Microbial transformation of deoxynivalenol (vomitoxin).

Microbial inocula from rumen fluid, soil, and contents of the large intestines of chickens (CLIC) and of swine (SLIC) were tested for their ability to transform deoxynivalenol (vomitoxin) in vitro. Microorganisms in (CLIC) completely transformed pure vomitoxin, and this activity was retained through six serial subcultures. No alteration of the toxin by incubation with SLIC was detected, whereas 35% of the vomitoxin was metabolized in the original culture of rumen fluid and 50% was metabolized by the soil sample, though metabolism was decreased in subsequent subcultures of either sample. A single metabolite was isolated and identified as deepoxy vomitoxin. The increase in concentration of deepoxy vomitoxin in the culture medium corresponded with the decrease in vomitoxin concentration. The vomitoxin transformation rate was not affected by either the ratio of CLIC to vomitoxin (5 to 0.2 g of CLIC per mg of vomitoxin) or the initial concentration of vomitoxin (14 to 1,400 ppm) in the medium. Biotransformation of vomitoxin was completely inhibited when the pH in the medium was lowered to 5.20. Sodium azide at a 0.1% (wt/vol) concentration in the medium blocked the transformation of vomitoxin, suggesting that the deepoxidation of vomitoxin is an energy-dependent process. About 50% of the vomitoxin in moldy corn in culture medium was transformed by microorganisms from CLIC. The vomitoxin transformation rate in moldy corn was not affected when the concentration of CLIC changed from 0.2 to 0.8 g/ml of medium. Vomitoxin in the moldy corn was not transformed when CLIC were added to corn without culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Microbial transformation of deoxynivalenol (vomitoxin).

Microbial inocula from rumen fluid, soil, and contents of the large intestines of chickens (CLIC) and of swine (SLIC) were tested for their ability to transform deoxynivalenol (vomitoxin) in vitro. Microorganisms in (CLIC) completely transformed pure vomitoxin, and this activity was retained through six serial subcultures. No alteration of the toxin by incubation with SLIC was detected, whereas 35% of the vomitoxin was metabolized in the original culture of rumen fluid and 50% was metabolized by the soil sample, though metabolism was decreased in subsequent subcultures of either sample. A single metabolite was isolated and identified as deepoxy vomitoxin. The increase in concentration of deepoxy vomitoxin in the culture medium corresponded with the decrease in vomitoxin concentration. The vomitoxin transformation rate was not affected by either the ratio of CLIC to vomitoxin (5 to 0.2 g of CLIC per mg of vomitoxin) or the initial concentration of vomitoxin (14 to 1,400 ppm) in the medium. Biotransformation of vomitoxin was completely inhibited when the pH in the medium was lowered to 5.20. Sodium azide at a 0.1% (wt/vol) concentration in the medium blocked the transformation of vomitoxin, suggesting that the deepoxidation of vomitoxin is an energy-dependent process. About 50% of the vomitoxin in moldy corn in culture medium was transformed by microorganisms from CLIC. The vomitoxin transformation rate in moldy corn was not affected when the concentration of CLIC changed from 0.2 to 0.8 g/ml of medium. Vomitoxin in the moldy corn was not transformed when CLIC were added to corn without culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Distribution of gluten proteins in bread wheat (Triticum aestivum) grain

Background and Aims

Gluten proteins are the major storage protein fraction in the mature wheat grain. They are restricted to the starchy endosperm, which forms white flour on milling, and interact during grain development to form large polymers which form a continuous proteinaceous network when flour is mixed with water to give dough. This network confers viscosity and elasticity to the dough, enabling the production of leavened products. The starchy endosperm is not a homogeneous tissue and quantitative and qualitative gradients exist for the major components: protein, starch and cell wall polysaccharides. Gradients in protein content and composition are the most evident and are of particular interest because of the major role played by the gluten proteins in determining grain processing quality.

