PLANT RESISTANCE Correlating Differences in Larval Survival and Development of Bollworm (Lepidoptera: Noctuidae) and Fall Armyworm (Lepidoptera: Noctuidae) to Differential Expression of Cry1A(c) d-Endotoxin in Various Plant Parts Among Commercial Cultivars of Transgenic Bacillus thuringiensis Cotton

Differences in larval survival and development of bollworm, Helicoverpa zea (Boddie), and fall armyworm, Spodoptera frugiperda(J.E. Smith), respectively,were found toexist among commercially available Cry1A(c) transgenic Bacillus thuringiensis Berliner (Bt) varieties. Using a quantiÞcation assay (ELISA) to measure the levels of d-endotoxin in two of these varieties (ÔDP 451B/RRÕ and ÔNuCOTN 33BÕ), differences in the amount of d-endotoxin present in various plant parts was correlated with larval survival of bollworms and larval development of fall armyworms throughout the growing season. Larvae thatwere fed onDP451B/RRcompleteddevelopment faster and exhibited better survivorship than those larvae fed NuCOTN 33B, whereas lower levels of d-endotoxinwere generally detected in plant parts fromDP451B/RRcomparedwithNuCOTN33B. These differences may impact population dynamics of these pests which may be a critical factor in managing resistance to Bt. Furthermore, the utility of using this system for providing information to the grower concerning varietal choices may be more common in the future.