All methods of plant breeding. Plant breeding methods - Knowledge Hypermarket

The main methods of selection are selection, hybridization (using heterosis and cytoplasmic male sterility), polyploidy and mutagenesis.

Selection and its creative role

The selection process is based on artificial selection. In combination with genetic methods, it allows you to create varieties, breeds and strains with predetermined traits and properties. In breeding, two main types of selection are distinguished: mass and individual.

Mass selection- this is the selection of a group of individuals according to external, phenotypic characteristics without checking their genotype. For example, in case of mass, or spontaneous, selection from the entire population of hens of a particular breed, birds are left for breeding on farms with an egg production of 200-250 eggs, a live weight of at least 1.5 kg, a certain color, which do not show incubation instincts, etc. All other chickens are culled. In this case, the offspring of each hen and rooster is evaluated only by phenotype. Consequently, mass selection can give good results only if the heritability coefficient of valuable traits chosen by the breeder is high.

Mass selection is most effective for qualitative traits controlled by one or more genes. However, it is rarely successful for polygenic traits with a low inheritance rate. In this case, it is necessary to apply individual, or methodical, selection.

At individual selection(by genotype) receive and evaluate the offspring of each individual plant or animal in a number of generations with mandatory control of the inheritance of traits of interest to the breeder. At the subsequent stages of selection, only those individuals that gave the largest number of offspring with high rates are used. As a result, it becomes possible to evaluate the hereditary qualities of individual individuals, that is, the ability to transfer properties to offspring.

The value of individual selection is especially great in those branches of agricultural production where it is possible to obtain a large number of descendants from one organism. So, using artificial insemination, up to 35,000 calves can be obtained from one bull with the help of deep freezing of the semen, which lasts for many years. Therefore, now in many countries of the world there are banks of animal sperm with valuable genotypes.

Selection in breeding is most effective if it is combined with certain types of crosses.

Hybridization methods (crossing types) in breeding

The whole variety of types of crosses is reduced to inbreeding and outbreeding. Inbreeding- it is closely related (intrabreed or intravarietal), and outbreeding- unrelated (interbreeding or intervarietal) crossing.

When inbreeding, brothers and sisters or parents and offspring are used as initial forms (father - daughter, mother - son, cousins - sisters, etc.). This type of crossing is used in cases where they want to transfer most of the breed's genes to a homozygous state and, as a result, to fix economically valuable traits that remain in the descendants. Such crossing is to some extent analogous to self-pollination in plants, which also leads to an increase in homozygosity.

At the same time, during inbreeding, the weakening of animals is often observed, their gradual degeneration due to the homozygotization of recessive alleles. At the same time, homozygotization for the genes that control the studied trait occurs the faster, the more closely related crosses are used for inbreeding. To avoid this phenomenon, it is necessary to conduct a strict selection of individuals with valuable economic traits.

In plants, pure lines also have reduced viability, which is probably due to the transition to the homozygous state of all recessive mutations, which are mainly harmful.

Pure lines obtained as a result of inbreeding differ not only in various traits, but also in the degree of viability reduction. If these pure lines are crossed with each other, then the effect of heterosis is usually observed.

Unrelated crossing between individuals of the same breed or between individuals of different breeds (crossbreeding) of animals allows you to maintain or improve their properties in the next generation of hybrids. Outbreeding increases the level of offspring heterozygosity and population heterogeneity.

Polyploidy and distant hybridization

When creating new plant varieties, breeders widely use the method autopolyploidy, which leads to an increase in the size of cells and the whole plant due to the multiplication of the number of sets of chromosomes. In addition, an excess of chromosomes increases their resistance to pathogenic organisms (viruses, fungi, bacteria) and a number of other adverse factors, such as radiation: if one or even two homologous chromosomes are damaged, the others remain intact. Polyploid individuals are more viable than diploid ones.

About 80% of modern cultivated plants are polyploids. Among them are cereals, vegetable and fruit crops, citrus fruits, technical, medicinal and ornamental plants, which are much more productive than the original diploid varieties. Thus, triploid sugar beet differs from the usual one not only in the higher yield of the vegetative mass and the larger size of root crops, but also in their increased sugar content, as well as disease resistance. However, triploids are sterile, so it is necessary each time to obtain hybrid seeds from crossing diploid and tetraploid forms. The discovery of male sterility in beets contributed to the successful solution of this problem. The sterility of triploid hybrids can be beneficial for seedless fruits such as grapes and watermelon.

Valuable results are obtained by using the phenomenon of allopolyploidy in breeding, which is based on the method distant hybridization, i.e., crossing organisms belonging to different species and even genera. For example, interspecific polyploid hybrids of cabbage and radish, rye and wheat have been obtained. The hybridization of wheat (Triticum) and rye (Secale) made it possible to obtain a number of forms, united by the common name triticale. They have a high yield of wheat and winter hardiness and unpretentiousness of rye, resistance to many diseases, including linear rust, which is one of the main factors limiting the yield of wheat.

Based on the hybridization of wheat and wheatgrass, the Russian academician N.V. Tsitsin obtained wheat-couch grass hybrids with high yield and resistance to lodging. However, distant hybrids tend to be sterile. This is due to the content in the genome of various chromosomes that do not conjugate during meiosis. To restore fertility in interspecific hybrids in 1924, the Soviet geneticist G. D. Karpechenko suggested using doubling the number of chromosomes (polyploidy) in distant hybrids.

G. D. Karpechenko crossed radish and cabbage. The number of chromosomes in these plants is the same (2n = 18). Accordingly, their gametes carry 9 chromosomes. A hybrid of cabbage and radish has 18 chromosomes, but it is sterile, since the chromosomes of cabbage and radish do not conjugate during meiosis, so the process of gamete formation cannot proceed normally. As a result of doubling the number of chromosomes, the sterile hybrid turned out to have 36 chromosomes, which were composed of two complete diploid sets of radish and cabbage. This created normal opportunities for meiosis; cabbage chromosomes and radish chromosomes were conjugated with each other. Each gamete carried one haploid set of radish and cabbage (9 + 9 = 18). The zygote again had 36 chromosomes; interspecific hybrid became fertile. In terms of phenotype, this new plant organism combined the characteristics of radish and cabbage, for example, in the structure of the pod.

