Bt cotton producing Cry1Ac and Cry2Ab does not harm the parasitoid Aenasius arizonensis (Girault): a host-mediated tritrophic assay

Abstract

Transgenic crops with genes from Bacillus thuringiensis (Bt) Berliner, a soil bacterium producing δ-endotoxin that is lethal to several phytophagous insects. Concerns related to possible effects of Cry proteins expressed in transgenic Bt crops on non-target organisms need to be addressed for environment risk assessment. Aenasius arizonensis (Girault) is the most important koinobiont parasitoid of cotton mealybug, Phenacoccus solenopsis Tinsley. Consequently, the impact of transgenic Bt cotton having dual toxins (Cry1Ac and Cry2Ab) on the parasitoid, A. arizonensis was studied through host mediated tritrophic analysis. Non-significant differences were observed for developmental duration from oviposition to adult emergence, proportion of adults emerged, proportion of females in progeny and longevity of A. arizonensis when reared on P. solenopsis offered with Bt cotton or non-Bt cotton leaves. The parasitism of mealybug nymphs and adults by A. arizonensis did not differ significantly on cotton with or without toxins. Despite higher expression of Cry1Ac and Cry2Ab toxins in Bollgard II cotton leaves, Cry proteins were not detected in the host, P. solenopsis or the parasitoid, A. arizonensis. Our study thus showed that Bt cotton having dual toxins (Cry1Ac/Cry2Ab) had no noticeable impact on development, longevity, parasitism rate and proportion of females in progeny of the parasitoid, A. arizonensis.