Methods

Protein gradients in the starchy endosperm were investigated using antibodies for specific gluten protein types for immunolocalization in developing grains and for western blot analysis of protein extracts from flour fractions obtained by sequential abrasion (pearling) to prepare tissue layers.

Key Results

Differential patterns of distribution were found for the high-molecular-weight subunits of glutenin (HMW-GS) and γ-gliadins when compared with the low-molecular-weight subunits of glutenin (LMW-GS), ω- and α-gliadins. The first two types of gluten protein are more abundant in the inner endosperm layers and the latter more abundant in the subaleurone. Immunolocalization also showed that segregation of gluten proteins occurs both between and within protein bodies during protein deposition and may still be retained in the mature grain.

Conclusions

Quantitative and qualitative gradients in gluten protein composition are established during grain development. These gradients may be due to the origin of subaleurone cells, which unlike other starchy endosperm cells derive from the re-differentiation of aleurone cells, but could also result from the action of specific regulatory signals produced by the maternal tissue on specific domains of the gluten protein gene promoters.     

疏剪不同穗位小穗对小麦籽粒结实和粒重的影响

１９９７～１９９８年在河南省农作物品种展览中心以中大穗小麦品种温麦６号为材料,设计了去除不同穗位小穗的试验。结果表明,去除不同位小穗对结实粒数和粒重的影响不同, 除顶端小穗的粒数下降较多,穗粒重最低,却除基部小重申对结实粒数和粒重的影响较小,穗粒数和粒重下降较少;却除中部小穗对结实粒数影响较大,穗粒数量小,其穗粒重因剩余籽粒单粒重增加而得以一定程度补偿。     

Investigation of the distribution of deoxynivalenol and ochratoxin A contamination within a 26 t truckload of wheat kernels

A study was conducted to determine the distribution of deoxynivalenol (DON) and ochratoxin A (OTA) in a lot of 261 of wheat kernels. Within this study, two different sampling and sample preparation strategies were carried out. On the one hand, following the official commission regulation 401/2006/EC, an aggregate sample out of 100 incremental samples was build, homogenized and prepared for laboratory analysis. On the other hand each individual subsample was investigated for its deoxynivalenol and ochratoxin A content. The determined concentration of DON in the individual samples was in a range from 830 up to 2655 (μg/kg, for OTA results ranged from < 0.2 up to 8.6 μg/kg. Thus, a coefficient of variance of 25% for DON and 200% for OTA was achieved. From this, a spot formation for OTA was observed and the average value of the 100 incremental samples did not correspond to the achieved value for the aggregate sample. While the DON contamination at this concentration range seems to be more even, consequently the result of the aggregate sample was in accordance with the average value. In addition a sample communition study was performed to answer the question whether the time consuming process of grinding of the whole aggregate sample is necessary or not. The results of this study show that contamination of whole wheat kernels with DON is at the same level within a 1 kg sample (CV 16%), while OTA contamination shows high variability (CV 94%). At least for OTA this study indicated that an extensive and complete sample communition of the high volume aggregate sample is necessary.     

A novel actinomycete derived from wheat heads degrades deoxynivalenol in the grain of wheat and barley affected by Fusarium head blight

Deoxynivalenol (DON) is a hazardous and globally prevalent mycotoxin in cereals. It commonly accumulates in the grain of wheat, barley and other small grain cereals affected by Fusarium head blight (caused by several Fusarium species). The concept of reducing DON in naturally contaminated grain of wheat or barley using a DON-degrading bacterium is promising but has not been accomplished. In this study, we isolated a novel DON-utilising actinomycete, Marmoricola sp. strain MIM116, from wheat heads through a novel isolation procedure including an in situ plant enrichment step. Strain MIM116 had background degradation activity, and the activity was enhanced twofold by the consumption of DON. Among Tween 20, Triton X-100 and Tween 80, we selected Tween 80 as a spreading agent of strain MIM116 because it promoted DON degradation and the growth of strain MIM116 in the presence of DON. The inoculation of MIM116 cell suspension plus 0.01% Tween 80 into 1,000 harvested kernels of wheat and barley resulted in a DON decrease from approximately 3 mg kg^?1 to less than 1 mg kg^?1 of dry kernels, even when cells had only basal levels of DON-degrading activity. To the best of our knowledge, this is the first report that describes (1) the isolation of a DON-degrading bacterium from wheat heads, (2) the effects of surfactants on the biodegradation of DON and (3) the decrease of DON levels in naturally contaminated wheat and barley grain using a DON-degrading bacterium.     

