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Natural occurrence of deoxynivalenol in wheat, wheat flour and bakery products in Argentina.

The objective of this study was to evaluate the natural occurrence of deoxynivalenol (DON) in wheat, wheat flour and different kinds of breads and pastries widely consumed by the population in Argentina. Of 60 wheat samples analysed, 93.3% were contaminated. The average DON contamination level over all samples was 1798 micrograms/kg, and the minimum and maximum values were 100 micrograms/kg and 9250 micrograms/kg, respectively. The wheat flour samples (61 samples) were contaminated with DON at levels ranging from 250 micrograms/kg to 9000 micrograms/kg with an average of 1309 micrograms/kg. The frequency of DON contamination over 42 samples of different bakery products was 92.8%, with levels ranging from 200 micrograms/kg to 2800 micrograms/kg with an average of 464 micrograms/kg. These results suggest a high risk for consumers of wheat products and the need to monitor final products before consumption.

Argentina↗

Influence of a Fusarium culmorum inoculation of wheat on the progression of mycotoxin accumulation, ingredient concentrations and ruminal in sacco dry matter degradation of wheat residues.

The Fusarium head blight (FHB)-susceptible winter wheat cv. Ritmo was inoculated with spores of Fusarium culmorum at the beginning of full blossom. Samples of whole wheat plants were taken once weekly from anthesis until harvest and subsequently fractionated into straw, glumes and spindles, which were examined for deoxynivalenol (DON) and zearalenone (ZON). Additionally, the content of crude protein (CP) and non-starch polysaccharides (NSP) was scrutinized. Synthesis of the Fusarium toxins DON and ZON generally differed in terms of date of formation and concentration. Final mean DON concentrations of 37.5, 28.1 and 5.0 mg/kg DM were measured in glumes, spindles and straw, respectively, at the time of harvest. At this time, maximal mean ZON concentrations of 587, 396 and 275 microg/kg DM in spindles, glumes and straw, respectively, were determined. Moreover, Fusarium infected wheat residues contained higher CP but lower NSP contents at the last three sampling dates. In addition, collective samples of wheat straw and chaff were taken to investigate the effect of the Fusarium contamination on their in sacco DM degradation in dairy cows. Samples were analysed for mycotoxins and selected quality parameters. The dried and milled collective samples of straw and chaff were weighed into nylon bags and subjected to ruminal incubation for 4, 8, 16, 24, 48, 72, 96 and 120 h in two dairy cows equipped with a permanent rumen cannula. Marked differences in level of mycotoxin contamination as well as in ingredient composition between the variants of straw and chaff were detected. Moreover, after 120 h rumen incubation the in sacco DM degradation of inoculated straw and chaff were lower compared to the accordant controls. The soluble fraction was increased in inoculated samples, whereas a diminishment in the potentially degradable but insoluble fraction was more pronounced. Thereby, a decrease in the potential degradability was obtained for inoculated straw and even if less pronounced for chaff compared to the non inoculated corresponding controls. In conclusion, infection with F. culmorum of wheat involves an increased risk of mycotoxin contamination in straw. Also, a Fusarium infection may have an impact on chemical composition and may result in Fusarium growth-related modifications of host cell wall components.

Animal Feed↗

Fermentation of wheat: effects of backslopping different proportions of pre-fermented wheat on the microbial and chemical composition.

The objective of the study was to examine effect of backslop on the chemical and microbiological characteristics of fermented wheat (FW). Coarsely ground wheat was mixed with water (1:3 wt/wt) and inoculated with 6 log cfu ml(-1) each of an overnight culture of Lactobacillus plantarum and Pediococcus pentosaceus. Four fermentation treatments were conducted in 45 1, closed, PVC containers over 48 hours. Three treatments investigated the benefits of the addition of previously fermented wheat (backslopping, BSL) at different proportions (0.20, 0.33 or 0.42 kg) to freshly prepared wheat. The control treatment contained no addition of BSL. Elimination of coliforms from the FW within 48 h was only achieved through backslopping; where coliform bacteria counts decreased from approximately 6.5 log10 cfu ml(-1) to less than 3 log10 cfu ml(-1). There was no apparent advantage in increasing the backslop proportion above 0.20. However, the exclusion of coliform bacteria required the pH to remain below 4.0 for at a minimum of 24 h. The results of these studies indicate that fermentation of wheat has the potential to reduce the risk of feed-borne colibacillosis and provides a practical alternative to producers that cannot ferment multiple diets or have limited fermentation capacity.

