Concurrent use of transgenic plants expressing a single and two Bacillus thuringiensis genes speeds insect adaptation to pyramided plants 9 Jian-Zhou Zhao*, Jun Cao. Hilda L. Collins, Sarah L. Bates, Richard T. Roush, Elizabeth D. Earle “Department of tneomology, Cornell University New York Sate Agricultural txperiment Station, Geneva, NY 144%·Department of Plant Breedng and Genetics, Cormell Univenity, Ithaca, NY 14853 and Statewide IPM Program, University of California Davis, CA 9561 Edited by May R Bererbaum, University of Illinois at urbana-Champaign, Urbana, and approved Aprg 27, 2005 tweived for eeview December 14, 2004) Transgenic plants expressing insecticidal proteins from the bacte plants sharing simalar Bt toxins continue to be deployed (6, 10). um BaciWus thuringiensis (B) were grown on over 13 million haNewly developed pyramided varieties of Bt cotton and corn in the United States and 22.4 million ha worldwide in 2004 curretly contain the same or similar genes as one-gene (CrylAc Preventing or slowing the evolutien of resistance by insects(e for Bt cotton, Cry1Ab for Bt corn) plants already marketed. In sistance management’) is critical for the sustainable use of Bt market forces result in a complicated landscape mix of one- and crops. Plants containing two dissimilar Bt toxin genes in the same two-gene Bt plants, the impact of the pyramided Bt plants on plant (“pyramided ) have the potential to delay insect resistance. slowing resistance evolution could be undermined (10). For However, the advantage of pyramided Bt plants for resistance cxample, a modeling study suggested that Cry2A resistance management may be compromised if they share similar toxins withevolution in a cotton pest was this hypothesis using a unique model system composed of broccoli that the overall durability of Bollgard II would be greater if it is plants transformed to express different Cry toxins (Cry1At, Cry1C, deployed alone, compared with a sequential or mosaic deploy- or both) and a synthetik population of the diamondback moth mentwith Bollgard (CrylAc alone) (12). However, the risk of Cry1C at frequencies of-0.10 and 0.34, respectively. After 24-26 of Bt plants. When only two-gene plants were used in the selection, rapidly than the use of two-gene plants alone. The results of this crucifers expeessing a high level of CrylAe (17-19) and CryIC (20, 21) proteins. An autosomal recessive gene in P. rylostella has resistance to CrylC in our strains was also autosomally inherited ransgenic plants expressing insecticidal proteins from the and did not show cross-resistance to CrylA protoxins (CrylAa bacterium Bacillus thuringiensis (Bt) were grown on over 13CrylAb, and CrylAc) (24). CrylC resistance appears to be million ha in the United States and 224 million ha worldwide in 2004 (1, 2). These crops have provided economie benefts to inheritance and biochemical studies (20, 21) Subsequent map growers and reduced the use of other insecticides (2, 3). After 8 crops in the field, there have been ping studies have demonstrated that the gene for CrylA resistance is located in a third linkape group(25) other issue related to the re-registration of Bt crops by the U.S CrylC, or both) and populations of P. nlostella carrying reis to delay resistance (6-8).However,theoretical models (7,9, 10) containing two dissimilar Bt toxin genes( pyramided”) have the Bollgard II with two genes derived from Bt (CrylAc and the United States in 2002 (12. 13), and several companies are t u developing new cotton and corn varieties with pyramided BtUnvty w York State Agrietural eren tion 30 West Nors genes. However, there is concern that the benefits of pyramided Geneva, NY นเนเ.ui pakonelo.. andkomelindu Bt genes for resistance management may be negated if one-gene 205 by The National Academy of Snes of the UA