Transgenic maize does no harm to bee larvae01/31/2012
How well do bees tolerate the pollen from genetically modified maize in their diet? Scientists from the University of Würzburg have examined this question for the very first time under controlled conditions in the field and in the laboratory. They have now produced an initial finding.
When bee larvae are given pollen from genetically modified varieties of maize in their diet, this has no consequences for them. At least, a comparison with larvae reared on conventional maize pollen reveals no differences: no increase in the mortality rate nor evidence of development disorders among the larvae. Weight gain also progresses absolutely identically.
This in a nutshell is the result of a study by scientists from the University of Würzburg’s Biocenter. Professor Ingolf Steffan-Dewenter, Chairman of the Department of Zoology III, his Research Associate Dr. Stephan Härtel, and Doctoral Student Harmen Hendriksma produced this result using a technique that allowed them to rear and study bee larvae under controlled conditions in the laboratory.
The laboratory experiment
The scientists spent five days feeding the bee larvae on a special diet. To the jelly that they administered they added exactly the same quantity of pollen that is naturally found in the special jelly of nurse bees. Three larvae groups received the pollen of conventional varieties of maize. The diet of one group was supplemented with pollen from the genetically modified maize variety MON810, which forms a protein that is poisonous to the European corn borer. Another group of bee larvae received pollen from a variety of maize that contains no fewer than three genes to combat maize pests, including the European corn borer and the corn rootworm.
“These genes ensure that the maize plants produce proteins that kill the pests even in the larval stage,” explains Harmen Hendriksma. Bt toxin is the technical name for these proteins. Once ingested, they exercise their toxic effect in the intestine. This is also where they ought to become active if they pose a threat to bee larvae. “The consequence of this should at the very least be a smaller weight gain,” says Hendriksma.
However, the scientists found absolutely no indication of this in their experiments. The bee larvae developed entirely normally. For the bee researchers this is a strong indicator that the protein from genetically modified maize is digested in the intestine of bee larvae without any problem.
Genetically modified pollen – a global reality for honey bees
“This finding is consistent with the latest scientific knowledge,” says Stephan Härtel. So, it was not a surprise. Nevertheless, the work does have international relevance: “We conduct safety research to minimize the potential risks of green genetic engineering for honey bees. Our motivation therefore comes from a desire to protect bees.”
Honey bees are found in all the world’s major plantations of genetically modified cultivated plants. So, any new horticultural developments have to be tested for their threat to bees using modern methods. This innovative study by Würzburg researchers is one of only a few independent assessments of the risks posed by genetically modified plants to honey bees. “The premise of the study, to test theoretically the most sensitive phase – the larval stage in bees – against Bt pollen, increases the safety of the world’s most important pollinator,” says Härtel.
The research method
For their analyses, the bee researchers used a technique developed by beekeepers which is based on an artificial honeycomb in which the queen bee lays her eggs. The floors of the honeycomb are removable and can be carried carefully by the scientists into the laboratory with the larvae still in place. There is no need for direct contact with the sensitive larvae. Once inside the laboratory, the scientists can then examine the impact of transgenic pollen on the growth of the larvae under controlled conditions, unlike in the hive.
The bee researchers see other possible uses for their new test procedure. “Our pollen feeding method would also, for example, be ideal for testing the effect of insecticides,” says Hendriksma. It would therefore make a good standard procedure for researching risks to bees. Incidentally, the work involving transgenic maize is not over for the Würzburg bee researchers. In a new project (AMIGA) funded by the EU, they will spend the next four years examining the effects of genetically modified potatoes and maize plants on honey bees and wild bees.
Testing Pollen of Single and Stacked Insect-Resistant Bt-Maize on In vitro Reared Honey Bee Larvae. Harmen P. Hendriksma, Stephan Härtel, Ingolf Steffan-Dewenter. PLoS ONE 6(12): e28174. doi:10.1371/journal.pone.0028174
Prof. Dr. Ingolf Steffan-Dewenter, T: +49 (0)931 31-86947
Dr. Stephan Härtel, T: +49 (0)931 31-81269
Harmen Hendriksma, T: +49 (0)931 31-82385