Fusarium mycotoxin content of UK organic and conventional oats

Every year between 2002 and 2005 approximately 100 samples of oats from fields of known agronomy were analysed by GC/MS for 10 trichothecenes: deoxynivalenol (DON), nivalenol, 3-acetylDON, 15-acetylDON, fusarenone X, T-2 toxin (T2), HT-2 toxin (HT2), diacetoxyscirpenol, neosolaniol and T-2 triol. Samples were also analysed for moniliformin and zearalenone by HPLC. Of the 10 trichothecenes analysed from 458 harvest samples of oat only three, 15-acetylDON, fusarenone X and diacetoxyscirpenol, were not detected. Moniliformin and zearalenone were absent or rarely detected, respectively. HT2 and T2 were the most frequently detected fusarium mycotoxins, present above the limit of quantification (10 µg kg^?1) in 92 and 84% of samples, respectively, and were usually present at the highest concentrations. The combined mean and median for HT2 and T2 (HT2 + T2) was 570 and 213 µg kg^?1, respectively. There were good correlations between concentrations of HT2 and all other type A trichothecenes detected (T2, T2 triol and neosolaniol). Year and region had a significant effect on HT2 + T2 concentration. There was also a highly significant difference between HT2 + T2 content in organic and conventional samples, with the predicted mean for organic samples five times lower than that of conventional samples. This is the largest difference reported for any mycotoxin level in organic and conventional cereals. No samples exceeded the legal limits for DON or zearalenone in oats intended for human consumption. Legislative limits for HT2 and T2 are currently under consideration by the European Commission. Depending on the limits set for unprocessed oats intended for human consumption, the levels detected here could have serious consequences for the UK oat-processing industry.     

Fusarium mycotoxin content of UK organic and conventional barley

Each year (2002–2005), approximately 100 samples of barley from fields of known agronomy were analysed for ten trichothecenes by gas chromatography-mass spectrometry (GC/MS) including deoxynivalenol (DON), nivalenol, 3-acetyl DON, 15-acetyl DON, fusarenone X, T-2 toxin (T2), HT-2 toxin (HT2), diacetoxyscirpenol, neosolaniol, and T-2 triol. Samples were also analysed for moniliformin and zearalenone by high-performance liquid chromatography (HPLC). Of the ten trichothecenes analysed from 446 harvest samples of barley, only two, diacetoxyscirpenol and neosolaniol, were not detected. The concentrations of type A trichothecenes were similar to those that occurred in wheat over the same period, whilst those of type B trichothecenes were markedly lower. Deoxynivalenol was the most frequently detected Fusarium mycotoxin, present above the limit of quantification (10 µg kg^?1) in 57% of samples, and was usually present at the highest concentration. A single sample (0.2%) exceeded the legal limit for DON in unprocessed barley over the 4-year period. Moniliformin and zearalenone were both rarely detected (2% of samples greater than 10 µg kg^?1 for both toxins) with maximum concentrations of 45 and 44 µg kg^?1, respectively. Year and region had a significant effect on DON and HT2 + T2, but there was no significant difference in the concentration of these mycotoxins between organic and conventional samples. Overall, the risk of UK barley exceeding the newly introduced legal limits for Fusarium mycotoxins in cereals intended for human consumption is very low, but the percentage of samples above these limits will fluctuate between years.     

Distribution of toxigenic Fusarium spp. and mycotoxin production in milling fractions of durum wheat

A reliable and sensitive PCR assay to specifically detect trichothecene-producing Fusarium spp. in milling fractions and kernel tissue of naturally infected durum wheat is reported. Assays were based on a combination of primers derived from the trichodiene synthase and the β-tubulin genes. The occurrence of toxigenic Fusarium spp. in semolina and wheat tissue (grain ends, crease, pericarp, aleurone layer, germ and albumen) was detected, even for a weakly contaminated wheat sample. Penetration of toxigenic Fusarium spp. into the interior of durum wheat kernel was demonstrated for the Nefer variety, indicating that none of the tissue structures within the wheat kernel acted as an effective barrier to fungal invasion. Moreover, after inoculation by toxigenic Fusarium strains, semolina was shown to allow high yields of trichothecenes, while bran was demonstrated to contain biochemical inhibitors able to significantly reduce trichothecene production. These results will be useful in improving breeding strategies to control trichothecene contamination of durum wheat kernels.     

