How can we explain the phenomenon of heterosis in unrelated hybridization?

One way to increase the diversity of breeding material is through hybridization. It can be of two types: closely related, which allows translating recessive genes into a homozygous state; unrelated, helping to unite in one organism the genes responsible for the valuable traits of different individuals.
Unrelated hybridization can be intraspecific – crossing individuals of different varieties or breeds of the same species and distant – crossing individuals of different species and genera.
By hybridizing individuals of different lines – outbreeding (Eng. Out – outside and breeding – breeding) – it is possible to obtain heterozygous hybrids that are superior in quality to their parental forms. In this case, the effect of heterosis (Greek heteroiosis – change, transformation) is manifested – a hybrid force, the main reason for which is the absence of manifestation of harmful recessive alleles in the heterozygous state. The effect of heterosis is widely used to obtain high-yielding hybrids of corn, cucumbers, sugar beets and other cultivated plants. In poultry farming, interline hybridization of meat breeds of chickens makes it possible to obtain heterotic chickens – broilers. Already from the second generation, the effect of heterosis fades.
Heterosis (hybrid power) is an increase in the viability and productivity of hybrids compared to parental forms. Heterosis is observed with outbreeding and distant hybridization. This effect is due to an increase in the degree of heterozygosity of the offspring in comparison with the parent forms, because of which harmful recessive mutations do not appear phenotypically.

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