Two groups of plant incorporated protectants (PIPs) are stacked by conventional breeding in SmartStax Pro maize, including three lepidopteran (Lep)-active PIPs the Cry1A.105, Cry2Ab2, and Cry1F proteins and three corn rootworm (CRW)-active PIPs, including Cry3Bb1 and Cry34/35Ab1 Bt proteins, and DvSnf7 dsRNA. An assessment of potential interaction among the PIPs produced in SmartStax Pro is required, along with PIP expression and molecular characterization data, by the United States Environmental Protection Agency to bridge to existing non-target organism assessments generated for the individual products to support the environmental risk assessment for the combined trait product. In the present study, six combinations produced by the events in SmartStax Pro were assessed to characterize their combined activity in bioassays with sensitive insect species. The combined activities of three Lep-active PIPs and the combined activity of three CRW-active PIPs were additive and consistent with predictions from either the concentration addition model or response addition model. Similarly, selected lower order Lep-active and CRW-active combinations acted independently, e.g., Cry1A.105 and Cry2Ab2 in MON 89034 and Cry3Bb1 and DvSnf7 and Cry3Bb1 and Cry34/35Ab1 in MON 87411 Pro. In addition, the combined activity of Lep-active PIPs was not altered by addition of CRW-active PIPs and vice-versa. The results demonstrate that all the insecticidal PIPs stacked in SmartStax Pro maize act independently and support this conclusion can be used to bridge to the existing non-target organism assessments for SmartStax Pro.
