The Role of Genes in Modern Bread Wheat
The growth characteristics of wheat are controlled by the genes
within the cells of the plants. These are linked into long chains,
the chromosomes, that together form the cell genome. Wheat has a
large genome of 42 chromosomes,
created during the evolution from the
three wild species.
|Wheat was originally a very tall plant,
as seen in "The Corn Harvest"
painted by Pieter Bruegel the Elder in 1565. This shows wheat
growing up to the heads of the men harvesting it with scythes.
|After the discovery of shorter landraces
in Japan, wheat breeders transferred selected Reduced-height (Rht)
genes from different landraces to create the shorter but higher
yielding wheat varieties more suited to modern farming. Most
modern combines are unable to harvest tall cereals with long straw
due to blockage problems.
|The picture shows the wheat variety
"Mercia" with a control and four lines with different
|Rht-0 (rht), with no reduced-height
gene, is used as the control for height comparison.
|Rht-1 (Rht-B1b) and Rht-2 (Rht-D1b)
typically produce semi-dwarf plants, about two-thirds the height
of the control.
|Rht-3 (Rht-B1c) and Rht-12 typically
produce dwarf plants, one-third the height of the control.
Plants with the Rht-12 gene also have awns on the ears, the awn
and Rht genes occurring close together on the same chromosome.
Almost all modern varieties of wheat now include height reducing
genes, often Rht-2 (Rht-D1b) or Rht-3 (Rht-B1c), to control the
final height of the plants.
The information displayed on the role of genes display board is
available as a 'pdf' file.