Animal Feed↗

Effects of oat bran, rice bran, wheat fiber, and wheat germ on postprandial lipemia in healthy adults.

Six normolipidemic males ingested on separate days a low-fiber test meal [2.8 g dietary fiber (TDF)] containing 70 g fat and 756 mg cholesterol, enriched or not with 10 g TDF as oat bran, rice bran, or wheat fiber or 4.2 g TDF as wheat germ. Fasting and postmeal blood samples were obtained for 7 h and chylomicrons were isolated. Adding fibers to the test meal induced no change in serum glucose or insulin responses. The serum triglyceride response was lower (P less than or equal to 0.05) in the presence of oat bran, wheat fiber, or wheat germ and chylomicron triglycerides were reduced with wheat fiber. All fiber sources reduced chylomicron cholesterol. Cholesterolemia decreased postprandially for 6 h and was further lowered in the presence of oat bran. Serum apolipoprotein (apo) A-1 and apo B concentrations were not affected. Thus, dietary fibers from cereals may reduce postprandial lipemia in humans to a variable extent.

Adult↗

Categories of resistance at different growth stages in halt, a winter wheat resistant to the Russian wheat aphid (Homoptera: Aphididae).

This study was designed to categorize the resistance to the Russian wheat aphid, Diuraphis noxia (Mordvilko), resistant hard red winter wheat, Halt, as compared with susceptible wheat, TAM 107, at four different growth stages. Antixenosis was expressed in Halt at growth stage Zadoks 30. Antibiosis in Halt affected fecundity, number of aphids produced per reproductive day, maximum number of nymphs produced in one day, and intrinsic rate of increase. Fecundity was lower on Halt than TAM 107, and more nymphs were produced on both varieties at growth stage 20 than 10 and 40. Fewer nymphs were produced per reproductive day and on maximum production days by aphids reared on Halt than by those reared on TAM 107. The intrinsic rate of increase of Russian wheat aphids reared on Halt was lower than aphids reared on TAM 107. Differences in plant height and plant dry weight did not occur. Chlorosis ratings showed greater damage at the earlier stages in Halt and TAM 107 and significantly more damage in TAM 107 than Halt at growth stages 10, 20, and 30. Leaf rolling occurred on infested plants of TAM 107 at growth stages 10, 20, and 30, but not growth stage 40. Halt plants did not exhibit leaf rolling. The presence of a significant level of tolerance could make Halt compatible with other integrated pest management programs. However, care should be taken with cultivars containing evidence of antixenosis or antibiosis that could cause selective pressure on the Russian wheat aphid, potentially causing biotypes to be produced.

Animals↗

Comparison of chlorophyll and carotenoid concentrations among Russian wheat aphid (Homoptera: Aphididae)-infested wheat isolines.

Russian wheat aphid, Diuraphis noxia (Mordvilko), feeding injury on 'Betta' wheat isolines with the Dn1 and Dn2 genes was compared by assessing chlorophyll and carotenoid concentrations, and aphid fecundity. The resistant Betta isolines (i.e., Betta-Dn1 and Betta-Dn2) supported similar numbers of aphids, but had significantly fewer than the susceptible Betta wheat, indicating these lines are resistant to aphid feeding. Diuraphis noxia feeding resulted in different responses in total chlorophyll and carotenoid concentrations among the Betta wheat isolines. The infested Betta-Dn2 plants had higher levels of chlorophylls and carotenoids in comparison with uninfested plants. In contrast, infested Betta-Dn1 plants had the same level of chlorophyll and carotenoid in comparison with uninfested plants. Our data provide essential information on the effect of D. noxia feeding on chlorophyll and carotenoid concentrations for Betta wheat and its isolines with D. noxia-resistant Dn1 and Dn2 genes.

Animals↗

Distribution of wheat germ agglutinin in young wheat plants.

