Table of Lectures - Society for Mycotoxin Research

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L-20 29 th Mycotoxin Workshop Toxigenic potential and pathogenicity of Fusarium poae and Fusarium avenaceum on cereals Susanne Vogelgsang1 , Michael Sulyok2 , Rainer Schuhmacher2 , Hans-Rudolf Forrer1 1 Research Station Agroscope Reckenholz-Tänikon ART, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland 2 Center for Analytical Chemistry, Department of Agrobiotechnology (IFA-Tulln), University of Natural Resources and Applied Life Sciences, Konrad Lorenz Strasse 20, A-3430 Tulln, Austria Fusarium head blight (FHB) is one of the most noxious cereal diseases, causing substantial yield losses in small-grain cereals, a decline in grain quality, and the contamination of grain and straw by mycotoxins. In many cases, FHB is caused by a complex of Fusarium species producing different toxins. In Europe, the predominant toxigenic FHB pathogens are F. graminearum, F. culmorum, F. avenaceum, and F. poae. The species composition varies in time and space and there is evidence that F. poae and F. avenaceum are more prevalent and that their impact might be greater than the high number of publications on F. graminearum suggests. Compared with toxins produced by F. graminearum (e.g. deoxynivalenol, zearalenone), some toxins of F. poae (nivalenol, diacetoxyscirpenol, monoacteoxyscirpenol, T-2, HT-2, beauvericin) and of F. avenaceum (enniatins, moniliformin) display a far greater toxicity. This could have significant implications on human and animal health since plants and harvested grains infected by F. poae and F. avenaceum lack symptoms as distinct as those observed from F. graminearum. Therefore, and due to the lack of systematic monitoring of the associated toxins, contaminated cereal lots could be overseen and used for consumption or fed to animals. Besides our work on epidemiology and prevention of FHB caused by F. graminearum (e.g. [1]), we have been examining the pathogenicity and toxigenicity of F. poae and F. avenaceum in vivo and in vitro. Ina 3-year field experiment, the susceptibility of 14 Swiss winter wheat varieties was investigated by artificial inoculation with suspensions of a mixture of 3 poly-conidia isolates of either F. poae or of F. avenaceum. In climate chamber trials, individual single-conidia isolates were used to inoculate the wheat cultivar Apogee. Collected data included visual assessment of FHB incidence, yield, the incidence of infected grains by Fusarium species with a seed health test (field experiment only), as well as the analysis for selected mycotoxins in finely ground grains. In an in vitro study, the toxigenic potential of these isolates was assessed through incubation on 4 different cereal substrates. For both, in vivo and in vitro experiments, sample preparation and HPLC-MS/MS analysis was conducted according to [2]. Half a gram of ground sample was extracted using an acidified acetonitrile/water mixture. The raw extract was diluted 1:2, 1:100, and 1:7 500, respectively, and all three dilutions were subsequently analysed. Quantification was performed via external calibration. Blank samples were spiked, extracted, and analysed for control purposes. We observed significant differences in the susceptibility of wheat varieties towards the mixture of F. poae and F. avenaceum isolates as well as substantial differences in pathogenicity between individual isolates on Apogee. Furthermore, the results from the in vitro experiment demonstrated strong substrate effects as well as isolate-specific substrate effects on the amount and type of toxins detected. Possible implications from these field and laboratory results for food and feed safety will be discussed. Reference [1] Forrer, H.-R., T. Musa, A. Hecker and S. Vogelgsang (2006): FusaPROG – a tool for the prediction of Fusarium head blight and deoxynivalenol in winter wheat (Abstract). Canadian Journal of Plant Pathology – Revue Canadienne de Phytopathologie, 28, 374. [2] Sulyok, M., F. Berthiller, R. Krska and R. Schuhmacher (2006): Development and validation of a liquid chromatography/tandem mass spectrometric method for the determination of 39 mycotoxins in wheat and maize. Rapid Communications in Mass Spectrometry, 20, 2649 – 2659. 40
May 14 th –16 th 2007, Fellbach L-21 Elucidating the mechanisms by which wheat tolerates the Fusarium mycotoxin deoxynivalenol. Stephanie Walter ∗ , Josephine M. Brennan, Khairul I. Ansari, Chanemougasoundharam Arunachalam, Mojibur R. Khan, Damian Egan, Fiona M. Doohan Molecular Plant Microbe Interactions Group, School of Biology and Environmental Sciences, Agricultural and Food Science Centre, University College Dublin, Belfield, Dublin 4, Ireland ∗ Author for correspondence: Phone: +353-1-7167110; e-mail: stephanie.walter@ucd.ie Deoxynivalenol (DON) is a mycotoxigenic compound produced by Fusarium fungi. This toxin acts as an aggressive factor for these fungi when they attack wheat heads and cause Fusarium head blight (FHB) disease. Wheat cultivars differ in their susceptibility to FHB disease and their tolerance of DON. We used functional genomics techniques (differential display RT-PCR, spotted microarray analyses and gene-specific RT-PCR analysis) to identify a) wheat genes that respond to DON and b) wheat genes that are associated with the DON tolerance of wheat cultivar CM 82036. Based on our results, we propose a model whereby the early oxidative stress response and detoxification pathway contribute to DON tolerance. In wheat spikelets, DON-responsive wheat transcripts included retrotransposons and transcripts that code for proteins involved in defence [1], detoxification, oxidative stress response, protein synthesis, DNA replication and repair. Analysis of gene expression in double haploid progeny from a ‚CM 82036‘ (DON tolerant)×‚Remus‘ (DON intolerant) cross showed that the effect of DON on the accumulation of several transcripts (including those coding for a bZIP transcription factor, an MRP ABC transporter, a glucosyltransferase and a cytochrome P450) was both genotype-specific and generally higher in progeny that inherited the FHB resistance QTL Fhb1 from ‚CM 82036‘. Both the MRP ABC transporter gene and Fhb1 are located on the short arm of chromosome 3B, but not in the same position. Reference [1] Ansari, K.I., Walter, S., Brennan, J.M., Lemmens, M., Kessans, S., McGahern, A., Egan, D., Doohan, F.M. (2007): Retrotransposon and gene activation in wheat in response to mycotoxigenic and non-mycotoxigenicassociated Fusarium stress. Theor. Appl. Genet., 114, 927 – 937 41
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Table of Lectures - Society for Mycotoxin Research

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