Heterosis and the inheritance of quantitative characters

Abstract

In three recent papers (Ashby 1930, 1932, 1937) observations have been recorded on the physiological basis of heterosis. These data suggest no obvious genetical interpretation, though they draw attention to the need for a re-examination of the existing hypothesis. This paper considers the requirements for a theory of heterosis and discusses the bearing of heterosis on other aspects of size inheritance. The Polymeric Factor Theory of Size Inheritance Heterosis involves quantitative characters. It is in fact usually described in plants with reference to height, for while many other qualities are affected in heterosis, increase in height is the most obvious phenomenon and the most easily measured. Any genetical theory of heterosis must therefore be consistent with a theory of the inheritance of size characters in general.