@article{jackson_gould_bradley_duyn_2006, title={Genetic variation for resistance to Bacillus thuringiensis toxins in Helicoverpa zea (Lepidoptera : Noctuidae) in eastern North Carolina}, volume={99}, DOI={10.1603/0022-0493-99.5.1790}, abstractNote={Abstract To evaluate resistance to Bacillus thuringiensis Berliner (Bt) toxins, adult female bollworms, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), were collected from four light trap locations in two eastern North Carolina counties from August to October during 2001 and 2002. Females were allowed to oviposit, and upon hatching, 24 neonates from each female (F1 lines) were screened for survival and growth rate on each of three diets: non-Bt diet, diet containing 5.0 &mgr;g/ml Cry1Ac toxin, or diet containing 5.0 &mgr;g/ml Cry2Ab toxin. These screens were designed to identify nonrecessive Bt resistance alleles present in field populations of bollworm. Of 561 and 691 families screened with both Cry1Ac- and Cry2Ab-containing diets in 2001 and 2002, respectively, no F1 lines were identified that seemed to carry a gene conferring substantial resistance to either Cry1Ac or Cry2Ab. Adults from F1 lines with growth scores in the highest (R) and lowest (S) quartiles were mated in four combinations, RxR, SxR, RxS, and SxS. Differences in growth rates of larvae from these crosses demonstrated that there is substantial quantitative genetic variation in eastern North Carolina populations for resistance to both Cry1Ac and Cry2Ab toxins. These findings, in addition to results suggesting partially dominant inheritance of resistance to Cry1Ac and Cry2Ab, are critically important for determining appropriate resistance management strategies that impact the sustainability of transgenic cotton, Gossypium hirsutum (L.).}, number={5}, journal={Journal of Economic Entomology}, author={Jackson, R. E. and Gould, Fred and Bradley, J. R. and Duyn, J. W. Van}, year={2006}, pages={1790–1797} }
 @article{jackson_mahaffey_bradley_van duyn_sorenson_2005, title={The impact of transgenic cottons expressing one or two proteins from Bacillus thuringiensis on survival and damage potential of first and second instars of Ostrinia nubilalis (Lepidoptera: Crambidae)}, volume={9}, ISBN={1524-3303}, number={4}, journal={Journal of Cotton Science (Online)}, author={Jackson, R. E. and Mahaffey, J. S. and Bradley, J. R., Jr. and Van Duyn, J. W. and Sorenson, C. E.}, year={2005}, pages={199} }
 @article{jackson_bradley_van duyn_gould_2004, title={Comparative production of Helicoverpa zea (Lepidoptera : Noctuidae) from transgenic cotton expressing either one or two Bacillus thuringiensis proteins with and without insecticide oversprays}, volume={97}, ISSN={["1938-291X"]}, DOI={10.1603/0022-0493-97.5.1719}, abstractNote={Abstract Transgenic cotton, Gossypium hirsutum (L.), expressing either one or two Bacillus thuringiensis ssp. kurstaki Berliner (Bt) proteins was compared with the conventional sister line in field experiments with regard to production of bollworm, Helicoverpa zea (Boddie), and bolls damaged by bollworm. The relative numbers of bollworms that developed on Bollgard (Monsanto Co., St. Louis, MO), Bollgard II (Monsanto Co.), and conventional cotton were estimated under nontreated conditions in 2000 and both insecticide-treated and nontreated conditions in 2001–2002 in North Carolina tests. Averaged across seven field studies under nontreated conditions, Bollgard cotton generated statistically similar numbers of large (L4–L5) bollworm larvae compared with the conventional variety; however, Bollgard cotton produced significantly fewer damaged bolls and bollworm adults than the conventional variety. Production of large larvae, damaged bolls, and adults was decreased dramatically by Bollgard II cotton as compared with Bollgard and conventional varieties. When comparing insecticide-treated and nontreated cotton genotypes, both Bt cotton sustained less boll damage than the conventional variety averaged across insecticide regimes; furthermore, Bollgard II cotton had fewer damaged bolls than the Bollgard variety. When averaged across cotton genotypes, pyrethroid oversprays reduced the numbers of damaged bolls compared with the nontreated cotton. Insecticide-treated Bollgard cotton, along with insecticide-treated and nontreated Bollgard II cotton reduced production of bollworm larvae, pupae, and adults. However, the addition of pyrethroid oversprays to Bollgard II cotton seemed to be the best resistance management strategy available for bollworm because no bollworms were capable of completing development under these conditions.}, number={5}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Jackson, RE and Bradley, JR and Van Duyn, JW and Gould, F}, year={2004}, month={Oct}, pages={1719–1725} }
 @article{jackson_bradley_van duyn_2004, title={Performance of feral and Cry1Ac-selected Helicoverpa zea (Lepidoptera : Noctuidae) strains on transgenic cottons expressing one or two Bacillus thuringiensis ssp kurstaki proteins under greenhouse conditions}, volume={39}, ISSN={["0749-8004"]}, DOI={10.18474/0749-8004-39.1.46}, abstractNote={Efficacy of Bollgard (DP50B) and Bollgard II (DP50BX) cottons that express either one or two Bacillus thuringiensis Berliner proteins, respectively, along with the conventional sister genotype (DP50), was determined for a feral strain of bollworm, Helicoverpa zea (Boddie), and a Cry1Ac-selected bollworm strain in 1999. In 2000, a greenhouse study was designed to compare the efficacy of three transgenic cottons expressing either the Cry1Ac endotoxin alone (DP50B), the Cry2Ab endotoxin alone (DP50X), or both the CrylAc and Cry2Ab endotoxins (DP50BX) against a feral and a Cry1Ac-selected bollworm strain. Results from the 1999 greenhouse study evaluating both a feral and a Cry1Ac-selected bollworm strain demonstrated that when averaged across bollworm strains, the Bollgard II genotype significantly reduced larval survival and fruit penetration by bollworm compared to the Bollgard variety. Also, the Cry1Ac-selected bollworm strain displayed increased larval survival, superficial fruit damage, and fruit penetration compared to the feral strain when averaged across genotypes. In the 2000 study, the Bollgard II genotype significantly reduced fruit penetration by bollworm below that of the Bollgard variety when averaged across strains; however, the single Cry2Ab-producing genotype performed similarly to both Bollgard and Bollgard II with respect to fruit penetration. The Cry1Ac-selected bollworm strain exhibited significantly greater larval survival and superficial fruit damage on the Bollgard variety compared to the feral strain, but no differences among larval strains were evident for other genotypes. Also, when averaged across genotypes, the Cry1Ac-selected bollworm strain penetrated a higher proportion of cotton fruit compared to the feral strain. These results suggest that commercialization of Bollgard II cottons would significantly reduce bollworm survival and damage compared to that experienced by current Bollgard varieties. Bollgard II plantings also should have a positive impact on Bt resistance management of bollworm.}, number={1}, journal={JOURNAL OF ENTOMOLOGICAL SCIENCE}, author={Jackson, RE and Bradley, JR and Van Duyn, JW}, year={2004}, month={Jan}, pages={46–55} }