Genetic basis of selection of plants, animals and microorganisms. Basics of genetics

WHAT IS SELECTION.

The word "selection" comes from the Latin. "selectio", which translated means "choice, selection". Breeding is a science that develops new ways and methods for obtaining plant varieties and their hybrids, and animal breeds. This is also a branch of agriculture that deals with the development of new varieties and breeds with properties necessary for humans: high productivity, certain product qualities, resistance to diseases, well adapted to certain growth conditions.

GENETICS AS THE THEORETICAL BASIS OF SELECTION.

The theoretical basis of selection is genetics - the science of the laws of heredity and variability of organisms and methods of controlling them. She studies the patterns of inheritance of traits and properties of parental forms, develops methods and techniques for managing heredity. By applying them in practice when breeding new varieties of plants and animal breeds, a person obtains the necessary forms of organisms, and also controls their individual development and montogenesis. The foundations of modern genetics were laid by the Czech scientist G. Mendel, who in 1865 established the principle of discreteness, or discontinuity, in the inheritance of traits and properties of organisms. In experiments with peas, the researcher showed that the characteristics of parent plants during crossing are not destroyed or mixed, but are transmitted to the offspring either in a form characteristic of one of the parents, or in an intermediate form, again appearing in subsequent generations in certain quantitative ratios. His experiments also proved that there are material carriers of heredity, later called genes. They are special for each organism. At the beginning of the twentieth century, the American biologist T. H. Morgan substantiated the chromosomal theory of heredity, according to which hereditary characteristics are determined by chromosomes - the organelles of the nucleus of all cells of the body. The scientist proved that genes are located linearly among chromosomes and that genes on one chromosome are linked to each other. A trait is usually determined by a pair of chromosomes. When germ cells form, paired chromosomes separate. Their full set is restored in the fertilized cell. Thus, the new organism receives chromosomes from both parents, and with them inherits certain characteristics. In the twenties, mutation and population genetics arose and began to develop. Population genetics is a field of genetics that studies the main factors of evolution - heredity, variability and selection - in specific environmental conditions of a population. The founder of this direction was the Soviet scientist S.S. Chetverikov. We will consider mutation genetics in parallel with mutagenesis. In the 30s, geneticist N.K. Koltsov suggested that chromosomes are giant molecules, thereby anticipating the emergence of a new direction in science - molecular genetics. It was later proven that chromosomes consist of protein and deoxyribonucleic acid (DNA) molecules. DNA molecules contain hereditary information, a program for the synthesis of proteins, which are the basis of life on Earth. Modern genetics is developing comprehensively. It has many directions. The genetics of microorganisms, plants, animals and humans are distinguished. Genetics is closely related to other biological sciences - evolutionary science, molecular biology, biochemistry. It is the theoretical basis of selection. Based on genetic research, methods have been developed for producing hybrids of corn, sunflower, sugar beet, cucumber, as well as hybrids and crossbreeds of animals that have heterosis due to heterosis (heterosis is accelerated growth, increased size, increased viability and productivity of first generation hybrids compared to parental organisms )increased productivity.

The theoretical basis of selection and seed production is genetics - the study of the laws of heredity and variability of organisms. Its position on the discreteness of heredity, the doctrine of mutations and modifications, the concepts of genotype and phenotype, dominance and recessiveness, homo- and heterozygosity, the establishment of the nature of heterosis, transgressions and neoplasms during hybridization, all achievements of genetics are of utmost importance for the development of effective methods of selection and seed production of agricultural crops crops

To develop effective methods for creating varieties and hybrids with high technological and nutritional qualities of grain, it is necessary to study the genetic and physiological-biochemical patterns of heredity and variability in carbohydrate content, fractional and amino acid composition of proteins in grain, the nature of variability and inheritance of grain quality traits in wheat, malting barley, millet, seeds of grain legumes and oilseeds and formulate the theoretical foundations of transgressive selection based on traits that determine the qualitative composition of the main substances (protein, oil, etc.). It is important to further improve the method of electrophoresis of storage proteins of wheat and barley grain for the selection of parental forms during hybridization and the selection of the most valuable recombinants for grain quality, frost resistance, disease resistance and other economically valuable traits, as well as for biotypic analysis of varieties in the primary stages of seed production. It is very important to study the genetic basis and morphological and anatomical features of the resistance of cereals to lodging and shedding and to create resistant varieties. It is necessary to develop and improve methods for obtaining new forms of plants using polyploidy, haploidy, culture of hybrid embryos, as well as cellular, chromosomal and genetic engineering.

