethiae belong to subgroups I and II respectively. We determined that the deletion in the intergenic spacer (IGS) region of the rDNA of F. langsethiae belonging to subgroup II is linked with temperature sensitivity and causes a decrease in strain growth at 30 °C. Four thiamine auxotrophic strains were found in subgroup I, while 21 biotin auxotrophic strains were detected in subgroups II. To the best of our knowledge, the spontaneous mutations in F. langsethiae observed in the present work have not been previously reported.

Mycotoxigenic Potentials of Fusarium Species in Various Culture Matrices Revealed by Mycotoxin Profiling

In this study, twenty of the most common Fusarium species were molecularly characterized and inoculated on potato dextrose agar (PDA), rice and maize medium, where thirty three targeted mycotoxins, which might be the secondary metabolites of the identified fungal species, were detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Statistical analysis was performed with principal component analysis (PCA) to characterize the mycotoxin profiles for the twenty fungi, suggesting that these fungi species could be discriminated and divided into three groups as follows. Group I, the fusaric acid producers, were defined into two subgroups, namely subgroup I as producers of fusaric acid and fumonisins, comprising of F. proliferatum, F. verticillioides, F. fujikuroi and F. solani, and subgroup II considered to only produce fusaric acid, including F. temperatum, F. subglutinans, F. musae, F. tricinctum, F. oxysporum, F. equiseti, F. sacchari, F. concentricum, F. andiyazi. Group II, as type A trichothecenes producers, included F. langsethiae, F. sporotrichioides, F. polyphialidicum, while Group III were found to mainly produce type B trichothecenes, comprising of F. culmorum, F. poae, F. meridionale and F. graminearum. A comprehensive picture, which presents the mycotoxin-producing patterns by the selected fungal species in various matrices, is obtained for the first time, and thus from an application point of view, provides key information to explore mycotoxigenic potentials of Fusarium species and forecast the Fusarium infestation/mycotoxins contamination.

Integrating gene expression, ecology and mycotoxin production by Fusarium and Aspergillus species in relation to interacting environmental factors

Environmental factors, such as water availability (water activity, aw), temperature and their interactions, have a significant impact on the life cycle of mycotoxigenic fungi. Growth and mycotoxin production are influenced by these interacting factors resulting in a broader range of aw × temperature conditions for germination, than growth or mycotoxin production. The biosynthetic genes are mostly clustered together and by using microarrays with sub-arrays for specific mycotoxins, such as trichothecenes, fumonisins and aflatoxins it has been possible to examine the relationship between interacting aw × temperature conditions on growth, toxin gene cluster expression and relate these to phenotypic toxin production. The data for groups of biosynthetic genes (Fusarium culmorum/Fusarium graminearum; Fusarium verticillioides; Aspergillus flavus) were integrated with data on growth and mycotoxin production under different aw × temperature conditions using a mixed growth model. This was used to correlate these factors and predict toxin levels which may be produced under different abiotic stress conditions. Indeed, the relative importance of the different genes could be examined using ternary diagrams of the relative expression of 3 genes at a time in relation to aw, temperature and mycotoxin production to identify the most important relationships. The effect of three-way interacting environmental factors representative of climate change (CC) scenarios (water stress × temperature (+2-4 °C) × elevated CO2 (350-400 vs 650 and 1000 ppm) on growth and mycotoxin production by A. flavus and by species of the Aspergillus section Circumdati and section Nigri have been determined. These studies on maize grain and coffee, respectively, suggest that while growth may not be significantly affected, mycotoxin production may be stimulated by CC factors. This approach to integrate such data sets and model the relationships could be a powerful tool for predicting the relative toxin production under extreme stress conditions, including CC scenarios.

