EFFECT OF INGESTED MERIDIC DIET AND CORN LEAVES ON MIDGUT DETOXIFICATION PROCESSES IN THE EUROPEAN CORN-BORER, OSTRINIA-NUBILALIS

Detoxification processes in the European corn borer, Ostrinia nubilalis, fed on either meridic diet or corn leaves from three plant lines with either low, intermediate, or high resistance to leaf damage were investigated by measuring cytochrome P450, cytochrome b5, cytochrome c reductase, NADPH and NADH oxidase, O- and N-demethylase, as well as, glutathione S-transferase activities. Feeding on corn leaves caused the absorbance maximum of cytochrome P450 to change from 449 to 448 nm, and the cytochrome b5 maximum shifted from 426 to 425 nm. When compared to insects fed on meridic diet, those fed on corn leaves had increased levels of cytochrome P450, cytochrome b5, NADPH-cytochrome c reductase, NADH oxidase, and O-demethylase activities. NADH-cytochrome c reductase and NADPH oxidase activities were decreased in the corn borers fed on corn leaves. Feeding on corn leaves had no effect on N-demethylase and glutathione S-transferase activities of the corn borers. The effects on the detoxification processes were correlated with the levels of resistance to leaf damage and with DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) levels found in the three corn lines. © 1992.