Solid substrate bioassay to evaluate impact of Trichoderma on trichothecene mycotoxin production by Fusarium species

BACKGROUND: Fusarium head blight of wheat is a destructive disease in various wheat‐growing regions and leads to significant yield losses for farmers and to contamination of cereal grains with mycotoxins, mainly deoxynivalenol and its derivatives. Toxigenic Fusarium species sporulate on cereal crop residues and produce significant inoculum for epidemics. Reduction of mycotoxin production and pathogen sporulation may be influenced by saprophytic fungal antagonists. RESULTS: Trichoderma isolates were examined in dual culture bioassays on rice with two isolates of Fusarium graminearum Schwabe and two isolates of Fusarium culmorum (W.G. Smith) Saccardo, belonging to three different chemotypes. Production of five trichothecene mycotoxins, deoxynivalenol (DON), 3‐acetyl‐deoxynivalenol (3AcDON), 15‐acetyl‐deoxynivalenol (15AcDON), nivalenol (NIV) and fusarenone X (FUS), was reduced by over 95%. Two Trichoderma isolates partially reduced the amounts of four metabolites when inoculated on autoclaved cultures of the same four Fusarium isolates. However, in the case of the 15AcDON chemotype of F. culmorum culture the content of DON increased and that of 15AcDON decreased. Isolates of Trichoderma varied in their ability to inhibit production of the five trichothecene mycotoxins by Fusarium. Susceptibility of the four Fusarium isolates to antagonistic activity of the same Trichoderma isolate differed significantly. CONCLUSION: Selected non‐toxigenic Trichoderma isolates proved to be useful biocontrol agents against toxigenic Fusarium pathogens of wheat, significantly reducing production of the trichothecene mycotoxins DON, NIV and their acetylated derivatives. Copyright © 2007 Society of Chemical Industry     

Occurrence and fate of Fusarium mycotoxins during commercial processing of oats in the UK

The commercial processing of oats is different from that of other cereals, such as wheat and maize. In northwest Europe, oats also appear to be more susceptible to contamination with HT-2 and T-2 toxins than other cereals. Mycotoxins, such as deoxynivanol and zearalenone, in cereals are already controlled by EU legislation. With regard to additional, impending legislation, this study examined HT-2 and T-2 toxins together with zearalenone, deoxynivalenol and other related toxins in a commercial oat mill and how the concentrations varied from raw oats to the final prepared oat flakes. Concentrations of each Fusarium mycotoxin fell by 90-95% during the process, with the major loss being a physical distribution occurring at the de-hulling stage. Initial studies of losses occurring at other stages, such as kilning or de-branning of prepared oat groats, suggest these to be small. The use of colour sorting after kilning showed higher concentrations of each mycotoxin in the discoloured groats. The feasibility of developing a predictive tool for the oat industry is examined.     

Impact of agronomic and climatic factors on the mycotoxin content of harvested oats in the United Kingdom

ABSTRACT

A survey was conducted to determine the concentration of Fusarium mycotoxins in UK oats over three seasons (2006–8). One hundred oat samples were collected each year at harvest, together with agronomic details, and analysed for 10 Fusarium mycotoxins. The incidence and concentration of most Fusarium mycotoxins, including deoxynivalenol and zearalenone, were relatively low in oats compared with values previously reported for wheat. HT-2 toxin (HT2) and T-2 toxin (T2) levels were relatively high with an overall combined (HT2+T2) mean of 450 μg kg^?1 for 2006–8. Data were combined with a previous dataset collected from 2002–5 to determine the effects of agronomic practices and climate. There was a negative relationship with late summer rainfall, indicating that drier conditions in July and August resulted in increased HT2 and T2 in UK oats. Agronomic factors that impacted upon HT2 and T2 in harvested oats were previous crop, cultivation, and variety. Analysis of the previous cropping history showed there was a stepwise increase in HT2+T2 as the cereal intensity of the rotation increased. Variety was an important factor, with higher levels and a wider range detected on winter versus spring varieties. Indicative levels for HT2 and T2 in cereals and cereal products were introduced by the EC in 2013. The indicative level for unprocessed oats for human consumption is a combined concentration (HT2+T2) of 1000 μg kg^?1. From 2002 to 2008, between 1% and 30% of samples exceeded 1000 μg kg^?1 HT2+T2 each year (overall mean, 16%). The introduction of European legislation on HT2 and T2 mycotoxins could have serious implications for UK oat production and oat-processing industries based on the levels detected within these studies.     

