Various branches of science involved in the cultivation of cultivated plant varieties, farm animal breeds and bacterial strains use both traditional and the latest practical techniques and methods. They will depend primarily on the object of breeding work. In other words, by conducting experiments with plants, a scientist can use mass selection or the mentor method, whereas in working with animals or microorganisms such techniques are used only to a limited extent, if not at all.
The purpose of this article will be to clarify the question of whether such a form of breeding work as the mentor method is theoretically possible and practically feasible when creating new or improving existing breeds of cattle, pigs and poultry.
Features of animal breeding
Widely known in scientific circles, the work of C. Darwin, “Changes in domestic animals and cultivated plants under the influence of domestication,” written in the mid-19th century, is still a reference book for a galaxy of modern scientists engaged in practical activities. It names the main breeding methods: hybridization, heterosis and closely related crosses based on artificial selection.
In experiments with animals, its mass form is avoided, since usually a couple of parental individuals produce a small number of hybrids, each of which has a certain value in material equivalent. Let us not forget that for representatives of the Birds and Mammals classes, which are mainly the main objects of breeding work, only sexual reproduction is characteristic. This means that methods based on vegetative forms (cuttings, budding, vaccination) are unacceptable for animals. To understand the question of whether the mentor method is used in animal breeding, it would be logical to first find out the essence of this technique.
Educator Method
The outstanding Russian scientist breeder I.V. Michurin, whose brilliant research became fundamental to world science, applied a focused vegetative rapprochement of plants of two different varieties. As a result of this, both individuals began to acquire new signs and properties. For example, the shape, size or color of the fruit, as well as their taste, changed. By vaccinating the rootstock plant in the crown, I.V. Michurin was able to create conditions under which the stem began to receive nutrients from the mother.
All this in the end result changed the course of metabolic reactions in the cells and tissues of the grafted graft, and hence its phenotypic signs. The above vaccination method has become known in plant breeding as a mentor method.
Examples of creating new varieties of fruit crops
One of the very first, obtained by I. Michurin back in 1908, is the Belfler-Kitayka apple tree variety. As a scion, the breeder took a shank of the American variety Belfler yellow with outstanding taste. The rootstock was Kitayka sapling large-fruited - a local variety, zoned in Central Russia. Its main advantages were frost resistance and resistance to the main diseases of apple trees - scab and powdery mildew. Using the mentor method, the scientist as a result of hybridization received a new variety that is best suited to the difficult climatic conditions of the northern latitudes, combined with the high palatability of the fruit. Apples of the Michurin variety have a snow-white flesh of a delicate dessert flavor with a delicate aroma.
For more than a hundred years, this culture continues to be grown in private households not only in Russia, but also in Ukraine, Armenia, and the republics of the North Caucasus. Gardeners appreciate this variety also for consistently high productivity and frost resistance. At breeding stations and fruit nurseries, Belfler-Kitayki seedlings are also used as a stock in hybridization processes, due to which about 13 new varieties were created.
Goals and objectives of the directed education of hybrid plants
Based on the above facts, it becomes clear the great importance of the experimental work of I.V. Michurin, who not only developed the mentor method, but also made it one of the leaders in the development of new varieties of fruit and berry crops.
The experiments of the successors of the scientist - E. S. Stroyev, E. N. Sedov and other employees of the All-Russian Research Institute for Fruit Crop Breeding summarized the goals achieved as a result of applying the methods of directed education of hybrid seedlings.
The most significant of them include the following: leveling of unfavorable phenotypic characters in hybrid individuals, as well as consolidation of desirable properties for humans in plants of the cultivar created. Summarizing the numerous results of plant breeding, researchers came to understand certain patterns that accompany the use of vaccines in practice. Let's consider them in more detail.
Conditions for obtaining vegetative hybrids
Using the mentor method in animal breeding, the following rules must be taken into account:
- the plant from which the stem or bud (graft) is taken should be vegetatively young, not older than 1-2 years, and the offspring of a perennial tree should be used as a mentor;
- next to the vegetative grafting shoot, a large number of rootstock branches are sure to remain, providing an effect on the phenotypic signs of the plant being planted.
Thanks to the above conditions, breeders manage to form economically valuable properties in fruit and berry crops. Being one of the most popular and widespread methods of breeding new varieties of crops, this technique, unfortunately, still remains poorly understood by modern biochemists and cytologists.
Tissue engineering
To the question of whether the mentor method is used in animal breeding or not, the answer will be negative. Interesting in this regard are biotechnology studies related to cloning, that is, synthesis by the matrix (one or more somatic cells) of a full copy of the body. In this case, an analogy with the vegetative form of reproduction of plant organisms is traced, since the resulting animal clone consists of cells homogeneous in genotype. Experiments in the field of tissue and genetic engineering are carried out by the method of growing them on a nutrient medium. In the chromosomes of nuclei all hereditary information about the body is stored, which means that you can get from just one cell an unlimited number of individuals - copies.
Characterization of animal breeding techniques
I.V. Michurin developed the mentor method exclusively for use in experiments with plant organisms, more specifically, with fruit and berry crops. As we said earlier, animal studies have their own specifics. First of all, this is the lack of vegetative reproduction in higher vertebrates.
It must be remembered that their organisms are characterized by a high degree of integration of all organs and systems, therefore, a change in one attribute of a certain organ under the influence of a mentor will inevitably lead to serious disruptions in the operation of the systems associated with it anatomically and physiologically. In practice, it would be advisable to introduce the following techniques into work with animals, namely: closely related crossbreeding (inbreeding) and distant hybridization. The first is used to create clean lines and in the future to obtain the effect of heterosis, and the second is used to breed new breeds of animals.