Methods of selection and genetic work by I. Michurin

Equipment: tables on general biology, illustrating the methods of plant breeding, methods of breeding work by I.V. Michurin and achievements in plant breeding.

DURING THE CLASSES

I. Knowledge Test

A. Card work

№ 1. Scientists have obtained a wheat-rye hybrid of triticale. How did you manage to create such a hybrid that successfully reproduces sexually?

№ 2. Bezostaya 1 (bred by P.P. Lukyanenko) and Mironovskaya 808 (bred by V.N. Remeslo) are recognized as the highest-yielding (up to 100 c/ha) wheat varieties. Their ears and grains are very large, the stems are thick, strong. These varieties are soft, polyploid ( 6n) wheat. The highest yield and large fruits in strawberries are also given by polyploid (8n) plants. Using this data, answer the questions:

a) how does polyploidy affect fruit size and other morphological features of wheat and strawberries?
b) how does polyploidy affect the productivity of these plants?
c) what is the economic significance of polyploidy for humans?

№ 3. Evolutionary theory was confirmed by the studies of the Danish geneticist V. Johansen. He studied the action of selection in populations and pure lines. It turned out that within the limits of a pure line, selection by size, seed weight, and other traits is inefficient. At the same time, selection in freely crossing populations is effective. Explain what pattern of evolutionary theory is supported by the results of this study.

№ 4. Currently, a hybrid tomato variety resistant to two viruses is widely used in the USA and England. The variety is obtained as a result of the fusion of germ cells of a wild tomato and a cultivated variety. Explain the importance of preserving the genes of wild species for breeding.

B. Oral knowledge test

1. What are the biological characteristics of plants taken into account in breeding?
2. What is inbreeding and interbreeding?
3. What is intervarietal and interspecific crossbreeding?
4. What is the phenomenon of heterosis and what are its genetic bases?
5. What is the method of G.D. Karpechenko on overcoming the infertility of interspecific hybrids?
6. What is mass and individual selection in plant breeding?
7. What is induced mutagenesis and what is the method of obtaining polyploids in plant breeding.

II. Learning new material

1. Methods of selection work I.V. Michurin

Ivan Vladimirovich Michurin (1855–1935) is an outstanding practical breeder, the author of 300 varieties of fruit and berry crops. At the beginning of his activity, I.V. Michurin was engaged in acclimatization according to the Grell method, grafting southern varieties into the crown of hardy and cold-resistant varieties in order to achieve their adaptation to new conditions. But it was impossible to change the genotype of southern varieties by a similar method. Michurin was convinced of this by testing about 200 foreign varieties: after 35 years, not a single tree remained of them, although Michurin lived and worked in the relatively mild climate of the Black Earth Zone of Russia (Kozlovsk, now Michurinsk, Tambov province).
Convinced of the futility of attempts at simple acclimatization, I.V. Michurin began to develop new breeding methods based on hybridization, selection and education (the impact of environmental conditions on developing hybrids). In their implementation, he used a variety of approaches (many of them for the first time in world breeding practice), the most important of which are as follows.

biologically distant hybridization - crossing representatives of different species to obtain varieties with the desired properties or crossing representatives of different genera. So, for example, Michurin crossed the Vladimirskaya cherry with the white Winkler cherry. In further work with hybrids, he developed the Krasa Severa cherry variety, which had good taste and winter hardiness. When crossing cherry with bird cherry, Michurin received a hybrid called cerapadus. He also obtained hybrids of blackberry and raspberry, plum and blackthorn, mountain ash and Siberian hawthorn, etc.

Geographically distant hybridization - crossing of representatives of contrasting natural zones and geographically remote regions in order to instill in the hybrid the desired qualities. For example, the well-known pear variety Bere winter Michurina was obtained as a result of hybridization of the wild Ussuri pear and the southern French variety Bere-royal.