Effect of individual Sumai 3 chromosomes on resistance to scab spread within spikes and deoxynivalenol accumulation within kernels in wheat

Two sets of substitution lines were developed by crossing individual monosomic lines of Chinese Spring (recipient) with scab (Fusarium graminearum) resistant cultivar Sumai 3 (donor) and then using the monosomics as the recurrent male parent for four backcrosses (without selfing after each backcross). The disomic substitution lines were separated from selfed BC4F2 plants. Chromosome specific SSR markers were analyzed for polymorphism between Sumai 3 and Chinese Spring. Polymorphic markers were used to identify substitution lines for specific chromosomes. Based on the specific SSR markers, chromosome substitutions occurred in thirty-six lines, and six lines segregated alleles from the two parents or were homozygous for the allele from Chinese Spring. These substitution lines were used to evaluate Type II (spread within the head) and Type V (deoxynivalenol accumulation within kernels) scab resistance. The objective was to use the substitution lines to evaluate the effect of individual chromosomes of Sumai 3 on Type 11 and Type V scab resistance in the greenhouse. Significant differences in Type II scab resistance and deoxynivalenol (DON) levels among different Chinese Spring (Sumai 3) substitution lines were detected. Positive chromosome substitution effects on Type II scab resistance were found on chromosomes 2B, 3B. 6B, and 7A from Sumai 3. Chromosomes 3B and 7A also reduced DON accumulation within the kernels, while chromosomes IB, 2D, and 4D from Sumai 3 increased DON concentration. Chromosome 7A from Sumai 3 had the largest effect on resistance to scab spread and DON accumulation. Additional research is in progress on the scab resistance conferred by chromosome 7A.     

A study of the correlation between the amount of deoxynivalenol in grain of wheat and triticale and percentage of<Emphasis Type="Italic">Fusarium</Emphasis> damaged kernels

The correlation between the amount of deoxynivalenol (DON) and the percentage ofFusarium damaged kernels (FDK) in samples of wheat and triticale was studied.Samples of naturally infected wheat grain, collected in 1986, 1987 and 1988 and of triticale collected in 1986 were used.Additionally, artificial inoculated wheat samples (10 genotypes inoculated with 3F. Culmorum strains of weak, medium and severe pathogenicity and samples of 10 triticale genotypes inoculated withF. culmorum. andF. graminearun) were studied. Using statistical methods (the variance analysis, method of least significant difference (LSD), orthogonal contrast (OC) and minimum within groups sum of squares criterion (MSSC)), the samples were divided into two groups with respect to the attribute DON/FDK.To the first group belong samples of wheat and triticale, of which the heads were artificially inoculated with severely pathogenic strainsF. culmorum. In the samples of this group the amount of DON in kernels damaged withFusarium increased by 0,46 mg/kg per 1% of FDK.In the second group, consisting of naturally infected samples and samples from artificially inoculated heads the amount of DON increased 0,30 mg DON/kg per 1% of FDK.The equation for the calculation of approximated amount of DON in farm and commercial lots of wheat and triticale after examination of percentage of FDK is given.     

