The progress of inbreeding in a pedigree-bred population of barley

in the pedigree of a group of several intervarietal crosses in barley, individual plant progenies from F₄ F₅ and F₆ generations were studied along with three of their parents for comparing the within-family variances (² w) in them using it as a measure of progress towards homozygosity. For plant height the value of w ² in F₆ was not significantly higher than the one in parents whereas for spike length there was observed a significant excess of within-family variability in F₆ over the parents. This excess was attributed to a differential survival of heterozygous progenies under selection despite some selection pressure against the heterozygosity in marked chromosome segments. The adaptive role of heterozygote advantage in the populations of such predominantly self-fertilized species has been briefly discussed.