A liquid phase, competition-binding radioimmunoassay for wheat germ agglutinin, with a detection limit of 10 nanograms, was developed in order to determine the distribution of this lectin in young wheat plants. Affinity columns for wheat germ agglutinin removed all antigenically detectable activity from crude extracts of wheat tissue; thus, the antigenic cross-reactivity detected by the assay possesses sugar-binding specificity similar to the wheat germ-derived lectin. The amount of lectin per dry grain is approximately 1 microgram, all associated with the embryo. At 34 days of growth, the level of lectin per plant was reduced by about 50%, with approximately one-third in the roots and two-thirds in the shoot. The data also indicate that actively growing regions of the plant (the bases of the leaves and rapidly growing adventitious roots) contain the highest levels of lectin. Half of the lectin associated with the roots could be solubilized by washing intact roots in buffer containing oligomers of N-acetylglucosamine, whereas the remainder is liberated only upon homogenization of the tissue.

Journal Article↗

Stress-induced accumulation of wheat germ agglutinin and abscisic Acid in roots of wheat seedlings.

Wheat germ agglutinin (WGA) levels in roots of 2-day-old wheat seedlings increased up to three-fold when stressed by air-drying. Similar results were obtained when seedling roots were incubated either in 0.5 molar mannitol or 180 grams per liter polyethylene glycol 6000, with a peak level of WGA after 5 hours of stress. Longer periods of osmotic treatment resulted in a gradual decline of WGA in the roots. Since excised wheat roots incorporate more [(35)S]cysteine into WGA under stress conditions, the observed increase of lectin levels is due to de novo synthesis. Measurement of abscisic acid (ABA) levels in roots of control and stressed seedlings indicated a 10-fold increase upon air-drying. Similarly, a five- and seven-fold increase of ABA content of seedling roots was found after 2 hours of osmotic stress by polyethylene glycol 6000 and mannitol, respectively. Finally, the stress-induced increase of WGA in wheat roots could be inhibited by growing seedlings in the presence of fluridone, an inhibitor of ABA synthesis. These results indicate that roots of water-stressed wheat seedlings (a) contain more WGA as a result of an increased de novo synthesis of this lectin, and (b) exhibit higher ABA levels. The stress-induced increase of lectin accumulation seems to be under control of ABA.

Journal Article↗

Wheat Ec metallothionein genes. Like mammalian Zn2+ metallothionein genes, wheat Zn2+ metallothionein genes are conspicuously expressed during embryogenesis.

A cDNA library was prepared from the bulk mRNA of mature wheat embryos and screened with mixed 32P-labeled oligonucleotide probes that encoded parts of the partial amino-acid sequence for the Zn-containing Ec protein. Each DNA insert in 11 positives from a screen of 10(5) plaques encoded a 5' untranslated and a 3' untranslated region, in addition to an open reading frame (of 81 amino acids) which, in every case, corresponded to at least 56 of the 59 amino acids in the partial polypeptide sequence previously determined for the Ec protein. The three different mRNA sequences encoded in the cDNA probably correspond to single-copy genes in the A, B and D genomes of hexaploid wheat. A wheat genomic library was screened with 32P-labeled cDNA and gave a single positive in a screen of 5 x 10(5) plaques. A 3.1-kb genomic fragment (gf-3.1) was sequenced and a cap site for the encoded mRNA was determined by primer extension. The gf-3.1 sequence encodes an intronless mRNA for the Ec protein and contains appreciable amounts of 5' and 3' flanking sequences. In addition to a putative TATA box, two inverted-repeat sequences and one direct-repeat sequence, the 5' flank in gf-3.1 contains a sequence similar to the abscisic-acid-responsive element in other higher-plant genes but does not contain sequences similar to the metal-responsive elements in animal metallothionein genes. Consistent with these findings, RNA blotting shows that accumulation of Ec mRNA is abundant in immature embryos, undetectable in germinated embryos and can be induced by adding abscisic acid, but not by adding Zn2+ to the medium in which mature wheat embryos are germinated. The findings suggest that the wheat Ec metallothionein genes, like mammalian liver metallothionein genes, are conspicuously expressed during embryogenesis.

Amino Acid Sequence↗

Cellulases and xylanase of an anaerobic rumen fungus grown on wheat straw, wheat straw holocellulose, cellulose, and xylan.

