Selection is a science that develops new varieties of plants, animal breeds, microorganisms. The main criterion for choosing a new, better material is individual and mass selection as a selection method.
Typically, breeding is done by crossing and mutating the genes of parental specimens, and then artificial selection is performed. All new breeds, varieties, strains created by man have certain morphological and physiological properties. Each species is adapted to certain climatic zones. All bred novelties are checked, compared with other varieties at special stations.
Mass plant selection method
Mass selection in breeding new varieties of plants involves the pollination of a large number of plants at once. Most often, this method is used when breeding new varieties of rye, corn, sunflower, wheat. When these crops are screened out, new varieties consist of heterozygous representatives of the species and have a unique genotype.
Mass selection in breeding allows you to get new varieties with improved qualities. However, this method is considered unsustainable due to the high probability of getting unplanned cross-pollination (by insects,birds).
Mass selection of plants is the determination of a group of plant specimens that are similar to each other in terms of established characteristics. For example, we can take the method of breeding a new generation of cereal crops. Usually, obtaining varieties by mass breeding involves sowing a large number of specimens with a further assessment of their development and growth, resistance to diseases, and pests. The level of precocity, climate requirements, and productivity are also assessed. When breeding new varieties of rye, breeders select only those plant specimens that are more resistant to various influences and have a large spike with the largest number of grains. When re-sowing the material obtained, only those plant species are again selected that have shown themselves from the best side. As a result of such work, a new variety is obtained, with homogeneous genes. This is mass selection. Rye breeding examples show how plants are selected.
Mass selection has many advantages, among which the main ones are simplicity, economy and the ability to obtain new varieties of plants in a short time. The disadvantages include the inability to obtain a detailed assessment of the offspring.
Efficiency of mass selection
When working with self-pollinators and cross-breeders, mass selection is used as a selection method. Its effectiveness depends on the gene, heredity, the size of the selected sample.
If the genes responsible for the traits havestable traits, then the selection result will be high.
When plants inherit the desired traits, selection stops and the variety is given a name. With poor performance, the selection work continues. It lasts until the breeders get all the desired results in terms of yield, fruit size, resistance to harmful factors, pests, and diseases. Moreover, during mass selection, sometimes the previously selected offspring differ from the next, taken from parents with poor performance.
For successful breeding work, the size of the sample is important. If material with low rates is taken, then the plant may exhibit inbreeding depression, as a result of which the yield decreases.
Mass selection is most effective when combined with additional selection methods. It is most often used in conjunction with hybridization, a polyploid breeding method.
Hybridization
A hybrid is a first-generation plant that has increased viability and higher productivity compared to parental forms. With further use of hybrid seeds, the genes laid down by the parents are destroyed.
Polyploid selection
The polyploidy method also applies to hybrid methods. When creating new varieties, breeders use polyploidy, which leads to an increase in the size of plant cells and the multiplication of chromosomes.
A large number of chromosomes increases the plant's resistance to various diseases and various adverse factors. In case of damage in plants of sever althe rest of the chromosomes remain unchanged. All plants obtained by polyploid selection have excellent viability.
Examples of mass draws
An example of obtaining a hybrid by mass selection is triticale. This plant was obtained by crossing wheat and rye. The new variety has high frost resistance, is unpretentious and resistant to many diseases.
Russian academician obtained new wheat-couch grass varieties with high resistance to lodging. However, the first plants were not suitable for obtaining planting material, since their genome contained different chromosomes that were not involved in meiosis. In further studies, it was proposed to double the number of some chromosomes. The result of the work was an amphidiploid.
Breeders crossed cabbage with radish. These plants have the same number of chromosomes. The last result carried 18 chromosomes, but he was infertile. Subsequent doubling of the number of chromosomes resulted in a plant with 36 chromosomes and bearing fruit. The resulting organism showed signs of cabbage and radish.
Another example of hybridization is corn. It was she who became the ancestor of heterotic hybrids. The yield of the hybrid crop was thirty percent higher than that of the parents.
Conclusion
When a new line appears, only pure plants are selected. During the experiments, the most successful combinations of hybrids are determined. The results obtained are recorded and used forfurther obtaining hybrid crops.
The development of new varieties, which are obtained only by mass selection, made it possible to obtain high-yielding varieties of wheat, rice, corn, and rye. An example of such work are varieties bred by Russian breeders. These are grain crops "Saratovskaya-29", "Saratovskaya-36", "Bezostaya-1", "Aurora". They are resistant to lodging, practically do not get sick, and are able to produce a stable crop in any climatic conditions.