It is very difficult to obtain polyploid animals experimentally, therefore such forms of animals are rare. Thus, the Soviet geneticist B. L. Astaurov, through interspecific hybridization, managed to obtain a polyploid form of the silkworm. To date, there are already polyploid fish, birds (for example, chickens), but the introduction of polyploid animal breeds into agricultural practice is a matter of the future.

Spontaneous and induced mutagenesis

Spontaneous mutants are used primarily in plant breeding. So, on the basis of the mutant yellow alkaloid-free lupine, several varieties of sweet lupine were obtained, which are grown for livestock feed. Lupine containing alkaloids is unsuitable for this purpose, since animals do not eat it.

A large number of mutants are known in fruit crops that are used as new varieties or in hybridization with other forms. One of the best known spontaneous mutants of maize, opaque, which has a high content of the amino acid lysine in the grain, is used to create so-called high-lysine maize hybrids.

In recent decades, in many countries of the world, work has been launched to obtain induced mutants. X-ray induced mutants have been isolated from many cereals (barley, wheat, rye, etc.). They are distinguished not only by increased productivity, but also by a shortened shoot. Such plants are resistant to lodging and have noticeable advantages in machine harvesting. In addition, a short and strong culm allows further selection for an increase in the size of the ear and seed mass without fear that an increase in grain yield will lead to plant lodging.

Especially successfully induced mutagenesis is used in the selection of microorganisms.

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.

Topic quiz

Report Evaluation

Average rating: 4.6. Total ratings received: 317.

The term "selection" itself comes from the Latin word "selection". This science studies the ways and methods of creating new and improving existing groups (populations) of organisms used for the life support of mankind. We are talking about varieties of cultivated plants, breeds of domestic animals and strains of microorganisms. The main criterion here is the value and sustainability of new features and properties in practice.

Plant and animal breeding: main directions

High yields of plant varieties, fertility and productivity of animal breeds.
Qualitative characteristics of products. In the case of plants, this can be the taste, appearance of fruits, berries and vegetables.
Physiological signs. In plants, breeders most often pay attention to the presence of precocity, drought resistance, winter hardiness, resistance to diseases, pests and the adverse effects of climatic conditions.
Intensive way of development. In plants, this is a positive dynamics of growth and development when fertilizing, watering, and in animals - "payment" for feed, etc.

Selection at the present stage

Modern breeding of animals, plants and microorganisms, in order to increase efficiency, necessarily takes into account the needs of the agricultural product sales market, which is especially important for the development of a particular industry of a particular production. For example, baking bread of high quality, good taste, elastic crumb and crispy crumbly crust should be made from strong (glassy) soft wheat varieties, which contain a large amount of protein and elastic gluten. The highest grades of biscuits are made from floury varieties of soft wheat, and durum wheat is best suited for the production of pasta.

Oddly enough, the selection of animals and microorganisms are related. The fact is that the results of the latter are used in the biological control of pathogens in animals, as well as various varieties of cultivated plants.

A striking example of selection based on the needs of the market is fur farming. The cultivation of fur-bearing animals, which differ in different genotypes, which are responsible for the color and shade of fur, depends on fashion trends.

Theoretical basis

In general, selection should develop on the basis of the laws of genetics. It is this science, which studies the mechanisms of heredity and variability, that makes it possible, with the help of various influences, to influence the genotype, which, in turn, determines the set of properties and characteristics of the organism.

Also, the breeding methodology uses the achievements of other sciences. These are systematics, cytology, embryology, physiology, biochemistry, molecular biology and biology of individual development. Due to the high rates of development of the above areas of natural science, new prospects in selection are opening up. Already today, research in the field of genetics is reaching a new level, where it is possible to purposefully model the necessary features and properties of animal breeds, plant varieties and strains of microorganisms.

Genetics plays a decisive role in the process of solving breeding problems. It allows, using the laws of heredity and variability, to carry out the planning of the selection process in such a way that it takes into account the peculiarities of inheritance of specific traits.

Selection of initial genetic material

The selection of animals, plants and microorganisms can be effective only if the source material is carefully selected. That is, the correctness of the choice of initial breeds, varieties, species is due to the study of their origin and evolution in the context of those properties and characteristics that the proposed hybrid should be endowed with. In the search for the right forms in a strict sequence, the entire world gene pool is taken into account. Thus, the priority is the use of local forms with the necessary features and properties. Further, the attraction of forms growing in other geographical or climatic zones is carried out, that is, the methods of introduction and acclimatization are used. The last resort is the methods of experimental mutagenesis and genetic engineering.

Animal breeding: methods

In this area of science, the most effective methods are being developed and studied to allow breeding new breeds of domestic animals and improving existing ones.

Animal breeding has its own specifics, which is due to the fact that animals lack the ability to reproduce vegetatively and asexually. They only reproduce sexually. From this circumstance, it also follows that in order to breed offspring, an individual must reach sexual maturity, and this affects the timing of research. Also, the possibilities of selection are limited by the fact that, as a rule, the offspring of individuals is not numerous.

The main methods of breeding new animal breeds, as well as plant varieties, can be called selection and hybridization.

Animal breeding, aimed at breeding new breeds, most often uses not mass, but individual selection. This is due to the fact that caring for them is more individualized compared to caring for plants. In particular, about 10 people take care of a livestock of 100 individuals. Whereas on the area where hundreds and thousands of plant organisms grow, from 5 to 8 breeders work.

Hybridization

One of the leading methods is hybridization. In this case, the selection of animals is carried out by inbreeding, unrelated crossing and distant hybridization.

Under inbreeding understand the hybridization of individuals that belong to different breeds of the same species. This method makes it possible to obtain organisms with new traits, which can then be used in the process of breeding new breeds or improving old ones.

