Abstract

BackgroundFusarium 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.ResultsSynchrotron 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.ConclusionsSynchrotron 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0357-5) contains supplementary material, which is available to authorized users.

Highlights

  • Fusarium head blight (FHB), a scab principally caused by Fusarium graminearum Schw., is a serious disease of wheat

  • It is noteworthy that Fusarium gramminearum constitutively expressing Green Fluorescent Protein (GFP) (Fg-GFP) can spread to 1 or 2 rachis nodes in both cultivars (Figure 1B), it rarely spread into non-inoculated spikelets (Figure 1C), suggesting that rachilla, the tissue connecting between rachis and spikelet, may play important role to prevent Fg spreading into spikelet in the resistant cultivars

  • We have presented a new approach for evaluating the resistance mechanisms of different lines to FHB based on the use of synchrotron based imaging techniques and Fourier Transform mid infrared (FTIR) spectroscopy in comparing resistance and susceptible wheat cultivars

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Summary

Introduction

Fusarium head blight (FHB), a scab principally caused by Fusarium graminearum Schw., is a serious disease of wheat. 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. In the rachis of the wheat cultivars, PCA underlines significant changes in pectin, cellulose, and hemicellulose characteristic absorption spectra. Symptoms of FHB on barley include isolated areas of tan to dark brown discoloration as well as evidence of watersoaking restricted to the initially infected inflorescence [6,9]. Other abiotic factors such as freezing damage With intricate irrigation systems and the total number of person hours needed to score multiple genotypes, the cost of one FHB data point has been reported as six US dollars [10]

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