Mar 9, 2006

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Rhizomania disease

Virus-resistant sugar beet in the meantime without genetic engineering

Farmers who grow sugar beet live in fear of the rhizomania disease, particularly in Southern Germany. Instead of producing large tuberous roots, infected plants show stunted growth and produce lots of long root-like threads are, hence the name rhizomania or “root madness”. It is the most economically damaging disease known in sugar beet cultivation. The sugar content of infected plants can fall to below 10 percent.

Healthy sugar beet

diseased sugar beet

infected with rhizomania
Photographs: syngenta (2), kws

The disease is caused by the beet necrotic yellow vein virus, or BNYVV. The first infected beets in Germany were discovered in 1974.

For a long time plant breeders had no means of combating the rhizomania disease. After intensive development work, conventional sugar beet varieties with increased resistance to the disease are now available.

Genetic engineering has opened up an alternative path. By transferring the gene for the coat protein of a pathogenic virus to plants, the plants in question were immunised. Since the mid-1990s, transgenic sugar beet with a genetically engineered resistance to the rhizomania virus has been intensively tested in the field.

At present there are no plans to introduce this sugar beet onto the market. In the meantime sugar beet varieties with increased resistance to rhizomania that have been bred without recourse to genetic engineering are now also available.

Accompanying research. The virus-resistant sugar beet has undergone almost ten years of research into the potential environmental risks.

The research focused on modified environmental behaviour in comparison with conventional sugar beet, as well as on outcrossing and dispersal of transgenic beet, it’s relationship with wild and weed beet and also with other related plants such as mangold.

Further topics of accompanying research included the effects of the virus-resistant beet on the soil, the possibility of a gene transfer from the plant to micro-organisms (horizontal gene transfer) and the emergence of new pathogenic viruses.