The term "inbreeding" comes from the English words meaning "inside" and "breeding". That is, the crossing of individuals belonging to closely related forms of the same population is carried out. In the case of animals, we are talking about the insemination of closely related organisms (mother, sister, daughter, etc.). The expediency of inbreeding is based on the fact that the original form of a particular trait is decomposed into a number of pure lines. They usually have a reduced viability. But if these pure lines are further crossed with each other, then heterosis will be observed. This is a phenomenon that is characterized by the appearance in hybrid organisms of the first generation of an increase in certain signs. These are, in particular, viability, productivity and fertility.

Animal breeding, whose methods have fairly wide limits, also uses distant hybridization, which is a process directly opposite to inbreeding. In this case, individuals of different species interbreed. The goal of distant hybridization can be called obtaining animals that will develop valuable performance properties.

Examples are crosses between a donkey and a horse, a yak and a tour. It should be noted that hybrids often do not produce offspring.

Research by M. F. Ivanov

The famous Russian scientist M.F. Ivanov was interested in biology since childhood.

Animal breeding became the object of his research when he studied the features of the mechanisms of variability and heredity. Seriously interested in this topic, M.F. Ivanov subsequently developed a new breed of pigs (white Ukrainian). It is characterized by high productivity and good adaptability to climatic conditions. For crossing, a local Ukrainian breed was used, which was well adapted to the conditions of existence in the steppe, but had low productivity and low quality meat, and an English white breed, which had high productivity, but was not adapted to exist in local conditions. Methodological methods of inbreeding, unrelated crossing, individual-mass selection, and upbringing were used. As a result of long-term painstaking work, a positive result was achieved.

Selection development prospects

At each stage of development, the list of goals and objectives of breeding as a science is determined by the peculiarities of the requirements of agricultural technology and animal husbandry, the stage of industrialization of crop production and animal husbandry. For the Russian Federation, it is very important to create plant varieties and animal breeds that retain their productivity in various climatic conditions.

Methods of plant and animal breeding, selection and hybridization, forms of selection

Introduction

1. Forms of selection

2. Methods of selection and hybridization in the selection of self-pollinating plants.

Conclusion

Bibliography

INTRODUCTION

Breeding is the science of breeding new varieties of plants and animal breeds and improving existing ones. Its name comes from the Latin word selectio - selection and correctly reflects the main feature of selection; various forms of selection are the main basis of the activity of all breeders. The selection of selection as an independent science was preceded by practical selection, which for a long time was carried out in a purely empirical way, and at first even completely unconsciously.

Plant breeding is one of the earliest human achievements. Selective breeding began when man began to domesticate plants, growing them under controlled conditions and selecting those forms that provided a reliable source of food. This primitive plant breeding, like animal breeding, became more and more productive, groups of people gradually settled around these food sources. With the development of villages and cities, the labor force increased and people could already find time for the pursuit of arts and religions. Consequently, the domestication of plants and animals is one of the most important phases in the transition of man from a nomadic, largely individualistic way of life, to the complexly organized society that exists today. Almost all modern food crops are the direct result of human activity during the era of primitive agriculture.

At this early stage, selection was slow and successive. It remained an art, not a science, until the beginning of the twentieth century. the Mendelian laws of heredity were not discovered and used in plant breeding. However, despite this, selection will always be to some extent an art. As an art, breeding is based on the knowledge of the plant itself, its morphological features and reactions to environmental conditions.

As a science, plant breeding is based on the principles of genetics. Genetics explained heredity, and its laws made it possible to foresee the results of selection in advance. At first, the attention of geneticists was focused on genes that affect qualitative traits: color, morphological features, disease resistance. Later, geneticists began to study quantitative traits: yield, plant height, early maturity, and others.

The selection of plants and animals is a form of evolution which in many respects follows the same principles as the evolution of species in nature, but with one important difference: natural selection has been replaced here, at least in part, by conscious selection by man.

The main breeding methods are selection and hybridization, along with new methods based on the achievements of genetics: the method of breeding self-pollinated lines and the subsequent production of linear hybrids, the method of experimental polyploidy, the method of experimental mutagenesis. The expediency of applying certain breeding methods to certain living organisms largely depends on the methods of their reproduction. These are self-pollinating, cross-pollinating, vegetatively propagated plants, animals and microorganisms.

1. FORMS OF SELECTION

Selection as a science was created by the works of Charles Darwin (1809-1882), who made a thorough analysis of the activities of breeders and, on the basis of this analysis, created the doctrine of artificial selection. Darwin's book "The Origin of Species by Means of Natural Selection, or the Preservation of Favored Breeds in the Struggle for Life" was published on November 24, 1859, and this date is considered the time of the appearance of selection as a science, since the doctrine of artificial selection in an expanded form was set forth precisely in this work of Darwin.

Darwin identified three forms of selection that take place in cultivated plants and domestic animals: methodical, unconscious, and natural selection. Natural selection created those forms of plants and animals, which were then introduced by man into culture and subjected to domestication, and continued and continues to act on them even after they have been domesticated by man. This effect of natural selection occurs in addition to the will and desire of man, causing changes associated with adaptation to new conditions that are created by man in the process of domestication. Many features of plant varieties and animal breeds, often completely undesirable for humans, are created by such an influence of natural selection. Unconscious selection has been carried out by man for a long time and was expressed in the preservation of the best specimens for the tribe and the destruction of the worst ones without a conscious intention to breed an improved breed. Many features of domestic animals are created as a result of such unconscious selection, carried out over tens of millennia. Methodical selection differs from the unconscious in that a person consciously and systematically strives to change the breed (variety) towards a known and predetermined ideal.

In ancient times, and at the present time among economically backward peoples, methodological selection had and still has a relatively primitive form, but already in ancient Rome it acquired a rather complex and perfect character. Methodological selection became most widespread and perfected after the development of capitalist relations in agriculture in some countries of Western Europe. In these countries, agricultural exhibitions were widely spread, at which the best representatives of breeds and varieties received valuable prizes and gold medals, which became a very profitable business and was carried out on a large scale by many enterprises and firms and took on an industrial character.

As a result, in a short period (less than 100 years), outstanding progress was made in improving cultivated plants and animals, and new breeds bred in England not only greatly increased agricultural productivity, but were also in great demand on the international market and brought great profits. English breeders and breeders. In the same period, a new breed of fine-fleeced sheep was bred in France, and in Russia, A. T. Bolotov, new varieties of apple trees.

