Physiological and morphological traits associated with Fusarium head blight response in a flavonoid-rich durum wheat genotype

Durum wheat is among the cereal crops with the highest susceptibility to Fusarium Head Blight (FHB), the most devastating wheat disease. Purple pericarp durum wheat genotypes, having anthocyanin-rich grains, are an unexplored group of accessions, which may provide valuable information about the role of flavonoids in wheat-Fusarium interaction. In this study, a purple pericarp durum wheat accession (Purple durum) was challenged with Fusarium graminearum infection, evaluating the different responses of physiological traits, in comparison with an FHB-resistant line (DBC-480) and a commercial FHB-susceptible cultivar (Svevo). Purple durum showed high susceptibility to FHB, but the infection did not affect the seed set, as for the resistant control. In Purple durum flag leaves, lower flavonoid content and higher temperature depression, compared to the resistant control, were detected. The infection affected the difference between the spike temperature and the flag leaf temperature in the resistant and the susceptible control in an opposite way, while the total phenolic content was always higher in the infected spikes. Instead, the total anthocyanin content (TAC) of the spikes was considerably lower in Purple durum subjected to the infection compared to the mock plants, while TAC increased in the infected resistant genotype, suggesting an involvement of anthocyanins in the resistance mechanism of DBC-480. Association among morphological spike traits and physiological traits are discussed. Our results corroborate the importance of phenylpropanoids in FHB-wheat interaction and point attention on anthocyanin metabolism, suggesting to further consider these metabolites, which are under-investigated for durum wheat resistance.