Using field-evolved resistance to Cry1F maize in a lepidopteran pest to demonstrate no adverse effects of Cry1F on one of its major predators.

Jun-Ce Tian,Anthony M Shelton,Jörg Romeis,Steven E Naranjo,Richard L Hellmich,Hilda L Collins

doi:10.1007/s11248-012-9604-4

Abstract

Spodoptera frugiperda (JE Smith) represents the first documented case of field-evolved resistance to a genetically engineered crop expressing an insecticidal protein from Bacillus thuringiensis (Bt). In this case it was Cry1F-expressing maize (Mycogen 2A517). The ladybird beetle, Coleomegilla maculata, is a common and abundant predator that suppresses pest populations in maize and many other cropping systems. Its larvae and adults are polyphagous, feeding on aphids, thrips, lepidopteran eggs and larvae, as well as plant tissues. Thus, C. maculata may be exposed to Bt proteins expressed in genetically engineered crops by several pathways. Using Cry1F-resistant S. frugiperda larvae as prey, we evaluated the potential impact of Cry1F-expressing maize on several fitness parameters of C. maculata over two generations. Using Cry1F resistant prey removed any potential prey-mediated effects. Duration of larval and pupal stages, adult weight and female fecundity of C. maculata were not different when they were fed resistant S. frugiperda larvae reared on either Bt or control maize leaves during both generations. ELISA and insect-sensitive bioassays showed C. maculata were exposed to bioactive Cry1F protein. The insecticidal protein had no effect on C. maculata larvae, even though larvae contained 20–32 ng of Cry1F/g by fresh weight. Over all, our results demonstrated that the Cry1F protein did not affect important fitness parameters of one of S. frugiperda’s major predators and that Cry1F protein did not accumulate but was strongly diluted when transferred during trophic interactions.

Highlights

Maize, Zea mays L., is one of the most important world crops with over 150 million hectares planted in 2009 (FAOSTAT 2009)
Samples of Cry1F maize (V5) leaves, non-Bacillus thuringiensis (Bt) maize (V5) leaves, fall armyworm (FAW) fed on Cry1F maize for 48 h, FAW fed on non-Bt maize for 48 h, 4th instar C. maculata fed on Cry1F maize-fed FAW and 4th instar C. maculata fed on non-Bt maize-fed FAW were used in this experiment
No Cry1F was detected in non-Bt maize or FAW fed on non-Bt maize and C. maculata fed on non-Bt maize-fed FAW

Summary

Introduction

Zea mays L., is one of the most important world crops with over 150 million hectares planted in 2009 (FAOSTAT 2009). Bt crops have been planted for 15 years and the vast majority of published reports have shown no negative effects of Bt crops on nontarget organisms (Romeis et al 2006; Marvier et al 2007; Wolfenbarger et al 2008; Naranjo 2009), the ecological safety of Bt plants continues to be debated Much of this debate has focused non-target beneficial species (predators and parasitoids) and on whether any purported negative effects are due to the Bt protein or quality of the host or prey on which the natural enemy feeds (Shelton et al 2009a). In 2001, Herculex IÒ (Cry1F) maize was approved in the United States and targeted both O. nubilalis and FAW (Hellmich et al 2008) Reports indicated that it could substantially reduce losses by FAW (Buntin et al 2004; Buntin 2008; Siebert et al 2008).

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