http://www.plosone.org/article/info:doi/10.1371/journal.pone.0028174
Testing Pollen of Single and Stacked Insect-Resistant Bt-Maize on In
vitro Reared Honey Bee Larvae

Abstract Top
The ecologically and economic important honey bee (Apis mellifera) is
a key non-target arthropod species in environmental risk assessment
(ERA) of genetically modified (GM) crops. Honey bee larvae are
directly exposed to transgenic products by the consumption of GM
pollen. But most ERA studies only consider responses of adult bees,
although Bt-proteins primarily affect the larval phases of target
organisms. We adopted an in vitro larvae rearing system, to assess
lethal and sublethal effects of Bt-pollen consumption in a
standardized eco-toxicological bioassay. The effects of pollen from
two Bt-maize cultivars, one expressing a single and the other a total
of three Bt-proteins, on the survival and prepupae weight of honey bee
larvae were analyzed. The control treatments included pollen from
three non-transgenic maize varieties and of Heliconia rostrata. Three
days old larvae were fed the realistic exposure dose of 2 mg pollen
within the semi-artificial diet. The larvae were monitored over 120 h,
until the prepupal stage, where larvae terminate feeding and growing.
Neither single nor stacked Bt-maize pollen showed an adverse effect on
larval survival and the prepupal weight. In contrast, feeding of H.
rostrata pollen caused significant toxic effects. The results of this
study indicate that pollen of the tested Bt-varieties does not harm
the development of in vitro reared A. mellifera larvae. To sustain the
ecosystem service of pollination, Bt-impact on A. mellifera should
always be a crucial part of regulatory biosafety assessments. We
suggest that our approach of feeding GM pollen on in vitro reared
honey bee larvae is well suited of becoming a standard bioassay in
regulatory risk assessments schemes of GM crops.

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