The activities of cellulolytic and xylanolytic enzymes produced by an anaerobic fungus (R1) which resembled Neocallimastix sp. were investigated. Carboxymethylcellulase (CMCase), cellobiase, and filter paper (FPase) activities had pH optima of 6.0, 5.5, and 6.0, respectively. CMCase and cellobiase activities both had a temperature optimum of 50 degrees C, whereas FPase had an optimum of 45 degrees C. The pH and temperature optima for xylanase activity were pH 6.0 and 50 degrees C, respectively. Growth of the fungus on wheat straw, wheat straw holocellulose, or cellulose resulted in substantial colonization, with at least 43 to 58% losses in substrate dry matter and accumulation of comparable amounts of formate. This end product was correlated to apparent loss of substrate dry weight and could be used as an indicator of fungal growth. Milling of wheat straw did not enhance the rate or extent of substrate degradation. Growth of the R1 isolate on the above substrates or xylan also resulted in accumulation of high levels of xylanase activity and lower cellulase activities. Of the cellulases, CMCase was the most active and was associated with either low or trace amounts of cellobiase and FPase activities. During growth on xylan, reducing sugars, including arabinose and xylose, rapidly accumulated in the medium. Xylose and other reducing sugars, but not arabinose, were subsequently used for growth. Reducing sugars also accumulated, but not as rapidly, when the fungus was grown on wheat straw, wheat straw holocellulose, or cellulose. Xylanase activities detected during growth of R1 on media containing glucose, xylose, or cellobiose suggested that enzyme production was constitutive.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobiosis↗

Seasonal variation in non-specific bronchial reactivity: a study of wheat workers with a history of wheat associated asthma.

To investigate seasonal variation in non-specific bronchial reactivity in wheat workers, we carried out histamine inhalation tests in 29 workers (28 of them men) from a small farming community with symptoms of wheat associated asthma before, during and after the 1983-4 Australian wheat harvest season. Four were cigarette smokers, and the age range was 12-54 (mean (SD) 30 (10)) years. Twenty eight subjects were atopic (one positive skinprick test result in tests with 10 common antigens), 60% reacting to house dust mite and all to at least one of eight wheat antigens. Baseline spirometry gave normal results (mean FVC1 90% (SD 8%) predicted; FVC 91% (7%) predicted). Bronchial reactivity was tested by the method of Yan et al. The cumulative doses of histamine acid phosphate (up to 3.91 mumol) that caused a fall of 20% from baseline in FEV1 was determined (PD20) and expressed as the geometric mean. In the low exposure season, May 1983, nine subjects had a PD20 (mean 1.2, range 0.3-3.9 mumol). The number rose to 19 in the summer harvest season, December 1983 (mean 0.8, range 0.07-3.9 mumol) and returned to nine in the subsequent winter, July 1984 (mean 1.8, range 0.4-3.9 mumol). The change in the number of subjects with a PD20 was significant (p less than 0.01). Four additional subjects probably had increased bronchial reactivity in the harvest season: in two the post-saline FEV1 was too unstable to give them histamine challenge and in two the challenge was inadvertently discontinued prematurely. Baseline FEV1 and FVC fell by 8% between the first and second studies (p less than 0.001); values were intermediate in the third study (FEV1 3.74, 3.44, and 3.57; FVC 4.66, 4.28, and 4.41 litres respectively). Linear modelling analysis of log PD20, season, FEV1, FVC, age, seasonality of asthma symptoms and skin test data indicated that the harvest season was the only significant determinant of variation in log PD20. It is concluded that in these wheat workers there is a seasonal variation in bronchial reactivity that may reflect a response to allergens associated with grain.

Adolescent↗

The Tsn1-ToxA interaction in the wheat-Stagonospora nodorum pathosystem parallels that of the wheat-tan spot system.

