Investigating the role of ethylene signalling in Fusarium head blight disease response in wheat

Fusarium head blight (FHB) is a devastating disease of cereals that is caused by a group of fungi belonging to the Fusarium genus. The species that cause FHB infect wheat heads (inflorescence structure) and produce mycotoxins that accumulate in the developing kernels, rendering them unsuitable for food/feed. Cultivation of FHB resistant lines is an important strategy to prevent mycotoxin contamination of grain. Resistance involves differential activation of plant defence hormones signaling pathways, including jasmonic acid and salicylic acid. The objective of this work is to investigate the role of the plant hormone ethylene (ET) in the FHB-wheat interaction, which is poorly understood at this time. In order to modify the ET signalling pathway in wheat heads using exogenous chemical treatments, a dissociated head assay was developed here that will be used to facilitate chemical treatments during infection with F. graminearum. Wheat heads will be cut at anthesis and placed in media containing one of four chemicals that affect the ET signalling pathway: two inhibitors of ET signalling (1-methylcyclopropene (MCP), cyclopropane-1,1-dicarboxylic acid (CDA)), and two activators of ethylene signalling (1-aminocyclopropane-1-carboxylic acid (ACC), and ethephon (a chemical releaser of ET)). Heads will then be inoculated with F. graminearum spores and disease evaluation will be carried out at 3, 6 and 9 days after inoculation. Prior to initiating the disease assays a preliminary experiment was carried out to confirm that the chemical treatments affecting ET signalling can stimulate a response in dissociated wheat heads. Heads of untreated wheat cultivar ‘Superb’ were transferred to media containing different concentrations (50, 100 and 150 µM) of ACC, ethephon, MCP and CDA. Differential expression of ethylene-responsive genes was assessed at 24 hours after treatment. Gene-expression data and preliminary disease assays results will be presented.