Uptake of Bt-endotoxins by generalist predators (Coleoptera: Carabidae) in transgenic corn fields
Julie A. Peterson, firstname.lastname@example.org, John J. Obrycki, email@example.com, and James D. Harwood, firstname.lastname@example.org. University of Kentucky, Department of Entomology, S-225 Agricultural Science Center North, Lexington, KY
The worldwide use of genetically modified Bacillusthuringiensis (Bt) corn has dramatically increased since its commercial release in the mid 1990’s. These crops express insecticidal proteins, which suppress populations of the European Corn Borer, Southwestern Corn Borer, and Corn Rootworm. However, it has been suggested that the tritrophic movement of Bt-endotoxins into higher-order generalist predators in the field could negatively affect the capacity of natural enemies as effective biological control agents of corn pests. Fields (2500 m2) of transgenic YieldGard Rootworm, YieldGard Corn Borer, YieldGard Plus (a stacked transgenic line), and a non-transgenic isoline were planted at the University of Kentucky Spindletop Research Station, Lexington, KY, USA, and grown under standard agronomic practices with no insecticidal application. Ground beetles (Coleoptera: Carabidae) were collected weekly from each plot and gut contents were screened for Bt-endotoxins using an enzyme-linked immunosorbent assay (ELISA). The facultatively phytophagous carabid Harpaluspennsylvanicus showed significant uptake of Cry1Ab Bt-endotoxin in the YieldGard Corn Borer field (39.1% positive, concentration: 0.0398±0.0104 µg endotoxin/g fresh weight, total n=64), minimal uptake of endotoxin in the YieldGard Rootworm (2.0%, 0.0328±0.0267 µg/g, n=149) and YieldGard Plus (5.3%, 0.0341±0.0125 µg/g, n=75) fields, and no uptake in the isoline field (n=42). In addition, immunoassay analyses ascertained the exposure of the remaining community of carabid beetles (Agonoderuspallipes, Scaritessubterraneus, Evarthrussodalis, Chlaeniustricolor, and Pterostichuslucublandus) to transgenic endotoxins, and thus elucidates the structure of food webs in transgenic corn and is the basis for future risk assessment of transgenic crops.
Species 1: Coleoptera Carabidae Scaritessubterraneus Species 2: Coleoptera Carabidae Harpaluspennsylvanicus Species 3: Coleoptera Carabidae Evarthrussodalis