Jun 1, 2004

Research Projects

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The persistence of genetically modified and conventionally bred oilseed rape

(2001 – 2004) University of Hohenheim, Institute for Crop Production and Grassland Research

Topic

The problem of “volunteer oilseed rape”, i.e. the emergence of oilseed rape plants in later crops in the rotation, is sufficiently well known in farming practice. Oilseed rape volunteers come from oilseed rape seeds that remain on the field as crop loss and continue to be germinable for years because of their high persistence, which develops under certain environmental conditions.

The aim of the research is to determine the persistence and emergence of genetically modified oilseed rape genotypes and conventionally bred varieties and to compare them. Cultivation strategies for reducing oilseed rape volunteers (or ferals) will also be investigated.

Summary

Laboratory and field trials have shown that the persistence of oilseed rape seeds depends on the variety (genotype). There are already transgenic and conventional rape varieties with low persistence.

It was possible to influence the abundance of oilseed rape volunteers through suitable soil cultivation after the oilseed rape harvest. Delayed stubble processing and deep burying of the shed seeds led to comparatively little volunteer oilseed rape the following year in the next crop of winter wheat.

The project extension will produce models for the population dynamics of oilseed rape volunteers over the longer term.

Experiment description

Persistence. Using laboratory and field trials, the project investigated the persistence tendency of various genetically modified genotypes and their near-isogenic conventionally bred comparative varieties.

Development of oilseed rape volunteers. Field trials investigated the impact of genotype and cultivation measures like soil cultivation (stubble tillage, ploughing, direct drilling) on the abundance of volunteer oilseed rape in the later crop.

The data collected in the field trials will also be fed into models intended to simulate the population dynamics of volunteer oilseed rape over the longer term under the influence of crop rotation, variety, soil cultivation and pest management. It is hoped that results from these calculations will provide further information for the risk analysis of a possible spread of genetically modified cultivated plants and/or of the transgenic cells.

Results

Persistence. Under laboratory and field conditions, genotypes with different levels of persistence were identified among the transgenic and conventional oilseed rape varieties. They included varieties with low persistence.

Development of volunteer oilseed rape. The timing and type of soil cultivation after the oilseed rape harvest had a significant impact on the persistence of oilseed rape volunteers (ferals) of both near-isogenic and transgenic varieties. Delaying stubble tillage proved an effective method of limiting the development of a soil seed bank. Winter wheat was planted after oilseed rape in the crop rotation. In the spring, oilseed rape volunteers emerged in the winter wheat and flowered between May and July. Despite a serious parasite infestation, the volunteer rape plants produced a certain quantity of germinable seeds. Fewer oilseed rape volunteers emerged when the shed oilseed rape seeds were buried in the deep soil layers after the harvest by means of deep soil cultivation.

Models. The project extension will produce models for the population dynamics of oilseed rape volunteers over the longer term.