Techniques and methods developed by individual breeders to maximize the effectiveness of artificial selection. This is:

the correct choice of source material for selection;

correct setting of the goal of selection;

carrying out selection on a sufficiently large scale and possibly more stringent interpretation of the material at all stages of selection;

selection by only one main property, and not by many at once.

The doctrine of artificial selection served as a theoretical basis for the practical activities of a whole generation of breeders and significantly increased the efficiency of their work. Thus, in particular, the teachings of C. Darwin had a strong influence on the activities of the largest Russian breeder in the field of breeding fruit and berry crops, I. V. Michurin, who bred varieties of great economic importance for the middle zone of our country.

2. METHODS OF INDIVIDUAL SELECTION AND HYBRIDIZATION IN THE BREEDING OF SELF-POLLINATING PLANTS. WORKS OF A. P. SHEKHURDIN AND V. N. MAMONTOVA

Among cultivated plants there is a large group of self-pollinating plants, which have a variety of adaptations that promote self-pollination and prevent the possibility of cross-pollination. So, barley, wheat, oats have non-opening, or cleistogamous, flowers, in which self-pollination often occurs even before the ear appears from the vagina. In cotton, the stamen filaments form a column through which the mature pistil moves, capturing pollen. There are other adaptations for constant self-pollination. The predominance of self-pollination leaves a sharp imprint on the biology of reproduction, physiology and genotypic features of such plants. Self-pollination causes all recessive mutations to be subjected to natural selection. Beneficial changes are fixed and become widespread, while harmful ones are destroyed. As a result, there are no harmful (lethal or semi-lethal) genes in the gene pool of self-pollinators; at the same time, self-pollinators do not have heterosis (hybrid power) associated with heterozygosity.

Populations of self-pollinating plants, formed under the influence of natural selection and unconscious artificial selection, are complex mixtures of various homozygous lines.

Methodological selection at first took the form of mass selection and consisted in isolating, preserving and using seeds of the best plants for sowing and using average and worst plants for consumer purposes.

The activities of the first breeding stations and seed companies began with a mass selection carried out within local varieties. The selection by specialist breeders was carried out on a large scale and carefully, according to a large number of economically valuable traits. As a result, the improvement of local varieties proceeded much faster, and the varieties created by mass selection were significantly superior to the original local ones in a number of economically valuable traits.

Nevertheless, such breeding varieties did not qualitatively differ from the local ones in their main features. They, like local varieties, were a mixture of many different homozygous lines, were not homogeneous enough and rather quickly "degenerated" as a result of increased reproduction of lines with less valuable properties. These shortcomings of varieties obtained by mass selection have long forced breeders to look for other ways of breeding self-pollinating plants.

Even before the publication of Charles Darwin's works, the English breeder Le Coeter (1836) successfully applied individual selection, based on the production and reproduction of offspring from single selected plants. But he took this method to the extreme; he was looking for not just the best plants, but the best ears on the best plants and the best grains on the best ears. This greatly complicated the selection and for a long time delayed its use in the selection of self-pollinating plants. Hjalmar Nilsson (1901) eliminated the extremes of Le Coeter, focusing on the selection of individual best plants on the basis that all seeds within a single plant in self-pollinators are hereditarily equivalent, and made individual selection in this form the main method of selection of self-pollinating plants.

Individual selection from self-pollinating plants makes it possible to divide the original local variety into its constituent homozygous lines, compare them with each other, identify the most valuable from an economic point of view, and then propagate the best ones for use as the best varieties.

Varieties bred using individual selection are qualitatively different from local varieties-populations and breeding varieties obtained using mass selection. They have high uniformity and stability, and the risk of degeneration during long-term reproduction without additional selection is minimal. The research of V. I. Johansen and his theory of pure lines created the theoretical basis for the method of individual selection, after which this method, called linate selection, became very widespread in all countries of the world. Even today individual selection is indispensable when it is necessary to improve a local variety by isolating from it pure lines that are the most valuable from an economic point of view.

The system of individual selection in Russia can be represented as follows. Seeds of the original local variety are sown under as uniform conditions as possible in the source material nursery. In this nursery, plants are monitored, the best are selected and seeds are collected from each separately. The following year, they are sown in the breeding nursery of the first year on separate plots, the plots are compared with each other, the worst are rejected, and the seeds from the best form the seed fund of the breeding nursery of the second year. In this nursery, the best families are also compared on separate plots (in 2-3 repetitions), the worst ones are rejected, and the seeds of the best are transferred to preliminary variety testing, where they are sown in a larger number of repetitions than in the breeding nursery. The seeds of the most outstanding families can be immediately transferred to the competitive station variety testing, which then includes the seeds of the families that turned out to be the best in the preliminary variety testing.

The offspring of families that have shown themselves to be the best in the competitive variety testing are considered as new varieties, receive names and are transferred to the State Variety Network. Varieties that have successfully passed a three-year test here are allowed to be used in certain regions of the country.

The success of such selection depends mainly on the quality of the initial local variety, the size of selection in nurseries, the correctness of rejection at all stages of the selection process. Such selection does not create new varieties, but only reveals existing ones.

In some cases, breeders are faced with the task of breeding new varieties of self-pollinating plants with properties that are not found in local varieties-populations. In such cases, it becomes necessary to use other selection methods.

One of these methods is systematic breeding, based on crossing the original forms, each of which has the characteristics desired by the breeder. This is the method of hybridization. The application and development of the hybridization method can be illustrated by the work of well-known breeders of our country A.P. Shekhurdin and V.N. Mamontova, who devoted their entire lives to working in the field of spring wheat breeding at the Saratov Breeding Experimental Station (now the Scientific Research Institute of Agriculture of the South-East).

A.P. Shekhurdin came to work at the experimental station from the first days of its organization, having only a lower agricultural school behind him. (He is one of his large family with five children, received an education). Experiencing a lack of education, A.P. Shekhurdin graduated from evening school at the age of 36 and entered the Saratov Agricultural Institute. Four years later, he graduates and receives an agronomist diploma, although, in fact, he has been one for a long time. Despite the difficulties of a personal nature (A.P. Shekhurdin's wife died during the difficult years of the civil war, and he was left alone with three children), he continued to work actively and, together with G.K. Meister, became the author of a special selection method - complex stepwise hybridization .

