What is called a variety, breed, strain, what features. Breed, variety, strain - these are populations of organisms obtained in. Explain why a variety, breed or strain cannot be considered a separate species.

Selection - the science of creating new and improving existing plant varieties, animal breeds and strains of microorganisms. The scientific foundations of selection were laid by Charles Darwin in his work On the Origin of Species (1859), where he highlighted the causes and nature of the variability of organisms and showed the role of selection in the creation of new forms. An important stage in the further development of selection was the discovery of the laws of heredity. A great contribution to the development of selection was made by M. I. Vavilov, author of the law of homological series in hereditary variability and the theory of the centers of origin of cultivated plants.

The subject of selection is the study, under conditions created by man, of the patterns of change, development, and transformation of plants, animals, and microorganisms. With the help of selection, methods of influencing cultivated plants and domestic animals are being developed. This happens in order to change their hereditary qualities in the direction necessary for a person. Selection has become one of the forms of evolution of the plant and animal world. It is subject to the same laws as the evolution of species in nature, but natural selection is partially replaced by artificial selection.

Theoretical basis of selection is genetics, evolutionary doctrine. Using evolutionary theory, the laws of heredity and variability, the doctrine of pure lines and mutations, plant breeders have developed various methods for breeding plant varieties, animal breeds and strains of microorganisms. The main selection methods are selection, hybridization, polyploidy, experimental mutagenesis, genetic engineering methods, etc.

The main tasks of modern breeding is to increase the productivity of varieties and breeds, transfer them to an industrial basis, create breeds, varieties and strains adapted to the conditions of modern agriculture, ensure full production food products at the lowest cost, etc.

Breeding is divided into three main sections: plant breeding, animal breeding and microbial breeding.

The concept of the breed, variety, strain

objects and end result The breeding process is breed, variety and strain.

animal breed- this is a set of individuals within a certain type of animal, as if it has genetically determined stable characteristics (properties and signs) , which distinguish it from other sets of individuals of this species of animals, steadily pass them on to their descendants and is the result of human intellectual activity. Animals of the same breed are similar in body type, productivity, fertility, color. This allows them to be distinguished from such other breeds. There must be a sufficient number of animals in the breed, otherwise the possibility of applying selection is limited, quickly leads to forced inbreeding and, as a result, to the degeneration of the breed. Except high performance and number, the breed should be fairly common. This increases the possibilities for creating in it various types which contributes to its further improvement. A great influence on the formation of features of rocks have natural and geographical conditions - features of soils, plants, climate, terrain, and the like. When animals are brought into new natural and climatic conditions, physiological changes occur in their bodies, and in some cases deep, in others - storey. The restructuring of body systems is the deeper, the more difference between new and old conditions of existence. The process of adaptation of animals to new conditions of existence is called acclimatization, it can last several generations.

plant variety - a group of cultivated plants that, as a result of selection, have received a certain set of characteristics (useful or decorative) , which distinguish this group of plants from other plants of the same species. Each variety of plants has a unique name and retains its properties with repeated cultivation.

Microorganism strain - a pure culture of a certain type of microorganisms, the morphological and physiological features of which are well studied. Strains can be isolated from different sources (soil, water, food) or from the same source at different times. Therefore, the same type of bacteria, yeast, microscopic fungi can have a large number of strains that differ in a number of properties, such as sensitivity to antibiotics, the ability to form toxins, enzymes, and other factors. Strains of microorganisms that are used in industry for the microbiological synthesis of proteins (in particular, enzymes), antibiotics, vitamins, organic acids, etc., are much more productive (as a result of selection) than wild strains.

Breeds, varieties, strains are not able to exist without constant attention person. For each variety, breed, strain is characteristic certain response to conditions environment. This means that their positive qualities can manifest themselves only at a certain intensity of environmental factors. Scientists in scientific and practical institutions comprehensively study the properties of new breeds and varieties and check their suitability for use in a certain climatic zone, that is, they carry out their zoning. zoning research - a set of measures aimed at checking the conformity of the qualities of certain breeds or varieties to the conditions of a certain natural area, which is a necessary condition for their rational use on the territory of any country. The best for use in a certain climatic zone are regionalized varieties, breeds, the positive properties of which can manifest themselves only under certain conditions.