The mentor method - one of the methods of "education" of hybrids developed by I.V. Michurin. It is based on the fact that the characteristics of a developing hybrid change under the influence of a scion or rootstock. Michurin used this method in two versions. In the first case, the hybrid seedling served as a scion, and it was grafted onto an adult fruit-bearing plant (rootstock), the properties of which it was desirable to obtain from the hybrid. In the second case, a stalk of a variety was grafted into the crown of a young hybrid seedling (rootstock), the characteristics of which they would like to obtain from the hybrid.
This method was applied by Michurin, for example, when creating the Bellefleur-Chinese apple variety. In the first year of fruiting hybrids, it turned out that their fruits are small and sour. To direct the further development of the hybrid in the right direction, Bellefleur cuttings were grafted into the crown of young trees. Under the influence of cuttings, the fruits of the hybrid began to acquire the taste qualities of Bellefleur.
The influence of the mentor should be seen as a change in dominance during the development of the hybrid. In this case, the mentor contributed to the phenotypic manifestation (dominance) of the genes obtained from the Bellefleur variety, without changing the genotype of the hybrid.

Mediator Method was used by Michurin for distant hybridization. It consists in using the wild species as an intermediary to overcome inbreeding. By crossing the wild Mongolian almond with the wild peach of David, Michurin obtained the Posrednik almond, which he later used to cross with the cultivated peach. The hybrid peach he received acquired winter hardiness, due to which he was promoted to the north.

Mixing pollen was used by Michurin to overcome interspecific inbreeding (incompatibility). The essence of the method was that when pollinated with a mixture of one's own pollen and pollen of another species, one's own pollen irritated the stigma of the pistil, and it perceived foreign pollen.

Exposure to environmental conditions . When "educating" young hybrids, Michurin used changes in the methods of storing seeds, the nature of nutrition and soil properties, exposure to low temperatures, and used frequent transplants. As a result, hybrids hardened and could endure adverse environmental conditions.

Selection – repeated and rigorous selection of plants in terms of size, shape, winter hardiness, immune properties, quality, taste, fruit color, etc.
Most of the varieties obtained by I.V. Michurin, were complex heterozygotes. To preserve their qualities, they are propagated vegetatively: by layering, grafting, etc.

2. Achievements in plant breeding

Selection work is of great national economic importance. Replacing low-yielding varieties with high-yielding breeding varieties is one of the main ways to increase yields. At present, both in our country and abroad, selection and genetic work leads to remarkable results.
Let's take a look at some of the latest advances in breeding for major crops.

Winter wheat . For Russia, wheat is the main grain crop. Academician Pavel Panteleimonovich Lukyanenko (1901–1973) created a number of high-yielding varieties of winter wheat, covering millions of hectares both in Russia and in other countries. Especially popular are the varieties Avrora and Kavkaz, yielding up to 100 c/ha, and Bezostaya 1 with a yield of up to 50 c/ha. On the basis of the latter variety, the varieties Krasnodarskaya 57 and Odessa semi-dwarf were bred.
No less high-yielding varieties were bred at the Mironovskaya breeding experimental station by Academician Vasily Nikolaevich Remeslo (1907–1983): Mironovskaya 264, Mironovskaya 808, etc. Over the past 50 years, the yield of winter wheat varieties has increased from 25 to 65 c/ha, i.e. 2.5 times. Ilyichevka also belongs to the new high-yielding varieties of winter wheat, bred at the same station. In 1974, this variety was released in 15 regions of Ukraine and, with proper irrigation and high agricultural technology, yields up to 100 c/ha.
Among the new varieties, perennial wheats are very promising, bred under the guidance of Academician Nikolai Vasilievich Tsitsin (1898–1980) on the basis of interspecific hybridization of wheat and wheatgrass. They are high-yielding, drought-resistant, withstand frosts down to -35 oC.

Spring wheat . Among the spring varieties, the most valuable is the high-yielding variety Saratovskaya 29, created by Alexei Pavlovich Shekhurdin (1886–1951) and Valentina Nikolaevna Mamontova (1895–1982), which is distinguished by high baking qualities. We have already mentioned the Novosibirskaya 67 spring wheat variety with a shortened and thickened straw, bred at the Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences. The yield of this variety in Western Siberia reaches 40 q/ha.

