title: Synchrotron based phase contrast X-ray imaging combined with FTIR spectroscopy reveals structural and biomolecular differences in spikelets play a significant role in resistance to Fusarium in wheat.
abstract: BACKGROUND
  Fusarium head blight (FHB), a scab principally caused by Fusarium graminearum Schw., is a serious disease of wheat. The purpose of this study is to evaluate the potential of combining synchrotron based phase contrast X-ray imaging (PCI) with Fourier Transform mid infrared (FTIR) spectroscopy to understand the mechanisms of resistance to FHB by resistant wheat cultivars. Our hypothesis is that structural and biochemical differences between resistant and susceptible cultivars play a significant role in developing resistance to FHB.
  
  
  RESULTS
  Synchrotron based PCI images and FTIR absorption spectra (4000-800 cm(-1)) of the floret and rachis from Fusarium-damaged and undamaged spikes of the resistant cultivar 'Sumai3', tolerant cultivar 'FL62R1', and susceptible cultivar 'Muchmore' were collected and analyzed. The PCI images show significant differences between infected and non-infected florets and rachises of different wheat cultivars. However, no pronounced difference between non-inoculated resistant and susceptible cultivar in terms of floret structures could be determined due to the complexity of the internal structures. The FTIR spectra showed significant variability between infected and non-infected floret and rachis of the wheat cultivars. The changes in absorption wavenumbers following pathogenic infection were mostly in the spectral range from 1800-800 cm(-1). The Principal Component Analysis (PCA) was also used to determine the significant chemical changes inside floret and rachis when exposed to the FHB disease stress to understand the plant response mechanism. In the floret and rachis samples, PCA of FTIR spectra revealed differences in cell wall related polysaccharides. In the florets, absorption peaks for Amide I, cellulose, hemicellulose and pectin were affected by the pathogenic fungus. In the rachis of the wheat cultivars, PCA underlines significant changes in pectin, cellulose, and hemicellulose characteristic absorption spectra. Amide II and lignin absorption peaks, persistent in the rachis of Sumai3, together with increased peak shift at 1245 cm(-1) after infection with FHB may be a marker for stress response in which the cell wall compounds related to pathways for lignification are increased.
  
  
  CONCLUSIONS
  Synchrotron based PCI combined with FTIR spectroscopy show promising results related to FHB in wheat. The combined technique is a powerful new tool for internal visualisation and biomolecular monitoring before and during plant-microbe interactions to understand both the differences between cultivars and their different responses to disease stress.
authors: Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK, S7N 2V3, Canada. Rachid.Lahlali@lightsource.ca.
authors: Rachid
authors: R
authors: Lahlali
authors: Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK, S7N 2V3, Canada. Chithra.Karunakaran@lightsource.ca.
authors: Chithra
authors: C
authors: Karunakaran
authors: National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK, S7N 0W9, Canada. Lipu.Wang@nrc-cnrc.gc.ca.
authors: Lipu
authors: L
authors: Wang
authors: University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, S7N 5A8, Canada. irw412@mail.usask.ca.
authors: Ian
authors: I
authors: Willick
authors: University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, S7N 5A8, Canada. Marina.Schmidt@lightsource.ca.
authors: Marina
authors: M
authors: Schmidt
authors: Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK, S7N 2V3, Canada. Xia.Liu@lightsource.ca.
authors: Xia
authors: X
authors: Liu
authors: Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK, S7N 2V3, Canada. Ferenc.Borondics@lightsource.ca.
authors: Ferenc
authors: F
authors: Borondics
authors: National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK, S7N 0W9, Canada. Lily.Forseille@nrc-cnrc.gc.ca.
authors: Lily
authors: L
authors: Forseille
authors: National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK, S7N 0W9, Canada. Pierre.Fobert@nrc-cnrc.gc.ca.
authors: Pierre R
authors: PR
authors: Fobert
authors: University of Saskatchewan, 51 Campus Drive, Saskatoon, SK, S7N 5A8, Canada. Karen.Tanino@usask.ca.
authors: Karen
authors: K
authors: Tanino
authors: Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK, S7N 0X2, Canada. Gary.Peng@agr.gc.ca.
authors: Gary
authors: G
authors: Peng
authors: Canadian Light Source Inc., 44 Innovation Boulevard, Saskatoon, SK, S7N 2V3, Canada. Emil.Hallin@lightsource.ca.
authors: Emil
authors: E
authors: Hallin
mesh_terms: D060467:Disease Resistance; D005670:Fusarium / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D025341:Principal Component Analysis; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D017356:Synchrotrons; D014908:Triticum / Q000033:anatomy & histology* / Q000382:microbiology*; D014965:X-Rays
chemical_list: D049452:Green Fluorescent Proteins
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