F. D. Enfield

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Estimation of the number of segregating genes affecting a quantitative trait in populations initiated from a cross of two homozygous lines is considered. Experimental data, for the trait in question, is assumed available on total response to recurrent selection initiated in the F2 or F3 generation, the initial additive genetic variance and the heterosis(More)
Two-way selection was practiced at three selection intensities for 21 day pupa weight inTribolium castaneum. Each of the 19 single-generation replicates of the project consisted of three populations, one each being selected upward and downward at 10, 30 and 50% selection intensities. Realized heritability for divergence was significantly lower for the least(More)
Ninety-five generations of stabilizing selection for pupa weight in Tribolium castaneum resulted in a significant decrease in phenotypic variance, moderate reductions in additive genetic variance, but only slight changes in heritability for the trait. Sterility was significantly lower and the average number of live progeny per fertile mating was(More)
Directional selection for heavier pupa weight in Tribolium castaneum was practiced for 18 generations in two replicates of an inbred line, each separately maintained in small population cages for more than 90 generations. Mutational variance was estimated in two ways, based on Hill's (1982a) prediction equation for response to directional selection where an(More)
The role of mutations in finite populations on response to artificial selection was investigated by a computer simulation model designed to mimic the biological model of pupal weight of Tribolium. Given the model, the results showed that with selection about 25–55 generations were needed for genetic variances to reach a maximum value depending on population(More)
The correlated responses in male and female sterility to 50 generations of individual selection for pupa weight in Tribolium were analyzed. Two replicate lines (S-lines) were selected for heavier pupa weight and stabilizing selection for pupa weight was practiced in two replicate control lines (C-lines). There was close agreement between replicates in both(More)
Two-way selection for 21-day pupa weight was conducted in two highly inbred lines of Tribolium castaneum. The results, after 17 generations of selection, indicated that one of these lines (CSI-10) possessed a moderate amount of genetic variation for the trait selected (21-day pupa weight). When the selected populations were allowed to mate at random for 13(More)
Twelve generations of family selection for 10-day post-irradiation male mating propensity resulted in significant divergence between the selected and unselected control populations. Much of this divergence was the result of a decline in the control population which was believed to have been a function of both inbreeding and environmental effects.(More)
Data on 16,557 chicks from 198 sire groups were analyzed to determine the importance of genotype-hatch interactions as sources of bias in the estimation of genetic parameters for eight-week weight in poultry. Estimates of heritability for eight-week weight obtained from a paternal half-sib correlation were .27±.04 and .29±.04 for males and females(More)