The European corn borer, Ostrinia nubilalis (Hübner), is one of the most important insect pests of corn in the U.S. With the advent of corn hybrids expressing Bacillus thuringiensis genes, specific management strategies are necessary to avoid resistance development in target pest species. Studies of the genetics of resistance are crucial for the success of efforts to manage resistance in the future, including resistance inheritance. Ostrinia nubilalis colonies have been selected for resistance to the B. thuringiensis Cry1Ab toxin in our laboratory for over 55 generations and have developed significant levels of resistance (up to 300-fold). The objectives of this study were to determine whether the resistance is sex-linked or autosomal, the degree of dominance, and the numbers of genes involved. Two selected populations and one susceptible population were used to establish reciprocal crosses between RR and SS parents. The F1 neonates were then used for bioassays. To establish parental populations, larvae were reared using standard procedures without exposure to the toxin for one generation. Pupae were sexed and arranged in cages so that RR males would mate with SS females, and vice-versa. Neonate larvae obtained from these crosses were assayed for Cry1Ab susceptibility and compared with both parental populations. These data indicate that the resistance is autosomal as there were no significant differences between the reciprocal crosses, and that the resistance is incompletely dominant. Backcrosses of the F1 generation to both the resistant and susceptible parents suggest that one or few genes are responsible for the resistance.
Species 1: Lepidoptera Crambidae Ostrinia nubilalis (European corn borer)
Keywords: resistance, Bacillus thuringiensis
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