How does selection for flowering in maize shapes defenses components against the European Corn Borer ?

Understanding how selection for flowering time affects maize susceptibility to the European corn borer (ECB, Ostrinia nubilalis) is essential in the context of climate change and increasing pest pressures. We investigated the consequences of divergent selection for flowering time on maize defense and susceptibility traits using two genetic backgrounds (MBS847 and F252). Three complementary approaches were combined: leaf palatability tests, ECB field incidence dynamics surveys, and biochemical analyses of maize stem walls. In the MBS847 background, early-flowering families exhibited lower content of defense compounds, higher leaf palatability, and higher field infestation compared to late-flowering families. In contrast, no significant differences were observed between early and late populations in the F252 background. Differences in susceptibility between families were associated with variation in stem biochemical composition, including fiber components which influence stem rigidity and resistance to ECB. Our results indicate that selection for flowering time can modify plant defense traits and susceptibility in a genetic-background-dependent manner. These findings highlight the interaction between plant phenology, biochemical defenses, and insect herbivory, with implications for breeding and adaptation under changing environmental conditions.