Inhibition of Fusarium Growth and Mycotoxin Production in Culture Medium and in Maize Kernels by Natural Phenolic Acids

The possible role of natural phenolic compounds in inhibiting fungal growth and toxin production has been of recent interest as an alternative strategy to the use of chemical fungicides for the maintenance of food safety. Fusarium is a worldwide fungal genus mainly associated with cereal crops. The most important Fusarium mycotoxins are trichothecenes, zearalenone, and fumonisins. This study was conducted to evaluate the potential of four natural phenolic acids (caffeic, ferulic, p-coumaric, and chlorogenic) for the control of mycelial growth and mycotoxin production by six toxigenic species of Fusarium . The addition of phenolic acids to corn meal agar had a marked inhibitory effect on the radial growth of all Fusarium species at levels of 2.5 to 10 mM in a dose-response pattern, causing total inhibition (100%) in all species except F. sporotrichioides and F. langsethiae . However, the effects of phenolic acids on mycotoxin production in maize kernels were less evident than the effects on growth. The fungal species differed in their responses to the phenolic acid treatments, and significant reductions in toxin concentrations were observed only for T-2 and HT-2 (90% reduction) and zearalenone (48 to 77% reduction). These results provide data that could be used for developing pre- and postharvest strategies for controlling Fusarium infection and subsequent toxin production in cereal grains.

Effect of temperature and water activity on growth and aflatoxin production by Aspergillus flavus and Aspergillus parasiticus on cured meat model systems

Dry-cured hams may be colonised by aflatoxin-producing Aspergillus flavus and Aspergillus parasiticus during the ripening process. The objective of this study was to evaluate the interaction between non-ionic water stress and temperatures may have on lag phases prior to growth, growth rates and aflatoxin production by two strains of each A. parasiticus and A. flavus on meat matrices over a period of 12days. Results showed that A. flavus CBS 573.65 had shorter lag phases than A. parasiticus CECT 2688, however the growth rates were quite similar. For both species, no growth occurred at 10°C and all aw tested and optimum growth happened at 25°C and 0.95 aw. Similar aflatoxin B1 production profiles between both species were found, however A. flavus produced much higher concentration of such toxin than A. parasiticus. Both species produced aflatoxins when the temperature and the aw were ≥15°C and ≥0.90.

Effects of Phenolic Acids on the Growth and Production of T-2 and HT-2 Toxins by Fusarium langsethiae and F. sporotrichioides

The effect of natural phenolic acids was tested on the growth and production of T-2 and HT-2 toxins by Fusarium langsethiae and F. sporotrichioides, on Mycotoxin Synthetic medium. Plates treated with 0.5 mM of each phenolic acid (caffeic, chlorogenic, ferulic and p-coumaric) and controls without phenolic acid were incubated for 14 days at 25 °C. Fungal biomass of F. langsethiae and F. sporotrichioides was not reduced by the phenolic acids. However, biosynthesis of T-2 toxin by F. langsethiae was significantly reduced by chlorogenic (23.1%) and ferulic (26.5%) acids. Production of T-2 by F. sporotrichioides also decreased with ferulic acid by 23% (p < 0.05). In contrast, p-coumaric acid significantly stimulated the production of T-2 and HT-2 toxins for both strains. A kinetic study of F. langsethiae with 1 mM ferulic acid showed a significant decrease in fungal biomass, whereas T-2 production increased after 10 days of incubation. The study of gene expression in ferulic supplemented cultures of F. langsethiae revealed a significant inhibition for Tri5, Tri6 and Tri12 genes, while for Tri16 the decrease in gene expression was not statistically significant. Overall, results indicated that phenolic acids had a variable effect on fungal growth and mycotoxin production, depending on the strain and the concentration and type of phenolic acid assayed.

A non-linear model for temperature-dependent sporulation and T-2 and HT-2 production of Fusarium langsethiae and Fusarium sporotrichioides

