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Long-Term Selection for Resistance to Bacillus thuringiensis Cry1Ac Endotoxin in a Minnesota Population of European Corn Borer (Lepidoptera: Crambidae)
Transgenic corn, expressing the insecticidal δ-endotoxin of Bacillus thuringiensis Berliner, provides high levels of control of some lepidopteran pests, particularly the European corn borer, Ostrinia nubilalis (Hübner). However, resistance to B. thuringiensis has been documented recently in laboratory colonies of agronomically important Lepidoptera, including O. nubilalis. For the past 4 yr, we have selected for Cry1Ac resistance in a population of O. nubilalis from southeastern Minnesota. Increasing resistance to B. thuringiensis was noted after only 8 generations of selection, with a peak at 162-fold resistance, based on comparisons of LC50s to a nonselected parental strain. This resistance was found to decrease at the same rate in the absence of B. thuringiensis selection, with one selected colony becoming nearly as sensitive to the Cry1Ac toxin as the nonselected colony after 9 generations without exposure to B. thuringiensis. The most resistant of the colonies, S-I, was only marginally cross-resistant to Cry1Ab, yet another selected colony, S-IV, did demonstrate a 16-fold cross-resistance. In addition, larvae from the S-IV colony had significantly greater weight gain when feeding on diet incorporated with B. thuringiensis-transgenic corn than did larvae from the nonselected parental colony. These findings emphasize the need for careful deployment of B. thuringiensis corn to preserve this effective pest management technology.
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Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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