ESTIMATION OF LIFE CYCLE COMPONENTS OF SELECTION IN AN EXPERIMENTAL PLANT POPULATION

Viability and fertility components of selection associated with linkage blocks marked by four electrophoretically detectable loci were estimated in an experimental population of barley [Composite Cross V (CCV)]. The intensity of selection affecting the distribution of pollen types in the outcross pool was also estimated and comparisons were made between the selective values of genes in the pools of uniting ovules and pollen. The estimates show that selection was intense at various stages of the life cycle and that viability and fertility components often opposed one another. Estimates of viability and fertility components of selection were also extended to the three-locus level. The multilocus estimates reveal large differences in viability and fertility among homozygous genotypes. It is concluded that strong selection operates at all life cycle stages in CCV, although often in differing directions.