Inbreeding with particular reference to maize
1931
Graber, R.J.
As a result of the intensive and extensive genic analyses of maize that have been carried on, the genetics of this plant is perhaps more thoroughly understood than that of any other one. Most of the characters that have been studied are not of direct agronomic importance. However, the determination of the manner of inheritance of these characters, the studies of hybrid vigor, and the earlier attempts to increase yield by breeding, all have helped to formulate the methods that are being used at present by technical breeders who are seeking to produce superior yields. The methods which have been most successful to date seem to possess one feature in common, namely, the utilization of a first generation cross as the superior yielding form. The problem then is to create strains of maize which are at least fairly productive, which produce seeds of sufficient size and uniformity to be dropped by a planter satisfactorily, and which give in first generation crosses yields that are distinctly greater than those of the better open-pollinated varieties. The corn breeding program has been carried forward to the point where results of economic importance are beginning to be realized. There was in the neighborhood of 30,000 acres of hybrid corn grown in the United States last year. Relative yield data indicate that a 10% increase in the yields of hybrid strains over the ordinary commercial varieties may reasonably be expected. If it is assumed that one-half this increase is profit, the potential annual value of the inbreeding experiments with maize in the United States is the equivalent of about 130 million bushels of corn, or about 5% of the present annual crop.
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