Genetics substantiated the use of individual selection methods and developed the theory of crossings. One of the most important tasks of breeding is the creation of varieties that produce high quality products. Grain of new highly productive varieties and hybrids of grain crops must have excellent technological and nutritional qualities, stable under changing growing conditions. In our country, more than 60 varieties of strong wheat have been bred and zoned (Bezostaya 1, Mironovskaya 808, Donskaya Bezostaya, Odesskaya 51, Obriy, Saratovskaya 29, Saratovskaya 44, Tselinnaya 60, Novosibirskaya 87, etc.), which serve as an excellent source material for creating more more high-quality varieties for all climatic zones. Among the new zoned varieties of spring wheat, Saratovskaya 54 stands out in terms of technological qualities of grain. This variety is characterized by a consistently high protein content in the grain and a high volumetric yield of bread, as well as its better porosity. Its gluten quality is higher than that of the Saratovskaya 29 variety. Among the samples of the world collection there are varieties and forms that have exceptionally high grain quality - they contain from 18 to 22% protein (samples from China, Canada, India). They are successfully used in hybridization. New wheat varieties should have a higher protein content (15-16%) and high quality gluten.

It is necessary to create varieties of winter and spring wheat that combine high yield (7-9 and 5-6 tons per 1 ha, respectively) with a high protein content in the grain (16-17 and 18-19%), high-quality gluten and improved amino acid composition. The most important task of breeding is to develop varieties with consistently high yields and grain quality under different weather conditions. The creation of high-protein varieties and hybrids of corn, wheat, barley and oats with a high content of lysine and other essential amino acids is also a very important breeding problem.

The task is to develop new varieties and hybrids of sunflower with seed oil content of 58-60%. At the same time, it is important to improve the quality of the oil, i.e. a certain composition of fatty acids, lipid ratio, and increased vitamin content. The creation of a new mutant variety Pervenets, containing up to 75% oleic acid in oil versus 30-35% in conventional varieties, shows the enormous opportunities available in sunflower breeding for product quality.

Selection of grain legumes should be carried out for increased protein content. It is necessary to create varieties of sugar beets with increased sugar content and high technological qualities, new technical varieties of potatoes with a large amount of starch and protein in the tubers. The most important task in the breeding of fiber flax and cotton is the development of new high-yielding varieties that give high yield and quality of fiber.

To successfully solve the problem of plant immunity, it is of great importance to improve methods for creating infectious backgrounds and determining the racial composition of rust of grain crops, late blight of potatoes and other most dangerous diseases. It is necessary to develop methods for identifying genes and donors of resistance to diseases and pests, to study the conditions for the manifestation of their action and the nature of inheritance of this property depending on the selection of parental pairs and weather conditions. Computers and mathematical modeling should be used to organize information-genetic systems for registration and documentation of breeding material, develop models of varieties and breeding programs, objective selection of parental pairs, and select the optimal breeding strategy.

It is necessary to continue to develop issues of organization and economics of industrial seed production, to improve methods of accelerated propagation and the introduction of new varieties and hybrids into production; develop cultivation technologies in relation to the conditions of various soil and climatic zones; high-yielding seeds at all levels of the seed production system; improve methods and schemes of primary seed production; continue research to identify the best environmental and agrotechnical conditions for the formation of high-yielding seeds.

The variety plays a very important role in the development of energy- and resource-saving technologies for cultivating agricultural crops. This is achieved by sowing lodging-resistant varieties of grain crops and non-shattering varieties of peas, which allows harvesting by direct combining, early ripening hybrids of corn and sunflower with rapid drying of grain and seeds during ripening, which reduces the cost of electricity or fuel for drying, early deciduous varieties of cotton , which makes it possible to carry out machine harvesting of raw cotton with high productivity and without losses, etc.