Fusarium mycotoxins in milling streams from the commercial milling of maize imported to the UK,and relevance to current legislation

A study in three large commercial UK maize mills showed that Fusarium mycotoxins, such as deoxynivalenol, zearalenone and fumonisins present at mill intake, are distributed in milling streams approximately according to their occurrence in the maize seed structure. Fractions derived from the endosperm tended to contain the lowest levels of mycotoxins. Concentrations of mycotoxins within the endosperm are also related to the particle size. However, the products derived from the embryo or outer seed layers contained the highest mycotoxin levels being concentrated up to five times or more, although these components are normally used for animal feed or industrial use. The general pattern of mycotoxin distribution found when milling French and Argentinean maize was similar, although very variable, and it is concluded that this variability stems from different milling strategies used at each mill and from the nature and condition of each consignment of maize. Mycotoxins in maize grits (particle sizes >500 µm) were usually reduced by the greatest amount when compared with the whole maize, while flour (≤500 µm) could be both reduced or increased depending on the mill and consignment. Thus, in most situations mycotoxin concentrations in whole maize that meet European Commission legislation on intake should give rise to levels in milled ingredients that should also do so. However, this was not always true in some ingredients, especially for fumonisins in those fractions with particle size ≤500 µm.     

Assessment of trichothecene chemotypes of Fusarium culmorum occurring in Europe

Fusarium trichothecenes are a group of fungal toxic metabolites whose synthesis requires the action of gene products from three different genetic loci. We evaluated, both chemically and by PCR assays, 55 isolates of Fusarium culmorum from eight European countries and different host plants for their ability to produce trichothecenes. Specific sequences in the Tri6-Tri5 intergenic region were associated with deoxynivalenol production. Sequences in the Tri3 gene were also associated with deoxynivalenol production and specific primer sets were selected from these sequences to identify 3-acetyl-deoxynivalenol or 15-acetyl-deoxynivalenol chemotypes. Specific sequences in the Tri5 and Tri7 genes were associated with the nivalenol chemotype but not with the deoxynivalenol chemotype. Two chemotypes were identified by chemical analysis and confirmed by PCR. Strains of the nivalenol chemotype produced nivalenol (up to 260 µg g^-1) and 4-acetyl-nivalenol (up to 60 µg g^-1), strains with the 3-acetyl-deoxynivalenol chemotype produced deoxynivalenol (up to 1700 µg g^-1) and 3-acetyl-deoxynivalenol (up to 600 µg g^-1). Three strains of F. culmorum from France, previously reported as 15-acetyl-deoxynivalenol producers, had the 3-acetyl-deoxynivalenol chemotype. The results are consistent with data from other European countries on the occurrence of the nivalenol and 3-acetyl-deoxynivalenol chemotypes and provide support for the hypothesis that European isolates of F. culmorum producing deoxynivalenol belong only to the 3-acetyl-deoxynivalenol chemotype. The production of trichothecenes from F. culmorum isolates from walnut (3-acetyl-deoxynivalenol chemotype) and leek (nivalenol chemotype) is reported for the first time.     

