Weed species within cereal crop rotations can serve as alternative hosts for Fusarium graminearum causing Fusarium head blight of wheat

Fusarium graminearum is the main causal agent of Fusarium head blight (FHB) of small grain cereals, but the importance of weeds in the FHB disease cycle and the establishment of F. graminearum in agroecosystems are still not fully understood. The objective of this study was to determine the potential role of weeds present within cereal crop rotations as alternative hosts. F. graminearum was isolated from different organs of asymptomatic weeds sampled from six fields with cereal-crop rotations in Lithuania for two consecutive years (2015 and 2016). The fungi were identified using morphological and molecular methods. Out of 57 weed species that were investigated, 41 (71.9%) harboured F. graminearum isolates. Twenty five weed species were identified as new, previously undocumented, hosts. The majority (73.3%) of the isolates of F. graminearum from this study belonged to the 15ADON genotype while a smaller proportion (23.4%) belonged to the 3ADON genotype. All F. graminearum isolates that were assessed induced FHB symptoms on artificially inoculated spring wheat tested in the field.     

On the toxicokinetics and the metabolism of deoxynivalenol (don) in the pig

Eleven castrated male pigs weighing 88.1?±?3.9?kg on average were adapted to a diet containing DON (4.2?mg DON/kg) over a period of 7 days. Feed was given restrictively with 1.1?kg per meal (two meals per day). On the day of measurement, all pigs were slaughtered at different time intervals following the morning meal containing DON (1, 2, 3, 4, 5, 6, 8, 15, 18 and 24?h after feeding), with the exception of one pig which was slaughtered unfed. DON and de-epoxy-DON were analysed in serum and digesta from consecutive segments of the digestive tract (stomach, small intestine divided into three parts of a similar length, caecum, colon, rectum). DON was rapidly and nearly completely absorbed while passing through the stomach and the proximal small intestine. Maximum serum concentration appeared 4.1?h after the DON-containing meal and half of the systemically absorbed DON was eliminated after 5.8?h. De-epoxy-DON appeared in increasing proportions from the distal small intestine and reached approximately 80% of the sum of DON plus de-epoxy-DON in faeces collected from the rectum. It was concluded that de-epoxydation of DON, which primarily occurs in the hindgut, probably does not contribute much to a detoxification in the pig.     

Transformation of Trichothecenes in Ileal Digesta and Faeces from Pigs

The capacity of pig gastrointestinal microflora to metabolise the trichothecenes 3-acetyl-deoxynivalenol (3-acDON) and nivalenol (NIV) was investigated. 3-acDON was deacetylated to DON in anaerobic incubations with pig faeces collected at different pig farms. Furthermore, both 3-acDON and NIV were metabolised to the corresponding de-epoxy metabolite in these incubates. Five pigs, in which the gastrointestinal microflora lacked the ability to transform 3-acDON and NIV to their corresponding de-epoxidated metabolites, were given low levels of DON in the feed for seven weeks. The gastrointestinal micro-organisms did not acquire the de-epoxidation ability during the seven week long exposure period. At the end of the exposure period, faeces from pigs with a known de-epoxidation ability was spread out in the pens and left for 24 hours. One week after the faeces had been spread out in the pens, the de-epoxidation ability was found in faecal incubations from four out of five experimental pigs. This change in metabolic ability of the intestinal de-epoxidation ability was not accompanied by any detectable changes in the DNA-profiles of the bacterial community composition. The results show that the intestinal de-epoxidation ability is common at pig farms in the Uppsala area, and that the ability may be transferred between pigs in a stock.     

