Abstract: To probe the pathogenic mechanism and provide theoretical basis for safety and sustainable utilization of Bt corn, the histopathological changes in the midgut of larvae of the Asian corn borer, Ostrinia furnacalis (Guenée), fed on Bt-transgenic corn expressing Cry1Ab protein were observed by transmission electron microscopy （TEM）. The results showed that the midgut cells and their cell organelles of the O. furnacalis larvae fed on the Bt corn tissues exhibited distinct pathological changes. The midgut cells began to change at 12 h after ingestion of Bt corn. The microvilli of the midgut epithelial cells began to fall off and the endoplasmic reticulum became swollen. After 24 h, the number of endoplasmic reticulum increased and the cavity of goblet cell enlarged. Many microvilli sloughed off and cells became vacuolated after 48 h. Cell vacuolation was more obvious with time going. The pathologic degrees were disparate among cells in the early period of infection. Desquamation of microvilli and swelling of endoplasmic reticulum occurred universally in most midgut cells. In conclusion, the insecticidal protein expressing in transgenic Bt corn can cause pathological changes to midgut cells of O. furnacalis larvae and kill them finally.

Key words: Ostrinia furnacalis, transgenic Bt corn, Cry1Ab protein, histopathological change, transmission electron microscopy (TEM)