Principles of Plant Genetics and Breeding

Adaptation
Wheat is best adapted to cool temperate climates where
rainfall is not excessive (40–60 cm per annum). Based
on season of production, there are two types of wheat –
winter wheat and spring wheat.
Winter wheat
Winter wheat is sown in the fall so that it can have some
growth before the onset of cold weather in winter.
Growth ceases and the plants remain dormant through
winter, resuming growth in spring for harvesting in
summer. About two-thirds of US wheat is winter wheat.
Winter wheat can survive cold temperatures as low as −
40°C if protected by snow.
Spring wheat
Spring wheat is planted in early spring and harvested
in July–August. Spring wheat is less tolerant of low
temperatures and is damaged by even a light frost of −2
to −1°C.
Wheat is a long-day plant. Short days of high temperatures
stimulate tillering and leaf formation but delay
flowering of wheat plants. Early maturing cultivars are
available for production under any photoperiod conditions.
However, the quality (nutritional uses such
as baking) of wheat is influenced by the production
environment. For example, growing hard wheats in
soft wheat regions results in grains that are starchy or
“yellow berry” (soft and starchy).
History of breeding in the USA
Wheat is one of a few food crops (the others being corn
and rice) that have been associated with the Nobel Peace
Prize. The 1970 Nobel Peace Price awarded to Norman
Borlaug, the father of the Green Revolution, recognized
his contribution to agricultural productivity through
the introduction of superior genotypes of wheat. These
superior varieties were high yielding, shorter (semidwarf
wheat), more lodging resistant, and responsive to high
levels or fertilizer. A significant contributor to this effort
was Orville Vogel, a USDA wheat breeder stationed at
Washington State University. Under his leadership, the
first successful commercial semidwarf wheat variety in
the Western Hemisphere was released to farmers in
1961. This variety, “Gaines”, was a soft white wheat and
yielded in excess of 100 bushels/acre under both dry-
BREEDING WHEAT 473
land and irrigated production. In spite of its agronomic
qualities, “Gaines” had milling quality problems. In
response to the demands of the milling industry, a new
selection with more desirable milling qualities, called
“Nugaines”, was released in 1965. The role of wheat in
the Green Revolution was discussed in Chapter 1.
Commercial wheat classes
Wheat breeders specialize in one of the special market
classes of wheat. There is a genetic basis for this
classification. Wheat may be classified into seven groups
based on time of year they are planted, and kernel
characteristics (hardness, color, shape). However, for
commercial production, the varieties may be narrowed
down to six basic classes: hard red winter, soft red
winter, hard red spring, hard white, soft white, and
durum wheat. The hard red wheat accounts for about
40% of total US wheat production and is the dominant
class in US wheat export.
Hard red winter wheat
This is grown mainly in the Great Plains (Kansas,
Oklahoma, Nebraska, Texas, Colorado). It is also grown
in the former Soviet Union, Argentina, and Danube
valley of Europe. It is used for bread flour.
Hard red spring wheat
This class of wheat is grown in regions with severe
winters in the north central states (North Dakota,
Montana, South Dakota, Minnesota). It is also produced
in Canada, Russia, and Poland. It is the standard
wheat for bread flour.
Soft red winter wheat
This class of wheat is grown predominantly in the eastern
USA (Ohio, Missouri, Indiana, Illinois, Pennsylvania).
It is also grown in Western Europe. Soft red winter
wheats are used mainly for pastry, cake, biscuit, and
household flour. For bread-making, it needs to be
blended with hard red wheat flour.
White wheat
White wheat (hard or soft) is produced in the four western
states and in the northeastern states (Washington,
Oregon, Michigan, California, New York). Some of this
is club wheat. It is also produced in Northern, Eastern,