Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 120

Selection as a process is ongoing in nature. Regarding characters that directly affect the fitness of a plant (i.e. viability, fertility), selection will always be directionally toward optimal phenotype for a given habitat. However, for other characters, once optimal phenotype has been attained, selection will act to perpetuate it as long as the habitat remains stable. Selection will be for the population mean and against either extreme expression of the phenotype. This mode of selection is called stabilizing selection (or also called balancing or optimum selection). Taking flowering for example; stabilizing selection will favor neither early flowering nor late flowering. In terms of genetic architecture, dominance will be low or absent or ambidirectional, whereas epistasis will not generally be present. Stabilizing selection promotes additive variation.