1. What is called a variety, breed, strain?

Breed, variety, strain are artificially obtained populations of animals, plants, fungi and bacteria with traits that are necessary for humans.

2. What features are characteristic of heterotic organisms?

For heterotic organisms, the superiority of the first generation of hybrids in a number of characteristics and properties over both parental forms is characteristic.

3. What is the relationship between artificial selection and selection?

Artificial selection is the choice by a person of the most valuable for him individuals of animals and plants of a given species, breed or variety in order to obtain offspring from them with desirable properties. It is the basis of selection. Breeding is a science that studies the biological foundations and methods for creating and improving animal breeds, plant varieties and strains of microorganisms.

4. What role does the selection of microorganisms play in the national economy?

Microorganisms are used in different areas industry (in baking and winemaking, in the production of feed protein, lactic acid products, antibiotics, vitamins, hormones, amino acids, enzymes), in agriculture(in the production of silage), for biological plant protection and cleaning Wastewater. In this regard, industrial microbiology is developing and intensive breeding work is underway to develop new strains of microorganisms with increased productivity, which produce substances necessary for humans.

5. Name the main selection methods.

Artificial selection, hybridization, mutagenesis, polyploidy.

6. Name the varieties of fruit or vegetable plants, animal breeds known to you.

Apple varieties: Antonovka, White filling. White and red cabbage, cauliflower and Brussels sprouts.

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Explain why a variety, breed or strain cannot be considered a separate species?

Species - a set of individuals characterized by a hereditary similarity of morphophysiological features, freely interbreed and produce fertile offspring, adapted to certain living conditions and occupying a certain area (territory). A species is a taxonomic category that is used in taxonomy to determine the diversity of life on Earth.

Breed - a group of farm animals of the same species, common origin, similar in appearance, constitution, productivity and other economically useful traits that are transmitted to offspring.

A variety is a form (variety) of cultivated plants artificially created in the process of selection, which have in specific conditions cultivation certain biological and economic properties.

Strain - a pure culture of a microorganism created under control conditions from a single source cell with the desired characteristics, acquired mainly due to mutation.

Speciation occurs in natural conditions without human influence, and the formation of breeds, varieties and strains is artificially created organisms due to mutations that humans use.

biology.kiev.ua

Answer to question 2 in biology from Sivoglazov's textbook for grade 10 on the topic § 32. Selection: basic methods and achievements

Varieties of Antonovka apples, Severyanka pear, dog breeds: Rottweiler, Miniature Poodle, Collie....
Questions for repetition and tasks1. What is selection? Selection (from Latin selectio - selection) is the science of creating new and improving existing plant varieties, animal breeds ...
What is called a breed, variety, strain? A breed, variety or strain is a collection of individuals of the same species, artificially created by man and characterized by certain us ...
What are the main selection methods you know?...
Select criteria and compare mass and individual selection....
What difficulties arise when staging interspecific crosses? Remote hybridization consists in crossing different species. In crop production, with the help of remote bending...
Are interspecific hybrids produced and used in your area? Using additional sources of information, find out what hybrids of species are such organisms that ...
Think! Remember! 1. What are the similarities and differences between plant and animal breeding methods?
Why does each region need its own plant varieties and animal breeds? What varieties and breeds are typical for your region? What are their features and advantages?Since...
Of the wide variety of animal species that live on Earth, man has selected relatively few species for domestication. How do you think this is explained? The process of one ...

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Basics of selection | Study-Easy.RF - the largest study portal

Breeding is a science that studies the possibilities of obtaining new breeds of animals, plant varieties, strains of microorganisms, with signs that are necessary for humans.

Breed, variety, strain are populations of animals, plants, microorganisms created by man with the help of breeding methods, which have the characteristics necessary for a person, fixed by heredity in a number of subsequent generations of individuals.

Mass selection is a method of plant breeding when a genetically homogeneous population of individuals with the necessary traits is selected.

Individual selection - a method of plant breeding, when individual individuals with certain characteristics are selected.

Inbreeding is a method of plant breeding when the preservation of a variety of self-pollinating plants is carried out by protecting it from the ingress of pollen from other plants.

Cross-pollination of self-pollinating plants is a method of plant genetics aimed at obtaining varieties with new traits. Distant plant hybridization is a plant breeding method in which plants of different species are crossed.

