EFFECT OF LIGHT ON CHANGES IN MAIZE RESISTANCE AGAINST THE EUROPEAN CORN-BORER, OSTRINIA-NUBILALIS (HUBNER)

The herbivore-resistant synthetic maize BS9 (C4) was grown in three environments, namely, greenhouse with reduced UV light, greenhouse with supplemental UV light, and outside, and leaves at the three-, five-, seven-, nine-, and 10-leaf stages of development were fed to the European corn borer, Ostrinia nubilalis (Hubner). Larvae preferred younger leaves, and leaves grown under reduced UV light, in spite of the high levels of the defence compound 2,4-dihydroxy-7-methoxy-2H-1,4 benzoxazin-3 (4H)-one (DIMBOA). The low level of feeding on leaves from plants grown outside was associated with increased toughness and increased photochemically derived phenolic dimers that cross-link hemicellulose. Tender young maize plants have a low level of cell wall phenolics and depend on a toxin (DIMBOA) for defence. In older plants, DIMBOA levels are low, leaves are tough, and resistance is largely structure-based.