Relations between genetic distance of parental pig breeds and heterozygosity of their F1 crosses measured by genetic markers.

The aim of this paper is to examine the extent to which increment of heterozygosity in F1 crosses can be predicted from genetic distance of parental breeds. For this purpose, 38 polymorphic marker loci (blood groups, allotypes, polymorphic proteins and enzymes) were tested in 1115 purebred animals (Duroc, Hampshire and Czech Meat Pig as sire breeds; Landrace, Large White and Black Pied Prestice as dam breeds) and in 1428 crossbred animals of the resulting nine crossbred groups. The number of animals in each genetic group ranged from 75 to 230. On the basis of the allele frequencies of the scored loci, three measures of genetic diversity (heterozygosity, standardized heterozygosity, effective number of alleles) were calculated in all 15 genetic groups. Furthermore, two measures of genetic distance (Nei's standard genetic distance and Gregorius' absolute genetic distance) were calculated between the parental populations. High correlations (Pearson product-moment correlation 0.62 to 0.73; Spearman rank correlation 0.58 to 0.85) were found between the increment of heterozygosity in the crosses (in relation to the mean of the heterozygosities of parental populations) and the genetic distance between the parental populations.