Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 124

In plants, random mating occurs when each female gamete has an equal chance of being fertilized by any male gamete of the same plant, or with any other plant of the population, and further, there is an equal chance for seed production. As can be seen from the previous statement, it is not possible to achieve true random mating in plant breeding since selection is involved. Consequently, it is more realistic to describe the system of mating as random mating with selection. Whereas true random mating does not change gene frequencies, existing variability in the population or genetic correlation between close relatives, random mating with selection changes gene frequencies and the mean of the population, with little or no effect on homozygosity, population variance, or genetic correlation between close relatives in a large population. Small populations are prone to random fluctuation in gene frequency (genetic drift) and inbreeding, factors that reduce heterozygosity in a population. Random mating does not fix genes, with or without selection. If the goal of the breeder is to preserve desirable alleles (e.g. in germplasm composites), random mating will be an effective method of breeding.