What is the main method for breeding new varieties and breeds?

The basis of all work on breeding a new variety of plants or animal breeds is the variability of traits in organisms and the selection by a person of carriers of such changes that most deviate in the direction desired for him. In a series of generations, such changes accumulate and become a stable sign of a breed or variety. For selection, only individual, uncertain (mutational) variability is relevant.
Consequently, artificial selection refers to the process of creating new breeds of animals and cultivated plant varieties through the systematic conservation and reproduction in a series of generations of individuals with certain signs and properties that are valuable to humans.
Darwin identified two forms of artificial selection: methodical, or conscious, and unconscious. Methodological, or conscious, selection consists in the fact that the breeder sets himself a certain task and conducts selection on one or two grounds. This technique allows us to achieve great success. Such selection was called unconscious because the person did not set the goal to develop any particular breed or variety. For example, the worst animals were killed and eaten in the first place, but the most valuable ones were preserved (a more milked cow, a well-carrying chicken, etc.)

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