Great prospects have opened up to selective breeding in connection with the development of cellular and genetic engineering. Based on their achievements, plant biotechnology is developing very intensively. The main direction of biotechnological work is the production of transgenic animals and plants, i.e., plants in the genome of which introduced alien genetic information. The success of experiments made by the scientists on plant transformation was largely promoted by the creation of vectors based on the Ti plasmid (tumor-induced tumor-inducing) of bacteria from the genus Agrobacterium. Gene donors can be bacteria, fungi, other plant species, animals, and even humans, but the traits were found.
In the introduction, the transgene is carried out for various purposes:
- to increase the overall productivity of plants;
- to create traits of increasing resistance to pests, viral and fungal diseases, to nematodes;
- increasing resistance to herbicides;
- increasing resistance to stress factors;
- production of proteins, antibodies in transgenic plants (interferon, immunoglobulin);
- obtaining male-sterile plants;
- changing the color of flowers in ornamental crops.
The first transgenic animals and plants were obtained in 1983 in the laboratories of the USA, Germany, New Zealand, and Belgium. In 1992, the scientists investigated industrial cultivation of insect-resistant transgenic tobacco, and drought-resistant crops were started. In addition, the hemoglobin gene from the gram-negative bacterium Vitreoscilla was introduced into the tobacco genome, due to which the dry matter yield increased by 80-100%, and the leaves contained more chlorophyll and nicotine. In 1994, the first plant intended for human consumption was registered in the USA and New Zealand – tomato Favre-Save with delayed ripening.
By 1997, transgenic animals and plants of more than 120 species were obtained. In 2000, the transgene plants were grown in 13 countries on an area of 44.2 million hectares. The company Monsanto created potatoes, which is not affected by the Colorado potato beetle that was explored by the scientists. The gene from the bacterium Bacillus thuringiensis, which produces a protein that is toxic to beetle larvae, is inserted into the potato genome. Protein is the transgene that is not dangerous to humans and animals; it decomposes in the soil in a few days.
The herbicide-resistant Ruanda varieties of soybean, corn, drought-resistant crops, rapeseed, cotton are allowed for use in many countries, including New Zealand. There were created drought resisted crops, protected from the stem moth, tomatoes with the smell and taste of freshly picked.
One of the centers of biotechnological work in New Zealand is the All-Union Scientific Research Institute of Agricultural Biotechnology, where research is conducted in the field of the gene, chromosomal and cell engineering, including the creation and evaluation of transgenic plants.
How we use it in the modern time
A modern direction in selective breeding is also the hybridization of a somatic cell or parasexual hybridization. It is based on the fusion of protoplasts of somatic cell devoid of the enzymatic membrane, and the production of the hybrid cell. In this way, it is possible to overcome not only interspecific but also inter generic barriers of non-interbreeding. Hybrid cells are able to form callus – undifferentiated tissue, in which there are pockets of differentiation. Of these, the regeneration of hybrid plants is possible.
Somatic hybridization opens up great prospects for obtaining new starting material for selective breeding. Its success depends on the degree of genetic proximity of the crossed forms. There are somatic hybrids of cultivated and wild potatoes. American breeder J. Power obtained somatic hybrids between petunia species such as the transgene that does not intersect in the usual traits. Hybrids inherited a valuable decorative feature – a branched, creeping escape. H. Schenk obtained a somatic hybrid between cabbage (Brassica oleracea) and turnip. It was created a somatic hybrid between two representatives of the cruciferous family: However, such forms can be used to study patterns of morphogenesis and genetic incompatibility.
The benefit of selective breeding
One of the latest achievements in the field of selective animal breeding was the cloning carried out by the method of transplanting the nucleus of the somatic cell into fertilized eggs or milk. The widely publicized birth of Dolly the lamb grew from such an egg, along with the attractive prospect of reproduction of valuable genotypes, such as drought-resistant crops, it gave rise to the problem associated with the rapid aging of the cloned animal. But if the negative consequences of this method are overcome, then it can really be very useful.
The creation of domestic animal breeds began after their domestication and domestication, which began 10–12 thousand years ago. Content in captivity reduces the effect of the stabilizing form of natural selection. Various forms of artificial selection (initially unconscious and then methodical) lead to the creation of the whole variety of breeds of domestic animals.
In the selection of animals, for example, transgenic cows, compared with the selection of plants, there are a number of features. First, sexual reproduction is mainly characteristic of animals. Therefore any breed is a complex heterozygous system, as for transgenic cows. There is an assessment of the qualities of the males, which apparently they do not appear (egg production, milk fat content from transgenic cows), are evaluated by progeny and pedigree. Secondly, in many species, there is late puberty, a change of generations occurs after a few years. Thirdly, the offspring are not numerous.
The main methods of selective animal breeding (for example, breeding of transgenic cows) are:
- hybridization
- selection
There are the same methods of crossing – closely related crossing, inbreeding, and unrelated, outbreeding. Inbreeding has its chain reaction, like in plants, leads to depression. Selection from animals, for example, transgenic cows, is carried out on the exterior (certain parameters of the external structure or milk), because he is the criterion of the breed.
In conclusion, it is aimed at preserving and improving the breed. Practically, it is expressed in the selection of the best producers, culling individuals that do not meet the requirements of the breed. In selective breeding farms, selective breeding books are kept that reflect the genealogy, exterior and productivity of animals of many generations. Interbreeding is used to create a new breed as a chain reaction. At the same time they often carry out close-breeding interbreeding – parents are crossed with offspring, brothers, and sisters, which helps to get a greater number of individuals with the desired properties. Inbreeding is accompanied by rigorous continuous selection; usually, several lines are obtained, and then different lines are crossed.