This method consists in crossing two distant geographical forms that differ from each other in a number of economically valuable traits, carrying out selection among hybrids of older generations on a large scale and thus creating a new variety that combines the positive properties of the original forms. Then such a variety is used as one of the parents for crossing with a distant form, which has economically valuable features that it lacks. Through selection carried out on a large scale, a variety is selected that combines the positive properties of parental forms. This variety is again used as one of the parents for crossing with a form that is far from it, etc. With such stepwise hybridization, there is a continuous improvement of newly bred varieties, which all the time acquire new and new positive economically valuable properties. By 1937, by stepwise hybridization, A.P. Shekhurdin bred an unprecedented variety of soft wheat vitreous-1 (albidum 1264), which had pasta, cereal and other grain qualities similar to the properties of durum wheat grain and even exceeding them. This variety served as the starting point for the creation of a large group of new varieties of strong soft wheat, obtained both by A.P. Shekhurdin himself and by V.N. Mamontova and their students.

In 1936, for outstanding achievements in the development of breeding and the creation of varieties of spring wheat, A.P. Shekhurdin was awarded the degree of Doctor of Agricultural Sciences, and in 1945 he became a professor, in 1946 - an honored worker of science of the RSFSR (he was awarded the Order Lenin, two orders of the Red Banner of Labor), and in 1942 (the year of the war) for the creation of spring wheat varieties, high-yielding and resistant to leaf rust, A.P. Shekhurdin was awarded the title of laureate of the State Prize.

But there was another, downside to this titanic work that found recognition. Everyone who knew A.P. Shekhurdin was struck by his inexhaustible diligence. His working day often began before sunrise and ended late in the evening. He spent hours in the lab culling grain. The result of his work is as follows: under his leadership, more than 28 varieties of spring wheat were bred, only during the war years - 4 new varieties. Before the Great Patriotic War, varieties bred by Shekhurdin occupied 10 million hectares, which accounted for 44% of all sown areas of spring wheat in the country. In 1977, the area occupied by varieties obtained in Saratov was over 27 million hectares.

This is how the director of the Saratov experimental station spoke about A.P. Shekhurdin: “... Specialist A.P. Shekhurdin is a man of rare knowledge and exceptional talents, a dedicated worker and at the same time an amazingly modest person. His whole life is a selection of wheat, an inextinguishable desire to give the best, most perfect varieties for agriculture ... "

A.P. Shekhurdin himself distinguished three stages in his scientific activity: from 1911 to 1918, when breeders mainly used the method of individual selection; from 1918 to 1927, when the hybridization method became dominant; from 1927 and, conditionally, until 1933, the method of complex stepwise hybridization was being developed. This method is still used today; he became the crowning achievement of Shekhurdin's scientific work and gave agriculture many outstanding varieties.

At the first stage of work, new varieties were obtained by individual selection from local ancient varieties. A huge number of plants were analyzed in the work. The laboriousness of the work is evidenced by the following fact: in order to breed only one variety, Lutescens-62, the offspring of 15 thousand individual plants were studied, tested over a number of years.

Shekhurdin was very useful to his natural observation: he noticed the smallest changes that were inaccessible even to an experienced eye. He could not only by the ear, its shape, scales, but also by the grain to determine the variety of the variety, he wandered for hours among his crops with a notebook - and by eye, and by all other methods he checked the grain, cracked it.

As a result of individual selection of the strongest plants (“elites”), on the basis of the local variety Poltavka, the well-known variety Lutescens-62 and two varieties of a then rare form with white grains, Albidum-604 and Albidum-721, were selected. From the local variety Selivanovsky rusak, the variety of spiny soft wheat erythrospermum-341 was bred in the same way, from the white Turk in 1929 the variety of durum wheat Gordeiforme-432 was created. These varieties were more drought tolerant than the native ones. Their productivity is 10-26% higher.

In addition, Albidum-604 grain had exceptionally high flour-grinding and baking qualities.

Of the bred varieties, the variety Lutescens-62 had a particularly great national economic importance.

A.P. Shekhurdin and his colleagues understood perfectly well that it was impossible to develop varieties with a complex set of valuable biological and economic properties using the selection method. Breeders came to the conclusion that in order to create more perfect varieties, a new hybridization method for that time should be used in combination with individual directional selection.

In the process of work, A.P. Shekhurdin developed a methodology and technique for artificial crossing; he noticed and proved in practice that it is better to pollinate flowers not with pollen harvested earlier, but directly from the ripe anthers of the paternal ears at the moment when the pollen is most viable. A.P. Shekhurdin was the first in the history of domestic breeding to carry out original crosses: intraspecific - between close varieties of wheat, interspecific - crossed durum wheat with soft, and even intergeneric - crossed wheat with rye, wheatgrass, wheatgrass, in fact, carrying out distant hybridization. At that time, Shekhurdin's student and successor, Valentina Nikolaevna Mamontova, a graduate of the Higher Women's Agricultural Courses named after V.I. I. A. Stebut in St. Petersburg.

Subsequently, like A.P. Shekhurdin, V.N. Mamontova graduated in absentia from the Saratov Agricultural Institute, Valentina Nikolaevna received the degree of candidate and doctor of science without defending a thesis - for breeding new varieties of wheat.

For varieties Saratovskaya-29, 210, 35 and 38 in 1968 Mamontova VG was awarded the Lenin Prize. In 1965, for great success in breeding and seed production and in connection with the 70th anniversary of the birth of VN Mamontov, she was awarded the title of Hero of Socialist Labor, she was awarded the title of honorary citizen of the city of Saratov.

But, returning to the period of the 20s, we can say about such successes: by continuous selection from the eighth generation of crossing durum white wheat with soft Poltava, the varieties sarrubra (Saratov red) and sarroza (Saratov pink) were created. These varieties exceeded the parental forms in terms of yield by 2-2.5 centners per hectare, were unique in terms of the quality of raw materials.

