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Resistance of Bollworm, Helicoverpa Zea, to CryIA(c) Toxin

A. D. Burd, J. R. Bradley, Jr., J. W. Van Duyn and F. Gould


 
ABSTRACT

In 1998, third-instar bollworm, Helicoverpa zea, larvae were collected from the ears of B.t. sweet corn grown in Plymouth and Clayton, North Carolina. Larvae were transferred to artificial diet containing 0.1 ug/ml of CryIA(c) toxin. A selection experiment was performed to determine the rate of adaptation to varying levels of this toxin. We found that after only 6 generations of selection, the selected colony had developed about 50-fold resistance to CryIA(c) toxin. Nearly 100-fold resistance was seen after 10 generations. The LC50 values for the control strain, the selected strain, the selected female by control male cross and the control female by selected male cross were 2.78, 240.98, 141.62, and 277.32 ug/ml, respectively for the F8 generation. This suggests that resistance to B.t. can be inherited as a dominant or incompletely dominant trait. The selected strain was only 3 times more resistant to CryIIA than the susceptible lab colony.



Reprinted from Proceedings of the 2000 Beltwide Cotton Conferences pp. 923 - 926
©National Cotton Council, Memphis TN

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Document last modified Saturday, Jun 17 2000