Assessing the effects of Bt maize on the non-target pest Rhopalosiphum maidis by demographic and life-history measurement endpoints.

Alberto Lanzoni,Francesco Camastra,Valeria Bregola,Giovanni Dinelli,Giovanni Burgio,Antonino Staiano,Sara Bosi,Angelo Ciaramella

doi:10.1017/s0007485321000481

Alberto Lanzoni, Francesco Camastra + Show 6 more

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https://doi.org/10.1017/s0007485321000481

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Abstract

The most commercialized Bt maize plants in Europe were transformed with genes which express a truncated form of the insecticidal delta-endotoxin (Cry1Ab) from the soil bacterium Bacillus thuringiensis (Bt) specifically against Lepidoptera. Studies on the effect of transgenic maize on non-target arthropods have mainly converged on beneficial insects. However, considering the worldwide extensive cultivation of Bt maize, an increased availability of information on their possible impact on non-target pests is also required. In this study, the impact of Bt-maize on the non-target corn leaf aphid, Rhopalosiphum maidis, was examined by comparing biological traits and demographic parameters of two generations of aphids reared on transgenic maize with those on untransformed near-isogenic plants. Furthermore, free and bound phenolics content on transgenic and near-isogenic plants were measured. Here we show an increased performance of the second generation of R. maidis on Bt-maize that could be attributable to indirect effects, such as the reduction of defense against pests due to unintended changes in plant characteristics caused by the insertion of the transgene. Indeed, the comparison of Bt-maize with its corresponding near-isogenic line strongly suggests that the transformation could have induced adverse effects on the biosynthesis and accumulation of free phenolic compounds. In conclusion, even though there is adequate evidence that aphids performed better on Bt-maize than on non-Bt plants, aphid economic damage has not been reported in commercial Bt corn fields in comparison to non-Bt corn fields. Nevertheless, Bt-maize plants can be more easily exploited by R. maidis, possibly due to a lower level of secondary metabolites present in their leaves. The recognition of this mechanism increases our knowledge concerning how insect-resistant genetically modified plants impact on non-target arthropods communities, including tritrophic web interactions, and can help support a sustainable use of genetically modified crops.

Highlights

Due to the increasing worldwide cultivation of insect-resistant genetically modified (GM) plants, an improved availability of information on their possible impact on non-target organisms is highly required
Risk assessment on non-target arthropods (NTA) cannot only rely on Bacillus thuringiensis (Bt) Cry toxicity tests (Romeis et al, 2011), but it should include tests that use the whole plant to cope with the effects of potentially complex physiological interaction as a consequence of the transformation process (Andow and Hilbeck, 2004; EFSA, 2010; Arpaia et al, 2017)
The aim of the current study is to evaluate the effects of Bt maize on the performance of R. maidis in comparison with its corresponding near-isogenic line, both in the short and long term, identifying and defining appropriate measurement endpoints

Summary

Introduction

Due to the increasing worldwide cultivation of insect-resistant genetically modified (GM) plants, an improved availability of information on their possible impact on non-target organisms is highly required. Less attention has been paid to potential effects on non-target pests In this context, insect-resistant GM plants present several features which require further information on existing protocols for non-target species environmental risk assessment (Andow and Hilbeck, 2004, EFSA, 2010; Arpaia et al, 2017). Risk assessment on NTA cannot only rely on Bt Cry toxicity tests (Romeis et al, 2011), but it should include tests that use the whole plant to cope with the effects of potentially complex physiological interaction as a consequence of the transformation process (Andow and Hilbeck, 2004; EFSA, 2010; Arpaia et al, 2017). The designation of appropriate measurement endpoints, and the definition of their adequacy to clearly explain what changes correspond to an adverse effect, should improve the scientific basis upon which potential adverse impacts of insect-resistant GM plants on NTA can be evaluated (EFSA, 2010; Romeis et al, 2011; Arpaia et al, 2014; Arpaia et al, 2017)

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