|Ali, Ibrahim -|
Submitted to: Journal of Invertebrate Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 28, 2011
Publication Date: July 13, 2011
Citation: Ali, I., Luttrell, R.G. 2011. Susceptibility of Helicoverpa zea and Heliothis virescens (Lepidoptera: noctuidae) to Vip3A insecticidal protein in VipCotTM cotton. Journal of Invertebrate Pathology. 108:76-84. Interpretive Summary: Baseline data were collected on the response of bollworm (Helicoverpa zea) and tobacco budworm (Heliothis virecens) to Vip3A, the insecticidal protein expressed in VipCot cotton. This insecticidal protein is distinctly different from the Cry proteins expressed in previous Bt cottons and considered to be an important new mode of toxin activity for resistance management. Baseline susceptibilities were established by diet incorporation and diet overlay assays of insects from laboratory and field colonies from 2004 to 2008. Variability in response among populations was observed similar to the magnitude of variability observed with Cry toxins. Interestingly, field strains were more susceptible than laboratory strains. These data should be important references for future Bt resistance studies.
Technical Abstract: Susceptibility of laboratory and field colonies of Helicoverpa zea (Boddie) and Heliothis virescens F. to Vip3A insecticidal protein was studied in diet incorporation and diet overlay assays from 2004 to 2008. Responses of field populations were compared to paired responses of University of Arkansas laboratory susceptible H. zea (LabZA) and H. virescens (LabVR) colonies. After 7 d of exposure, observations were made on number of dead larvae (M) and the number of larvae alive but remaining as first instars (L1). Regression estimate using M (LC50) and M plus L1 (MIC50) data were developed for laboratory and field populations. Susceptibility of laboratory and field populations exposed to Vip3A varied among different batches of protein used over the study period. Within the same batch of Vip3A protein, susceptibilities of two reference laboratory colonies were similar. Field colonies were significantly more susceptible to Vip3A than the respective reference colonies of both species. Within field populations, susceptibility to Vip3A varied up to 75-fold in H. zea and 132-fold in H. virescens in LC50 estimates. Variabilities in MIC50s were up to 59- and 11-fold for H. zea and H. virescens, respectively.