The wheat tan spot fungus (Pyrenophora tritici-repentis) produces a well-characterized host-selective toxin (HST) known as Ptr ToxA, which induces necrosis in genotypes that harbor the Tsn1 gene on chromosome 5B. In previous work, we showed that the Stagonospora nodorum isolate Sn2000 produces at least 2 HSTs (SnTox1 and SnToxA). Sensitivity to SnTox1 is governed by the Snn1 gene on chromosome 1B in wheat. SnToxA is encoded by a gene with a high degree of similarity to the Ptr ToxA gene. Here, we evaluate toxin sensitivity and resistance to S. nodorum blotch (SNB) caused by Sn2000 in a recombinant inbred population that does not segregate for Snn1. Sensitivity to the Sn2000 toxin preparation cosegregated with sensitivity to Ptr ToxA at the Tsn1 locus. Tsn1-disrupted mutants were insensitive to both Ptr ToxA and SnToxA, suggesting that the 2 toxins are functionally similar, because they recognize the same locus in the host to induce necrosis. The locus harboring the tsn1 allele underlies a major quantitative trait locus (QTL) for resistance to SNB caused by Sn2000, and explains 62% of the phenotypic variation, indicating that the toxin is an important virulence factor for this fungus. The Tsn1 locus and several minor QTLs together explained 77% of the phenotypic variation. Therefore, the Tsn1-ToxA interaction in the wheat-S. nodorum pathosystem parallels that of the wheat-tan spot system, and the wheat Tsn1 gene serves as a major determinant for susceptibility to both SNB and tan spot.

Alleles↗

Glycoproteins from Russian wheat aphid infested wheat induce defence responses.

Elicitors are molecules which can induce the activation of plant defence responses. Elicitor activity of intercellular wash fluid from Russian wheat aphid, Diuraphis noxia (Mordvilko) infested resistant (cv Tugela DN), and susceptible (cv Tugela), wheat (Triticum aestivum L.), was investigated. Known Russian wheat aphid resistance related responses such as peroxidase and beta-1,3-glucanase activities were used as parameters of elicitor activity. The intercellular wash fluid from infested resistant plants contains high elicitor activity while that from infested susceptible plants contains no or very little elicitor activity. After applying C-18 reverse phase and concanavalin A Sepharose chromatography, elicitor active glycoproteins were isolated from the intercellular wash fluid of Russian wheat aphid infested resistant wheat. The elicitor-active glycoproteins separated into three polypeptides during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isolated glycoproteins elicited peroxidase activity to higher levels in resistant than in susceptible cultivars. It was evident that the glycoproteins were probably a general elicitor of plant origin. Information gained from these studies is valuable for the development of plant activators to enhance the defence responses of plants.

Animals↗

Seasonal dynamics of cereal aphids on Russian wheat aphid (Homoptera: Aphididae) susceptible and resistant wheats.

Field experiments were conducted in 1997 and 1998 to evaluate the impact of resistance to Russian wheat aphid, Diuraphis noxia (Mordvilko), on the cereal aphid complex in wheat. Two spring wheats were planted: the variety "Centennial" (Russian wheat aphid susceptible) and the advanced line IDO488 (Russian wheat aphid resistant). IDO488 incorporates the resistance found in PI 294994 into a Centennial background. Field plots were artificially infested with adult D. noxia and sampled weekly. The most abundant aphid species in 1997 were Metopolophium dirhodum (Walker), Sitobion avenae (F.), D. noxia, and Rhopalosiphum padi (L.). In 1998, the order of abundance was M. dirhodum, R. padi, S. avenae, and D. noxia. The resistant genotype had significantly fewer D. noxia than the susceptible one during both years. However, plant genotype had no significant effect on the other aphid species in either year. Both the initial density of D. noxia and plant growth stage, had a significant effect on D. noxia population development, but had no effect on the other aphid species. There was no interaction between D. noxia resistance and the population density of the other aphid species observed.

Animals↗

[Development of Triticale and soft wheat forms with substituted wheat and rye chromosomes].

During hybridization between winter forms of hexaploid (6x) triticale and soft wheat varieties the intergenomic substitution of alian chromosomes occurs. As a result of these crosses the forms of 6x-triticale with D(R)-substitution of chromosomes in R-rye genome by wheat ones of D-genome and wheat revertants with rye chromosomes replacing the wheat ones are originated. This is the simplest and the most effective technique for developing of selected lines of triticale and soft wheat with alien substituted chromosomes and valuable genes transfer.

Chromosomes↗

Determination of deoxynivalenol in whole wheat flour and wheat bran.

