Abstract
Fusarium head blight (FHB), caused by Fusarium graminearum, is one of the most devastating diseases of wheat and barley. Resistance to FHB is highly complex and quantitative in nature, and is most often classified as resistance to spikelet infection and resistance to spread of pathogen through the rachis. In the present study, a resistant (CI9831) and a susceptible (H106-371) two-row barley genotypes, with contrasting levels of spikelet resistance to FHB, pathogen or mock-inoculated, were profiled for metabolites based on liquid chromatography and high resolution mass spectrometry. The key resistance-related (RR) metabolites belonging to fatty acids, phenylpropanoids, flavonoids and terpenoid biosynthetic pathways were identified. The free fatty acids (FFAs) linoleic and palmitic acids were among the highest fold change RR induced (RRI) metabolites. These FFAs are deposited as cutin monomers and oligomers to reinforce the cuticle, which acts as a barrier to pathogen entry. Quantitative real-time PCR studies revealed higher expressions of KAS2, CYP86A2, CYP89A2, LACS2 and WAX INDUCER1 (HvWIN1) transcription factor in the pathogen-inoculated resistant genotype than in the susceptible genotype. Knockdown of HvWIN1 by virus-induced genes silencing (VIGS) in resistant genotype upon pathogen inoculation increased the disease severity and fungal biomass, and decreased the abundance of FFAs like linoleic and palmitic acids. Notably, the expression of CYP86A2, CYP89A2 and LAC2 genes was also suppressed, proving the link of HvWIN1 in regulating these genes in cuticle biosynthesis as a defense response.
Highlights
About two-thirds of the global barley crop is used as animal feed, while the remaining one-third is used for malting, brewing and distillation (Newton et al, 2011)
Metabolites were profiled in the spikelets of resistant and susceptible genotypes at 3 dpi, inoculated with F. graminearum or with water and analyzed based on liquid chromatography and high resolution mass spectrometry (LC-HRMS)
A total of 1864 monoisotopic peaks were detected and the significant ones were categorized into RRC and RR induced (RRI) metabolites
Summary
About two-thirds of the global barley crop is used as animal feed, while the remaining one-third is used for malting, brewing and distillation (Newton et al, 2011). Barley is critical for food and feed, and has unparalleled impact on the social and economic development of several countries (McMullen et al, 2012). The crop is severely affected by the devastating disease Fusarium head blight (FHB) caused by a fungus, Fusarium graminearum (Trail, 4128 | Kumar et al.2009). Developing kernels are infected through the epicarp, which destroys layers of the seed coat and starch and protein in the endosperm (Jansen et al, 2005). Plant resistance through genetic improvement is considered to be the most efficient, economic and ecofriendly approach to reduce disease intensity (Bai and Shaner, 2004)
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