Influence of CrylAb protein on feeding and ovipositional behavior of European corn borer, Ostrinia nubilalis (Hübner)
Date
1998
Authors
Higgins, Laura Sue
Major Professor
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Tollefson, Jon J.
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Abstract
Corn transformed with a synthetic gene expressing a protein derived from the soil bacterium Bacillus thuringiensis (Bt) to produce an insecticidal protein to control the European corn borer (ECB) Ostrinia nubilalis (Hübner) was commercially released in 1996. This body of work was aimed at exploring ECB/transgenic plant interactions to determine how the presence of the transgenic protein influences the behavior of larvae and adult ECB. Choice tests were conducted using ECB to determine if larvae at different developmental stages can detect the presence of a Bacillus thuringiensis (Bt) toxin in transgenic corn leaf tissue. Tests using a factorial design with all combinations of high, moderate, low and non-Bt corn leaf discs in an isoline compared feeding behavior of 1st, 3rd and 5th instar ECB larvae.
Mortality, weight change and the amount of leaf tissue consumed at 96 hours was recorded. Larvae in the control comparisons (non-Bt vs. non-Bt) exhibited similar consumption rates of both discs for all instars. First instar larvae showed significant feeding differences when Bt discs were offered with non-Bt discs. These differences were less evident in the later instars. Mortality and weight data indicate that a portion of the larvae are surviving low doses of Bt without significant weight losses. These data support a high dose, whole plant expression approach for resistance management. Field experiments were conducted in 1995 and 1996 to determine if ECB moths show an ovipositional preference for corn transformed with Bt over non-Bt corn.
Comparisons using three different Cry1Ab events expressing high, moderate, and low levels of Bt protein in hybrid and inbred corn along with their non-Bt isolines were evaluated using both first and second generation ECB. Plots of Bt and non-Bt corn were caged together and ECB moths were allowed to emerge from pupation rings. Ten days after moth emergence, egg masses were counted on individual plants to determine if the moths had an ovipositional preference for either the Bt or non-Bt corn. No significant preference was found in any comparison that can be attributed to the presence of the CryIAb protein.
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