Distribution and remobilization of Zn and Mn during grain development in wheat

Wheat (Triticum aestivum cv. Aroona) was grown in siliceoussand with essential nutrients for unlimited growth except forthe following treatments: controls (sufficient Zn and Mn), lowMn (sufficient Zn) and low Zn (sufficient Mn) until anthesis.Replicate plants were harvested at anthesis; the remaining plantswere transferred to a chelate-buffered nutrient solution containingall essential nutrients except Zn and Mn to allow monitoringof the remobilization of existing Zn and Mn reserves withinthe plant. These plants were harvested 14 d post-anthesis andat grain maturity. At each harvest plants were separated intoindividual components. There were no growth differences between any of the treatmentsat the three harvests. Large amounts of Zn and Mn found in theroots and stems at anthesis were rapidly depleted during graindevelopment. The Zn content of the leaves increased from anthesisto 14 d post-anthesis, but then declined. The Mn content ofthe leaves increased throughout grain development in the controlswhilst remaining constant in the plants pre-grown at low Mn.The Zn and Mn content of the glumes, palea and lemma rose inthe controls from anthesis to 14 d post-anthesis; thereafterZn content declined but Mn content continued to increase. TheZn and Mn content of the grain rose sharply toward grain maturity.We conclude that Mn was not remobil-ized from the leaves ofwheat during grain development. Zinc was remobilized from theleaves, especially the flag leaf and from the leaves of thelow Zn plants. The post-anthesis accumulation of Zn and Mn withinthe glumes will be discussed in relation to the transport pathwaythat Zn and Mn use to enter the developing seed. Key words: Zinc, manganese, wheat, distribution, remobilization     

Effect of plant water deficit on the deoxynivalenol concentration in Fusarium-infected maize kernels

In current climate change scenarios, mean air temperatures and summer droughts are expected to increase over the long-term average in large parts of Europe. These changes will strongly affect the growth and health of cultivated plants. In a field experiment in 2009 and 2010 in rain-out shelters, the consequences of plant water availability under three water regimes on the severity of Fusarium ear rot, deoxynivalenol (DON) contamination and yield of maize were investigated. Water was provided exclusively to the plants by a mobile sprinkler system installed in the rain-out shelter. Three maize cultivars were supplied with 50, 75, and 125% of the long-term average monthly precipitation of the experimental site. In 2009, Fusarium graminearum-infected oat kernels were placed on the soil surrounding maize plants to promote ear infection, whereas in 2010, the maize silks were directly inoculated with suspensions of F. graminearum conidia. Heavy drought stress in the 50% water regime was reflected in the average ear yield of the three maize cultivars of 75?dt ha^-1 compared with 192?dt ha^-1 at 125% water. In this comparison, the DON concentrations in the kernels were fivefold higher at 50% water than at the high water regime: 380 compared with 75???g DON kg^-1 DM. In 2010, the drought stress symptoms were less pronounced than in 2009, and a much lower ear yield loss from 128 to 108?dt DM ha^-1 was observed with decreasing water supply. The DON contamination of the kernels was at a higher level than in 2009, but a similar upward trend from 330???g?kg ^-1 DM at 125% water supply to about 3.5-fold higher DON levels at 75 and 50% water supply was observed. These different yield responses presumably resulted from variable climatic conditions at the experimental site in the 2?years. The results of this study suggest that the risk of DON contamination of maize kernels increases when plants are grown under conditions of long-term water deficit.     

Influence of water activity on deoxynivalenol accumulation in wheat

The influence of water activity (a_w) on deoxynivalenol accumulation in wheat at 25°C was studied. Gnotobiotic grains were conditioned at different a_w levels, inoculated with a toxigenic Fusarium graminearum strain, and incubated for ten weeks. The highest accumulation of deoxynivalenol (1130 ug/kg) was detected at a_w 0.980. At a_w 0.945 and 0.925 the maximum quantities of toxin accumulated were 113 ug/kg and 93 ug/kg respectively. Deoxynivalenol was not detected in the substrate at a_w 0.900. Results suggest that intermediate a_w levels (0.97 – 0.92) are particularly critical at post harvest time because those are conditions under which deoxynivalenol production is most likely to be initiated naturally.     