Sunflower . In this area of ​​plant breeding, the achievements of academician Vasily Stepanovich Pustovoit (1886–1972) are remarkable. Until the middle of the XX century. The best varieties of sunflower oil content did not exceed 33%. Currently, the average oil content of seeds reaches 50%.

Sugar beet . In recent years, the sugar content and yield of sugar beets have increased dramatically. A large role in the selection of this culture was played by polyploidy (works by A.N. Lutkov, V.P. Zosimovich).

Corn . When creating new promising varieties of this crop, self-pollinating homozygous lines are used with their subsequent hybridization (M.I. Khadzhinov and G.S. Galeev).

III. Consolidation of knowledge

Generalizing conversation in the course of learning new material.

IV. Homework

To study the paragraph of the textbook (methods of breeding work by I.V. Michurin and the achievements of plant breeding).

Lesson 8–9. Animal breeding, its methods and achievements

Equipment: tables on general biology, illustrating the methods of selection work by I.V. Michurin, achievements in plant breeding, methods of animal breeding.

DURING THE CLASSES

I. Knowledge Test

A. Card work

№ 1. What important pattern of trait dominance in hybrids was established by I.V. Michurin? What is the significance of this pattern for selection? Give examples.

№ 2. What are the positive and negative aspects of self-pollination in the selection of cultivated plants?

№ 3. There is an expression: "A person is fed and clothed by polyploids." How should it be understood?

№ 4. When selecting parent pairs for hybridization, I.V. Michurin made extensive use of geographically distant forms. So, for example, the apple-tree variety Bellefleur-Chinese was created, obtained as a result of hybridization of a Chinese apple tree from Siberia and the American variety Bellefleur yellow. Why did Michurin pay much attention to the crossing of geographically distant forms?

B. Oral knowledge test

1. What breeding methods did I.V. Michurin?
2. What are the latest advances in plant breeding?

II. Learning new material

1. Features of animal biology taken into account in breeding

When selecting animals, it is necessary to take into account the following features:

- a small number of offspring in a pair of parents;
- long life expectancy;
- the impossibility of vegetative reproduction of highly organized animals and the presence of only sexual reproduction in them;
- dichotomy;
- often late puberty;
- more complex than in plants, relationships with the environment due to the presence of the nervous system;
- the difficulty of studying the genotype, because it contains a large number of heterozygotes, and genes are in complex interaction (meat, milk, wool productivity, fertility, fur density in fur animals and other economically valuable traits are very difficult to inherit).

2. Types of crosses and breeding methods used in animal husbandry

In breeding work, it is important to represent the ultimate goal that the breeder is striving for. Whether it is desirable to increase milk production, increase its fat content, or change the meat qualities of livestock - all this requires different directions for the selection and selection of producers, the use of various crossing systems.
When selecting breeders, it is important to consider their pedigrees. In breeding farms, pedigree books are always kept, in which the exterior features and productivity of parental forms are taken into account in detail over a number of generations. According to the signs of the ancestors, one can judge the genotype of the producers.
The types of crossbreeding in breeding work with animals are varied. There are mainly two types of crossing: unrelated and related.

unrelated crossbreeding , or outbreeding (from English. out- outside and breeding- breeding) is carried out between individuals of the same breed or between individuals of different breeds of animals. With strict selection, it leads to the maintenance of properties or their improvement in the next generations of hybrids, tk. in the offspring, a successful combination of genes can be obtained, which ensures the formation of a number of economically important traits.

Inbreeding, or inbreeding, held between siblings or parents and offspring. This type of crossing is used in those cases when they want to transfer most of the genes of the breed to a homozygous state, i.e. to obtain pure lines, preserve economically important traits, increase the stability of these traits for subsequent crossing and obtain the effect of heterosis.
To a certain extent, such crossing is similar to self-pollination in plants, since. leads to an increase in homozygosity. With closely related crossing, weakening of animals, loss of resistance to external factors, to diseases is often observed. All these negative manifestations of inbreeding are called depression.