In 1935, Academician N. I. Vavilov wrote: “Among the most important practical achievements of the Saratov station, we note a awnless hybrid of durum and soft sarrubra wheat obtained from crossing Poltava and White Turk. This hybrid now occupies hundreds of thousands of hectares in cultivation and is the largest practical achievement in the world of interspecific hybridization.

Applying the method of conventional hybridization, Shekhurdin and his colleagues realized that, despite the significant volume and long period of work on hybridization, single crosses still slightly increase yield and drought resistance.

Using repeated crossings of hybrids with one of the best parental varieties or with another valuable form, Shekhurdin thus developed a method of complex, stepwise hybridization. Of particular importance here was the selection of parents of a new variety. Thus, the outstanding varieties Albidum-43, Albidum-24, Saratovskaya-210, Saratovskaya-29, Saratovskaya-36, Saratovskaya-38, Saratovskaya-39 were created.

The new varieties favorably differed from the parental forms, for example, albidum-43 on average over 20 years exceeded the yield of the parent variety by 35%, it ripens 4-5 days earlier than poltavka and lutescens-62.

The application of the method of complex stepwise hybridization brings tangible results, but this process can be very long. So, the Albidum-43 variety entered production 33 years after the start of work and was obtained by complex stepwise crossing of 12 forms.

A.P. Shekhurdin and his collaborators widely used crossbreeding of geographically distant forms. The first such crossing was carried out as early as 1913 by combining Grecum wheat, originating from Central Asia, and the local Poltavka variety. A number of high-yielding varieties of spring wheat were created in the same way. Canadian Keychener and Marquis wheats were crossed with locally bred varieties, the most valuable of the obtained varieties were Lutescens-758 and Saratovskaya-33, which have a strong culm and do not lodging under irrigation conditions with a yield of 30-35 centners per hectare.

Much attention was paid to breeding varieties resistant to fungal diseases - dusty and hard head, brown, mites and stem rust, powdery mildew. After the death of A.P. Shekhurdin (1951), V.N. Mamontova successfully continued his research. She fruitfully used in her breeding work distant hybridization and the method of step hybridization. During the difficult period of 1948, when the stepwise hybridization method was sharply criticized, she showed great firmness and adherence to principles and continued to work in this direction. As a result, she managed to obtain 13 very valuable new varieties of spring wheat, which in 1964 occupied an area of 16.5 million hectares. And in the 70s. wheat, bred by Shekhurdin and Mamontova, occupied 21 million hectares in the fields of the country. This has never happened before. The first huge flows of grain from the virgin lands of Kazakhstan came just at the expense of the variety, which received the world-famous name - Saratovskaya-29. It has become so popular not only because it gives high yields and endures the arid conditions of the steppes open to all winds. The protein content in grain in favorable years reaches a huge figure - 21%. Bread from her flour is high and lush. Saratovskaya-29 has no equal among strong wheats in terms of flour quality.

According to the guide: wheat is considered excellent if its flour strength exceeds 400 joules, good when this figure is 350-400 joules, and weak if it is less than 180. Saratovskaya-29 has flour strength, depending on weather conditions and agricultural cultivation techniques , ranges from 640 to 1000 joules! The London Technological Laboratory of Kent-Jones gave this grade this grade: "The Saratovskaya-29 variety has an unusually high flour strength and is an absolutely outstanding variety."

The varieties of V. N. Mamontova were sown on the lands of Kazakhstan, the fields of Bashkiria, Siberia. There were not enough elevators for the unprecedented harvests of virgin wheat. For 57 years of work at the Research Institute of Agriculture of the South-East (Saratov), V. N. Mamontova created alone and in co-authorship 20 varieties released in the country. Amber grain of the famous variety Saratovskaya-29 was purchased by foreign countries for baking bread.

CONCLUSION

The famous varieties created by A.P. Shekhurdin and V.N. Mamontova once again consolidated the glory of the Saratov land, which has always been famous for excellent rolls throughout Russia, large, lush, with a ruddy, overhanging mushroom crust. If at the beginning of the century bakers sought to improve the quality of bread by simple mechanical mixing of flour from various local varieties, then Saratov breeders solved this problem when they managed to create new varieties of spring wheat with a sufficiently high flour strength.

Based on the excellent varieties created by A.P. Shekhurdin and V.N. Mamontova, breeders are currently developing new varieties that meet the modern requirements of agro-industrial production and the world market. And this became possible thanks to the existence of such methods as complex stepwise hybridization and individual selection.

BIBLIOGRAPHY

Guzhov Yu. L., Fuks A., Valichek P. Breeding and seed production of cultivated plants. Moscow: RUDN University, 1999.

Sowers and keepers. M.: Sovremennik, 1992.

Life in science. Saratov: Volga book. publishing house, 1979.

A. P. Shekhurdin. Selected writings. M.: Publishing house of agricultural literature, 1961.

N. I. VAVILOV Theoretical foundations of selection. T. II. 1935.

A good example of interbreeding is the breed of pigs bred by Academician Mikhail Fedorovich Ivanov (1871–1935) - the Ukrainian White Steppe. When creating this breed, sows of local Ukrainian pigs were used with a small weight and low quality of meat and fat, but well adapted to local conditions. Male sires were white English breed boars. The hybrid offspring were again crossed with English boars, inbreeding was used in several generations, pure lines were obtained, and when they were crossed, the ancestors of a new breed, which did not differ in meat quality and weight from the English breed, and in endurance - from Ukrainian pigs.

Polyploidy is extremely rare in animals. An interesting fact is the interspecific crossing of the silkworm with subsequent doubling of the number of chromosomes, carried out by academician Boris Lvovich Astaurov (1904–1974), which led to the creation of a new animal species.

3. The phenomenon of heterosis in domestic animals

As with plants, domestic animals exhibit the phenomenon of hybrid vigor, or heterosis. It lies in the fact that when crossing different breeds (as well as interspecific crossings), a particularly powerful development and increase in viability is sometimes observed in the first generation of hybrids. This property, however, fades in subsequent generations. The genetic basis of heterosis in animals and plants is the same.

