ECOTOXICOLOGY Effect of Transgenic Plants Expressing High Levels of a Tobacco Anionic Peroxidase on the Toxicity of Anagrapha falcifera Nucleopolyhedrovirus to Helicoverpa zea (Lepidoptera: Noctuidae) R. W. BEHLE, 1 P. F. DOWD, 2 P. TAMEZ-GUERRA, 3 AND L. M. LAGRIMINI 4 J. Econ. Entomol. 95(1): 81Ð88 (2002) ABSTRACT Wild type and corresponding transgenic tomato (Lycopersicon esculentum Miller) and twotobacco(Nicotiana spp.)plantsthatexpresshighlevelsofatobaccoanionicperoxidasewereused to determine what type of interactions occurred between peroxidase altered plant chemistry and the baculovirus Anagrapha falcifera nucleopolyhedrovirus (AfMNPV) for control of neonate corn ear- worms, Helicoverpa zea (Boddie). Transgenic plants expressed approximately Þve to 400 times higher peroxidase activity than corresponding tissues of wild type plants. The H. zea larvae typically fed 1.5 times less on transgenic compared with wild type leaf disks. There was only one experiment (of three with tomato leaves) where the larvae that fed on transgenic leaves were less susceptible to the virus based on nonoverlapping 95% conÞdence intervals for LC50 values. When the exposure dose was corrected for reduced feeding on the transgenic leaf disks, the insecticidal activity of the virus was notsigniÞcantlydifferentforlarvaefedontransgenicversuswildtypeplants.Eightotherexperiments (with tomato and two species of tobacco) indicated either no signiÞcant effect or enhanced suscep- tibility (when corrected for feeding rates) to the virus of larvae fed on the transgenic leaves. These results indicate enhanced insect resistance in plants expressing high levels of a speciÞc anionic peroxidase may be compatible with applications of AfMNPV. Potential reasons for this compatibility are discussed. KEY WORDS Helicoverpa zea, Anagrapha falcifera nucleopolyhedrovirus, peroxidase, transgenic plants MANY INDIVIDUAL INSECT management strategies, such as insecticides, host plant resistance, and biological control, can be effective. However, in developing in- tegrated management programs, combining different managementstrategiesmayresultintheidentiÞcation ofincompatiblecombinations.Thistypeofassociation is most commonly recognized when, for example, in- secticides used against pest insects also result in un- desirable kill of beneÞcial insect predators or parasi- toids, which may result in pest resurgence (e.g., Price 1976). Host plant resistance and augmentative biological control (such as the application of insect pathogens) are two distinct insect management strategies that are considered relatively benign to the agroecosystem. However, applying insect pathogens to plants that have allelochemical-based resistance to insects may result in synergistic, antagonistic, or additive interac- tions. Compatible and incompatible interactions be- tween insect pathogens and host plants or their sec- ondary chemistry have been summarized (Duffey et al. 1995). Relevant studies on these interactions that involvebaculovirusessuchasnucleopolyhedroviruses (NPVs),indicatethattheefÞcacyofthebaculoviruses is often antagonized. Some types of incompatible re- actions for baculoviruses in Solanaceous plants have been attributed to the interaction of polyphenoloxi- dases or peroxidases with allelochemical substrates suchaschlorogenicacidorrutin(review,Duffeyetal. 1995; Felton et al. 1987; Felton and Duffey 1990; Hooveretal.1998a,1998b),althoughvirusefÞcacyhas been enhanced in some cases (Ali et al. 1998). When planttissueisdamagedduringfeeding,thesebiochem- ical combinations presumably produce reactive com- pounds such as semiquinones, quinones or active ox- ygen species that derivatize or destroy the integrity of viral proteins before successful infection of the target insect occurs (Duffey et al. 1995), although sloughing of gut cells may also be involved in reducing viral This article reports the results of research only. Mention of a proprietary product does not constitute an endorsement or a recom- mendation by the USDA for its use. 1 Crop Bioprotection Research Unit, National Center for Agricul- turalUtilizationResearch,USDA,AgriculturalResearchService,1815 N. University Street, Peoria, IL 61604. 2 To whom reprint requests should be addressed: Crop Bioprotec- tion Research Unit, National Center for Agricultural Utilization Re- search, USDA, Agricultural Research Service, 1815 N. University Street, Peoria, IL 61604 (e-mail: dowdpf@mail.ncaur.usda.gov). 3 Dep.deMicrobiologõ ´aeInmunologõ ´a,Fac.deCienciasBiolo ´ gcias, UANL, AP. 46-F, San Nicola ´ s de los Garza, N.L. Mexico 66451. 4 Current address: Syngenta Biotechnology, 3054 Cornwallis Drive, Research Triangle Park, NC 27709.