Effect of a Semi‐Lethal Factor upon Yield in Soybeans When Present in the Heterozygous Condition 1

Extensive self-pollination of corn in the newer breeding projects has brought to light ,a large number of lethal and so-called semilethal defects. These defects are almost invariably recessive in nature and range from those which are completely lethal to other~ which have only a slight effect upon rig.or and yield. It is very_ apparent that if the homozygous recessive abnormalities occurred in large numbers in a commercial field of corn the yield would be reduced. This source of yield reduction, however, is overcome to a large extent by the fact that, as has been shown by several investigators, only a very small amount of self-pollination takes place in corn. Thus, comparatively few of these defects show up under field conditions. The question arises then, as to the effect of these recessives upon yield when they occur in the heterozygous condition, since it is known that the average commercial variety contains large numbers of defects in the heterozygous state. The authors have some data on the effect of a semi-lethal factor in soybeans upon the yield of individual plants when the factor occurs in the heterozygous condition. While these data are not presented as having a direct bearing on the corn breeding Work, it is thought that they may contribute something to the general knowledge of the subject.