An Evaluation of Effects of Mass Selection and Seed Irradiation With Thermal Neutrons on Yield of Corn 1

Although the irradiation treatment was detrimental to yield, the irradiated strain significantly outyielded the original variety and yielded only slightly less than the mass-selected control strain after four generations of selection. It is doubtful that irradiation of an already genetically variable population will prove to be particularly valuable as a breeding procedure; yet it is too early to draw definite conclusions. Additional generations of selection are needed. Because of its simplicity and apparent effectiveness, the use of mass selection of individual plants is suggested as a possible method of yield improvement in populations of corn segregating for genes controlling yield. Where the advantages of hybrids other than yield are desired, mass selection is suggested as a possible means of increasing the frequency of favorable genes in segregating populations prior to inbreeding. If over-dominance exists at any locus, mass selection will not be successful in altering gene frequency for that locus after an equilibrium point is reached. Some possible explanations are advanced for the apparent lack of success of early corn breeders using mass- selection and ear-to-row breeding techniques.