@article{blanco_andow_abel_sumerford_hernandez_lópez_adams_groot_leonard_parker_et al._2009, title={Bacillus thuringiensis Cry1Ac Resistance Frequency in Tobacco Budworm (Lepidoptera: Noctuidae)}, volume={102}, ISSN={0022-0493 0022-0493}, url={http://dx.doi.org/10.1603/029.102.0149}, DOI={10.1603/029.102.0149}, abstractNote={ABSTRACT The tobacco budworm, Heliothis virescens (F.) (Lepidoptera Noctuidae), is one of the most important pests of cotton, Gossypium hirsutum L., that has become resistant to a wide range of synthetic insecticides. Cry1Ac-expressing cotton has proven its effectiveness against this insect since its introduction in North America in 1996. However, the constant exposure of tobacco budworm to this protein toxin may result in the development of resistance to it. To estimate the frequency of alleles that confer resistance to a 1.0 µg of Bacillus thuringiensis Cry1Ac diagnostic concentration in field-collected insects, the second generation (F2) of 1,001 single-pair families from seven geographical regions representing 2,202 alleles from natural populations was screened in 2006 and 2007 without finding major resistant alleles. Neonates of 56 single-pair families were able to develop to second instar on the diagnostic concentration in the initial screen, but only seven of these lines did so again in a second confirmatory screen. Minor resistance alleles to Cry1Ac may be quite common in natural populations of H. virescens. Our estimated resistance allele frequencies (0.0036 – 0.0263) were not significantly different from a previously published estimate from 1993. There is no evidence that H. virescens populations have become more resistant to Cry1Ac.}, number={1}, journal={Journal of Economic Entomology}, publisher={Oxford University Press (OUP)}, author={Blanco, Carlos A. and Andow, David A. and Abel, Craig A. and Sumerford, Douglas V. and Hernandez, Gerardo and López, Juan D., Jr and Adams, Larry and Groot, Astrid and Leonard, Rogers and Parker, Roy and et al.}, year={2009}, month={Feb}, pages={381–387} } @article{blanco_perera_gould_sumerford_hernandez_abel_andow_2008, title={An empirical test of the F(2) screen for detection of Bacillus thuringiensis-resistance alleles in tobacco budworm (Lepidoptera : Noctuidae)}, volume={101}, ISSN={["0022-0493"]}, DOI={10.1603/0022-0493(2008)101[1406:AETOTF]2.0.CO;2}, abstractNote={Abstract Insects exposed to genetically modified crops expressing Bacillus thuringiensis (Bt) toxins are under intense selection pressure that could result on widespread Bt resistance. Screening for early indications of Bt resistance developing in targeted Lepidoptera is conducted in many of the regions where genetically modified cotton and corn have been commercialized. Heliothis virescens (F.) (Lepidoptera: Noctuidae) has been selected in the laboratory to have a gene for resistance to Cry1Ac. We used this laboratory line to test the assumptions and theoretical predictions related to detection of recessive Bt-resistant alleles in field populations based on a second generation (F2) screen. By creating single-pair families from mating a heterozygous Cry1Ac-resistant moth with a Cry1Ac-susceptible moth, we simulated the most common genotype when Bt-resistance alleles are at low frequency in the field. The second generation (F2) neonates of single-pair families were screened daily with diagnostic concentration bioassays. Cry1Ac-resistant homozygous larvae were detected, but the proportion of resistant larvae was generally below the theoretical expectation of 6.25% and was influenced by the moth F1 sib-mating density and by the day of oviposition of F2 eggs. Logistical considerations such as F1 sib-mating density and F2 neonate screening are important for the successful implementation of a reliable method.}, number={4}, journal={JOURNAL OF ECONOMIC ENTOMOLOGY}, author={Blanco, Carlos A. and Perera, O. P. and Gould, Fred and Sumerford, Douglas V. and Hernandez, Gerardo and Abel, Craig A. and Andow, David A.}, year={2008}, month={Aug}, pages={1406–1414} } @article{gould_anderson_jones_sumerford_heckel_lopez_micinski_leonard_laster_1997, title={Initial frequency of alleles for resistance to Bacillus thuringiensis toxins in field populations of Heliothis virescens}, volume={94}, ISSN={["0027-8424"]}, DOI={10.1073/pnas.94.8.3519}, abstractNote={ The risk of rapid pest adaptation to an insecticide is highly dependent on the initial frequency of resistance alleles in field populations. Because we have lacked empirical estimates of these frequencies, population–genetic models of resistance evolution have relied on a wide range of theoretical estimates. The recent commercialization of genetically engineered cotton that constitutively produces an insecticidal protein derived from the biocontrol agent, Bacillus thuringiensis (Bt) has raised concern that we lack data needed to quantify the risk of insect pests such as Heliothis virescens rapidly adapting to this ecologically valuable class of toxins. By individually mating over 2,000 male H. virescens moths collected in four states to females of a Bt toxin-resistant laboratory strain, and screening F 1 and F 2 offspring for tolerance of the toxic protein, we were able to directly estimate the field frequency of alleles for resistance as 1.5 × 10 −3 . This high initial frequency underscores the need for caution in deploying transgenic cotton to control insect pests. Our single-pair mating technique greatly increases the efficiency of detecting recessive resistance alleles. Because alleles that decrease target site sensitivity to Bt toxins and other insecticides are often recessive, this technique could be useful in estimating resistance allele frequencies in other insects exposed to transgenic insecticidal crops or conventional insecticides. }, number={8}, journal={PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA}, author={Gould, F and Anderson, A and Jones, A and Sumerford, D and Heckel, DG and Lopez, J and Micinski, S and Leonard, R and Laster, M}, year={1997}, month={Apr}, pages={3519–3523} }