Non-Specific Heterosis on a Complex of Features of Adaptability on the Example of Mini-Pigs

Abstract

The authors studied the genetic diversity of the reproductive nucleus of mini-pigs at the Institute of Cytology and Genetics (IC&G) of the Siberian Branch of the Russian Academy of Sciences (SB RAS). To do this, the authors used the indicators of individual homo- and heterozygosity, calculated based on the «blood fractions» of large and small forms of domestic pigs, initial for the breeding group. The study showed that the average value of individual heterozygosity (conditionally actual) is 0.800±0.004, while homozygosity for the contribution of large and small forms of the domestic pig is 0.020±0.002 and 0.180±0.010, respectively. The indicator «blood fraction» can have two interpretations: 1) the probability of transmission of the ancestral allele in several generations; 2) the proportion of the genome of the ancestor that is present in the descendant. The authors determined their frequencies, which turned out to be 0.424 and 0.576 as if assuming the presence of a hypothetical locus with different alleles in the large and small forms of the domestic pig (respectively Ak and Am). The authors calculated heterozygosity for the breeding nucleus based on these frequencies while respecting the Hardy-Weinberg law. As a result, it turned out that the unbiased value is 0.493±0.067, which is significantly (P<0.001) less than the observed conditional-actual value. Selection is carried out according to a set of signs of general fitness (state of health, reproductive qualities, the viability of offspring, etc.) during the formation of the reproductive core of the breeding group of mini-pigs of the IC&G SB RAS. Therefore, the authors concluded that the increased heterozygosity of the breeding stock is due to the preferential selection of heterozygotes. But since selection is carried out according to a set of signs of general fitness, it can be stated that in the reproductive core of the selection group there is an effect of nonspecific heterosis due to heterozygosity. As a result, selection into the reproductive nucleus of individuals with high values of individual heterozygosity calculated by the proposed method can provide heterosis based on general adaptiveness.