Inbreeding is a method of animal genetics when new breeds of animals are obtained by carrying out closely related crosses.

Outbreeding is a method of animal genetics, when new breeds of animals are obtained by carrying out unrelated crosses.

Inbreeding is a method of animal genetics when new breeds of animals are obtained by crossing the most suitable individuals of the same breed.

Progeny testing is a method of animal genetics when new breeds of animals are obtained by selecting males whose offspring are considered productive for one or another trait. The same goal is pursued by artificial insemination.

Distant hybridization of animals is a method of animal breeding in which animals of different species are crossed.

Genetic engineering is a method of genetics of microorganisms, which is based on the transfer of genes from one type of microorganism to another.

Biology. General biology. Grade 10. Basic level Sivoglazov Vladislav Ivanovich

32. Breeding: main methods and achievements

Remember!

What is a selection?

Give examples of animal breeds and plant varieties known to you.

More than 10 thousand years ago, humanity switched to a settled way of life and became completely dependent on a limited number of plant and animal species that it could use as its food and economic resources. There was an urgent need to improve the quality of cultivated plants and domestic animals, that is, to engage in selection. Selection(from lat. selectio- selection) - the science of creating new and improving existing varieties of plants, animal breeds and strains of microorganisms. At the same time, selection is understood as the very process of creating varieties, breeds and strains. Theoretical basis breeding is genetics.

At present, out of the entire plant diversity, man cultivates about 150 species as cultivated plants, and out of many tens of thousands of species of vertebrate animals, man has domesticated only about 20.

Centers of origin of cultivated plants. A great contribution to the study of the origin of cultivated plants was made by the outstanding Russian geneticist and breeder Nikolai Ivanovich Vavilov. Having made at the beginning of the XX century. More than 60 expeditions around the world, Vavilov and colleagues discovered that in certain areas of the globe the greatest variety of varieties of a particular cultivated plant is concentrated. For example, for potatoes, the maximum genetic diversity is associated with South America, most of the rice varieties were found in China and Japan, and corn in Mexico. After analyzing the results of the trips, Vavilov came to the conclusion that the areas of maximum diversity are the centers of origin of this culture and, as a rule, are associated with the ancient centers of agricultural civilizations. Vavilov identified seven main such centers (Fig. 102).

During the expeditions, a unique collection of plant seeds was collected, which was subsequently constantly replenished and studied by employees of the All-Union Institute of Plant Growing in St. Petersburg, which now bears the name of N. I. Vavilov. Currently, it has more than 300 thousand species, varieties and forms. Starting work on the creation of a new variety of plants, the breeder can choose from the richest available source material those samples that fully possess the features of interest to him.

Variety and breed. IN modern conditions In the development of society, the intensification of agricultural production, i.e., obtaining the maximum amount of products at minimum cost, is of great importance. For this purpose, they create highly productive breeds animals and plant varieties resistant to extreme conditions environment, to diseases and pests, possessing certain necessary qualities (Fig. 103). Breed, grade or strain- this is a collection of individuals of the same species, artificially created by man and characterized by certain hereditary properties. All organisms that make up such a collection have similar, hereditarily fixed morphological and physiological properties and are able to maximize their qualities in the conditions for which they were created. The Dachshund can be an excellent burrowing hunting dog, but it is pointless to use it as a hound. Similarly, a greyhound that easily overtakes a hare will be a poor guard compared to a German Shepherd.

Rice. 102. Centers of origin of cultivated plant species (according to N. I. Vavilov)

Rice. 103. Breeds of cattle

By creating certain breeds of animals, we often doom them to the need for constant coexistence with humans. A cow producing 10,000 liters of milk per year will die within days if she is not milked.

Basic selection methods. The main breeding methods are selection and hybridization.

Selection. The selection is mass and individual. Mass selection is carried out according to external, phenotypic characteristics and, as a rule, is used in crop production when working with cross-pollinated plants (rye, corn, sunflower, etc.). From a huge number of plants, a group of the best plants according to certain properties is selected. Their seeds are sown the next year and the best plants are again selected from the resulting offspring, the seeds of which are sown in a new field. If productivity and other traits of the population have improved, we can assume that mass selection for the phenotype was effective. Many varieties of cultivated plants are bred in this way.

