Hayes and Garber - Cucurbit Breeding

CHAPTER XIII
COTTON AND SORGHUM
1
Little is definitely known of the antiquity and origin of cotton.
Evidence has been obtained which indicates that it was cultivated
in India in 1,500 B.C. and in Egypt 1,300 years later.
Species of cotton are indigenous both to tropical America and to
India. Because of the extent of natural crossing (5-13 per cent.)
(Balls, 1912) the difficulties of studying inheritance and of carrying
on practical breeding operations are very great. It seems
reasonable, however, to consider this crop in the self-fertilized
group, as the extent of crossing leads to the belief that continued
self-fertilization will not give harmful results. It also seems
reasonable to conclude that deterioration in a selected variety is
largely the result of natural crossing.
Methods of pedigreed seed
production should, therefore, be developed to their highest
possible efficiency.
Classification and Inheritance. Gossypium contains several
species. The two species of cotton grown commercially in the
United States, upland (G. hirsutuni) and sea-island (G.barbadense)
cross readily with each other. The varieties cultivated in Egypt
also belong to G. barbadense, but in India the forms derived from
G. herbaceum are chiefly grown. Webber (1905) was unable to
cross Aiden cotton which he classified as G. herbaceum, with either
sea-island or upland varieties. The commercial value of cotton
and the separation into the above species groups is largely determined
by three characteristics of the fiber: namely, length,
tensile strength, and fineness. Other morphological characters
have been used in classification. These are presence or absence
of fuzz on the seed, color of fiber and flower, form of boll and
general habit of growth.
The wide range of environmental or
place effect exhibited by the cotton plant generally, as well as
heterozygosis due to natural crossing, has made clear-cut classification
difficult. G. hirsutum is a vigorous annual plant with a
1
While sorghum is botanically one of the grasses, yet from the standpoint
of the breeder it is better treated with the self-fertilized group of
crop plants.
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