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

Question 1. What is selection?

Breeding is the science of creating new and improving existing varieties of plants, animal breeds and strains of microorganisms. At the same time, the very process of creating varieties, breeds and strains is also called selection. Theoretical basis selection is genetics. Through selective breeding of approximately 150 species cultivated plants and 20 species of domesticated animals, thousands of different breeds and varieties have been created. Selection has replaced the spontaneous, formed at the household level, methods for keeping and breeding plants and animals that a person has been using for thousands of years.

Question 2. 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 hereditary properties. All organisms of this population have a set of genetically fixed morphological and physiological features. This means that all key genes are transferred to the homozygous state and there is no splitting in a number of generations. Breeds, varieties and strains are able to maximize their useful qualities for humans only under the conditions for which they were created.

Question 3. What are the main breeding methods you know?

The main breeding methods are selection and hybridization.

Selection is the choice in each generation of individuals with certain characteristics with the aim of their subsequent crossing. Selection is usually carried out over several successive generations. Distinguish between mass selection and individual selection.

Hybridization is a directional crossing of certain individuals to obtain new ones or to consolidate the necessary traits in order to develop a breed (variety) that does not yet exist or to preserve the properties of an existing population of individuals. Hybridization is intraspecific and interspecific (remote).

Question 4. What is mass selection, individual selection?

Mass selection is carried out according to phenotypic traits and is usually used in crop production when working with cross-pollinated plants. If the necessary characteristics of the population (for example, seed weight) have improved, then we can assume that mass selection for the phenotype was effective.

It was in this way that many varieties of cultivated plants were created. In the case of selection of microorganisms, only mass selection can be used.

With individual selection, individual individuals are selected, and the offspring of each of them are studied and controlled over several generations. This makes it possible to determine the genotypes of individuals and use for further selection those organisms that have the optimal combination of traits and properties useful for humans. As a result, varieties and breeds are obtained with high uniformity and constancy of characters, since all the individuals included in them are descendants of a small number of parents. For example, some breeds of cats and varieties of ornamental plants are the result of the preservation of a single mutation (i.e., the altered genotype of one individual ancestor).

Question 5. What difficulties arise when setting up interspecific crossings?material from the site

Interspecific crossing is possible only for biologically close species (horse and donkey, ferret and mink, lion and tiger). However, even in this case, hybrids, although they are characterized by heterosis (that is, they are superior in their properties to their parents), often turn out to be barren or low-fertile. The reason for this is the impossibility of conjugation of chromosomes of different biological species, as a result of which meiosis is disrupted and gametes are not formed. Various methods are used to solve this problem. In particular, in order to obtain a fertile hybrid of cabbage and radish, the breeder G. D. Karpechenko used the method of polyploidization. He crossed not diploid, but tetraploid plants. As a result, in the first prophase of meiosis (prophase I), chromosomes belonging to the same species could form bivalents. The division proceeded normally, and full-fledged gametes were formed. This experiment has become milestone in the development of selection.

"Evolution of the organic world" - Caudal appendage. Blind cave fish. ? Polymastia is an additional pair of mammary glands. 3. 4. Limb? 12. 11. 6. Human coccyx. Hairiness of the face.

"Charles Darwin" - In the spring of 1817, Charles entered the primary school. Darwin's drawing of the geological structure of the Andes. Darwin's first expedition to the Andes June - November 1834 Charles Darwin's notebook. Charles' father Robert Erasmus Darwin had an extensive medical practice. Exposition of the State Darwin Museum.

"Biology Darwin" - A.S. Pushkin. The first mention of entomological observations of Darwin. Megatheria is an extinct sloth. Darwin's wife is Emma Darwin. Huxley. Darwin's handwritten diary. Darwin's mother is Susanna Darwin. November 24, 1859 ... Galapagos tortoises. Thomas Huxley is a zoologist. Cambridge period of life 1828-1831.

"Evolution of the Earth" - Scheme of work: determination of the causes of the phenomena of the consequences of evolution. 3rd stage - planning the work of groups. Lesson - conference on the topic: The work was done by students using the programs "Power Point" and "Visual Basic 6.0". Svetlovsky urban district Municipal educational institution secondary school No. 5.

"Artificial selection Darwin" - The teachings of Charles Darwin on artificial selection. Centers of origin of cultivars of plants and animal breeds. Variability is the ability of an organism to acquire new features and properties. Plants. Animals. Ch. Darwin's study of practice Agriculture England. selection methods. Breeding by breeders of 150 breeds of pigeons, many breeds of dogs, varieties of cabbage ...

