Influence of inducible benzoxazinoid derivatives in maize on larval dispersal of the European corn borer (Ostrinia nubilalis)
Abstract: The dynamics of interactions between plants and herbivores is a major subject in ecology. In particular, the levels of defense traits are highly variable among and within plant species, including the occurrence and concentrations of defensive metabolites during a plant’s lifetime. In grasses, which include an important range of crop species, benzoxazinoid derivatives (BXDs) have been recognized as an important family of compounds mediating resistance to antagonists such as insects, pathogens and weeds. We studied the role of inducible BXD in plant-insect interactions using two sets of maize lines: a bx1 mutant which expresses only low levels of BXDs and its wild type. Sixty plants of each line were grown within a maize field. Half of the plants were experimentally induced with methyl-jasmonate one day prior to an artificial infestation with egg clutches of Ostrinia nubilalis (European corn borer, ECB). In September, buffer plants surrounding the two maize lines were examined for symptoms of ECB damage. The results show that ECB larvae disperse more to neighboring plants when feeding on wild type plants than when feeding on bx1 mutants. Similarly, a higher proportion of larvae emigrated from induced than from non-induced plants. This suggests that BXDs stimulate larval dispersal, thereby increasing resistance at the level of individual plants. However, by spreading larval attack over several plants, an increase in resistance may potentially decrease yield at the field level.