Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 133

Mating is a way by which plant breeders impact the gene frequencies in a population. Four mating systems are commonly used to effect inbreeding: self‐fertilization, full‐sib mating, half‐sib mating, and backcrossing. Self‐fertilization is the union of male and female gametes; full‐sib mating involves the crossing of pairs of plants from a population. In half‐sib mating, the pollen source is random from the population, but the female plants are identifiable. In a backcross, the F₁ is repeatedly crossed to one of the parents. Self‐fertilization and backcrossing are the most extreme forms of inbreeding attaining a coefficient of inbreeding (F) of 15/16 after four generations of mating. Autopolyploids have multiple alleles and hence can accumulate more deleterious alleles that remain masked. Inbreeding depression is usually more severe in autopolyploids than diploid species. However, the progression to homozygosity is much slower in autopolyploids than in diploids.