Interline crossing is carried out between representatives of pure homozygous lines in order to avoid the adverse effects of recessive genes, transfer them to a heterozygous state and cause the effect of heterosis. Usually representatives of several lines are used for crossing.

distant hybridization , i.e. interspecific crossing has been known in animals since ancient times. Most often, interspecific hybrids are sterile, because. they have disrupted meiosis, which leads to disruption of gametogenesis. Since ancient times, man has been using a hybrid of a mare with a donkey - a mule, which is distinguished by endurance and long life expectancy. Overcoming the infertility of interspecific hybrids of animals is an important task of breeding.
Sometimes gametogenesis in distant hybrids proceeds normally, and this made it possible to obtain new valuable breeds of animals. An example is the archa-merino, which can graze high in the mountains like argali and, like merino, produce good wool. Prolific hybrids have been obtained from crossing local cattle with yaks and zebu (a subspecies of cattle common in Asia and Africa). Productive hybrids of beluga and sterlet (bester), ferret and mink (honorik) , carp and carp. Also prolific are the offspring obtained by crossing between one-humped and two-humped camels, domestic horses and Przewalski's horses, bison and bison.
In animal husbandry, two main breeding methods are used: interbreeding and interbreed.

Inbreeding, or breeding in oneself , aimed at preserving and improving the breed. In practice, it is expressed in the selection of the best producers, the culling of individuals that do not meet the requirements of the breed.

Interbreeding used to create a new breed. In this case, inbreeding is often carried out, which helps to obtain a large number of individuals with the desired properties.

To be continued

Michurin plant breeding

I.V. Michurin is an outstanding scientist-breeder, one of the founders of the science of breeding fruit crops. He lived and worked in the county town of Kozlov (Tambov province), renamed in 1932 to Michurinsk. Working in the garden from a young age was his favorite thing. He set the goal of his life to enrich the gardens of Russia with new varieties and achieved this dream, despite incredible difficulties and hardships. He developed original practical methods for obtaining hybrids with new properties useful for humans, and also made very important theoretical conclusions. Having set himself the task of promoting southern varieties of fruit trees to central Russia, Michurin first tried to solve it by acclimatizing these varieties in new conditions. But the southern varieties grown by him froze out in winter. A mere change in the conditions of existence of an organism cannot change a phylogenetically developed stable genotype, moreover, in a certain direction. Convinced of the unsuitability of the acclimatization method, Michurin devoted his life to breeding work, in which he used three main types of influence on the nature of a plant: hybridization, the upbringing of a developing hybrid in various conditions, and selection. Hybridization, i.e., obtaining a variety with new, improved characteristics, was most often carried out by crossing a local variety with a southern one, which had higher palatability. At the same time, a negative phenomenon was observed - the dominance of the features of the local variety in the hybrid. The reason for this was the historical adaptation of the local variety to certain conditions of existence. One of the main conditions contributing to the success of hybridization, Michurin considered the selection of parental pairs. In some cases, he took for crossing parents who were distant in their geographical habitat. If for parental forms the conditions of existence do not correspond to their usual ones, he reasoned, then the hybrids derived from them will be able to more easily adapt to new factors, since there will be no one-sided dominance. Then the breeder will be able to control the development of a hybrid that adapts to new conditions.

By this method, the Bere winter Michurina pear variety was bred. As a mother, the Ussuri wild pear was taken, which is distinguished by small fruits, but winter-hardy, as a father, the southern variety Bere royale with large juicy fruits was taken. For both parents, the conditions of central Russia were unusual. The hybrid showed the qualities of the parents that the breeder needed: the fruits were large, long-lived, had high palatability, and the hybrid plant itself endured cold up to - 36 °.

In other cases, Michurin selected local frost-resistant varieties and crossed them with southern heat-loving, but with other excellent qualities. Michurin brought up carefully selected hybrids in Spartan conditions, believing that otherwise they would have traits of thermophilicity. Thus, the Slavyanka apple variety was obtained from crossing Antonovka with the southern variety Ranet pineapple. In addition to crossing two forms belonging to the same systematic category (apple trees with apple trees, pears with pears), Michurin also used hybridization of distant forms: he received interspecific and intergeneric hybrids. He obtained hybrids between cherry and bird cherry (cerapadus), between apricot and plum, plum and blackthorn, mountain ash and Siberian hawthorn, etc.

