|Lopez, Juan De Dios|
Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2008
Publication Date: 2/1/2009
Citation: Blanco, C.A., Andow, D.A., Gould, F., Abel, C.A., Sumerford, D.V., Hernandez, G., Lopez, J., Adams, L.C., Groot, A., Leonard, R., Parker, R., Payne, G., Perera, O.P., Teran-Vargas, A.P. 2009. Bacillus thuringiensis Cry1Ac Resistance Frequency in Tobacco Budworm (Lepidoptera: Noctuidae). Journal of Economic Entomology. 102:381-387 Interpretive Summary: After more than ten years of the use of transgenic cotton (Bt cotton) for the control of the tobacco budworm, this pest has not shown signs of becoming resistant to this technology. This insect has develop resistance to pretty much all the insecticides used for its control, that is why it has been considered to be the most important insect of cotton for the past 24 years. This study reports a detailed evaluation of more than a thousand individual moths looking for all types of resistance mechanism to the main toxin of Bt cottons, without finding evidence of Cry1Ac resistance. It also compares the results with a seminal report made prior to the release of Bt cotton in the U.S. (1995) showing that after more than a decade, this pest is still susceptible to this Bacillus thuringiensis toxin.
Technical Abstract: The tobacco budworm (Heliothis virescens F.) is one of the most important pests of cotton and 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 are resistant to a Bacillus thuringiensis Cry1Ac diagnostic concentration in field-collected populations, the second generation (F2) of 1,001 single-pair families from seven geographical regions representing 1,101 alleles was screened without finding major Cry1Ac 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 7 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 were not significantly different from a previously published estimate from 1995. This indicates that H. virescens populations are not becoming more resistant to Cry1Ac.