A liquid chromatographic (LC) method was developed for determining deoxynivalenol (DON) in whole wheat flour and wheat bran. A 15 g test sample was extracted with acetonitrile-water (84 + 16, v/v) and applied to a Romer MycoSep cleanup column. The eluate was dried and then reconstituted in a 0.1 M phosphate buffer, pH 7.0, and applied to a Vicam DONtest-LC cleanup column. The methanol eluate was chromatographed with a methanol-water (17 + 83, v/v) mobile phase on a C18 column with UV detection at 220 nm. Five replicates at each of 5 fortification levels (0.25, 0.50, 1.0, 2.0, and 4.0 ppm), plus 5 controls, were determined for both whole wheat flour and wheat bran. For flour, the average recoveries were 72.2-91.5% with relative standard deviations (RSDs) of 4.9-18.4%. The intra-assay flour recovery was 82.4% with 9.8% RSD. A 5 replicate sample of naturally incurred wheat had an average of 1.1 ppm DON with 6.7% RSD. For bran, average recoveries of fortified samples were 69.5-99.7% with RSDs of 1.7-18.8%. The intra-assay bran recovery was 81.5% with 8.9% RSD. The limit of detection (about 3x noise) for the method is 0.05 ppm; the correlation coefficient (linearity) was >0.9995. The DON peak was clearly identified and easily integrated in the chromatograms.

Buffers↗

A comparative study of the localization of wheat-germ agglutinin and its potential receptors in wheat grains.

Wheat-germ agglutinin is located only in the embryo of a dry wheat seed and not in the endosperm tissue. This distribution remains unaltered for up to 96 h of germination and growth. The lectin is found not only in a freely soluble form but also in reversible association with particulate subcellular components. There appear to be no poly-peptides that can be solubilized with sonication and aqueous buffers from the embryo tissue that can interact with the agglutinin. This suggests that in vivo the lectin remains uncomplexed to endogenous glycoconjugates or is only able to bind to glycosylated integral membrane polypeptides. Alternatively the potential endogenous receptor(s) to wheat-germ agglutinin may not contain a polypeptide. Although the lectin is not present in the endosperm, seven polypeptides able to interact in a reversible way with wheat-germ agglutinin could be purified from that tissue.

Chromatography, Affinity↗

Food allergy to wheat: identification of immunogloglin E and immunoglobulin G-binding proteins with sequential extracts and purified proteins from wheat flour.

BACKGROUND: Cereal-associated allergy is particularly considered a serious problem, because cereals are essential in our daily diet. Wheat proteins are classified into albumins, globulins and prolamins (insoluble gliadins and glutenins). OBJECTIVES: Our objectives were to study the involvement in food allergy to wheat of these different protein types by using purified fractions and to identify those binding IgE and IgG antibodies. METHODS: Sera were obtained from 28 patients with food allergy to wheat. Albumins/globulins, gliadins and glutenins were obtained by sequential extraction based on differential solubility; alpha-, beta-, gamma- and omega-gliadins and low molecular weight (LMW) and high molecular weight (HMW) glutenin subunits were purified by chromatography. IgE binding to these extracts and fractions were analysed by radioallergosorbent test (RAST), and immunoblotting; IgG binding was detected by enzyme-linked immunosorbent assay (ELISA). RESULTS: In RAST, 60% of sera were shown to have specific IgE antibodies against alpha-, beta-gliadins and LMW glutenin subunits, 55% to gamma-gliadins, 48% to omega-gliadins and 26% to HMW glutenins. Immunoblotting analysis confirmed results obtained in RAST concerning LMW and HMW glutenin subunits and showed that 67% of patients have IgE antibodies to the albumin/globulin fraction. CONCLUSION: Results obtained in the different tests showed common features and in agreement with other studies indicated the presence of numerous allergens in food allergy to wheat; alpha-, beta-, gamma- and omega-gliadins, LMW glutenin subunits and some water/salt-soluble proteins appeared as major IgE binding allergens, whereas HMW glutenins were only minor allergens. The same type of antigenic profile against gliadins and glutenins was observed with IgG antibodies. Important sequence or structural homologies between the various gliadins and LMW glutenin subunits could certainly explain similarity of IgE binding to these proteins.

Adult↗