In contrast to the mass individual selection individual individuals are selected and the offspring of each of them are studied in a number of generations. This makes it possible to accurately estimate the genotype of each parent organism and choose for further work those individuals that turn out to be the most optimal in terms of a combination of traits and properties that are useful for humans. Varieties and breeds obtained as a result of individual selection are distinguished by high uniformity and constancy of characters (Fig. 104).

Hybridization. Along with selection, an important selection method is hybridization (crossing).

Hybridization can be closely related, which allows rare genes to appear in a homozygous state and thereby reveal hidden recessive alleles, and unrelated, used to combine in one organism the characteristics of different varieties, breeds, and sometimes even species and genera.

Closely related hybridization (inbreeding) translates most recessive alleles into a homozygous state, due to which they begin to appear in the phenotype. Any organism always contains recessive genes in its genotype in a latent state ( aa). If among them there are genes that reduce viability, then repeated inbreeding, transferring these genes to a homozygous state, can lead to the degeneration of the breed or variety. This pattern is also true for people practicing closely related marriages. Many families are known who married only close relatives, with each generation increasing the number of hereditary diseases. Thus, for example, the Spanish royal dynasty of the Habsburgs degenerated and died out. Of course, rare recessive alleles can also be useful, in which case their manifestation in a homozygous form can increase the viability, endurance, or other useful qualities of their owner. If this happens, then the breeders deliberately use inbreeding in the new breed they develop, which allows them to keep the discovered original or useful trait.

Unrelated hybridization (outbreeding) are subdivided into intraspecific and remote.

Rice. 104. Cultivated varieties of cabbage and their wild ancestor

At the core intraspecific hybridization lies the directional crossing of individuals with certain properties in order to obtain offspring with the maximum manifestation of these qualities. For example, one plant variety is highly productive but easily infected by fungal diseases, while another, which is highly resistant to diseases, produces much less seeds. By crossing these two varieties, various combinations of traits can be obtained in the offspring, among which there will be highly productive and at the same time infection-resistant plants.

Rice. 105. Ligers - interspecific hybrids between a lion and a tigress - look like huge lions with blurry stripes. A female liger (left) and a male liger (right)

distant hybridization consists in crossing different species (Fig. 105). In crop production, with the help of distant hybridization, a new grain crop has been created - triticale, a hybrid of rye and wheat. This crop combines many properties of wheat (high baking qualities) and rye (the ability to grow on poor sandy soils).

A classic example of interspecific hybrids in animal husbandry is the mule, obtained by crossing a donkey with a mare, which significantly exceeds its parents in endurance and performance. In Kazakhstan, when crossing wild mountain sheep-argali with fine-fleeced sheep, the famous archa-merino breed of sheep was created.

However, the use of interspecific crosses has certain difficulties, because the resulting hybrids often turn out to be sterile (sterile) or low-fertile. The sterility of hybrids is associated with the absence of paired homologous chromosomes. This makes the conjugation process impossible. Therefore, meiosis cannot be completed and germ cells are not formed. The famous Russian scientist Georgy Dmitrievich Karpechenko (1899–1942) was the first to propose a method for restoring fertility in distant plant hybrids using the polyploidy method.

Rice. 106. Heterosis in the productivity of a hybrid (in the center) obtained by crossing two different lines of corn (nearby)

When crossing different breeds animals or plant varieties, as well as interspecific crosses in the first generation, the viability of hybrids increases and powerful development is observed. The phenomenon of the superiority of hybrids in their properties of parental forms is called heterosis, or hybrid power(Fig. 106).

Often in crop production, polyploid plants are also obtained, which are distinguished by their larger size, high yield and more active synthesis of organic substances. Polyploid varieties of clover, sugar beet, rye, and buckwheat are widely distributed.

Humanity currently uses about 10% of the entire land surface for agricultural production. It is no longer possible to increase this share, because practically all the reserves have been exhausted. All the more important is the selection work of scientists who, relying on the basic laws of heredity and variability, create new highly productive breeds and varieties. IN last years selection is actively introducing into practice the techniques and methods of genetic and cell engineering.

Review questions and assignments

1. What is a selection?

2. What is called a breed, variety, strain?

3. What are the main selection methods?

4. Select criteria and compare mass and individual selection.

5. What difficulties arise when setting up interspecific crosses?

6. Are interspecific hybrids produced and used in your area? Using additional sources of information, find out what kind of hybrids organisms such as bester, honorik, hinny, rafanobrassica are. What is their interest in agriculture?

