ScientistsfromtheBavarianStateResearchCentreforAgriculture (Bayerische Landesanstalt fürLandwirtschaft,LfL)andtheUniversityof Technology in Munich (TUM)have for the first time investigated what happens to Bt protein fromgenetically modified MON810 maize throughout the agricultural cycle — from cultivation to use of the plants as cattle fodder, to the spreading of liquid manurefrom these animals on the fields.

The experiments were headed by Dr.Martin Müllerfrom the working group ongenetransfer and GMO safety research at LfL’sInstiute for Crop Science and PlantBreeding.

Bt protein is known to enter the soil,particularly throughrotting plant remains afterharvesting. But it is only now that researchers haveinvestigated the extent towhich this occurs and whether Bt protein can accumulate in the soil as a result oflong‐termcultivation. The researchers were unable to find evidence of anyaccumulation of Btproteinin the soil oftrial fieldsonwhich Bt maize had beengrown for nine years in succession. “Our results show that Bt protein that enters the soil through crop residues breaks down quickly. In the spring before thenext crop of maize wassown,wewerenolongerable to detect anyBtproteinon any of the plots,” says Helga Gruber, the scientistin chargeofthefield trials. To evaluate the trials, the Bavarian researchers developed a special method fordetectingthe Bt protein in the varioussample materials.

SinceBt protein andgenetically modified DNA could alsoenterthesoil throughliquidmanure, theresearchersinvestigatedthis route as well. First of all,they needed to find out whether Bt protein does in fact enter the soilvia liquid manure. Then it wasimportant to find a way of measuring theBt proteinthroughoutthe entire agricultural process.

“Ourmost importantresult was demonstrating, firstly, that Bt proteindoesnot accumulatein thesoilas a result of long‐term cultivation, and secondly, that only minimalresidual amounts of Bt protein arecontained in theliquid manure spread on the fields. The remaining Bt protein breaks down so fast there that it does notenter thefeedagainviathe harvested crop,”says Helga Gruber summarizingthe results.

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Does Bt proteinaccumulateor breakdownduringtheagricultural cycle?