Mar 9, 2006

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Wild, weed and cultivated beet

Meet the Beta family

Mangold, beetroot, sea beet - a number of plants which share a common ancestry with sugar beet are native to Central Europe. The barriers to cross-breeding between such closely related species are low. Genetically modified sugar beet will not behave any differently from conventional sugar beet in this respect and will pass on its genes to related species.

Beet in Europe. In Northern Italy and Southern France in particular, there are large seed production areas (sites numbered on map) and wild (sea) beet populations. These tend to be found in coastal areas (horizontal lines). Hatched areas: weed beet populations.

A bolter: A flowering beet plant is unusual. Beet plants normally flower only in the second year.

Sea beet in Northern Italy. (Photograph: D. Bartsch)

Relatives of sugar beet: Wild beet

mangold ( Beta vulgaris subsp. vulgaris )

Two conditions must be met before outcrossing from the cultivated plant to a wild plant can actually occur:

• The sugar beet must flower at the same time as the potential hybridisation partner.
  With sugar beet however, this is not self-evident. It is a biennial plant, which produces the beet itself in the first year (vegetative phase) and flowers in the second year (generative phase). Sugar beet is normally harvested before it produces pollen and seeds, but a proportion of plants flower prematurely in the first year (bolters).
  For the purposes of seed production the beets are required to flower and produce seed.
• Cultivated and wild beet or other hybridisation partners must be located at a distance from one another that can be bridged by pollen drift.
  Some production areas for sugar beet seed are found in coastal areas, such as Northern Italy and Southern France (see map). These areas satisfy the two preconditions for the emergence of hybrids of cultivated and wild beet. Here, wind dispersal of sugar beet pollen is likely to result in the pollination of neighbouring wild varieties.

Beta vulgaris - an extended family

The Beta vulgaris family includes a range of crop species, some of which were bred for their tuberous roots (e.g. sugar beet and beetroot) and some of which were bred for leaf growth (e.g. mangold). Today it is generally believed that present-day crop varieties are descended from wild beet. The boundaries between pure wild beet and feral cultivated beet are blurred.

Wild beet, or sea beet (Beta vulgaris maritima) occurs throughout the Mediterranean area and also in the coastal regions of Northern Europe. In Germany it is known to exist in Helgoland and on the Baltic coast, particularly on the island of Fehmarn. Sea beet currently seems to be spreading along the German Baltic coast.

Compared with cultivated beet, sea beet has thicker, fleshier leaves, a smaller tuberous root and the plant parts are often red. Sea beet is not very frost-hardy and can survive only in sparsely populated biotopes.

Weed beets are feral cultivated beets. They are thought to have originated in areas where wild beet populations existed alongside cultivated beet. In Germany weed beets are found in the Rhineland, on the Baltic coast and in the Breisgau region.

Weed beets can create economic problems on agricultural land. As annual plants, they produce no beet and so produce no harvest. Since they are closely related to cultivated beets, they can be controlled only by mechanical means and not with pesticides. They also compete for energy and nutrients with the cultivated plants.

Weed beets have different flowering and propagation behaviour compared with cultivated beet. They have become annual plants through incrossing with wild beet. On cultivated beet fields they flower before the beet is harvested. The wild beet seeds are then able to persist in the soil for long periods of time and can accumulate there despite crop rotation.