THE DETECTION AND MEASUREMENT OF THE EFFECTS OF INDIVIDUAL GENES INVOLVED IN THE INHERITANCE OF A QUANTITATIVE CHARACTER IN WHEAT

Abstract

IN the study of quantitative inheritance it has been customary, since the first formulation of the necessary statistical procedures by FISHER in 1918, to base genetic analyses on covariances between relatives. The characterizations of the inheritance of continuously varying characters provided by these statistical anal- yses are in terms of the action of systems of genes, and although these characteri- zations have been highly informative, they do not suffice to answer many ques- tions concerning the nature of polygenes. THODAY (1961) has emphasized that the isolation of individual genes affecting quantitative characters is a prerequisite to answering questions about the randomness of distribution of polygenes in chro- mosomes, about the relationship of polygenes to major genes and to heterochro- matin and about the homogeneity of polygenes as a class of genes. This paper describes a technique based on common breeding procedures which appears to be useful in identifying some of the major genes (effective factors) in the pre- sumably complex genetic systems responsible for the heritable differences in quantitative characters between pure lines. It also describes the results of an application of this technique to the determination of genetic differences between two varieties of wheat (Triticum aestivum L.) .