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Title: Mortality impact of transgenic maize roots expressing eCry3.1Ab, mCry3A, and eCry3.1Ab + mCry3A on western corn rootworm larvae in the field

Author
item Hibbard, Bruce
item Frank, Daniel
item KURTZ, RYAN - Syngenta Biotech, Inc
item BOUDREAU, ERIC - Syngenta Biotech, Inc
item ELLERSIECK, MARK - University Of Missouri
item ODHIAMBO, J.F - University Of Missouri

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/30/2011
Publication Date: 10/10/2011
Citation: Hibbard, B.E., Frank, D.L., Kurtz, R., Boudreau, E., Ellersieck, M.R., Odhiambo, J. 2011. Mortality impact of transgenic maize roots expressing eCry3.1Ab, mCry3A, and eCry3.1Ab + mCry3A on western corn rootworm larvae in the field. Journal of Economic Entomology. 104(5):1584-1591.

Interpretive Summary: Transgenic corn with resistance to corn rootworm larval feeding offers a viable alternative to insecticides for managing the most economically important insect pests of corn. Maintaining insect susceptibility to transgenic crops (resistance management) is in the interest of growers, the Environmental Protection Agency, and the industry, but requires an understanding of corn rootworm biology that does not currently exist. The mortality of the western corn rootworm larvae due to feeding on transgenic corn expressing insecticidle proteins relative to survivorship on the same genetic background of non-transgenic control corn was evaluated in five Missouri sites in 2007, 2008, and 2009. An average of 890 beetles emerged from control plots while the average beetle emergence from three transgenic lines was 2, 19, and 1, respectively when averaged across 22 replications in five environments. There was an 8.0 d delay in time to 50% beetle emergence from one of the transgenic lines (5307) compared to controls, which was significantly later than for the other maize lines. Our results showed that beetles recovered from the transgenics were slightly more likely to be females than those emerging from non-transgenic controls. These quantitative data are important to seed companies and modelers in their attempts to optimize resistance management plans for transgenic corn and are required by the Environmental Protection Agency.

Technical Abstract: Mortality of the western corn rootworm (Diabrotica virgifera virgifera LeConte) larvae due to feeding on maize (Zea mays L.) expressing the eCry3.1Ab (5307), mCry3A (MIR604), and eCry3.1Ab + mCry3A proteins relative to survivorship on maize with the same genetic background without these genes (isoline maize) was evaluated in five Missouri sites in 2007, 2008, and 2009. An average of 890.8 ± 152.3 beetles emerged from isoline plots while average beetle emergence from eCry3.1Ab, mCry3A, and eCry3.1Ab + mCry3A was 1.9 ± 0.6, 19.3 ± 6.3, and 0.8 ± 0.3, respectively when averaged across 22 replications in five environments. Mortality due to eCry3.1Ab, mCry3A, and eCry3.1Ab + mCry3A was 99.79%, 97.83%, and 99.91%, respectively. There was an 8.0 d delay in time to 50% beetle emergence from eCry3.1Ab compared to isoline maize, which was significantly later than to the other three maize lines. The average delay to 50% emergence from mCry3A and eCry3.1Ab + mCry3A averaged 4.1 d and 4.6 d, respectively later than 50% emergence from isoline maize. Female beetles had a significant delay in time to 50% emergence compared with male beetles from all treatments with the exception of eCry3.1Ab + mCry3A. Our results showed that 67, 50, 63, and 51% of beetles recovered from eCry3.1Ab, mCry3A, eCry3.1Ab + mCry3A, and isoline maize, respectively, were female. Data are discussed in terms of insect resistance management in relation to other control measures for western corn rootworm.