Plant breeding is the most important factor in accelerating scientific and technological progress in agriculture. In recent years, it has been rapidly developing in our country and abroad. Important practical results have been obtained based on the development of highly effective methods for creating new varieties. These primarily include the breeding of short-stemmed varieties of wheat and rice, which make it possible to obtain a yield of more than 10 tons per 1 hectare on a high agricultural background, the creation of hybrid corn and hybrid sorghum with a potential yield of 15 tons per 1 hectare, the development of methods for radically improving the amino acid composition of the protein of the most important grains and grain feed crops, the creation of varieties of some crops that are resistant to dangerous diseases, doubling the oil content of sunflower seeds and other achievements. Selection and well-established seed production have become of paramount importance in increasing the yield and gross yield of grain and other agricultural crops.

Further development of this science led to the development of fundamentally new methods for creating source material and techniques for managing heredity. Along with classical methods of obtaining source material through hybridization, the use of local varieties and natural populations, new genetic methods are playing an increasingly important role: heterosis, experimental mutagenesis, polyploidy, haploidy, tissue culture, somatic hybridization, chromosomal and genetic engineering. The use of these methods in the breeding process has already yielded positive results.

The Main Directions of Economic and Social Development set the task of strengthening, through the use of biotechnology and genetic engineering, the creation and introduction into production of new highly productive varieties and hybrids of agricultural crops that meet the requirements of intensive technologies, are resistant to adverse environmental influences, are suitable for machine harvesting and satisfy requests from the food industry; improve the organization of seed production and improve the quality of seeds.

GENETICS - THEORETICAL BASIS OF SELECTION. BREEDING AND ITS METHODS.

• Selection is the science of breeding new and improving existing old varieties of plants, animal breeds and strains of microorganisms with properties necessary for humans.
• A variety is a plant population artificially created by man, which is characterized by a certain gene pool, hereditarily fixed morphological and physiological characteristics, and a certain level and nature of productivity.
• A breed is a population of animals artificially created by man, which is characterized by a certain gene pool, hereditarily fixed morphological and physiological characteristics, and a certain level and nature of productivity.
• A strain is a population of microorganisms artificially created by man, which is characterized by a certain gene pool, hereditarily fixed morphological and physiological characteristics, and a certain level and nature of productivity.

2. What are the main objectives of selection as a science?

1. Increasing the productivity of plant varieties, animal breeds and strains of microorganisms;
2. Studying the diversity of plant varieties, animal breeds and strains of microorganisms;
3. Analysis of patterns of hereditary variability during hybridization and mutation process;
4. Study of the role of the environment in the development of characteristics and properties of organisms;
5. Development of artificial selection systems that contribute to the strengthening and consolidation of traits useful for humans in organisms with different types of reproduction;
6. Creation of varieties and breeds resistant to diseases and climatic conditions;
7. Obtaining varieties, breeds and strains suitable for mechanized industrial cultivation and breeding.

3. What is the theoretical basis of selection?

Answer: The theoretical basis of selection is genetics. It also uses advances in the theory of evolution, molecular biology, biochemistry and other biological sciences.

4. Fill out the table "Selection methods".

5. What is the importance of selection in human economic activity?

Answer: Selection allows you to increase the productivity of plant varieties, animal breeds and strains of microorganisms; develop artificial selection systems that help strengthen and consolidate traits beneficial to humans in various organisms; create varieties and breeds resistant to diseases and climatic conditions; obtain varieties, breeds and strains suitable for mechanized industrial cultivation and breeding.

TEACHING N.I. VAVILOV ABOUT THE CENTERS OF DIVERSITY AND ORIGIN OF CULTURED PLANTS.

1. Give definitions of concepts.

• The center of diversity and origin is the territory (geographical area) within which a species or other systematic category of agricultural crops was formed and from where it spread.
• Homologous series is a similar series of hereditary variability in genetically close species and genera.

2. Formulate the law of homological series of hereditary variability.

Answer: Species and genera that are genetically close are characterized by similar series of hereditary variability with such regularity that, knowing the series of forms within one species, one can predict the presence of parallel forms in other species and genera. The closer the genera and species are genetically located in the general system, the more complete the similarity in the series of their variability. Entire families of plants are generally characterized by a certain cycle of variation, passing through all the genera and species that make up the family.

