Genotype, nitrogen and herbivory shape plant defense: the case of a vitamin-enriched maize

ABSTRACT The cultivation of crops with novel traits could interfere with ecosystem services delivered by arthropods through bottom-up effects. Here we tested the hypothesis that a vitamin enriched maize (Carolight R ) is similar in terms of plant-arthropod interactions to its wild type when compared in controlled environment and under field conditions. In order to assess the robustness of their equivalence we tested two nitrogen availability regimes. We used arthropod field abundance, the behavior and fitness of a keystone maize herbivore - the leafhopper Zyginidia scutellaris - and above ground chemistry of maize plants (volatile, hormone and metabolite profiling) as indicators of potential changes in plant-insect interactions. Nitrogen availability was the key driver of herbivore abundance and behavior, and determined direct and indirect chemical defense in maize plants. Both genotypes presented similar constitutive and inducible phytohormone profiles independently of the nitrogen regime. However, feeding by the herbivore suppressed the levels of JA-Ile and JA, without impairing the release of induced plant volatiles. Carolight R and M37W differed to some degree in the concentrations of phenolics (hydroxycinnamic acids and lignans) and in the abundance of a volatile compound. Overall the effect of maize genotype on the herbivores was smaller than the effect of nitrogen fertilization. HIGHLIGHT We show the separate and interactive effects of nitrogen availability and genotype on the performance and behavior of a herbivore, and related these changes to constitutive and inducible maize defenses.