The Analysis of Genetic-Environmental Interactions by Means of Diallel Crosses.

LTHOUGH it is a matter of importance both theoretically and practically, A little is known about the constancy under different environmental conditions of the genetic components of continuous variation. This is not surprising, for study of the effects of environment upon the various genetic parameters required to specify continuous variation could not proceed until the parameters themselves were clearly defined and techniques had been developed for their detection or measurement. Recently, as a result of an expansion and generalization of the method of analysis of diallel crosses, JINKS (1952, 1955) has shown that the various statistics obtained from measurements of parents and their FI progeny in diallel crosses provide estimates of overall dominance, the relative dominance of parents, and the distribution of dominant and recessive alleles in the parental lines entering the diallel system. Even more important, the analysis permits the separation of certain types of nonallelic interaction from overdominance. Further extensions of the analysis and applications to a variety of experimental data (JINKS and HAYMAN 1953; HAYMAN 1954b, 1955; JINKS 1954, 1955) have demonstrated the usefulness of diallel crosses in the investigation of certain of the genetic components of continuous variation. Diallel crosses may also be useful in the investigation of genetic-environmental interactions, and it is with this aspect of the analysis of diallel experiments that the present discussion is concerned. It will be shown that estimates of stability under different environmental conditions of certain genetic parameters can be obtained from diallel experiments replicated in time or in space.