This research has produced new quantitative data on the sporulation and T-2+HT-2 toxin production that could be further integrated to develop a comprehensive disease or toxin prediction model for Fusarium langsethiae and Fusarium sporotrichioides. Experiments were conducted to determine the effect of temperature or incubation time on sporulation and the effect of temperature on T-2+HT-2 toxin production of strains of the two species. F. sporotrichioides demonstrated a preference for higher temperatures than F. langsethiae during sporulation; the optimum temperature was 24.5 ± 0.7 °C for F. langsethiae and 32.3 ± 2.1 °C for F. sporotrichioides, according to the Beta equation fitted to the data. The dynamics of sporulation over different incubation times were fitted by a Gompertz function. The maximum spore production was estimated to be after 18 and 8 d incubation at optimum temperatures for F. langsethiae and F. sporotrichioides, respectively. F. sporotrichioides produced more T-2+HT-2 than F. langsethiae. The best fit of the effect of temperature on T-2+HT-2 production in wheat grains was obtained with a Beta equation showing an optimum temperature of 14.7 ± 0.8 °C for F. langsethiae and 12.1 ± 0.2 °C for F. sporotrichioides. The optimum temperature for mycotoxin production was lower than for sporulation.

Climate change factors and Aspergillus flavus: effects on gene expression, growth and aflatoxin production

The objectives of this study were to obtain scientific data on the impact that interactions between water stress (water activity (aw); 0.97, 0.95, 0.92), temperature (34, 37 °C) and CO2 exposure (350, 650, 1000 ppm) may have on the growth, gene expression of biosynthetic genes (aflD, aflR), and phenotypic aflatoxin B1 (AFB1) production by a type strain of Aspergillus flavus on a conducive medium. The study showed that while aw affected growth there was no statistically significant effect of temperature or CO2 exposure. The effect of these interacting factors on aflD and aflR gene expression showed that at 34 °C there was maximum relative expression of aflD under the control conditions (34 °C, 350 ppm) with a decrease in expression with elevated CO2 and water stress. For aflR expression at 34 °C, there was a significant increase in expression, but only at 0.92 aw and 650 ppm CO2. However, at 37 °C, there was a significant increase in expression of both aflD and aflR at 0.95 and 0.92 aw and 650 and 1000 ppm CO2. There was an associated increase in AFB1 in these treatments. In contrast, at 34 °C there were no significant differences for interacting treatments. This is the first study to examine these three-way interacting climatic factors on growth and mycotoxin production by a strain of A. flavus. This provides data that are necessary to help predict the real impacts of climate change on mycotoxigenic fungi.

Natural occurrence, analysis, and prevention of mycotoxins in fruits and their processed products

Mycotoxins are small toxic chemical products formed as the secondary metabolites by fungi that readily contaminate foods with toxins in the field or after harvest. The presence of mycotoxins, such as aflatoxins, ochratoxin A, and patulin, in fruits and their processed products is of high concern for human health due to their properties to induce severe acute and chronic toxicity at low-dose levels. Currently, a broad range of detection techniques used for practical analysis and detection of a wide spectrum of mycotoxins are available. Many analytical methods have been developed for the determination of each group of these mycotoxins in different food matrices, but new methods are still required to achieve higher sensitivity and address other challenges that are posed by these mycotoxins. Effective technologies are needed to reduce or even eliminate the presence of the mycotoxins in fruits and their processed products. Preventive measures aimed at the inhibition of mycotoxin formation in fruits and their processed products are the most effective approach. Detoxification of mycotoxins by different physical, chemical, and biological methods are less effective and sometimes restricted because of concerns of safety, possible losses in nutritional quality of the treated commodities and cost implications. This article reviewed the available information on the major mycotoxins found in foods and feeds, with an emphasis of fruits and their processed products, and the analytical methods used for their determination. Based on the current knowledge, the major strategies to prevent or even eliminate the presence of the mycotoxins in fruits and their processed products were proposed.