Fusarium head blight and associated mycotoxin occurrence on winter wheat in Luxembourg in 2007/2008

Fusarium head blight (FHB) is among the major causes of reduced quality in winter wheat and its products. In addition, the causal fungi produce a variety of toxins. A relatively high FHB infection rate in winter wheat was observed in 2007 and 2008 in Luxembourg. A fusariotoxin survey was carried out in 17 different geographical locations. Three groups of Fusarium mycotoxins (trichothecenes A and B and zearalenone) were analysed by a multi-detection HPLC–MS/MS method. Fusarium strains were also investigated by morphological and molecular methods. In addition, questionnaires relating to cultural practices were sent to the farmers managing the 17 fields investigated. FHB prevalence ranged from 0.3 to 65.8% (mean: 8.5%) in 2007 and from 0 to 24.5% (mean: 8.3%) in 2008. Results of morphological and molecular identification showed that the most common species isolated from diseased wheat spikes was F. graminearum (33.1%), followed by F. avenaceum (20.3%) and F. poae (17.8%). The chemical analysis revealed that 75% of the investigated fields were contaminated by deoxynivalenol (DON, range 0–8111 µg/kg). The preceding crop was highly and significantly correlated to the number of grains infected and had a significant impact on disease prevalence (p = 0.025 and 0.017, respectively, Fisher's F-test). A trend was found for maize as the preceding crop (p = 0.084, Tukey's test) to predict the amount of DON in the fields. This is the first report on the occurrence of DON and ZON in naturally infected wheat grains sampled from Luxembourg.     

Relationship between environmental factors,dry matter loss and mycotoxin levels in stored wheat and maize infected with Fusarium species

This study examined the relationship between storage environmental factors (water activity (a _w) (0.89–0.97) and temperature (15°C–30°C)), colonisation of wheat and maize by Fusarium graminearum and F. verticillioides respectively and the dry matter losses (DMLs) caused and quantified by contamination with deoxynivalenol (DON), zearalenone (ZEA) and fumonisins (FUMs) during storage. Fungal growth was assessed by the amount of CO₂ produced under different interacting conditions of a _w and temperature. DMLs were quantified using the cumulative CO₂ data, and these were shown to increase as temperature and a _w increased. The amount of DON, ZEA (wheat for human consumption) and FUMs (feed maize) produced was significantly affected by the storage conditions. The three toxins however showed different patterns of production. Optimum for DON was at the wettest conditions (0.97a _w) and the highest temperature assessed (30°C), whereas for ZEA this shifted to 25°C. FUMs were produced in higher amounts in maize at 30°C and 0.97a _w; however, at intermediate a _w levels (0.955a _w), the highest production occurred at 25°C followed by 20°C. Polynomial models were developed for the effect of the storage factors on DMLs and toxin production. DMLs under different environmental conditions were significantly correlated with DON and FUMs. DON contamination was above the EU limits in at least 80% of the wheat samples with DMLs >1%, whereas at least 70% of the same samples contained ZEA above the respective EU legislative limits. Similarly, at least 75% of the maize samples with DMLs?≥?0.9% exceeded the EU limits for the sum of FUMs in feed. These results show that it may be possible to use temporal CO₂ production during storage of grains as an indicator of the level of contamination of the grain with mycotoxins.     

Fusarium mycotoxins in various barley cultivars and their transfer into malt

BACKGROUND: Fusarium toxins, secondary metabolites of toxinogenic Fusarium species, are found in a range of cereal grains. In this study the occurrence of the most commonest Fusarium toxins, namely nivalenol (NIV), deoxynivalenol (DON), deoxynivalenol‐3‐glucoside, fusarenon‐X, 3‐ and 15‐acetyldeoxynivalenol, HT‐2 and T‐2 toxins and zearalenone, in various barley cultivars harvested in 2005–2008 was monitored. The impact of weather, locality, fungicide treatment and barley cultivar (hulless or covered) on contamination was evaluated. The transfer of these mycotoxins into malt was assessed. RESULTS: The most prevalent toxin was DON, which was found in 83% of samples (maximum level 180 µg kg^?1), while HT‐2 was detected in 62% of samples (maximum level 716 µg kg^?1). Using analysis of covariance, weather was found to be the key factor in all years (P < 0.001). A relationship between cultivar and contamination was confirmed only for HT‐2 (P < 0.001) and T‐2 (P = 0.037), with higher levels of these toxins being observed in hulless cultivars. With the exception of NIV (P = 0.008), no significant relationship was found between fungicide treatment and contamination. No distinct trend regarding DON levels in malt was found, with both decreases and increases occurring. CONCLUSION: The results show an inter‐annual variation in mycotoxin occurrence in barley cultivars as well as differences in contamination of malt produced from fungicide‐treated and untreated barley. Copyright © 2010 Society of Chemical Industry     

