Nov 14, 2002

Research Projects

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Ecological research into possible environmental risks of genetically modified virus-resistant sugar beet (Main focus: Analysis of the gene flow between cultivated, wild and volunteer beet)

(1992 – 2000) RWTH Aachen University; Chair of Biology V

Topic

Three successive projects investigated whether genetically modified sugar beet with resistance to rizomania, a disease triggered by viruses, behaves differently in the environment to conventional beet.

The project focused on three key topics.

Key topic (3): Analysis of the gene flow between cultivated, wild and volunteer beet

If genetically modified sugar beet is cultivated, gene exchange between these plants and their crossable relatives can be expected.

In order to be able to assess more accurately the consequences of this kind of vertical gene transfer between cultivated and wild beet populations, the gene flow that takes place under natural conditions between wild, cultivated and volunteer beet was investigated in more detail.

  • One aim of the project was to record the biodiversity of natural wild beet populations in the vicinity of seed production areas.
  • The other was to establish an artificial wild beet population in a seed production area so that naturalisation and dispersal experiments can be carried out here later using transgenic plants.

Unlike sugar beet cultivation, seed production involves flowering of the sugar beet plants.

Other key topics:

Summary

  • Gene exchange between transgenic sugar beet and crossable relatives must be anticipated. Studies in Northern Italy showed a very high genetic diversity in wild beet populations.
  • A final assessment of the ecological impacts of a gene flow of the transgenic traits into wild beet habitats cannot be made on the basis of this data.
  • Gene flow from cultivated to wild beet does not necessarily have to lead to a reduction in genetic diversity.

Experiment description

In order to investigate the gene flow within the Beta vulgaris species in more detail, various wild, volunteer and cultivated beet populations in Europe were studied.

It was possible to establish relationship links between plants/populations using genetic analysis. From these it is possible to draw conclusions about the gene flow.

Schematic overview of the gene flow between wild, volunteer and cultivated forms of sugar beet. (according to Bartsch/Schuphan)

Results

Gene flow between wild and cultivated beet

To be able to trace the gene flow between cultivated and wild beet populations, relationship links between individual plants were investigated. This is possible using special detection methods (PCR, isoenzyme analysis etc.).

The focus for wild beet was on new finds along the German Baltic coast and on the Italian Adriatic coast. The investigation looked at 26 populations of cultivated beet, 20 of wild beet from seed production areas and 19 of wild beet from parts of Europe not influenced by seed production.

  • The wild beet populations on the Baltic coast are increasing both in terms of distribution and size. It was possible to demonstrate that the German wild beet originates from Danish wild populations.
  • The diversity within a single population was very high for the Italian wild populations. The population from Helgoland was much more homogeneous. As expected, the cultivated lines were very homogeneous.
  • A sugar-beet-specific gene was found which can be used to identify gene transfer from cultivated to wild beet. Another gene is far more common in mangold/beetroot than in sugar beet. Both genes are rare in wild beet populations situated a long way from seed production areas, but are frequent in wild populations in regions with seed production. These findings allow the conclusion that gene flow takes place when cultivated and wild beet plants grow in close proximity.
  • Interestingly, the genetic diversity of wild populations in the vicinity of cultivated beet is higher than that of isolated populations.

Investigating bolters

Beet bolters were investigated from areas in the Po Delta (Italy) and the Rhineland as being typical European sugar beet cultivation areas.

  • The beet bolters found in European sugar beet cultivation areas are volunteer beet plants with an annual habit. An area-wide “epidemic” of these undesirable forms of the beet can be anticipated.
  • It was demonstrated that the volunteer beet plants are more closely related to cultivated beet than to wild beet.
  • The annual habit/bolting tendency does come from wild beet, but there is a stronger gene flow within the agroecosystem between cultivated and volunteer beet (cf. diagram above).