Under natural conditions, alien pollen of another species is not perceived by the mother plant and crossing does not occur. To overcome non-crossing in distant hybridization, Michurin used several methods.

Method of preliminary vegetative approach

One-year-old stalk of a hybrid rowan seedling (graft) is grafted into the crown of a plant of another species or genus, for example, to a pear (rootstock). After 5-6 years of nutrition due to the substances produced by the stock, there is some change, the convergence of the physiological and biochemical properties of the scion.

During the flowering of mountain ash, its flowers are pollinated with pollen from the rootstock. This is where the crossover takes place.

Mediator method

It was used by Michurin in the hybridization of cultivated peach with wild Mongolian almond bean (in order to move the peach to the north). Since direct crossing of these forms was not possible, Michurin crossed the beaver with the semi-cultivated peach David. Their hybrid crossed with a cultivated peach, for which he was called an intermediary.

Pollination method with a mixture of pollen

I. V. Michurin used various variants of the pollen mixture. A small amount of pollen from the mother plant was mixed with pollen from the father. In this case, its own pollen irritated the stigma of the pistil, which became capable of accepting foreign pollen. When pollinating apple flowers with pear pollen, a little apple pollen was added to the latter. Part of the ovules was fertilized by its own pollen, the other part - by someone else's (pear). Non-crossing was also overcome when the flowers of the mother plant were pollinated with a mixture of pollen from different species without the addition of pollen of their own variety.

Essential oils and other secretions secreted by foreign pollen irritated the stigma of the mother plant and contributed to its perception.

Throughout his many years of work on breeding new varieties of plants, I. V. Michurin showed the importance of the subsequent education of young hybrids after crossing.

When raising a developing hybrid, Michurin paid attention to the composition of the soil, the method of storing hybrid seeds, frequent replanting, the nature and degree of nutrition of seedlings, and other factors.

The mentor method

In addition, Michurin widely used the mentor method he developed. In order to cultivate desirable qualities in a hybrid seedling, the seedling is grafted onto a plant that possesses these qualities. Further development of the hybrid is under the influence of substances produced by the parent plant (mentor); the desired qualities are enhanced in the hybrid. In this case, in the process of development of hybrids, a change in the properties of dominance occurs. Both a rootstock and a scion can be a mentor. In this way, Michurin bred two varieties - Kandil-Chinese and Bellefleur-Chinese.

Kandil-Chinese is the result of crossing Kitaika with the Crimean variety Kandil-Sinap. At first, the hybrid began to deviate towards the southern parent, which could develop insufficient cold resistance in it. In order to develop and consolidate the sign of frost resistance, Michurin grafted a hybrid into the crown of Kitayka's mother, who possessed these qualities. Nutrition mainly with its substances brought up the desired quality in the hybrid. The breeding of the second grade Bellefleur-Chinese was associated with some deviation of the hybrid towards the frost-resistant and early ripe Kitayka. The fruits of the hybrid could not withstand long storage.

In order to cultivate the keeping quality property in the hybrid, Michurin planted several cuttings of late-ripening varieties into the crown of the Bellefleur-Chinese hybrid seedling. The result turned out to be good - the fruits of Chinese Bellefleur acquired the desired qualities - late ripeness and keeping quality. The mentor method is convenient in that its action can be regulated by the following methods: 1) the ratio of the age of the mentor and the hybrid; 2) the duration of the mentor; 3) the quantitative ratio of the leaves of the mentor and the hybrid.

For example, the intensity of the mentor's action will be the higher, the older his age, the richer the crown foliage and the longer he acts. In selection work, Michurin attached significant importance to selection, which was carried out repeatedly and very rigorously. Hybrid seeds were selected according to their size and roundness: hybrids - according to the configuration and thickness of the leaf blade and petiole, the shape of the shoot, the location of the lateral buds, according to winter hardiness and resistance to fungal diseases, pests and many other traits, and, finally, according to the quality of the fruit.