"Darwin's Theory" - The ability of organisms to reproduce indefinitely. Indefinite, individual, hereditary (modern - mutational). Struggle for existence. Certain, group, non-hereditary (modern - modification). Caused by external environment. Characteristics of artificial and natural selection.

There are 13 presentations in total in the topic

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 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.

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 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.

Centers of origin Location Cultivated plants 1. South Asian tropical Tropical India, Indochina, Southeast Asian islands Rice, sugar cane, citrus, eggplant, etc. (50% of cultivated plants) 2. East Asian Central and East China, Japan, Korea, Taiwan Soybean, millet, buckwheat, fruit and vegetable crops plum, cherry, etc. (20% of cultivated plants) 3. Southwest Asian Asia Minor, Central 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 Sea Cabbage, sugar beet, olives, clover (11% of cultivated plants) 5. Abyssinian Abyssinian Highlands of Africa Durum wheat, barley, bananas, coffee tree, sorghum 6. Central American South Mexico Corn, cocoa, pumpkin, tobacco, cotton 7. South American West Coast of South America Potato, pineapple, cinchona

Mass selection is used in the selection of 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 is 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. Pure line A pure line is 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.

This type of selection plays a decisive role in selection. A complex of factors acts on any plant during its life. environment, and it must be resistant to pests and diseases, adapted to a certain temperature and water regime.

So 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.

This 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. P AAbbCCdd×aaBBccDD F 1 AaBbCcDd

The hypothesis of overdominance explains the phenomenon of heterosis by the effect of overdominance. Overdominance Overdominance is 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. Aa × Aa AA 2Aa aa

It 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.

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.

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 radish (2n = 18) and cabbage (2n = 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 that combine different genomes in one organism, and then multiply them, are called allopolyploids.

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.

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.

The mentor's method With the help of the mentor's method 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, on poor soils, their frost resistance increases.

Breeding is the science of creating new breeds of animals, plant varieties, strains of microorganisms. Breeding is also called the branch of agriculture engaged in the development of new varieties and hybrids of crops and animal breeds. Selection and seed production of winter wheat in Siberia.

Plant breeding Methods of plant breeding. The main methods of plant breeding are selection and hybridization. However, it is impossible to obtain forms with new features and properties by the selection method; it only allows one to isolate genotypes already present in the population. To enrich the gene pool of the created plant variety and obtain optimal combinations of traits, hybridization is used with subsequent selection. In breeding, two main types of artificial selection are distinguished: mass and individual. plant mutation breeding

Mass and individual selection Mass selection is the selection of a group of individuals that are similar in one or a set of desired traits, without checking their genotype. For example, from the entire population of cereals of one variety or another, only those plants are left for further reproduction that are resistant to pathogens and lodging, have a large ear with a large number of spikelets, etc. When they are re-sown, plants with necessary qualities. The variety obtained in this way is genetically homogeneous, and the selection is periodically repeated. With individual selection (by genotype), the offspring of each individual plant in a number of generations is obtained and evaluated with mandatory control of the inheritance of traits of interest to the breeder. As a result of individual selection, the number of homozygotes increases, i.e., the resulting generation becomes genetically homogeneous. Such selection is usually used among self-pollinated plants (wheat, barley, etc.) to obtain pure lines. A pure line is a group of plants that are descendants of one homozygous self-pollinated individual. They have the highest degree of homozygosity and represent a very valuable source material for selection.

Animal breeding Features of animal breeding. The basic principles of animal breeding are no different from the principles of plant breeding. However, the selection of animals has some features: they are characterized only by sexual reproduction; mostly very rare alternation of generations (in most animals after a few years); the number of individuals in the offspring is small. Therefore, in breeding work with animals, the analysis of the totality of external signs, or exterior, characteristic of a particular breed.

Selection of goldfish and parrots By selection, a veiled form was obtained. Professional experience in breeding and selection of 27 years.

Selection of microorganisms Microorganisms (bacteria, microscopic fungi, protozoa, etc.) play an extremely important role in the biosphere and economic activity person. Of the more than 100 thousand species of microorganisms known in nature, several hundred are used by man, and this number is growing. A qualitative leap in their use has taken place in recent decades, when many genetic mechanisms for the regulation of biochemical processes in microorganism cells have been established. The selection of microorganisms (unlike the selection of plants and animals) has a number of features: 1) the breeder has an unlimited amount of material for work: billions of cells can be grown in Petri dishes or test tubes on nutrient media in a matter of days; 2) more efficient use of the mutation process, since the genome of microorganisms is haploid, which makes it possible to detect any mutations already in the first generation; 3) the simplicity of the genetic organization of bacteria: a significantly smaller number of genes, their genetic regulation is simpler, gene interactions are simple or absent.