Biochemical factors of maize silks associated with host susceptibility to Fusarium graminearum

Fusarium graminearum is the causal agent of Gibberella ear rot (GER) in maize, a devastating fungal disease leading to yield reduction and contamination of grains with type B trichothecene mycotoxins (TCTB). Reducing GER damage requires the implementation of an integrated strategy in which the use of resistant maize genotypes is a key pillar. F. graminearum infects maize ears most often by the silk channel, which represents the first plant tissue encountered by the pathogen. The present study aimed at providing new phenotyping tools to improve breeding pipelines by investing the importance of maize silk composition in GER resistance. Here we used targeted and untargeted metabolomics approaches to characterize differences between genotypes reported as susceptible or tolerant to GER. Promising results were obtained with the LC-HRMS/MS analysis that led to outline 25 m/z signals, among which 14 were assigned to a unique compound, that could distinguish tolerant and susceptible genotypes. We notably evidenced that a metabolite putatively identified as feruloyl-hexose could contribute to GER tolerance, while two others putatively identified compounds (chlorogenic acid and eupatilin) could be susceptibility-associated biomarkers. The present study paves the avenue for the use of new approaches based on silk composition to improve the breeding programs aiming at increasing maize resistance.