3. Fill out the table " Centers of origin and diversity of cultivated plants."

BIOTECHNOLOGY, ITS ACHIEVEMENTS AND DEVELOPMENT PROSPECTS.

1. Give definitions of concepts.

• Biotechnology is a discipline that studies the possibilities of using living organisms, their systems or products of their vital activity to solve technological problems, as well as the possibility of creating living organisms with the necessary properties using genetic engineering.
• Cellular engineering is the creation of a new type of cells based on their hybridization, reconstruction and cultivation. In the narrow sense of the word, this term refers to the hybridization of protoplasts or animal cells, in the broad sense - various manipulations with them aimed at solving scientific and practical problems.
• Genetic engineering is a set of techniques, methods and technologies for obtaining recombinant RNA and DNA, isolating genes from an organism, manipulating genes and introducing them into other organisms.

2. What is the role of biotechnology in practical human activities?

Answer: Biotechnology processes are used in baking, winemaking, brewing, and the preparation of fermented milk products; microbiological processes - for the production of acetone, butanol, antibiotics, vitamins, feed protein; biotechnology also includes the use of living organisms, their systems or products of their vital activity to solve technological problems, the possibility of creating living organisms with the necessary properties.

3. What are the prospects for the development of biotechnology?

Further development of biotechnology will help solve a number of important problems:

1. Solve the food shortage problem.
2. Increase the productivity of cultivated plants, create varieties that are more resistant to adverse effects, and also find new ways to protect plants.
3. Create new biological fertilizers, vermicompost.
4. Find alternative sources of animal protein.
5. Propagate plants vegetatively using tissue culture.
6. Create new medicines and dietary supplements.
7. Conduct early diagnosis of infectious diseases and malignant neoplasms.
8. To obtain environmentally friendly fuels by processing industrial and agricultural waste.
9. Process minerals in new ways.
10. Use biotechnology methods in most industries for the benefit of humanity.

4. What do you see as possible negative consequences of uncontrolled research in biotechnology?

Answer: Transgenic products can be harmful to health and cause malignant tumors. Human cloning is inhumane and contrary to the worldviews of many nations. The latest developments in biotechnology can lead to uncontrollable consequences: the creation of new viruses and microorganisms that are extremely dangerous to humans, as well as controlled ones: the creation of biological weapons.

The modern period of development of selection begins with the formation of a new science - genetics. Genetics is a science that studies the heredity and variability of organisms. A very important contribution to elucidating the essence of heredity was made by G. Mendel (1822-1884), whose experiments in plant crossing form the basis of most modern research on heredity. A Czech by nationality, a monk of the Franciscan monastery in Brunn (now Brno), G. Mendel at the same time taught natural sciences at a real school and was very interested in gardening. For many years, he devoted all his free time to experiments in crossing various cultivated plants. As a result, patterns of transmission of traits to offspring were discovered. G. Mendel reported his results at a meeting of the “Society of Natural Scientists” in Brno, and then published them in 1866 in the scientific works of this Society. However, these provisions contradicted the existing ideas about heredity at that time and therefore received recognition 34 years after their rediscovery.

In 1900, three works appeared simultaneously, carried out by three geneticists: Hugo de Vries from Holland, K. Correns from Germany and E. Cermak from Austria. They confirmed the laws of heredity discovered by G. Mendel.

The published work of de Vries, Correns and Cermak is usually called the rediscovery of Mendel's laws and 1900 is considered the official date of the beginning of the existence of experimental genetics as an independent science.

Genetics as an independent science was separated from biology at the suggestion of the English scientist Bateson in 1907. He also suggested the name of the science – genetics.

Since the rediscovery of Mendel's laws, N.P. Dubinin (1986) distinguishes three stages in the development of genetics.

First stage - This is the era of classical genetics, which lasted from 1900 to 1930. This was the time of the creation of the gene theory and the chromosomal theory of heredity. The development of the doctrine of phenotype and genotype, the interaction of genes, the genetic principles of individual selection in breeding, and the doctrine of mobilizing the planet's genetic reserves for selection purposes were also of great importance. Some of the discoveries of this period deserve special mention.

