UNITED STATES DEPARTMENT OF AGRICULTURE 
DEPARTMENT BULLETIN No. 1489 
Washington, D. C. 
November, 1927 
CORN BREEDING 
By Frederick D. Richey, Agronomist in Charge of Corn Investigations, Office 
of Cereal Crops and Diseases, Bureau of Plant Industry 
CONTENTS 
Page 
Importance and scope of corn breed- 
ing 1 
Principles of corn breeding 2 
Reproduction in corn 2 
Relation between reproduction 
and inheritance 5 
Theory of inheritance in corn 5 
Some heritable characters of 
corn 15 
Inheritance of productiveness in 
corn 21 
Page 
Principles of corn breeding — Contd. 
Hybrid vigor and productive- 
ness : 22 
Practice of corn breeding 25 
Mass selection 25 
Ear-to-row selection 28 
Hybridization 33. 
Selection within selfed lines 35 
Discussion 55 
Literature cited 59 
IMPORTANCE AND SCOPE OF CORN BREEDING 
Corn is the one outstanding crop of the United States. Not only 
is it in a class by itself in quantity and value, but its cultivation in 
every State and in nearly every county makes it the preeminent 
American crop. With more than 100,000,000 acres in the United 
States annually devoted to corn, any improvement, however slight, 
is significant. It is for this reason that corn breeding, which may be 
defined as a systematic effort to improve the crop by controlling the 
parentage of the seed, is of the utmost importance. 
The improvement sought may be in quantity or in quality. Yield 
generally is the chief consideration either directly or indirectly. 
Quality also is of importance and may be related directly to yield. 
Thus, the breeding of strains resistant to damage by insects reduces 
the damage and loss and so increases the yield of marketable corn. 
The development of disease-resistant strains not only reduces the 
percentage of moldy or rotten ears but also directly increases the 
yield. A study of the specific factors affecting progress in experi- 
mental corn breeding is essential to determining the fundamental 
principles involved. In practical breeding, however, the individual 
factors operating in any given environment are taken care of auto- 
matically if selection is based upon the quantity of sound grain 
produced under conditions of equal opportunity. 
36919°— 27 1 1 
