ABSTRACT
BACKGROUND: Busseola fusca is a major pest of maize in Africa but unfortunately is difficult to control using chemical insecticides. Insect-resistant transgenic crops may provide an alternative viable strategy to control this pest. RESULTS: Recombinant Cry1Ab (1%) reduced larval weight by 60% over the trial period, while larval weight in the control group increased by 25%; no effects on mortality were observed. Insect survival, developmental rate and pupal and adult weight were significantly reduced (P < 0.05) on maize expressing Cry1Ab (MON810) compared with the non-transformed parental line. These differences were more pronounced with second-instar larvae than with third-instar larvae. Leaf area consumed by Bacillus thuringiensis (Bt)-fed larvae was significantly lower (0.5 cm(2) larva(-1) day(-1)) compared with the area consumed by control-fed insects (3.3 cm(2) larva(-1) day(-1)). EM studies revealed that consumption of Bt maize deleteriously affected gut integrity. Effects were observed in columnar cells of the midgut epithelium, with the cytoplasm becoming highly vacuolated; the microvilli were disorganised, the mitochondria were abnormal and there was an increase in the number of lysosomal bodies. The rough endoplasmic reticulum had also become dilated. CONCLUSION: This study confirms the potential for Bt maize, when used as part of an IPM programme, for control of B. fusca.