Comparative effects of fungicides and environmental factors on growth and T-2 + HT-2 toxin production by Fusarium sporotrichioides and Fusarium langsethiae strains on an oat-based matrix

The objective of this study was to compare the effect of the fungicides prochloraz and tebuconazole (0-1 µg/ml) on lag phase, growth rate, and T-2 + HT-2 toxin production by strains of Fusarium sporotrichioides and Fusarium langsethiae on oat-based media under different conditions of water activity (aw; 0.98 and 0.95) × temperature (15 and 25 °C). Relative effective dose values for the fungicides required to inhibit growth by 50% (ED50) and 90% (ED90) and T-2 + HT-2 production were determined. The lag phases prior to growth were prolonged at the marginal aw × temperature conditions tested and by the presence of the fungicides. The growth rates of F. sporotrichioides and F. langsethiae were similarly inhibited by prochloraz compared with the controls. However, in the presence of tebuconazole, F. langsethiae was much more tolerant with very little inhibitory effects of the fungicide. The ED50 values ranged from 0.08 to ≯1.0 µg/ml for prochloraz and from 0.34 to ≯1.0 µg/ml for tebuconazole in the case of F. sporotrichioides. For F. langsethiae, these values were 0.09 to ≯1.0 and 0.31 to ≯1.0 µg/ml at the two temperatures and aw levels tested. Prochloraz (0.2-0.4 µg/ml) effectively inhibited toxin production at 15 °C and the two aw levels examined. However, at 25 °C the fungicide was less effective, regardless of the aw level. For tebuconazole, there were significant differences in efficacy against the F. sporotrichioides and F. langsethiae strains. The latter species produced consistently higher amounts of T-2 + HT-2 toxin at both 15 and 25 °C and 0.98 aw. The differential tolerance to the fungicides between the fungal species is discussed in terms of growth and toxin production.

Kinetics of mould growth in the stored barley ecosystem contaminated with Aspergillus westerdijkiae, Penicillium viridicatum and Fusarium poae at 23-30 °C

BACKGROUND

Owing to the lack of a rapid method for determining fungi on cereals, the best way to enhance the safety and nutritive value of stored grain is to develop prognostic tools based on the relationship between easily measurable online parameters, e.g. water activity (a(w)) and temperature (t) of grain, and fungal growth. This study examined the effect of unfavourable temperature (23 and 30 °C) and humidity (0.80-0.94 a(w)) storage conditions on mould growth in the stored barley ecosystem with its adverse microbiological state provided by contamination with Aspergillus westerdijkiae, Penicillium viridicatum and Fusarium poae.

RESULTS

Among the applied storage parameters, a(w) turned out to be the main factor affecting mould development. The longest lag phase and period of fungal activation were observed for grain with 0.80 a(w), which was not threatened with fungal development for at least 30 days. However, in grain with 0.92 and 0.94 a(w), fungal activation occurred within 24-48 h.

CONCLUSION

The obtained data and the identification of critical points in mould growth may be used to develop a control system for the postharvest preservation of barley based on a(w) and temperature of grain, which are easy to measure in practice.

Comparative study of water and temperature relations of growth and T-2/HT-2 toxin production by strains of Fusarium sporotrichioides and Fusarium langsethiae

This study has compared the effect of water activity (aw, 0.995-0.93) and two temperatures (15, 25 °C) on the growth and HT-2 and T-2 toxin production by three strains of Fusarium sporotrichioides and Fusarium langsethiae in an oat-based medium. There were very little intra-strain differences for each of the species in relation to growth at 0.995-0.93 aw and 15 and 25 °C. Inter-species comparisons showed that at 0.995 and 0.98 aw growth was similar at both temperatures. However, under water stress at 0.95 and 0.93 awF. sporotrichioides strains were more tolerant than those of F. langsethiae. Statistical analyses showed that aw and temperature were significant factors for both species, while strain differences were not (P=0.05). In contrast, the patterns of production of T-2 and HT-2 toxins were very different from that for growth. For F. sporotrichioides, a generally higher amount of toxin was produced at 15 than at 25 °C, with a maximum produced at 0.995 aw, while the production decreased with water stress. Interestingly, maximum production of T-2+HT-2 toxin was achieved by F. langsethiae at 0.98 aw and 25 °C, with very little produced at 0.93 aw. Statistically, aw was the most significant (P=0.05) factor for the mean of the three strains of both species with a significant inter-species difference in terms of toxin production. This was confirmed by the changes in the ratio of HT-2:T-2 toxin in relation to the aw × temperature conditions studied. These results are discussed in the context of the effect of environment on the relative importance of these two species in contaminating oats with these toxins.

