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B. T. Resistance Evolution in the H. Zea Population in Eastern North Carolina

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

ABSTRACT

Adult female bollworm moths were collected from various light trap locations in eastern North Carolina from August-October during 2000-2002. Female moths were allowed to oviposit, and upon hatch, 24 neonates from each female (F1 families) were screened for growth rate on each of three diets: non-B. t., Cry1Ac, and Cry2Ab; B. t. diets contained 5.0 mg toxin per milliliter of diet. One individual out of 1834 screened was found that appeared to carry a major dominant gene for resistance to Cry1Ac. Assuming four genomes per individual, then the gene frequency is 1/7336 or 0.000136. Another individual was also found out of 1897 screened that appeared to carry a major gene for resistance to Cry2A. The gene frequency for Cry2A resistance would be estimated at 1/7588 or 0.000132. Adults from F1 families with growth scores in the highest (R) and lowest (S) quartiles were mated in 4 combinations, RxR, SxR, RxS, and SxS. Differences in growth rates of larvae from these crosses demonstrated that there is substantial quantitative genetic variation for resistance to both CryIAc and Cry2Ab. Along with results suggesting partially dominant inheritance of resistance to Cry1Ac and Cry2A, these estimates become critically important when determining appropriate resistance management strategies for the sustainability of transgenic cottons.





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Document last modified April 16, 2003