Tell us about the methods of selective work of I. V. Michurin.

In his work, I.V. Michurin used the following methods:
1. The hybridization method. In order for hybridization to be successful, Michurin took for crossing parents from very remote geographic areas. Michurin believed that in this case one-sided dominance would not occur, since the conditions of existence would not be habitual for any of the parental forms. Based on this, it is possible to control the development of a new hybrid obtained.
2. The method of preliminary vegetative rapprochement. This method was used by Michurin when crossing mountain ash and pear. It consists of two stages. First, the annual stem of a hybrid rowan seedling (scion) is grafted into the crown of a plant of another species or genus, for example, to a pear (stock). After 5-6 years of nutrition due to the substances produced by the stock, a certain change occurs, the physiological and biochemical properties of the scion come closer. Then, during the flowering of mountain ash, its flowers are pollinated by the pollen of the stock. In this case, crossing is carried out.
3. The method of intermediary. The essence of this method is that in the case of the impossibility of direct hybridization of two forms of plants, a third is used. This plant is crossed with one of the first two, and then the resulting hybrid is crossed with the second, resulting in a hybrid of the first two forms. The third form serves as an intermediary.