Influence of agronomic and climatic factors on Fusarium infestation and mycotoxin contamination of cereals in Norway

A total of 602 samples of organically and conventionally grown barley, oats and wheat was collected at grain harvest during 2002-2004 in Norway. Organic and conventional samples were comparable pairs regarding cereal species, growing site and harvest time, and were analysed for Fusarium mould and mycotoxins. Agronomic and climatic factors explained 10-30% of the variation in Fusarium species and mycotoxins. Significantly lower Fusarium infestation and concentrations of important mycotoxins were found in the organic cereals. The mycotoxins deoxynivalenol (DON) and HT-2 toxin (HT-2) constitute the main risk for human and animal health in Norwegian cereals. The impacts of various agronomic and climatic factors on DON and HT-2 as well as on their main producers F. graminearum and F. langsethiae and on total Fusarium were tested by multivariate statistics. Crop rotation with non-cereals was found to reduce all investigated characteristics significantly--mycotoxin concentrations as well as various Fusarium infestations. No use of mineral fertilisers and herbicides was also found to decrease F. graminearum, whereas lodged fields increased the occurrence of this species. No use of herbicides was also found to decrease F. langsethiae, but for this species the occurrence was lower in lodged fields. Total Fusarium infestation was decreased with no use of fungicides or mineral fertilisers, and with crop rotation, as well as by using herbicides and increased by lodged fields. Clay and to some extent silty soils seemed to reduce F. graminearum in comparison with sandy soils. Concerning climate factors, low temperature before grain harvest was found to increase DON; and high air humidity before harvest to increase HT-2. F. graminearum was negatively correlated with precipitation in July but correlated with air humidity before harvest. F. langsethiae was correlated with temperature in July. Total Fusarium increased with increasing precipitation in July. Organic cereal farmers have fewer cereal intense rotations than conventional farmers. Further, organic farmers do not apply mineral fertiliser or pesticides (fungicides, herbicides or insecticides), and have less problem with lodged fields. The study showed that these agronomic factors were related to the infestation of Fusarium species and the concentration of mycotoxins. Hence, it is reasonable to conclude that farming system (organic versus conventional) impacts Fusarium infestation, and that organic management tends to reduce Fusarium and mycotoxins. However, Fusarium infestation and mycotoxin concentrations may be influenced by a range of factors not studied here, such as local topography and more local climate, as well as cereal species and variety.

Mycotoxin production of Fusarium langsethiae and Fusarium sporotrichioides on cereal-based substrates

The present study investigated and compared the mycotoxin production of two Fusarium species, F. sporotrichioides and F. langsethiae, isolated from grain samples. Fusarium strains were cultivated at 25°C for 7 days on two types of solid media, i.e. rice-flour and cereal-flour agar. Toxins produced were measured after the incubation period with a multi-mycotoxin method based on liquid chromatography-tandem mass spectrometry (LC-MS/MS). Both F. sporotrichioides and F. langsethiae synthesised type-A trichothecenes, i.e. T-2 and HT-2 toxins, diacetoxyscirpenol (DAS) and neosolaniol (NEO). In addition, both species could be verified as beauvericin producers. The toxin production occurred in both cereal-based assays but was more predominant on the carbohydrate-rich rice-flour medium. The two species were potent producers of T-2 toxin, the highest amounts measured being at a level of 20,000 μg/kg after 7 days' incubation. Differences between the species were observed regarding the quantitative production of the other trichothecenes: F. sporotrichioides was a more prolific producer of HT-2 toxin and beauvericin, whereas F. langsethiae produced higher amounts of DAS and NEO. On rice-flour assay, the toxin production was monitored during the growth period. The production started rapidly at an early growth phase and several toxins could be detected already after the 1st day of incubation, the highest concentrations being at mg/kg level. The results also indicated that the biosynthesis by F. sporotrichioides and F. langsethiae shifted towards the other type-A trichothecenes at the expense of T-2 toxin at the end of the cultivation.