The German biologist August Weismann (1834-1914) created a theory that in many ways anticipated the chromosomal theory of heredity.

Weisman's hypotheses about the meaning of reduction division. In addition, he distinguished between traits that are inherited and traits that are acquired under the influence of external conditions or exercise

A. Weisman tried to experimentally prove the non-heritability of mechanical damage (for generations he cut off her tails, but did not get tailless offspring).

Subsequently, A. Weisman’s general concept was refined taking into account cytological data and information about the role of the nucleus in the inheritance of characteristics. In general, he was the first to prove the impossibility of inheriting characteristics acquired during ontogenesis, and emphasized the autonomy of germ cells, and also showed the biological significance of the reduction in the number of chromosomes in meiosis as a mechanism for maintaining the constancy of the diploid chromosome set of the species and the basis of combinative variability.

In 1901, G. De Vries formulated a mutation theory that largely coincides with the theory of heterogenesis (1899) of the Russian botanist S. I. Korzhinsky (1861–1900). According to the mutation theory of Korzhinsky - De Vries, hereditary characteristics are not absolutely constant, but can change abruptly due to changes - mutation of their inclinations.

The most important milestone in the development of genetics - the creation of the chromosomal theory of heredity - is associated with the name of the American embryologist and geneticist Thomas Gent Morgan (1866–1945) and his school. Based on experiments with fruit flies - Drosophila melanogaster By the mid-20s of our century, Morgan formed the idea of ​​​​the linear arrangement of genes in chromosomes and created the first version of the theory of the gene - the elementary carrier of hereditary information. The gene problem has become the central problem of genetics. It is currently being developed.

The doctrine of hereditary variability was continued in the works of the Soviet scientist Nikolai Ivanovich Vavilov (1887–1943), who formulated the law of homological series of hereditary variability in 1920. This law summarized a huge amount of material about the parallelism of variability of close genera and species, thus linking together systematics and genetics. The law was a major step towards the subsequent synthesis of genetics and evolutionary teaching. N.I. Vavilov also created the theory of genetic centers of cultivated plants, which greatly facilitated the search and introduction of the necessary plant genotypes.

During the same period, some other areas of genetics important for agriculture began to develop rapidly. These include works on the study of patterns of inheritance of quantitative traits (in particular, studies by the Swedish geneticist G. Nilsson-Ehle), on elucidation of hybrid power - heterosis (works of American geneticists E. East and D. Jones), on interspecific hybridization of fruit plants (I V. Michurin in Russia and L. Burbank in the USA), numerous studies devoted to the private genetics of various types of cultivated plants and domestic animals.

The formation of genetics in the USSR also belongs to this stage. In the post-October years, three genetic schools emerged, headed by prominent scientists: N.K. Koltsov (1872–1940) in Moscow, Yu.A. Filipchenko (1882–1930) and N.I. Vavilov (1887–1943) in Leningrad, who played important role in the development of genetics research.

Second phase, - This is the stage of neoclassicism in genetics, which lasted from 1930 to 1953. Start second stage can be associated with the discovery by O. Avery in 1944 of the substance of heredity - deoxyribonucleic acid (DNA).

This discovery symbolized the beginning of a new stage in genetics - the birth of molecular genetics, which formed the basis for a number of discoveries in biology of the 20th century.

During these years, the possibility of artificially causing changes in genes and chromosomes (experimental mutagenesis) was discovered; it was discovered that a gene is a complex system that can be divided into parts; the principles of population genetics and evolutionary genetics are substantiated; biochemical genetics was created, which showed the role of genes for all major biosyntheses in the cell and organism;

The achievements of this period primarily include artificial mutagenesis. The first evidence that mutations can be induced artificially was obtained in 1925 in the USSR by G. A. Nadson and G. S. Filippov in experiments on irradiation of lower fungi (yeast) with radium, and decisive evidence of the possibility of experimentally obtaining mutations was given in 1927 d. experiments of the American Meller on the effects of x-rays.