Progression of mycotoxin and nutrient concentrations in wheat after inoculation with Fusarium culmorum

The objective of this study was to follow the mycotoxin formation and changes in nutrient composition of wheat (cv. Ritmo) artificially inoculated with Fusarium culmorum. From anthesis until harvest, samples were taken once a week from the inoculated and control plots. The investigations were focused on monitoring the progression of the contamination of the wheat kernels with deoxynivalenol (DON) and zearalenone (ZON). Both the uncontaminated control kernels and the contaminated kernels were examined also for the presence of zearalenone-4-beta-D-glucopyranoside and several trichothecenes at harvest. Furthermore, the impact of the Fusarium inoculation on some nutrients as starch, crude protein, amino acid composition, crude ash, non starch polysaccharides (NSP) as well as viscosity and thousand seed weight (TSW) was examined. Also proteolytic and amylolytic activity as well as the NSP-degrading enzyme activities of inoculated and control samples were analysed at the time of harvest. DON was detected in higher concentrations and in earlier stages, while ZON was found later and in smaller amounts. On average 7.79?mg/kg DM of DON and 100?μg/kg DM of ZON were found in the inoculated kernels at the time of harvest. Neither in the contaminated nor in the control samples glucose conjugates of ZON (Zearalenone-4-beta-D-glucopyranoside) were detected. Moreover, the infection with Fusarium culmorum had pronounced effects on some quality parameters. The crude protein content of the inoculated kernels showed significantly higher values over the whole period compared to the control kernels. The protein content of the inoculated kernels amounted 13.9% DM at harvest, while only a concentration of 12.5% DM was detected in the control samples. Similarly, in almost all stages of development the crude ash content of inoculated samples was higher than in control samples. These distinct differences in kernel composition resulted possibly from the changes of the thousand seed weight. In the present work the grain harvested from the control plots showed a significantly higher TSW (24.2?g) as compared to their inoculated counterparts (15.5?g). Despite lower extract viscosity of inoculated samples at time of harvest, the content of soluble NSP of inoculated plots was higher than in control samples at the same time. Moreover, inoculation resulted in markedly increased activities of protease, amylase and several NSP-degrading enzyme activities. This would suggest that the cell wall penetrating properties of the fungus itself and/or that the fungus induced alterations of the metabolic activity of the embryo or other constituents of the wheat kernel could be responsible.     

Influence of deoxynivalenol on feed consumption by dairy cows

The present results would suggest that diets providing up to 14.6 mg kg⁻¹ concentrate or 31 mg DON per 100 kg body weight for relatively high levels of milk production did not affect feed intake or milk production over a 3 week period. Caution is suggested as DON-contaminated barley can at times contain other mycotoxins.     

On the distribution and metabolism of Fusarium-toxins along the gastrointestinal tract of endotoxaemic pigs

The aim of this study was to investigate the potential modulatory effect of E. coli lipopolysaccharides (LPS) on residues of deoxynivalenol (DON), de-epoxy-deoxynivalenol (DOM-1), zearalenone (ZEN) and its metabolites α-zearalenol (α-ZEL), β-zearalenol (β-ZEL), zearalanone (ZAN), α-zearalanol (α-ZAL) and β-zearalanol (β-ZAL) after pre- or post-hepatic administration along the gastrointestinal axis. Fifteen barrows were exposed to a naturally mycotoxin contaminated diet (4.59 mg DON/kg feed and 0.22 mg ZEN/kg feed) and equipped with jugular (ju) and portal (po) catheters. On sampling day (day 29), the barrows were infused with LPS or a control fluid (LPS, 7.5 µg/kg body weight; control, 0.9% NaCl) either pre- or post-hepatically, resulting in three infusion groups: CON_ju-CON_po, CON_ju-LPS_po and LPS_ju-CON_po. At 195 min relative to infusion start (210 min post-feeding), pigs were sacrificed and content of stomach and small intestine (proximal, medial and distal part) as well as faeces were collected. In all LPS-infused animals, higher amounts of dry matter were recovered irrespective of LPS entry site suggesting a reduced gastric emptying and a decreased gastrointestinal motility under endotoxaemic conditions. DON metabolism in the gastrointestinal tract (GIT) remained unaltered by treatments and included an increase in the proportion of DOM-1 along the GIT, particularly from distal small intestine to faeces. Variables describing ZEN metabolism suggest a stimulated biliary release of ZEN and its metabolites in LPS-infused groups, particularly in the LPS_ju-CON_po group. In conclusion, the GIT metabolism of ZEN was markedly influenced in endotoxaemic pigs whereby a jugular induction of an acute phase reaction was more effective than portal LPS infusion hinting at a strong hepatic first-pass effect.     

