The assessment of induced continuous variation in pure-breeding lines following selfing

Abstract

A simple method is described for assessing the genetical and environmental components of the continuous variation observed in a hierarchically structured selfing series which has been initiated from a pure-breeding line followiag mutagenic treatment. The simplicity of the method and its independence of any assumptions about the distribution of mutational events arises from the omission of all rank 0 statistics from the analysis. By proceeding in this way, from the M3 generation onwards sufficient statistics are generated within a single generation to provide estimates of all the components of variation. The estimates of the genetical components provide direct comparisons of the additive and dominance gene action and predictions of the long-term outcome of the inbreeding programme. Alternative methods, to accommodate statistics of rank 0 and the generation means, both of which were previously discussed by Aastveit and Gaul (1967), are also presented. The new procedures are illustrated by the analysis of the data of Borojevic and Borojevic (1969) on plant height and kernel number in the M5, M6 and M7 generations of two pure-breeding varieties of wheat which had been subjected to gamma ray treatments.