Breeding is a science that introduces 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, selection is carried out by crossing and mutating the genes of the parental copies, and then artificial selection is performed . All new breeds, varieties, strains created by man have certain morphological and physiological properties. Each species is adapted for certain climatic zones. All new products are checked, compared with other varieties at special stations.
Bulk Plant Selection Method
Mass selection in the breeding of new plant varieties involves pollination of a large number of plants at once. Most often, this method is used in the cultivation of 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 unstable due to the high probability of obtaining unplanned cross-pollination (by insects, birds).
Mass selection of plants is the definition of a group of plant instances that are similar to each other according to established criteria. For example, we can take the method of breeding a new generation of cereal crops. Typically, obtaining varieties by the mass selection method involves sowing a large number of specimens with a further assessment of their development and growth, resistance to diseases, pests. Also estimated the level of early maturity, climate requirements, productivity. When new varieties of rye are bred, only those plant specimens that are more resistant to various influences and have a large spike with the largest number of grains are selected by breeders. When re-sowing the obtained material, only those plant species that have shown their best side are again selected. As a result of this work, a new variety is obtained, with homogeneous genes. This is mass selection. Examples of rye breeding show how plants are selected.
Mass selection has many advantages, among which the main thing is simplicity, profitability and the ability to quickly obtain new varieties of plants. The disadvantages include the inability to obtain a detailed assessment of the offspring.
Mass Selection Efficiency
When working with self-pollinators and crosshairs, mass selection is used as a selection method. Its effectiveness depends on the gene, heredity, size of the sample selected.
If the genes responsible for the traits have persistent traits, then the selection result will be high.
When plants inherit the desired traits, selection ceases, the variety is given a name. With poor performance, 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 previously selected offspring differs from the subsequent, taken from parents with poor performance.
For successful breeding, the size of the sample is important. If material with low rates is taken, then the plant may display inbreeding depression, resulting in reduced yield.
Mass selection is most effective when combined with additional selection methods. Most often, it is used in conjunction with hybridization, a polyploid method for removing plants.
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 parents are destroyed.
Polyploid selection
The polyploidy method also refers to hybrid. 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. If several chromosomes are damaged in plants, the rest remain unchanged. All plants obtained by the polyploid selection method have excellent viability.
Bulk Sample Examples
An example of a hybrid by mass selection is triticale. This plant was obtained by crossing wheat and rye. The new variety has high frost resistance, unpretentious and resistant to many diseases.
The Russian academician obtained new wheatgrass varieties of plants that are highly resistant 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 amphidiploid.
Breeders crossed cabbage with radish. In these plants, the number of chromosomes is identical. The last result carried 18 chromosomes, but it was barren. Subsequent doubling of the number of chromosomes resulted in a plant with 36 chromosomes and having fruits. The resulting organism had signs of cabbage and radish.
Another example of hybridization is corn. It was she who became the ancestor of heterosis hybrids. The yield of the hybrid culture 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 to further obtain hybrid cultures.
The breeding of new varieties, which are obtained only by mass selection, made it possible to obtain high-yielding varieties of wheat, rice, corn, rye. An example of such work is varieties bred by Russian breeders. These are the crops “Saratov-29”, “Saratov-36”, “Bezostaya-1”, “Aurora”. They are resistant to lodging, practically do not get sick, are able to give a stable crop in any climatic conditions.