BT crops may not cause protein accumulation in the soil

October 17, 2011

Scientists from the Bavarian State Research Centre for Agriculture (LfL) and the University of Technology in Munich (TUM) have for the first time investigated what happens to Bt protein from genetically modified MON810 maize throughout the agricultural cycle—from cultivation to use of the plants as cattle fodder, to the spreading of liquid manure from these animals on the fields. The experiments were headed by Martin Müller from the working group on gene transfer and GMO safety research at LfL’s Institute for Crop Science and Plant Breeding.

Bt protein is known to enter the soil, particularly through rotting plant remains after harvesting. But it is only now that researchers have investigated the extent to which this occurs and whether Bt protein can accumulate in the soil as a result of long-term cultivation. The researchers were unable to find evidence of any accumulation of Bt protein in the soil of trial fields on which Bt maize had been grown for nine years in succession.

To evaluate the trials, the Bavarian researchers developed a special method for detecting the Bt protein in the various sample materials. Since Bt protein and genetically modified DNA could also enter the soil through liquid manure, the researchers investigated this route as well. First of all, they needed to find out whether Bt protein does in fact enter the soil via liquid manure. Then it was important to find a way of measuring the Bt protein throughout the entire agricultural process.

“Our most important result was demonstrating, firstly, that Bt protein does not accumulate in the soil as a result of long-term cultivation, and secondly, that only minimal residual amounts of Bt protein are contained in the liquid manure spread on the fields. The remaining Bt protein breaks down so fast there that it does not enter the feed again via the harvested crop,” said Helga Gruber, scientist in charge of the field trials.