The results of IV Michurin's work are striking. He created hundreds of new varieties of plants. A number of varieties of apple trees and berry crops are advanced far to the north. They have high palatability and at the same time are perfectly adapted to local conditions. The new variety Antonovka 600 grams yields up to 350 kg per tree. Michurin grapes withstood the winter without powdering the vines, which is done even in the Crimea, and at the same time did not reduce their commodity indicators. Michurin showed with his works that the creative possibilities of a person are endless.

Ivan Vladimirovich Michurin, an outstanding Soviet scientist and breeder, dedicated 60 years of hard work to the development of new varieties of fruit trees and other cultivated plants. His work began back in the 70s of the last century in a small nursery in the city of Kozlov (now Michurinsk), the former Tambov province.

Expand the research of I.V. Michurin could only after the October Revolution, when his nursery was turned into a large state institution. V.I. was interested in Michurin's activities. Lenin, who attached great importance to her. M.I. Kalinin visited Michurin's nursery and assisted his work in every possible way.

I.V. Michurin did not immediately come to those methods and views that led to great success. In the first period of his activity, he spent a lot of time and effort on experiments on simple acclimatization (training) of southern varieties to the relatively harsh climate of the Tambov province with cold winters. These attempts were unsuccessful. All southern varieties froze out in winter.

Convinced of the futility of the method of simple acclimatization, I.V. Michurin set about developing new methods for changing the nature of plants.

The works of I.V. Michurin is a combination of three main methods: hybridization, selection and exposure to environmental conditions on developing hybrids(their "education" in the desired direction).

Much attention to I.V. Michurin paid attention to the selection of initial parental forms for hybridization. He crossed local frost-resistant varieties with the best southern ones. The resulting seedlings were subjected to strict selection. I.V. Michurin kept the hybrids obtained in this way under relatively harsh conditions, not giving them rich soil. IV Michurin points to the possibility of controlling the dominance of traits during the development of a hybrid, and the influence of external factors on dominance is effective only in the early stages of hybrid development. Among the varieties obtained by this method, for example, is the Slavyanka apple tree, bred as a result of the hybridization of Antonovka with the southern variety Ranet pineapple.

Of particular importance in the selection of parental forms for hybridization I.V. Michurin gave crossbreeding geographically distant forms that do not grow in the area where hybridization is carried out. He wrote on this occasion: “The farther the pairs of crossed producing plants are separated from each other in the place of their homeland and environmental conditions, the easier hybrid seedlings adapt to environmental conditions in a new area.” This way I.V. Michurin created a number of first-class varieties of fruit trees. Among them is the apple-tree variety Bellefleur-Chinese, obtained as a result of hybridization of the Chinese apple tree native to Siberia and the American variety Bellefleur yellow. The Chinese is characterized by its endurance to frost and resistance to diseases, the Bellefleur - by the wonderful taste of the fruit. Received I.V. Michurin, the new variety is distinguished by excellent taste and significant frost resistance.

The widely known Michurin pear variety Bere winter Michurina was obtained as a result of hybridization of the wild Ussuri pear and the southern French variety Bere-royal.

Among the methods of "education" that I.V. Michurin, one should point to mentor method. Its essence boils down to the fact that the characteristics of a developing hybrid change under the influence of a scion or rootstock. This method was used by Michurin in two versions.

The first of them boiled down to the fact that the hybrid seedling served as a scion and was grafted onto an adult fruit-bearing plant (rootstock), in the direction of the properties of which it was desirable to change the properties of the hybrid.

The second variant of the mentor's method consisted in the fact that in the crown of a young hybrid seedling, which in this case served as a stock, a cutting from the variety in the direction of which it was desirable to change the properties of the hybrid was grafted.

