Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 153

The kinds of selection methods used in plant breeding are discussed in Chapters 15–18. The genetic control of the trait of interest determines the most effective selection method to use. The breeder should pay attention to the relative contribution of the components of genetic variance (additive, dominance, epistasis) and environmental variance in choosing the best selection method. Additive genetic variance can be exploited for long‐term genetic gains by concentrating desirable genes in the homozygous state in a genotype. The breeder can make rapid progress where heritability is high by using selection methods that are dependent solely on phenotype (e.g. mass selection). However, where heritability is low, methods of selection based on families and progeny testing are more effective and efficient. When overdominance predominates, the breeder can exploit short‐term genetic gain very quickly by developing hybrid cultivars for the crop.

It should be pointed out that as self‐fertilizing species attain homozygosity following a cross, they become less responsive to selection. However, additive genetic variance can be exploited for a longer time in open‐pollinated populations because relatively more genetic variation is regularly being generated through the ongoing intermating.