免疫亲和柱的制备及在真菌毒素检测中应用的研究进展

真菌毒素是真菌的次生代谢产物,是引起谷物和饲料污染的重要元凶,其检测手段日趋完善。目前免疫亲和柱在真菌毒素检测分析方面已经被广泛使用,本文综述了免疫亲和柱的原理及其制备方式,及其在几种常见真菌毒素检测方面的应用。      

Less Fusarium infestation and mycotoxin contamination in organic than in conventional cereals

A total of 602 samples of cereals, consisting of organically and conventionally produced barley, oats and wheat, were collected at harvest during 2002–2004 in Norway. Organic and conventional cereals were sampled in comparable numbers regarding cereal species, localisation and harvest time, and analysed for Fusarium mould and mycotoxins. Fusarium infestation and mycotoxin content were dependent on cereal species and varied year-by-year. However, in all cereal species, Fusarium infestation and levels of important mycotoxins were significantly lower when grown organically than conventionally. Concerning the most toxic trichothecenes, HT-2 and T-2 toxin, lower concentrations were found in organic oats and barley. Wheat was not contaminated by HT-2 and T-2, but lower concentrations of deoxynivalenol (DON) and moniliformin (MON) were found when organically produced. For mycotoxins considered to constitute the main risk to humans and animals in Norwegian cereals, i.e. HT-2 in oats and DON in oats and wheat, the median figures (mean levels in brackets) were as follows: HT-2 in organic and conventional oats were <20 (80) and 62 (117) µg/kg, DON in organic and conventional oats were 24 (114) and 36 (426) µg/kg, and DON in organic and conventional wheat were 29 (86) and 51 (170) µg/kg, respectively. Concentrations of HT-2 and T-2 in the samples were strongly correlated (r = 0.94). Other mycotoxins did not show a significant correlation to each other. Both HT-2 and T-2 concentrations were significantly correlated with infestation of F. langsethiae (r = 0.65 and r = 0.60, respectively). Concentrations of DON were significantly correlated with F. graminearum infestation (r = 0.61). Furthermore, nivalenol (NIV) was significantly correlated with infestation of F. poae (r = 0.55) and MON with F. avenaceum (r = 0.37). As lower Fusarium infestation and mycotoxin levels were found in organic cereals, factors related to agricultural practice may reduce the risk of contamination with Fusarium mycotoxins. Studies of these issues will be presented separately.     

Impact of agronomic factors on fusarium mycotoxins in harvested wheat

ABSTRACT

The aim of this study was to model fusarium mycotoxins against agronomic factors in order to identify those that have the greatest impact on mycotoxin levels in harvested wheat. To achieve this, fusarium mycotoxins levels were monitored, and associated agronomic data collected, in approximately 150 English wheat fields/year between 2006 and 2013. Results showed large seasonal variation in fusarium mycotoxin levels, with high levels in 2008 (13% and 29% exceeding legal limit for unprocessed soft wheat intended for human consumption for deoxynivalenol (DON) and zearalenone (ZON), respectively) and 2012 (10% and 15% exceeding legal limit for unprocessed soft wheat intended for human consumption for DON and ZON, respectively) and low levels in 2006 and 2011 (no samples exceeding legal limits for unprocessed soft wheat intended for human consumption for DON or ZON). Analysis of agronomic factors identified previous crop, cultivation and variety as the greatest risk factors. The greatest risk of mycotoxin development in grain was following maize as a previous crop and minimum tillage. The combined effect of these factors gave respective average DON and ZON levels 20 and 14 times higher than other previous crop and cultivation combinations. A newly quantified risk factor was harvest date. A 1-month delay in harvest resulted in a 10 and 25 times greater mean DON and ZON concentration, respectively, when compared to crops harvested around the long-term regional average harvest date. These results highlight the highly seasonal variation in fusarium mycotoxins in wheat and the agronomic factors that should be avoided to minimise fusarium mycotoxin levels in harvested wheat.     

