Principles of Plant Genetics and Breeding

Taxonomy
Kingdom Plantae
Subkingdom Tracheobionta
Superdivision Spermatophyta
Division Magnoliophyta
Class Magnoliopsida
Subclass Rosidae
Order Fabales
Family Fabaceae
Genus Glycine Willd
Species Glycine max (L.) Merr
Economic importance
Soybean (Glycine max (L.) Merrill) is the major world
oil seed. It is also a major source of meal used for livestock
feed. It consists of about 35–40% protein and less
than 20% oil. The USA is the world’s leading producer
of soybean, accounting for nearly 50% of the world’s
total production, and about 40% of the cultivated
acreage. The average yield of US soybean was only
about 11 bushels/acre in 1924, but increased to 25.4
bushels/acre in 1966 (see Appendix 2 for conversion
rates of units). In 1994, the production reached a new
high of 41.9 bushels/acre. In that year, producers in
Iowa recorded a yield of 50.5 bushels/acre. Similarly,
the acreage of soybean in 1924 was 1.8 million acres,
18.9 million acres in 1954, and 63.4 million acres in
1996. It rose to 72.7 million acres in 2000.
Soybean production in the US occurs primarily in the
north central states, which overlap the Corn Belt states.
The major producing states are Iowa, Illinois, Minnesota,
Indiana, Ohio, Missouri, and Nebraska, these states
together accounting for 72% of the US total production
in 2000. Iowa and Illinois produce more than 30%
of the US crop. Soybean is important in the southern
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Breeding soybean
and southeastern states of Arkansas, Mississippi, North
Carolina, Kentucky, Tennessee, Louisiana, and Alabama,
these states together producing about 10% of the US
total crop. Other producers are South Dakota, Kansas,
Missouri, Wisconsin, and North Dakota.
On the world scene, the US has dominated production
since the 1950s, growing more than 75% of the
world crop by the 1970s. By 2000, the USA, though
still the world’s leader, had a share of 45%, with
Argentina and Brazil taking up about 15% and 21%,
respectively. China ranks fourth in the world, with
about 12% of the world’s total production. Other producers
in the world include Japan, Indonesia, and the
former Soviet Union.
History and origin
The soybean is considered among the oldest cultivated
crops. The first record of the crop is contained in a
2838 bc Chinese book in which Emperor Cheng-Nung
described the plant. Soybean was a “Wu Ku”, one of the
sacred five grains (the others being rice, wheat, barley,
and millet) considered essential for the existence of
Chinese civilization. Cultivated soybean is believed to
have derived from a wild progenitor, Glycine ussuriensis,
which occurs in eastern Asia (Korea, Taiwan, Japan,
Yangtze Valley of central China, northeastern provinces
of China, adjacent areas of Russia). The plant was first
domesticated in the eastern half of north China in the
11th century bc. It was introduced into Korea from this
region and then into Japan between 200 bc and 300 ad.
Soybean was known to be grown in Europe in the
17th century. Its first introduction into the USA is
traced to a Samuel Bowen, an employee of East India
Company, a seaman, who brought it to Savannah,
Georgia, from China via England. Between 1804 and
1890, numerous soybean introductions were made into