The mentor method was applied by I.V. Michurin, for example, when creating the Belle Fleur-Chinese apple variety already mentioned above. In the first year of fruiting of the hybrids that gave rise to the variety, it turned out that in terms of fruit quality they deviate towards Kitaika, which has small sour fruits. In order to change the further development of the hybrid in the desired direction, Bellefleur cuttings were grafted into the crown of young hybrids, under the influence of which the formation of the hybrid trait in subsequent years went in the direction of acquiring the high taste qualities of Bellefleur. This method was applied by I.V. Michurin and when creating some other varieties, but it has not received wide application. The influence of the mentor should obviously be considered as a change in the property of dominance in the process of hybrid development. In this case, the mentor contributed to the phenotypic expression (i.e., dominance) of genes derived from the Bellefleur variety.

In his work I.V. Michurin also used distant hybridization - crossing between different species and even genera, and thus obtained several valuable new fruit crops.

He received hybrids of blackberry and raspberry, plum and blackthorn, mountain ash and Siberian hawthorn, etc.

Most received by I.V. Michurin varieties were complex heterozygotes. To preserve their qualities, they propagated vegetatively: layering, grafting, etc.

The outstanding Russian scientist-breeder Ivan Vladimirovich Michurin spent most of his life in the county town of Kozlov (Tambov province), which was later renamed Michurinsk in recognition of his work. He is considered one of the founders of the science of breeding fruit crops. From a young age, he was fascinated by gardening. His whole life was devoted to one goal: to develop new high-yielding varieties of agricultural crops in the climatic conditions of Russia. And he managed to achieve the realization of this dream, despite the incredible difficulties and hardships.

One of the most important results of his many years of work was the original practical methods he developed for obtaining hybrids with new, valuable properties. In addition, on the basis of the work done, he made very important theoretical conclusions.

Initially, Michurin set himself the task of acclimatizing southern varieties of fruit trees to the conditions of central Russia. However, failure awaited him here, due to the fact that the heat-loving southern varieties of plants, even if grown in new conditions, could not stand the harsh winter. This is due to the fact that one change in the conditions of existence of an organism cannot change a phylogenetically developed stable genotype, moreover, in a certain direction.

Thus, Michurin realized that the acclimatization method did not give the desired results. This led him to the idea that it is possible to obtain varieties with the required properties if one variety is crossed with another, that is, by engaging in selection work. Michurin used three main types of influence in his work: hybridization, education of a developing hybrid in various conditions, and selection.

^

hybridization method

Obtaining a variety with new, improved characteristics is called hybridization. As a rule, it is carried out by crossing a local variety with a southern one with higher palatability. However, due to the historical adaptation of the local variety to the conditions of existence of the given area, the obtained hybrids were dominated by the characteristics of the local variety.

In order for hybridization to be successful, Michurin took parents from very distant geographical areas for crossing. Michurin believed that in this case unilateral dominance would not occur, since the conditions of existence would not be familiar to any of the parental forms. Based on this, the development of the newly obtained hybrid can be controlled.

Subsequently, Michurin practically proved the validity of the above statement, having received a completely new pear variety Bere winter Michurina. It was distinguished by large, storable fruits with good taste, while the hybrid plant itself endured cold up to -36 °. The southern pear variety Bere royale with large juicy fruits was taken as the father, and the wild Ussuri pear with small fruits and high winter hardiness was taken as the mother. For both parents, the conditions of central Russia were unusual.

Michurin also selected and crossed local frost-resistant varieties with southern heat-loving varieties, which differed in other ways. He strictly monitored that the resulting hybrids were frost-resistant. Thanks to this, the apple variety Slavyanka was obtained from crossing Antonovka with the southern variety Ranet pineapple.

Michurin's experiments on crossing plants of different species were also widely known, while interspecific and intergeneric hybrids were obtained, such as hybrids between cherries and bird cherry (cerapadus), between apricot and plum, plum and blackthorn, mountain ash and Siberian hawthorn, etc.

Under natural conditions, crossing of different species plants does not occur due to the fact that alien pollen of another species is not perceived by the mother plant. Michurin used several methods to overcome non-crossing in distant hybridization.

