RELATIONSHIP BETWEEN PUREBRED AND CROSSBRED PARAMETERS .2. GENETIC CORRELATION BETWEEN PUREBRED AND CROSSBRED PERFORMANCE UNDER THE MODEL WITH 2 LOCI

The present study under the model with two loci showed that the genetic correlation between purebred and crossbred performance (r(pc)) reflects not only dominance levels at loci but also the gene frequency difference between parental populations. The value of r(pc) was found to vary over all values between -1 and 1 depending on dominance and gene frequency difference between parental populations. The r(pc) is 1 in the case of no dominance or with equal gene frequencies in parental lines. It is positive in any case of partial dominance, and becomes negative only in some cases of overdominance. In general, r(pc) decreases with increasing dominance level or gene frequency difference between parental lines. With a high r(pc), it is generally impossible to distinguish whether the gene frequency difference between parental lines is large or dominance effects are small. It was concluded that r(pc) is a reliable indicator for the effect of selection method on genetic response. For a long term selection, r(pc) is expected to increase with no or partial dominance, but with overdominance r(pc) decreases after crossbred selection.