Effect of fungal strain and cereal substrate on in vitro mycotoxin production by Fusarium poae and Fusarium avenaceum

Single conidia strains of Fusarium poae and Fusarium avenaceum were investigated for their ability to synthesise mycotoxins in vitro. In a first experiment, rice was inoculated with three strains of F. poae and three strains of F. avenaceum. In a second experiment, the same strains were cultivated on four different cereal substrates. For both experiments, the colonised substrates were analysed using liquid chromatography coupled with tandem mass spectrometric detection (LC-MS/MS) for the content of Fusarium mycotoxins. On rice, a strong effect of strains on mycotoxin content was found. With the analyses of different cereal types, substantial substrate effects were observed. For F. poae, these effects were highly dependent on the strain. The results of this study are of benefit for risk assessment concerning naturally infected grain samples since substrate effects could also be triggered by different cereal species or varieties, and thus could lead to variable mycotoxin contamination in cereal products intended for human consumption.     

Characterization of the conventional and organic cotton fibres

The characterization of the conventional and organic cotton fibres to understand the differences present between them is presented. The cotton fibres were characterized for their fibre properties such as the surface morphology, surface chemical composition, surface elemental composition and internal fibre structure. The results show that the surface morphology and surface chemical composition of both the cotton fibres are similar. The surface elemental composition of both the cotton fibres shows that organic cotton fibres have higher percentage of metals than the conventional cotton fibres. Based on the FTIR spectrum analysis, it is observed that the organic cotton fibres may have a higher proportion of representative groups compared to that of the conventional cotton fibres. The fraction of I _α and I _β cellulose shows that I _β cellulose dominates in both cotton fibres. The crystallinity of both the cotton fibres was determined using the wide angle X-ray diffraction data. The results show that crystallinity of both fibres is similar.     

Determination of trichothecenes in cereals and cereal-based products by liquid chromatography-tandem mass spectrometry

A sensitive, accurate and precise method for the simultaneous determination of nivalenol (NIV), deoxynivalenol (DON), T-2 toxin (T-2) and HT-2 toxin (HT-2) in different food matrices, including wheat, maize, barley, cereal-based infant foods, snacks, biscuits and wafers, has been developed. The method, using liquid chromatography coupled with atmospheric pressure chemical ionization triple quadrupole mass spectrometry (LC-APCI-MS/MS), allowed unambiguous identification of the selected trichothecenes at low µg per kg levels in such complex food matrices. A clean-up procedure, based on reversed phase SPE Oasis® HLB columns, was used, allowing good recoveries for all studied trichothecenes. In particular, NIV recoveries significantly improved compared to those obtained by using Mycosep® #227 columns for clean-up of the extracts. Limits of detection in the various investigated matrices ranged 2.5-4.0 µg kg^-1 for NIV, 2.8-5.3 µg kg^-1 for DON, 0.4-1.7 µg kg^-1 for HT-2 and 0.4-1.0 µg kg^-1 for T-2. Mean recovery values, obtained from cereals and cereal products spiked with NIV, DON, HT-2 and T-2 toxins at levels from 10 to 1000 µg kg^-1, ranged from 72 to 110% with mean relative standard deviation lower than 10%. A systematic investigation of matrix effects in different cereals and cereal products was also carried out by statistically comparing the slopes of standard calibration curve with matrix-matched calibration curve for each of the four toxins and the eight matrices tested. For seven of the eight matrices tested, statistically significant matrix effects were observed, indicating that, for accurate quantitative analysis, matrix-matched calibration was necessary. The method was applied to the analysis of 57 samples of ground wheat originated from South Italy and nine cereal food samples collected from retail markets.