Distribution of aphids in cereal crops

Cereal crops were examined weekly for aphids during 1969. Plants in twenty samples of row 0.3 m long were examined in a sheltered perimeter of a crop and along a transect 36.6 m into the crop. Aphids were usually first found within 1–4 weeks of the first alatae caught in a suction trap operating 12.2 m above ground. When first alatae caught in a suction trap operating 12.2 m above ground. When the first found from 10 to 27% of the 0.3 m lengths sampled contained aphids. Rhopalosiphum padi, first found late in May, were scarce (< 0.53/0.3 m) throughout June and July. Sitobium spp. and Metapolophium dirhodum, which appeared in mid-June, were more numerous than R. padi; most occurred during the second half of July, and populations decreased just before harvest in early August. Sitobium avenae was more abundant (max. 19.3/sample) than either S. fragariae (0.91) or M. dirhodum (2.51). More aphids occurred in oats (max. 52/0.3 m) during July than in wheat (45), and barley had fewer (6.8). S. avanae was more abundant than M. dirhodum in sheltered areas of barley and wheat, and in exposed areas of the same crop M. dirhodum was commonest. Along sheltered perimeters, the ratio of S. avenae to M. dirhodum was largest in barley (11:1), intermediate in oats (6:1) and smallest in wheat (3.7:1). Sitobium spp. were most numerous on the ears, when most M. dirhodum were on the leaves. Regression analyses of log. S² on log. m suggested that S. avenae was more evenly distributed within (36.6 m) the field (b = 1.056 + 0.109) than along the sheltered perimeter (b = 1.432 + 0.132), though it seemed similarly distributed along perimeters of barley, oats and wheat. The distributions of M. dirhodum and Sitobium spp. along sheltered perimeters of all crops were apparently similar.     

Behavioural responses of Oryzaephilus surinamensis, Tribolium castaneum and Tribolium confusum to naturally and artificially damaged durum wheat kernels

Observations on behavioural activity involved in the host selection by secondary pests of stored grains, Oryzaephilus surinamensis (Linnaeus), Tribolium castaneum (Herbst) and Tribolium confusum J. du Val, with respect to intact and mechanically or naturally damaged kernels are reported. Our results indicate that the attraction of secondary pests is facilitated by broken grain kernels, which resulted from either mechanical damage during harvesting and/or binning procedures, or the feeding activity of primary insect pests. Insect damaged kernels were more attractive to O. surinamensis, T. castaneum and T. confusum than whole kernels; in addition insect damaged kernels elicit more attractiveness than mechanically split kernels. The damage caused by primary pests, such as Rhyzopertha dominica (Fabricius) and Sitophilus oryzae (Linnaeus), on whole kernels may facilitate colonization by secondary pests, which continue damaging the cereals. O. surinamensis, T. castaneum and T. confusum utilize the grain volatile odours to distinguish whether the grain kernels of the stored cereals are damaged mechanically or by insects.     

Comparison of environmental profiles for growth and deoxynivalenol production by Fusarium culmorum and F. graminearum on wheat grain

AIMS: Comparisons were made of the effect of water activity (a(w) 0.99-0.85), temperature (15 and 25 degrees C) and time (40 days) on growth/production of the trichothecene mycotoxin deoxynivalenol (DON) by Fusarium culmorum and Fusarium graminearum on wheat grain. METHODS AND RESULTS: Studies examined colonization of layers of wheat grain for 40 days. Fusarium culmorum grew optimally at 0.98 a(w) and minimally at 0.90 a(w) at 15 and 25 degrees C. Colonization by F. graminearum was optimum at 0.99 a(w) at 25 and 0.98 a(w) at 15 degrees C. Overall, temperature, a(w) and their interactions significantly affected growth of both species. Production of DON occurred over a much narrower range (0.995-0.96 a(w)) than that for growth. Optimum DON was produced at 0.97 and 0.99 a(w) at 15 and 25 degrees C, respectively, by F. culmorum, and at 0.99 a(w) and 15 degrees C and 0.98 a(w) at 25 degrees C for F. graminearum. Statistically, one-, two- and three-way interactions were significant for DON production by both species. CONCLUSIONS: This suggests that the ecological requirements for growth and mycotoxin production by such species differ considerably. The two-dimensional profiles on grain for DON production by these two species have not been examined in detail before. SIGNIFICANCE AND IMPACT OF THE STUDY: This type of information is essential for developing climate-based risk models for determining the potential for contamination of cereal grain with this trichothecene mycotoxin. It will also be useful information for monitoring critical control points in prevention of such toxins entering the wheat production chain.     

