Consumption of Bt Maize Pollen Expressing Cry1Ab or Cry3Bb1 Does Not Harm Adult Green Lacewings, Chrysoperla carnea (Neuroptera: Chrysopidae)

Yunhe Li,Michael Meissle,Jörg Romeis,John Obrycki

doi:10.1371/journal.pone.0002909

Abstract

Adults of the common green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae), are prevalent pollen-consumers in maize fields. They are therefore exposed to insecticidal proteins expressed in the pollen of insect-resistant, genetically engineered maize varieties expressing Cry proteins derived from Bacillus thuringiensis (Bt). Laboratory experiments were conducted to evaluate the impact of Cry3Bb1 or Cry1Ab-expressing transgenic maize (MON 88017, Event Bt176) pollen on fitness parameters of adult C. carnea. Adults were fed pollen from Bt maize varieties or their corresponding near isolines together with sucrose solution for 28 days. Survival, pre-oviposition period, fecundity, fertility and dry weight were not different between Bt or non-Bt maize pollen treatments. In order to ensure that adults of C. carnea are not sensitive to the tested toxins independent from the plant background and to add certainty to the hazard assessment, adult C. carnea were fed with artificial diet containing purified Cry3Bb1 or Cry1Ab at about a 10 times higher concentration than in maize pollen. Artificial diet containing Galanthus nivalis agglutinin (GNA) was included as a positive control. No differences were found in any life-table parameter between Cry protein containing diet treatments and control diet. However, the pre-oviposition period, daily and total fecundity and dry weight of C. carnea were significantly negatively affected by GNA-feeding. In both feeding assays, the stability and bioactivity of Cry proteins in the food sources as well as the uptake by C. carnea was confirmed. These results show that adults of C. carnea are not affected by Bt maize pollen and are not sensitive to Cry1Ab and Cry3Bb1 at concentrations exceeding the levels in pollen. Consequently, Bt maize pollen consumption will pose a negligible risk to adult C. carnea.

Highlights

Engineered (GE) maize varieties expressing Cry proteins from the bacterium Bacillus thuringiensis (Bt) are the most widely grown insect-resistant transgenic plants to date
While stem borers are often left uncontrolled by insecticides due to difficulties in the timing of their application, insecticides used against Diabrotica spp. in the USA alone comprise 25–30% of global total insecticide used in maize [2]
In particular Coleoptera-active Bt maize shows a greater potential for insecticide reduction in the near future [2]

Summary

Introduction

Engineered (GE) maize varieties expressing Cry proteins from the bacterium Bacillus thuringiensis (Bt) are the most widely grown insect-resistant transgenic plants to date. First commercialized in 1996, Bt maize was grown in 13 countries on a total of over 35 million hectares (.24% of maize area worldwide) in 2007 [1,2]. Most Bt maize varieties are protected against lepidopteran pests, i.e. the European corn borer, Ostrinia nubilalis (Hubner) (Lepidoptera: Crambidae), and other stemborers, by expression of Lepidoptera-specific Cry proteins such as Cry1Ab. More recently, varieties have become commercially available in the USA that express Coleoptera-active toxins such as Cry3Bb1 for the control of corn rootworms (Diabotica spp.; Coleoptera: Chrysomelidae). Varieties have become commercially available in the USA that express Coleoptera-active toxins such as Cry3Bb1 for the control of corn rootworms (Diabotica spp.; Coleoptera: Chrysomelidae) These two groups of herbivores are major pests of maize worldwide and cause substantial economic losses to maize farmers every year. In particular Coleoptera-active Bt maize shows a greater potential for insecticide reduction in the near future [2]

Methods

Results

Conclusion