Analysis of Fusarium toxins in maize and wheat using thin layer chromatography

Thin layer chromatography (TLC) methods for identifying and quantifying deoxynivalenol (DON), fumonisin B1 (FB1) and zearalenone in grain samples were compared to immunoassay (ELISA) and high performance liquid chromatography (HPLC) methods to determine the reliability of the less expensive TLC. There was a very good agreement between levels of DON measured by TLC and competitive-direct ELISA, and between levels of fumonisin B1 measured by TLC and HPLC, over a wide range of concentrations. Correlation coefficients (Pearson's) were 0.978, 0.914 and 0.953 for DON in maize, DON in wheat and FB1 in maize respectively. A lower correlation coefficient (r = 0.672) was obtained when zearalenone was quantified by TLC and HPLC. Possible reasons for this are discussed. A cost comparison of the various methods revealed that TLC was the least expensive for sample analysis. It is recommended that researchers choose which analytical method to use based upon individual considerations of cost and precision. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cystathionine gamma-synthase is essential for methionine biosynthesis in Fusarium graminearum

Methionine (Met) plays an important role in various cellular processes in both eukaryotes and prokaryotes. Cystathionine gamma-synthase encoded by STR2 gene is a key enzyme in Met biosynthesis in Saccharomyces cerevisiae. In this study, we identified FgMETB, a homologue of S. cerevisiae STR2, from Fusarium graminearum using the Protein Basic Local Alignment Search Tool (BLASTP) program. The FgMETB deletion mutants were unable to grow on fructose gelatin agar (FGA) medium containing SO₄²⁻ as sole sulphur source. In addition, more than 90 % conidia of the mutants were not able to germinate in 2 % sucrose solution within 6 or 12 h of incubation. Supplementation of 1 mM Met or 0.5 mg ml⁻¹ homocysteine, but not 1 mM cysteine or 0.5 mg ml⁻¹ glutathione, rescued the defect of mycelial growth and spore germination of FgMETB deletion mutants. These results indicated that the enzyme encoded by FgMETB is involved in conversion of cysteine into homocysteine. Inoculation tests showed that the FgMETB deletion mutant exhibited decreased virulence significantly on wheat heads, which is consistent with a low level of deoxynivalenol (DON) production of the mutant in wheat kernels. Fungicide sensitivity assays revealed FgMETB deletion mutants showed increased sensitivity to the sterol demethylation inhibitor tebuconazole, but did not change their sensitivities to other fungicides. Taken together, results of this study indicated that FgMETB plays a critical role in the regulation of various cellular processes in F. graminearum.     

Zearalenone,deoxynivalenol and aflatoxin B<Subscript>1</Subscript> and their metabolites in pig urine as biomarkers for mycotoxin exposure

Methods to determine zearalenone (ZEA), deoxynivalenol (DON), aflatoxins (AF) and their metabolites in pig urine were developed as biomarkers for pig exposure to the mycotoxins in feed. Urine samples were incubated with β-glucuronidase to cleave conjugates, extracted and cleaned-up with solid phase and immunoaffinity columns, followed by HPLC with UV and fluorescence detection. Good recoveries (83–130%), low variation (2–10%), and low detection limits (0.3–9.9 ng/ml) were obtained. The results of controlled AFB₁ feeding trials found no difference in urine concentrations of AFB₁ or AFM₁ from pigs fed three different levels (127, 227, 327 μg/kg) of AFB₁ in diets. The excretion of AFB₁ and AFM₁ in urine was on average 30% of the oral dose and the ratio AFB₁ to AFM₁ was around 23%. The analysis of 15 Vietnamese pig urine samples indicate a relatively high exposure of ZEA, DON and AF, which were found as toxin or metabolites in 47, 73, and 80% of the urine samples, respectively.