Another American biologist J. Stadler (1927) discovered similar effects in plants. Then it was discovered that ultraviolet rays can also cause mutations and that high temperature has the same ability, although to a weaker extent. Soon there was also information that mutations could be caused by chemicals. This direction gained wide scope thanks to the research of I. A. Rapoport in the USSR and S. Auerbach in Great Britain. Using the method of induced mutagenesis, Soviet scientists led by A. S. Serebrovsky (1892–1948) began studying the structure of the gene in Drosophila Melanogaster. In their studies (1929–1937), they were the first to show its complex structure.

At the same stage in the history of genetics, a direction arose and developed with the goal of studying genetic processes in evolution. Fundamental works in this area belonged to the Soviet scientist S. S. Chetverikov (1880–1959), the English geneticists R. Fisher and J. Haldane and the American geneticist S. Wright. S.S. Chetverikov and his collaborators carried out the first experimental studies of the genetic structure of natural populations on several species of Drosophila. They confirmed the importance of the mutation process in natural populations. Then these works were continued by N.P. Dubinin in the USSR and F. Dobzhansky in the USA.

At the turn of the 40s, J. Bill (born in 1903) and E. Tatum (1909–1975) laid the foundations of biochemical genetics.

Priority in deciphering the structure of the DNA molecule belongs to the American virologist James Dew Watson (born in 1928) and the English physicist Francis Crick (born in 1916), who published the structural model of this polymer in 1953.

From this moment, namely 1953, the third stage in the development of genetics begins - the era of synthetic genetics . This time is usually called the period of molecular genetics.

Third stage , which began with the construction of a DNA model, continued with the discovery of the genetic code in 1964. This period is characterized by numerous works on deciphering the structure of genomes. So, at the end of the 20th century, information appeared about the complete decoding of the genome of the Drosophila fly, scientists compiled a complete map of Arabidopsis or small mustard, and the human genome was deciphered.

Deciphering only individual sections of DNA already allows scientists to obtain transgenic plants, i.e. plants with introduced genes from other organisms. According to some sources, an area equal to Great Britain is sown with such plants. These are mainly corn, potatoes, and soybeans. Nowadays, genetics is divided into many complex areas. It is enough to note the achievements of genetic engineering in producing somatic and transgenic hybrids, the creation of the first map of the human genome (France, 1992; USA, 2000), the production of cloned sheep (Scotland, 1997), cloned piglets (USA, 2000), etc.

The beginning of the 21st century is called the post-genomic period and, apparently, will be marked by new discoveries in the field of genetics related to the cloning of living beings and the creation of new organisms based on genetic engineering mechanisms.

The methods accumulated to date make it possible to decipher the genomes of complex organisms much faster, as well as introduce new genes into them.

Major discoveries in the field of genetics:

1864 – Basic laws of genetics (G. Mendel)

1900 – G. Mendel’s laws were rediscovered ( G. de Vries, K. Correns, E. Cermak)

1900–1903 – Mutation theory (G.de Vries)

1910 – Chromosomal theory of heredity (T. Morgan, T. Boveri, W. Sutton)

1925–1938 – “one gene - one protein” (J. Bill, E. Tatum)

1929 – gene divisibility (A.S. Serebrov, N.P. Dubinin)

1925 – artificial mutations (G.A. Nadson, G.S. Filippov)

1944 – DNA – the carrier of hereditary information (O. Avery, K. McLeod)

1953 – DNA structural model (J. Watson, F. Crick)

1961 – genetic code (M. Nirenberg, R. Holley, G. Khorana)

1961 – operon principle of gene organization and regulation of gene activity in bacteria (F. Jacob, J. Monod)

1959 – gene synthesis (G. Khorana )

1974–1975 – methods of genetic engineering ( K. Murray, N. Murray, W. Benton, R. Davis, E. Southern, M. Granstein, D. Hognes)

1978–2000 – deciphering genomes (F. Blatner, R. Clayton, M. Adams, etc.)

Genetics methods

HYBRIDOLOGICAL – p An analysis is made of the patterns of inheritance of individual characteristics and properties of organisms during sexual reproduction, as well as an analysis of the variability of genes and their combinatorics (developed by G. Mendel).

