Jul 25, 2011

Research Projects

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What happens to Bt protein from GM maize when it enters the soil? (long-term monitoring)

(2007 – 2009) Bayerische Landesanstalt für Landwirtschaft, Institut für Pflanzenbau und Pflanzenzüchtung

Topic

This project investigated the effects of long-term cultivation (9 years) of GM maize (MON810 Bt maize) on the soil. The Bt protein (Cry1Ab) from the maize plants enters the soil via root exudates, harvest residues and pollen deposits. There it can break down in chemical and microbial processes, but it can also bind to organic or inorganic soil constituents. The project investigated the following question:

• What quantities of Bt protein enter the soil via harvest residues of Bt maize, and is there any evidence that Bt protein accumulates during long-term cultivation?

Summary

There was no indication that the Bt protein had accumulated or persisted in any of the various soil types after the nine years of Bt maize cultivation.

Experiment description

Experiment design for studying Cry1Ab protein in farmland soil, with 8 large maize plots (30 m x 25 m) and 16 small slurry plots (2 m x 3 m). Kuratus variety: MON810 Bt maize; Gavott variety: closely related isogenic parent variety

Ten sampling points were marked on each plot on the trial fields.

The project was a collaboration between the Bavarian State Research Centre for Agriculture (LfL) and Technische Universität München (TUM). From 2000 to 2008, MON810 Bt maize and the isogenic parent variety were grown at five trial sites in Bavaria (Puch, Baumanshof, Schwarzenau, Neuhof and Grub), which meant they were grown without interruption under a range of different site conditions. Once the maize plants had been harvested, harvest residues like root remains and maize stubble were left on the field.

In order to investigate what happens to Bt protein in the soil, in the years 2007 and 2008, soil samples were taken at various depth levels (0-30 cm and 30-60 cm) at these trial sites from the plots on which the Bt maize and isogenic maize were grown. No trial planting took place in 2009 because of the ban on the cultivation of Bt maize. Sampling therefore took place in the spring of 2009.

To measure the Bt protein, a very sensitive ELISA test developed at TUM was adapted and validated during the project for use with soil samples.

Results

No Bt protein was found in the soil on any of the five sites in the spring before the next maize crop was sown. On one of the trial sites, very small concentrations of Bt protein (2.91 ng and 2.57 ng Cry1Ab protein per g of soil, in the upper and lower depth levels respectively) were found six weeks after harvest in 2007. However, even on this site, no Bt protein was detected the following spring. The long-term field trial therefore provided no indication that Bt protein accumulates or persists in various types of soil during long-term cultivation of Bt maize.