ABSTRACT
USDA-ARS-CMAVE, Center for Biological Control, Florida A&M University Tallahassee, FL 32307, USA; *Department of Entomology
INTRODUCTION Transgenic insecticidal crop cultivars are in the process of revolutionizing agriculture and are likely to become a major insect management tactic worldwide. Introducing novel resistance genes into economically-important crops can develop insect-resistant crops. This tactic has a potentially key role in integrated pest management of several important pests (Gatehouse and Gatehouse, 1998). Most of the research and development thus far has focused on the transfer of genes expressing toxins produced by the soil-borne bacterium, Bacillus thuringiensis (Berliner) (Bt) into food, grain and fiber plants. The insecticidal Bt dendotoxins are a family of related proteins with different levels of activity against species of Lepidoptera, Coleoptera and Diptera (see Vaeck et al., 1987). Bt-transgenic cultivars have been produced for tobacco (Nicotiana tabacum), potato (Solanum tuberosum), cotton (Gossypium hirsutum), maize (Zea mays), rice (Oryza sativa), tomato (Lycopersicon esculentum), broccoli (Brassica oleracea botrytis), alfalfa (Medicago sativa) and other crops (Hilder and Boulter, 1999). In March 2000, Bt maize and Bt cotton each comprised 18% of the total acreages
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planted to these crops in the USA (USDA ERS, 2000). These acreages are expected to increase dramatically in the near future, both in developed and developing countries (Carozzi and Koziel, 1997; Gould, 1998). Field evaluations of Bt transgenic cultivars have produced mixed results. Effective pest suppression was reported for Bt cotton against cotton bollworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) and pink bollworm, Pectinophora gossypiella (Saunders) (Lepidoptera: Gelechiidae), Bt potato against Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), and Bt maize against European corn borer, Ostrinia nubilalis (Hiibner) (Lepidoptera: Pyralidae) (Hilder and Boulter, 1999). However, the failure of the 800,000 ha. planted with Bt cotton against H. zea and P. gossypiella was widely reported in 1996. Furthermore, Bt cotton was also reported to have failed against H. armigera (Hiibner) in Australia (Hilder and Boulter, 1999).