Think! Execute!

1. What are the similarities and differences between plant and animal breeding methods?

2. Why does each region need its own plant varieties and animal breeds? What varieties and breeds are typical for your region? What are their features and benefits?

3. Of the wide variety of animal species that live on Earth, man has selected relatively few species for domestication. How do you think this is explained?

4. Heterosis in subsequent generations usually does not persist, it fades. Why is this happening?

5. Why do you think ligers are born only in zoos and are not found in wild nature? Explain your point of view.

6. Do you think mass selection can be used in animal breeding? Prove your opinion.

7. Using additional literature and Internet resources, prepare a report or presentation about the history of breeding from ancient times to the present.

8. Are there breeding stations or centers in your area? What kind of research do they do? What are their achievements? Together with the teacher, organize an excursion to such a station.

9. Organize an exhibition "Breeding Achievements" dedicated to the activities of local breeding centers and stations, seed farms, variety testing plots (group project).

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artificial mutagenesis. One of the modern trends in breeding is artificial mutagenesis As you know, spontaneous mutations occur extremely rarely in nature, and therefore the breeder has to wait a very long time, sometimes all his life, until a plant with the desired mutation appears in his farm. But the mutation process can be greatly accelerated by using factors that increase the frequency of mutations, i.e., mutagenic factors. We have already talked about these factors, they can be different kinds electromagnetic radiation, temperature change or some chemical substances. As a result of the use of artificial mutagenesis, organisms with a wide variety of mutations can appear. Most of these mutations will turn out to be useless or harmful, but sometimes there may be those that are of practical interest to the breeder. In this case, mutant individuals can be crossed with each other, and as a result of numerous repeated crosses, a new variety or breed with new useful traits can be obtained. Especially significant results using artificial mutagenesis are obtained in the selection of microorganisms.

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This is the science of creating new and improving existing breeds of animals, plant varieties, strains of microorganisms. Selection is based on methods such as hybridization and selection. The theoretical basis of selection is genetics.

To successfully solve the problems facing selection, Academician N.I. Vavilov emphasized the importance of studying the varietal, species, and generic diversity of crops; study of hereditary variability; the influence of the environment on the development of traits of interest to the breeder; knowledge of the patterns of inheritance of traits during hybridization; features of the selection process for self- or cross-pollinators; artificial selection strategies.

Breeds, varieties, strains- populations of organisms artificially created by man with hereditarily fixed features: productivity, morphological, physiological characteristics.

Each animal breed, plant variety, strain of microorganisms is adapted to certain conditions, therefore, in each zone of our country there are specialized variety testing stations and breeding farms for comparing and testing new varieties and breeds.

For successful work, the breeder needs a varietal diversity of the source material. At the All-Union Institute of Plant Industry N.I. Vavilov collected a collection of varieties of cultivated plants and their wild ancestors from all over the globe, which is currently being replenished and is the basis for breeding any crop.

The centers of origin of cultivated plants identified by N.I. Vavilov

Centers of origin	Location	cultivated plants
1. South Asian tropical	Tropical India, Indochina, islands of Southeast Asia	Rice, sugar cane, citrus fruits, eggplant, etc. (50% of cultivated plants)
2. East Asian	Central and Eastern China, Japan, Korea, Taiwan	Soy, millet, buckwheat, fruit and vegetable crops- plum, cherry, etc. (20% of cultivated plants)
3. Southwest Asian	Asia Minor, middle Asia, Iran, Afghanistan, Southwest India	Wheat, rye, legumes, flax, hemp, turnip, garlic, grapes, etc. (14% of cultivated plants)
4. Mediterranean	Countries along the shores of the Mediterranean	Cabbage, sugar beets, olives, clover (11% of cultivated plants)
5. Abyssinian	Abyssinian highlands of Africa	Durum wheat, barley, bananas, coffee tree, sorghum
6. Central American	Southern Mexico	Corn, cocoa, pumpkin, tobacco, cotton
7. South American	West coast of South America	Potato, pineapple, cinchona

The richest in the number of cultures are the ancient centers of civilization. It is there that the earliest culture of agriculture is carried out, artificial selection and plant breeding are carried out for a longer time.