CYTOLOGICAL - with Using optical and electron microscopes, the material basis of heredity is studied at the cellular and subcellular levels (chromosomes, DNA).

CYTOGENETIC – with the integration of hybridological and cytological methods ensures the study of the karyotype, changes in the structure and number of chromosomes.

POPULATION-STATISTICAL – o It is based on determining the frequency of occurrence of various genes in a population, which makes it possible to calculate the number of heterozygous organisms and thus predict the number of individuals with a pathological (mutant) manifestation of the gene’s action.

BIOCHEMICAL- metabolic disorders (proteins, fats, carbohydrates, minerals) resulting from gene mutations are studied.

MATHEMATICAL – n A quantitative accounting of the inheritance of traits is carried out.

GENEALOGICAL – Expressed in the compilation of pedigrees. Allows you to establish the type and nature of inheritance of traits.

ONTOGENETIC – Allows you to trace the action of genes in the process of individual development; in combination with a biochemical method, it makes it possible to establish the presence of recessive genes in a heterozygous state by phenotype.

Selection is the science of methods for creating highly productive varieties of plants, animal breeds and strains of microorganisms.

Modern selection is a vast area of ​​human activity, which is a fusion of various branches of science, production of agricultural products and their complex processing.

Problems of modern breeding

Creation of new and improvement of old varieties, breeds and strains with economically useful traits.

Creation of technologically advanced, highly productive biological systems that make maximum use of the planet’s raw materials and energy resources.

Increasing the productivity of breeds, varieties and strains per unit area per unit of time.

Improving the consumer qualities of products.

Reducing the share of by-products and their comprehensive processing.

Reducing the share of losses from pests and diseases.

Theoretical basis of selection is genetics, since it is knowledge of the laws of genetics that makes it possible to purposefully control the occurrence of mutations, predict the results of crossing, and correctly select hybrids. As a result of the application of genetic knowledge, it was possible to create more than 10,000 varieties of wheat based on several original wild varieties, and to obtain new strains of microorganisms that secrete food proteins, medicinal substances, vitamins, etc.

Breeding methods the main specific selection methods remain hybridization And artificial selection.Hybridization

Crossing organisms with different genotypes is the main method of obtaining new combinations of traits.

The following types of crossings are distinguished:

Intraspecific crossing– different forms are crossed within a species (not necessarily varieties and breeds). Intraspecific crossings also include crossings of organisms of the same species living in different environmental conditions.

Inbreeding– inbreeding in plants and inbreeding in animals. Used to obtain clean lines.

Interline crossings– representatives of pure lines are crossed (and in some cases, different varieties and breeds). Backcrosses (back crosses) are crossings of hybrids (heterozygotes) with parental forms (homozygotes). For example, crossing heterozygotes with dominant homozygous forms is used to prevent the phenotypic manifestation of recessive alleles.

Analyzing crosses- These are crossings of dominant forms with an unknown genotype and recessive-homozygous tester lines.

Remote crossing– interspecific and intergeneric. Usually distant hybrids are sterile and are propagated vegetatively

Selection is the process of differential (unequal) reproduction of genotypes. It should not be forgotten that, in fact, selection is carried out according to phenotypes at all stages of ontogenesis of organisms (individuals). Ambiguous relationships between genotype and phenotype require testing of selected plants by progeny.

Mass selection– the entire group is selected. For example, seeds from the best plants are pooled and sown together. Mass selection is considered a primitive form of selection, since it does not eliminate the influence of modification variability (including long-term modifications). Used in seed production. The advantage of this form of selection is the preservation of a high level of genetic diversity in the selected group of plants.

Individual selection– individual individuals are selected, and the seeds collected from them are sown separately. Individual selection is considered a progressive form of selection, since it eliminates the influence of modification variability.

A type of family selection is sib selection . Sib selection is based on selection for closest relatives (siblings - brothers and sisters). A special case of sib-selection is the selection of sunflower for oil content method of halves. When using this method, the sunflower inflorescence (basket) is divided in half. The seeds of one half are checked for oil content: if the oil content is high, then the second half of the seeds is used in further selection.