Heterosis is widely used in animal husbandry and poultry farming - the first generation of hybrids that reveal the phenomenon of hybrid strength are directly used for economic purposes. For example, when crossing two meat breeds of chickens, heterozygous broiler chickens are obtained. To obtain early maturing pigs (for meat and lard), the Durokgersey and Berkshire breeds are crossed. Hybrids give an increase of 10-12% higher than the representatives of the original breeds.

4. Method of analysis of hereditarily valuable sires by offspring

When selecting domestic animals, it is very important to determine the hereditary qualities of males according to traits that do not appear directly in them, for example, milk and milk fat in bulls or egg production in roosters. To do this, use the method of analysis (testing) of producers by offspring.

First, a few offspring are obtained from the male producer and their productivity is compared with the productivity of the mother and the productivity of the breed. If the productivity of daughters is higher than the productivity of the breed and the productivity of the mother, then this indicates a greater value of the manufacturer, which should be used to further improve the breed.

From a good male, you can get a lot of offspring, especially if artificial insemination is used. Sperm obtained from a good producer can be stored for a long time using the liquid nitrogen cryostorage method.

With hormonal superovulation and transplantation, dozens of embryos per year can be taken from outstanding cows with record milk yields and then implanted into other less valuable cows. Embryos are also stored at liquid nitrogen temperature. This makes it possible to increase several times the number of descendants from outstanding producers.

5. Features of selection in animal breeding

In animal breeding, artificial selection also takes place in two forms.

Mass selection - culling of individuals that do not meet breed standards according to the phenotype. Its purpose is to maintain the constancy of pedigree qualities.

Individual selection - selection of individual individuals, taking into account the hereditary stability of traits that ensure the improvement of breed qualities.

In animal breeding, individual selection is more often used. Moreover, the selection is based on exterior features. Exterior(from lat. exterior- external) - a set of external signs of an animal - physique, ratio of body parts, etc. Any organism is an integral system, so a certain physique of an animal may indicate its high meat or dairy productivity (remember the correlative, or correlation, variability). Thus, through the exterior, they are trying to find out the genotype of the animal.

6. Animal breeding achievements

great success in the 20th century. breeders have achieved. Based on the methods of selection and hybridization, the effectiveness of which was clearly demonstrated, in particular, in the already mentioned works of M.F. Ivanov, new wonderful breeds of all kinds of domestic animals were created. Based on the aforementioned hybridization of wild argali sheep with merinos, followed by the selection of animals that combine the desired qualities, and using closely related crossing, N.S. Baturin and Ya.Ya. Lusin bred in Kazakhstan a breed of merino argali, which has a high wool productivity of fine-wooled sheep and a good adaptability inherent in argali to the conditions of high mountain pastures.

Based on the use of interbreeding methods and further strict selection, cattle breeds with a high level of milk productivity and a high fat content in milk were bred. An example is the Kostroma breed of cattle, created on the basis of crossing local livestock with producers of other breeds, followed by strict selection and selection based on an assessment of the breeding qualities of animals. The high productivity of animals of this breed is characterized by the fact that individual cows give more than 16 thousand kg of milk from one calving to another.

Interbreeding was also used to create a new meat-wool breed of sheep. The Altai fine-fleece breed, which is characterized by good wool quality and high adaptability to local conditions, and two English early maturing meat-wool breeds were chosen as the initial parent breeds. The breed obtained as a result of long-term selection work and hybridization is characterized by a strong constitution, large live weight (rams - 110-115 kg, uterus - 60-62 kg) and high wool shearing, which is distinguished by shine, elasticity, etc.

On the basis of selection using intraspecific interbreeding, as well as interspecific and even intergeneric crossings with subsequent selection, highly productive, fast-growing, high-tasting fish breeds have been created. As an example, we point to the highly productive Ropsha carp (from the name of the village of Ropsha near St. Petersburg), which has high productivity and winter hardiness (bred by V.S. Kirpichnikov), and Ukrainian carp breeds (A.I. Kuzema and others). A very promising intergeneric hybrid of sterlet and beluga is bester, which has high growth rates (heterosis) and excellent taste.

Using the methods of selection and hybridization, man has radically changed the nature of the plants and animals he uses. Modern biology, especially genetics and cytology, have significantly enriched the theory and practice of breeding, armed and will continue to arm it with new highly effective methods for controlling the formation of organisms and creating highly productive plant varieties and animal breeds.

III. Consolidation of knowledge

Generalizing conversation in the course of learning new material.

IV. Homework

1. Study the paragraph of the textbook (features of animal biology taken into account in breeding; methods, methods of breeding and achieving animal breeding).

2. Fill in the table. 3 "Basic methods of plant and animal breeding".

3. Repeat the material on the topic "Plant Breeding" (in the next lesson - a test of knowledge).

Table 3. Main methods of plant and animal breeding

Methods	plant breeding	Animal breeding
Selection of parent pairs	Geographically distant or genetically distant (unrelated) forms	According to economically valuable features and exterior
Crossing unrelated (outbreeding)	Intraspecific, interspecific, intergeneric, leading to heterosis and high productivity	Crossbreeding of distant breeds with contrasting traits to obtain heterozygous populations and manifestation of heterosis in their representatives
Crossbreeding closely related (inbreeding)	Self-pollination of cross-pollinating plants by artificial influence to obtain clean lines	Crossing between close relatives to produce pure lines with desirable traits
Mass selection	Applies to cross-pollinated plants	It is used to cull individuals whose phenotype does not meet breed standards.
Individual selection	It is used for self-pollinating plants and for artificial self-pollination of cross-pollinated plants in order to isolate pure lines - descendants of one self-pollinating individual	Rigid selection is applied according to economically valuable traits, endurance, exterior, etc.
Progeny test method	Not applicable	The method of artificial insemination from the best male sires is used, the qualities of which are checked by daughters
Experimental production of polyploids	Used to obtain more productive forms	Almost never used
induced mutagenesis	Used to obtain source material	Almost never used

Lesson 10-11. selection of microorganisms. Biotechnology

Equipment: tables on general biology, schemes illustrating the methods and achievements of animal and microorganism breeding.

