Present-day problems of corn breeding

The modern method of corn breeding has resulted from the development of a sensible genetic interpretation of the results of selfing and crossing in naturally cross-pollinated species and in these studies the work with corn has played an important role. Perhaps, of equal importance is the fact that adapted varieties cannot, as a rule, be further improved by the use of earlier methods. To the agronomist or other investigator not primarily trained in genetics the best evidence of the value of modern methods is the experimental proof that real progress in obtaining improved sorts has been made. The evidence of experiments now available has been reviewed. The results of these experiments justify the belief that higher yielding sorts or improved quality of product or both can be secured by present-day methods of breeding. In many cases yields have been increased as much as 30%. Such diseases as smut and the ear, root, and stalk rots can be controlled apparently. In order to accomplish the desired results extensive studies must be made and it must be appreciated that breeding cross-pollinated plants by some system of controlled pollination cannot be carried out without considerable effort. The importance of obtaining the best possible selfed lines warrants extensive studies. Desirable selfed lines must contain necessary genetic factors for resistance to specific diseases combined with as many favorable growth factors as possible. Whether large numbers of original selfed lines should be used or smaller numbers with more extensive selection within each line is not yet known. Perhaps better selfed lines can be obtained by selection from crosses between selfed lines which contain necessary complementary growth factors or factors for resistance to disease. In certain cross-pollinated crops self-fertilized lines which in themselves appear as vigorous or more vigorous than normal varieties have been obtained. Extensive study is needed to determine the possibilities with corn. After obtaining what appear to be desirable selfed lines the study of performance of these lines in F1 crosses is a logical step. The only sure method of learning which strains combine to produce the greatest vigor in F1 is by testing all possible F1 combinations. After this the relative value of single crosses, double crosses, and synthetic varieties can be determined.