Hydrothermal treatment of naturally contaminated maize in the presence of sodium metabisulfite, methylamine and calcium hydroxide; effects on the concentration of zearalenone and deoxynivalenol

Fusarium toxin-contaminated ground maize was hydrothermally treated in the presence of different combinations of chemicals in order to simultaneously reduce zearalenone (ZEA) and deoxynivalenol (DON) concentrations. Treatments were carried out in a laboratory conditioner at 80 °C and 17 % moisture. Six different treatments were performed, consisting of 3 doses of methylamine (MMA; 2.5, 5 and 10 g/kg maize) at a constant dose of 5 g sodium metabisulfite (SBS)/kg, either with or without the addition of 20 g calcium hydroxide (Ca(OH)₂)/kg. The used maize was contaminated with approximately 45.99 mg DON/kg and 3.46 mg ZEA/kg. Without the addition of Ca(OH)₂, DON reductions reached approximately 82 % after 1-min treatment and the toxin disappeared nearly completely after 10 min when 2.5 or 5 g MMA were applied. ZEA concentrations were only marginally affected. In the presence of Ca(OH)₂, reductions in DON concentrations were lower, but were enhanced by increasing doses of MMA. ZEA concentrations were reduced by 72, 85 and 95 % within the first 5 min of the treatment at MMA dosages of 2.5, 5 and 10 g/kg maize, respectively. The application of SBS in combination with a strong alkaline during hydrothermal treatment seems to be a promising approach to simultaneously decontaminate even high amounts of DON and ZEA in ground maize and may contribute to reduce the toxin load of diets     

Immunochemical assessment of mycotoxins in 1989 grain foods: evidence for deoxynivalenol (vomitoxin) contamination

To assess the potential for mycotoxin contamination of the human food supply following the 1988 U.S. drought, 92 grain food samples were purchased from retail outlets in the summer of 1989 and surveyed for aflatoxin B1, zearalenone, and deoxynivalenol (DON [vomitoxin]) by monoclonal antibody-based competitive enzyme-linked immunosorbent assay (ELISA). Only one sample (buckwheat flour) was found to contain aflatoxin B1 (12 ng/g), whereas zearalenone was found in 26% of the samples at a mean concentration of 19 ng/g. In contrast, the DON ELISA was positive in 50% of the samples at a detection level of 1.0 micrograms/g. Between 63 and 88% of corn cereals, wheat flour/muffin mixes, rice cereals, and corn meal/muffin mixes yielded positive results for DON, whereas 25 to 50% of oat cereals, wheat- and oat-based cookies/crackers, corn chips, popcorn, and mixed-grain cereals were positive for DON. The mean DON content of the positive samples was 4.0 micrograms/g, and the minimum and maximum levels were 1.2 and 19 micrograms/g, respectively. When positive ELISA samples were also analyzed by high-performance liquid chromatography, a strong correlation between the two methods was found. The presence of DON in the two highest samples, corn meal and mixed-grain cereal, which contained 19 and 16 micrograms/g, respectively, was quantitatively confirmed by gas chromatography-mass spectrometry. The results indicated that DON was present in 1989 retail food products at concentrations that exceeded those found in previous market surveys and that have been experimentally associated with impaired animal health.     

Inheritance of grain proteins in wheat

Summary Diallel crosses between five divergent vulgare wheat cultivars were made in order to evaluate the mode of inheritance and combining ability of grain proteins. Significant differences in grain protein content were found between cultivars and their hybrids. It was established that the inheritance of seed protein in the F₁ generation included both additive and non-additive gene action.