Genetic parameters in two populations of chickens under reciprocal recurrent selection1

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Abstract
Genetic information on two traits, age at sexual maturity and survivors’ per cent production, was obtained from two strains of the White Leghorn breed under a reciprocal recurrent selection scheme where the reciprocal crosses were raised at three locations representing diversified environments. Genotype by environment interactions were detected by a number of methods; (1) from analyses of variance of sire means within years and over locations where sires, locations, and sire by location interactions were important sources of variation; (2) from genetic correlations of the same trait at different locations; (3) from comparisons of the components that constitute the genetic correlations between the two traits at the same versus different locations. The sire by location interaction variance components when taken as a percentage of the total variation, although not large, 10 per cent for sexual maturity and 8 per cent for egg production, were found to be significant sources of variation. The genetic correlations between the age at sexual maturity and per cent production had a negative relationship when studied at the same or at different locations. Positive relationships, with one exception, of small magnitude were observed from genetic correlations of the sire's purebred and crossbred progeny.