Role of Hydroxycinnamic Acids in the Infection of Maize Silks by Fusarium graminearum Schwabe

In the current study, the hydroxycinnamic acids in silks of diverse maize inbred lines differing in Fusarium resistance were determined at several times after inoculation with Fusarium graminearum or sterile water as control. The main objective was to determine the possible relationship between the hydroxycinnamic acid changes in silks and ear rot resistance. Several changes in the cell-wall-bound hydroxycinnamic acid concentrations were observed after inoculation with E graminearum, although these changes were not directly correlated with genotypic resistance to this fungus. Ester-bound ferulic acid decreased, probably due to degradation of hemicellulose by hydrolytic enzymes produced by Fusarium spp., while p-coumaric acid and diferulates showed slight increases that, in conjunction, did not result in delayed F. graminearum progression through the silks. It is important to note that the decrease of ferulic acid in the E graminearum treatment was faster in susceptible than in resistant genotypes, suggesting a differential hemicellulose degradation in silk tissues. Therefore, the ability of the maize genotypes to slow down that process through hemicellulose structural features or xylanase inhibitors needs to be addressed in future studies.