Recommendations for the design of laboratory studies on non-target arthropods for risk assessment of genetically engineered plants

Abstract

This paper provides recommendations on experimental design for early-tier laboratory studies used in risk assessments to evaluate potential adverse impacts of arthropod-resistant genetically engineered (GE) plants on non-target arthropods (NTAs). While we rely heavily on the currently used proteins from Bacillus thuringiensis (Bt) in this discussion, the concepts apply to other arthropod-active proteins. A risk may exist if the newly acquired trait of the GE plant has adverse effects on NTAs when they are exposed to the arthropod-active protein. Typically, the risk assessment follows a tiered approach that starts with laboratory studies under worst-case exposure conditions; such studies have a high ability to detect adverse effects on non-target species. Clear guidance on how such data are produced in laboratory studies assists the product developers and risk assessors. The studies should be reproducible and test clearly defined risk hypotheses. These properties contribute to the robustness of, and confidence in, environmental risk assessments for GE plants. Data from NTA studies, collected during the analysis phase of an environmental risk assessment, are critical to the outcome of the assessment and ultimately the decision taken by regulatory authorities on the release of a GE plant. Confidence in the results of early-tier laboratory studies is a precondition for the acceptance of data across regulatory jurisdictions and should encourage agencies to share useful information and thus avoid redundant testing.

Development of a Tier-1 Assay for Assessing the Toxicity of Insecticidal Substances Against <I>Coleomegilla maculata</I>

“…All three diets met basic assay acceptability criteria (i.e., Ͼ80% survival; Romeis et al 2010). Over 95% of C. maculata larvae survived and developed to adults in diet 2 or diet 3 after 18 d feeding exposure (Table 2).…”

Eliminating host-mediated effects demonstrates Bt maize producing Cry1F has no adverse effects on the parasitoid Cotesia marginiventris

“…Such 'host/prey-quality mediated effects' have been observed in numerous tri-trophic feeding studies with Bt crops (Romeis et al 2006;Naranjo 2009) and have erroneously been interpreted as direct toxic effects of Bt proteins (Shelton et al 2009a, b). An excellent way to avoid the impact of 'host/prey-quality mediated effects' in tri-trophic study systems is to use Bt-resistant herbivores as a Bt protein carrier (Romeis et al 2011). To date, Btresistant strains of Lepidoptera have been used to assess the impact of Bt crops on several natural enemies (Romeis et al 2011), but these have primarily been with predators that generally consume multiple species of prey over their lifetimes.…”

“…An excellent way to avoid the impact of 'host/prey-quality mediated effects' in tri-trophic study systems is to use Bt-resistant herbivores as a Bt protein carrier (Romeis et al 2011). To date, Btresistant strains of Lepidoptera have been used to assess the impact of Bt crops on several natural enemies (Romeis et al 2011), but these have primarily been with predators that generally consume multiple species of prey over their lifetimes. In contrast, a parasitoid depends on a single host to develop and therefore could be more susceptible to the effects of a Bt protein.…”

“…Therefore, much of the debate about the effect of Bt proteins on natural enemies has focused on whether any purported negative effects are, in fact, due to the Bt protein or quality of the host or prey on which the natural enemy fed (Romeis et al 2006;Shelton et al 2009a, b). One of the best ways to eliminate the potential impact of host or prey quality is to use a Btresistant host or prey that can develop well on the Bt crop, and thereby transfer a high concentration of the Bt protein to the host or prey and eventually the natural enemy (Romeis et al 2011).…”

“…This resistance afforded us an opportunity to use it for studies on tri-trophic interactions with natural enemies of S. frugiperda. By using Cry1F-resistant S. frugiperda, we could overcome prey-mediated effects (Romeis et al 2011).…”