Hybridization and selection have been and remain the classical methods of plant breeding. There are two main forms of artificial selection: mass and individual.

Mass selection

Mass selection used in breeding cross-pollinated plants (rye, corn, sunflower). In this case, the variety is a population of heterozygous individuals, and each seed has a unique genotype. With the help of mass selection, varietal qualities are preserved and improved, but the selection results are unstable due to random cross-pollination.

Individual selection

Individual selection used in the selection of self-pollinated plants (wheat, barley, peas). In this case, the offspring retains the characteristics of the parental form, is homozygous and is called a pure line. Clean line- the offspring of one homozygous self-pollinated individual. Since mutation processes are constantly occurring, there are practically no absolutely homozygous individuals in nature. Mutations are most often recessive. Under the control of natural and artificial selection, they fall only when they pass into the homozygous state.

Natural selection

This type of selection plays a decisive role in selection. Any plant during its life is affected by a complex of environmental factors, and it must be resistant to pests and diseases, adapted to a certain temperature and water regime.

Inbreeding (inbreeding)

In the center are heterosis corn, on the left and on the right are parental individuals.

This is called inbreeding. Inbreeding occurs during self-pollination of cross-pollinated plants. For inbreeding, plants are selected whose hybrids give the maximum effect of heterosis. Such selected plants undergo forced self-pollination for a number of years. As a result of inbreeding, many unfavorable recessive genes go into a homozygous state, which leads to a decrease in plant viability, to their "depression". Then the resulting lines are crossed with each other, hybrid seeds are formed, giving a heterotic generation.

heterosis (« hybrid power”) is a phenomenon in which hybrids surpass parental forms in a number of characteristics and properties. Heterosis is typical for hybrids of the first generation, the first hybrid generation gives an increase in yield up to 30%. In subsequent generations, its effect weakens and disappears. The effect of heterosis is explained by two main hypotheses. The dominance hypothesis suggests that the effect of heterosis depends on the number of dominant genes in the homozygous or heterozygous state. The more genes in the genotype in the dominant state, the greater the effect of heterosis.

R	♀AAbbCCdd	×	♂aaBBccDD
F1	AaBbCcDd

The hypothesis of overdominance explains the phenomenon of heterosis by the effect of overdominance. overdominance- a type of interaction of allelic genes, in which heterozygotes are superior in their characteristics (in weight and productivity) to the corresponding homozygotes. Starting from the second generation, heterosis fades, as part of the genes passes into the homozygous state.

Diploid plants (2 n= 16) and tetraploid (2 n= 32) buckwheat.

Aa × Aa
AA 2Aa aa

Cross-pollination of self-pollinators makes it possible to combine the properties of different varieties. For example, when breeding wheat, proceed as follows. Anthers are removed from the flowers of a plant of one variety, a plant of another variety is placed next to it in a vessel with water, and plants of two varieties are covered with a common insulator. As a result, hybrid seeds are obtained that combine the traits of different varieties that the breeder needs.

Method for obtaining polyploids. Polyploid plants have a larger mass of vegetative organs, larger fruits and seeds. Many crops are natural polyploids: wheat, potatoes, varieties of polyploid buckwheat, sugar beets have been bred.

Species in which the same genome is multiply multiplied are called autopolyploids. The classic method for obtaining polyploids is the treatment of seedlings with colchicine. This substance blocks the formation of spindle microtubules during mitosis, the set of chromosomes doubles in the cells, and the cells become tetraploid.

distant hybridization

Restoring the fertility of a cabbage-rare hybrid: 1 - cabbage; 2 - radish; 3, 4 - cabbage-rare hybrid.

distant hybridization It is the crossing of plants belonging to different species. Distant hybrids are usually sterile, since they have impaired meiosis (two haploid sets of chromosomes from different species cannot conjugate) and, therefore, no gametes are formed.

The technique for overcoming infertility in distant hybrids was developed in 1924 by the Soviet scientist G.D. Karpechenko. He acted as follows. First I crossed the radish (2 n= 18) and cabbage (2 n= 18). The diploid set of the hybrid was equal to 18 chromosomes, of which 9 chromosomes were "rare" and 9 - "cabbage". The resulting cabbage-rare hybrid was sterile, since during meiosis the "rare" and "cabbage" chromosomes were not conjugated.