DURING THE CLASSES

I. Generalization of the knowledge of the section

A. Card work

№ 1. Suppose, for a farm, two bulls were purchased, in which the milk fat gene is not exactly known. How should one proceed when using the hybridization method to decide which of the bulls is more efficient to use as a sire?

№ 2. With what individual should a heterozygous individual of a pig be crossed in order to transfer the recessive gene of precocity into a homozygous state in the offspring? Why?

№ 3. Show by example why when breeding highly productive breeds of domestic animals in breeding practice, closely related crossing is used, which, as a rule, leads to a decrease in the viability and fertility of the organism and is not used in industrial animal husbandry.

B. Oral knowledge test

1. What are the biological characteristics of animals taken into account in breeding?

2. What are the types of crosses used in animal breeding?

3. What are the breeding methods used in animal husbandry?

4. What is heterosis in pets?

5. What is the method of testing economically valuable producers by offspring?

6. What are the features of selection in animal breeding?

7. What are the achievements of animal breeding?

B. Test verification of knowledge by options

You must choose one correct answer from the four offered.

Option 1

1. What selection should be used in pea breeding?

a) individual;
b) mass;
c) spontaneous;
d) stabilizing.

2. What is a "clean line"?

a) offspring from a self-pollinating plant;
b) offspring from a cross-pollinated plant;
c) offspring from crossing two plants of the same variety;
d) a plant with clearly manifested varietal characteristics.

3. Why self-pollinate cross-pollinated plants?

a) to obtain biologically distant hybrids;
b) to obtain the effect of heterosis;
c) to obtain clean lines;

4. How to overcome the infertility of biologically distant plant hybrids?

a) there are currently no methods to overcome infertility;
b) with the help of polyploidy;
c) with the help of inbreeding;
d) through individual selection.

5. Which plant is not self-pollinating?

a) peas;
b) rye;
c) wheat;
d) tomato.

6. Winter wheat variety Mironovskaya 808 was bred:

a) V.S. Empty volume;
b) P.P. Lukyanenko;
c) N.V. Tsitsin;
d) V.N. Craft.

7. The mentor method in plant breeding is used to:

a) acclimatization;
b) reacclimatization;
c) strengthening the dominance of the trait;
d) hardening of hybrids.

8. Inbreeding in animals leads to:

a) heterosis;
b) improving the properties of the breed;
depressed;
d) the creation of a new breed.

9. A systematic taxon that cannot be created as a result of selection is:

a) view;
b) grade;
c) breed;
d) strain.

10. The phenomenon of heterosis, as a rule, is observed when:

a) inbreeding;
b) distant hybridization;
c) creation of genetically pure lines;
d) self-pollination.

Option 2

1. What selection should be used in the selection of cucumbers?

a) individual;
b) mass;
c) stabilizing;
d) tearing.

2. What is self-pollination of cross-pollinating plants called?

a) outbreeding;
b) inbreeding;
c) distant hybridization;
d) aneupolyploidy.

3. What is heterosis?

a) increasing the fertility of the hybrid;
b) geographically distant hybrids;
c) depression that occurs during self-pollination of cross-pollinated plants;
d) increased viability and productivity of interline hybrids.

4. Why is cross-pollination used in self-pollinating plants?

a) to obtain the effect of heterosis;
b) to obtain clean lines;
c) to obtain biologically distant hybrids;
d) to obtain hybrids that combine the characteristics of different varieties.

5. Which plant is not cross-pollinated?

a) sunflower;
b) barley;
c) corn;
d) rye.

6. Ukrainian white steppe breed of pigs was bred:

a) A.I. Kuzema;
b) N.S. Baturin;
c) M.F. Ivanov;
d) Ya.Ya. Lusin.

7. Very rarely used in animal breeding:

a) inbreeding;
b) outbreeding;
c) mass selection;
d) individual selection.

8. Selection based on phenotype is called:

a) massive;
b) individual;
c) natural;
d) artificial.

9. Pets, unlike plants:

a) have numerous offspring;
b) live longer
c) reproduce only sexually;
d) do not need careful maintenance.

10. In plant and animal breeding, the following is used:

a) analysis of the quality of producers by offspring;
b) hybridization;
c) obtaining polyploid forms;
d) mentor method.

Answers to test tasks

Option 1:

1a; 2a; 3c; 4b; 5 B; 6g; 7c; 8c; 9a; 10b.

Option 2:

1b; 2b; 3g; 4g; 5 B; 6c; 7c; 8a; 9c; 10b.

D. Checking the completion of the table "Basic methods of plant and animal breeding"

II. Learning new material

1. Biological features of microorganisms and methods of selection work with them

As always, let's start talking about a new object of selection with its biological features. The biological characteristics of microorganisms taken into account in breeding should include:

– high reproduction rate;
– higher frequency of mutations;
– strain heterogeneity and selection efficiency.

Strain (from him. Stamm- trunk, base; family, tribe) - a pure culture of a microorganism isolated from a specific source or obtained as a result of mutations.

By the middle of the last century, a new branch of industry arose - microbiological, which uses unicellular fungi, bacteria to produce complex organic substances. The microbiological industry is an integral part of biotechnology.

Such branches of the food industry as baking, the production of alcohol, some organic acids and vitamins, winemaking and many others are based on the activity of microorganisms.

Antibiotics are of great importance for human health. These are special substances - the waste products of some bacteria and fungi that kill pathogenic microbes. Thanks to antibiotics, many diseases are cured relatively easily, while previously they gave a high percentage of mortality. Vitamins, so necessary for humans, are produced by plants and some microorganisms.

To be continued

Popular

Fujifilm X-T10 System (Mirrorless) Camera

« The Fujifilm X-T10 is a mid-range mirrorless camera aimed at enthusiasts who want the quality and flexibility of the X series, but in a smaller... »

NetGuard - ad blocker without ROOT rights

« AdAway One of the best apps for . The program blocks advertising banners in games and applications, and also allows you to create white and black... »

Timesheet Okud 0504421 timesheet

« Is the institution obliged to use the time sheet (f. 0504421) in its activities? Can I make changes to this document? How... »

*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	Different species interbreed, the descendants are usually sterile, tk. 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