PLANT RESISTANCE Field Evaluation of Transgenic Tobacco Containing Genes Encoding Bacillus thuringiensis &Endotoxin or Cowpea Trypsin Inhibitor: Efficacy Against Helicoverpa xea (Lepidoptera: Noctuidae) MICHAEL P. HOFFMANN,’ FRANK G. ZALOM, LLOYD T. WILSON,2 JANET M. SMILANICK, LORRAINE D. MALYJY3 JOHN KISER,3 VAUGHAN A. HILDER,4 AND WAYNE M. BARNES5 Department of Entomology, University of California, Davis, CA 95616 J. Econ. Entomol. 85(6): 2516-2522 (1992) ABSTRACT Transgenic tobacco plants expressing Bacillus thuringiensis var. kurstaki HD-73 delta-endotoxin or cowpea, Vigna Unguiculata, trypsin inhibitor (CpTI) were eval- uated for efficacy against artificial infestations of Helicouerpa zea (Boddie) under field conditions. Mortality of H. zea larvae was significantly higher and leaf damage significantly lower for the genotype containing Bacillus thuringiensis gene compared with nontrans- genic control. Few H. zea larvae survived beyond first instar on the Bacillus thuringiensis genotype. Larval mortality was also higher and leaf damage lower on the CpTI genotype than its corresponding control, but the effect was less consistent and less pronounced than that produced by the Bacillus thuringiensis genotype. Neither transgenic genotype had a significant effect on natural infestations of the other phytophagous or predacious insects that were monitored. KEY WORDS Transgenic tobacco, Helicouerpa zea, Bacillus thuringiensis PROTECTION OF FOOD AND FIBER CROPS from insect attack has relied heavily on the use of synthetic insecticides for the past several dec- ades. The disadvantages of this dependence are now evident, and alternative control tactics are actively being sought including the use of trans- genic plants which are resistant to insect attack. This alternative offers several advantages, in- cluding relatively selective control of target pest species, crop protection throughout the season, and protection that is independent of environ- mental conditions. Genes targeted for introduc- tion into crop plants include Bacillus thuringien- sis genes coding for delta-endotoxins and a protease inhibitor gene from cowpea, Vigna un- guiculata (L.), that codes for a trypsin inhibitor (CPTI). When Bacillus thuringiensis is applied to foli- age, several applications may be required for long-term protection because it can be washed 1 Current address: Department of Entomology, Comstock 2 Current address: Department of Entomology, Texas A&M SCalgene, 1920 Fifth St., Davis, CA 95616. 4 Department of Botany, University of Durham, South Road, Durham DHI 3LE, United Kingdom. 5 Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110. Hall, Cornell University, Ithaca, NY 14853. University, College Station, TX 77843. off by rain, diluted by plant growth, and inacti- vated by sunlight (Aronson et al. 1986).The clon- ing of genes encoding insecticidal proteins and expression in transgenic plants may provide an alternate delivery system for crop protection. B. thuringiensis genes have been genetically engi- neered into tobacco (Barton et al. 1987, Vaeck et al. 1987) and tomato (Fischhoff et al. 1987) and found to be efficacious in laboratory testing. More recently, transgenic tomato plants express- ing the Bacillus thuringiensis var. kurstaki HD- 1 (cryZA(b)) genes (Delannay et al. 1989) and cot- ton plants expressing the HD- 1 and HD- 73 (cryZA(c)) genes (Perlak et al. 1990) have been demonstrated to be efficacious against major in- sect pest species in the greenhouse or field. Cowpea trypsin inhibitor is a small polypep- tide belonging to the Bowman-Birk type of double-headed serine protease inhibitors. Feed - ing trials using artificial diets containing CpTI have demonstrated it to be efficacious against several insect species (Gatehouse & Boulter 1983). When expressed in transgenic tobacco, it enhances resistance to Heliothis virescens (F.) (Hilder et al. 1987). The objectives of this trial were to evaluate, under field conditions, the effect of transgenic tobacco containing genes encoding Bacillus thu- ringiensis HD-73 or CpTI on survival of larvae of 0022-0493/92/2516-2522$02.00/0 0 1992 Entomological Society of America