Further, with the help of colchicine G.D. Karpechenko doubled the chromosome set of the hybrid, the polyploid began to have 36 chromosomes, during meiosis "rare" (9 + 9) chromosomes conjugated with "rare", "cabbage" (9 + 9) with "cabbage". Fertility has been restored. In this way, wheat-rye hybrids (triticale), wheat-couch grass hybrids, etc. were obtained. Species in which different genomes have been combined in one organism, and then their multiple increase, are called allopolyploids.

Use of somatic mutations

Somatic mutations are used to select vegetatively propagating plants. This was used in his work by I.V. Michurin. By vegetative propagation, a beneficial somatic mutation can be maintained. In addition, only with the help of vegetative propagation, the properties of many varieties of fruit and berry crops are preserved.

experimental mutagenesis

It is based on the discovery of the impact of various radiations to obtain mutations and on the use of chemical mutagens. Mutagens allow you to get a wide range of different mutations. Now more than a thousand varieties have been created in the world, leading a pedigree from individual mutant plants obtained after exposure to mutagens.

Plant breeding methods proposed by I.V. Michurin

Using the method of mentor I.V. Michurin sought to change the properties of the hybrid in the right direction. For example, if it was necessary to improve the taste of a hybrid, cuttings from a parent organism that had good taste were grafted into its crown, or a hybrid plant was grafted onto a rootstock, in the direction of which it was necessary to change the quality of the hybrid. I.V. Michurin pointed to the possibility of controlling the dominance of certain traits during the development of a hybrid. For this, in the early stages of development, it is necessary to influence certain external factors. For example, if hybrids are grown in open ground, their frost resistance increases on poor soils.

Breeding is the science of improving the individual qualities of animals and plants necessary for man, as well as breeding new plant varieties, animal breeds, strains of microorganisms. Plant breeding methods are used to create cultivars.

Selection

Most of the plants that modern mankind eats are a selection product (potato, tomato, corn, wheat). For several centuries, people have been cultivating wild plants, moving from gathering to farming.

Selection areas are:

high yield;
plant nutrition (eg protein content of wheat);
improved taste;
resistance of crops to weather conditions;
early ripening of fruits;
intensity of development (for example, "responsiveness" to fertilizers or watering).

Rice. 1. Comparison of wild and agricultural corn.

Breeding has solved the problem of food shortage and continues to develop, introducing genetic engineering methods. Breeders not only improve the taste and increase the nutritional value of plants, but also make them healthy, rich in vitamins and chemical elements important for metabolism.

For successful selection, it is necessary to understand the patterns of inheritance of traits, the features of the influence of the environment, the morphological structure and methods of reproduction of cultivated plants.

Methods

The main selection methods are:

What have we learned?

From the lesson we learned about why breeding is necessary and what methods are used in plant breeding. Considered the classical methods of breeding - individual and mass selection, intraspecific and distant hybridization, mutagenesis.

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*Method*	*essence*	*Examples*
Individual selection	Carried out in relation to self-pollinated plants. Breeding single individuals with the desired qualities and obtaining improved offspring from them	Wheat, barley, peas
Mass selection	Carried out in relation to cross-pollinated plants. Plants interbreed en masse. The best specimens are selected from the resulting offspring and crossed again. Can be repeated until desired plant qualities are developed	Sunflower
Inbreeding	Occurs during self-pollination of cross-pollinated plants. As a result, pure (homozygous) lines are obtained in order to fix the resulting trait. There is a decrease in viability (inbreeding depression), because. offspring gradually become homozygous recessive	Varieties of pears, apple trees
outbreeding	interbreed different types, the offspring are usually sterile, because when crossing, meiosis is disturbed, gametes are not formed. In the first generation, the effect of heterosis is observed - the superiority of offspring over parental forms due to the formation of heterozygous genes. The more distant the parents are in relationship, the more clearly heterosis manifests itself.	Hybrids of wheat and rye (triticale), currant and gooseberry (yoshta)
Mutagenesis	Plants are exposed to ionizing, laser radiation, chemical or biological effects, resulting in mutations. Most often, resistance to diseases and pests is developed in this way. The method has been improved by genetic engineering - the desired gene can be “turned on” or “turned off” manually without losing other useful features.	Wheat varieties