^ Method of preliminary vegetative approach

This method was used by Michurin when crossing mountain ash and pear. It consists of two stages.

First, a one-year-old cutting of a hybrid rowan seedling (graft) is grafted into the crown of a plant of another species or genus, for example, to a pear (rootstock). After 5-6 years of nutrition, due to the substances produced by the rootstock, there is some change, the convergence of the physiological and biochemical properties of the rootstock.

Then, during the flowering of mountain ash, its flowers are pollinated with the pollen of the rootstock. This is where the crossover takes place.

^ Mediator Method

The essence of this method is that in case of impossibility of direct hybridization of two forms of plants, the third one is used. This plant is crossed with one of the first two, and then the resulting hybrid is crossed with the second, resulting in a hybrid of the first two forms. The third form acts as an intermediary.

The intermediary method was used by Michurin when crossing a cultivated peach with a wild Mongolian almond bean (to increase the frost resistance of a peach). Since direct crossing of these forms was not possible, Michurin crossed the beaver with the semi-cultivated peach David. Their hybrid crossed with a cultivated peach, for which he was called an intermediary

^ Pollination method with a mixture of pollen .

I. V. Michurin used various variants of the pollen mixture. A small amount of pollen from the mother plant was mixed with pollen from the father. In this case, its own pollen irritated the stigma of the pistil, which became capable of accepting foreign pollen. When pollinating apple flowers with pear pollen, a little apple pollen was added to the latter. Part of the ovules was fertilized by its own pollen, the other part - by someone else's (pear).

Non-crossing was also overcome when the flowers of the mother plant were pollinated with a mixture of pollen from different species without the addition of pollen of their own variety. Essential oils and other secretions secreted by foreign pollen irritated the stigma of the mother plant and contributed to its perception.

Throughout his many years of work on breeding new varieties of plants, I. V. Michurin showed the importance of the subsequent education of young hybrids after crossing.

When raising a developing hybrid, Michurin paid attention to the composition of the soil, the method of storing hybrid seeds, frequent replanting, the nature and degree of nutrition of seedlings, and other factors.

^

The mentor method

This method was developed by Michurin and widely used by him in practice. It consists in the fact that the seedling is grafted onto a plant that has the necessary qualities for nurturing the desired qualities in the hybrid seedling. As a result, the desired qualities are enhanced in the hybrid, and its further development is under the influence of substances produced by the parent plant (mentor). In this case, in the process of development of hybrids, a change in the properties of dominance occurs. At the same time, both a rootstock and a scion can be a mentor.

Using the method of a mentor, Michurin bred two varieties - Bellefleur-Chinese and Kandil-Chinese.

Kandil-Chinese is the result of crossing Kitaika with the Crimean variety Kandil-Sinap. Michurin grafted the hybrid into the crown of the frost-resistant Kitaika mother in order to develop and consolidate the trait of frost resistance. Thanks to the nutrition of the mother's substances, the hybrid has the desired quality.

The second variety, Bellefleur-Chinese, was bred to prevent the hybrid from deviating towards the frost-resistant and early ripe Kitayka, and therefore the fruits of the hybrid could not be stored for a long time. Michurin planted several cuttings of late-ripening varieties into the crown of the Bellefleur-Chinese hybrid seedling in order to increase the keeping quality in the hybrid. As a result of the hybridization carried out, the fruits of Bellefleur-Chinese became more late-ripening and keeping quality.

This method can be controlled in the following ways:

1) the duration of the mentor; 2) the ratio of the age of the mentor and the hybrid; 3) the quantitative ratio of the leaves of the mentor and the hybrid.

The older the age of the mentor, the richer the foliage of the crown and the longer it acts, the higher the intensity of its action. When carrying out breeding work, Michurin made repeated and rather rigorous selection, which made it possible to obtain hybrids of excellent quality. Hybrid seeds were selected for their roundness and size; hybrids - according to the configuration and thickness of the leaf blade and petiole, the shape of the shoot, the location of the lateral buds, the winter hardiness and resistance to fungal diseases, pests and many other features, and, finally, the quality of the fruit.

As a result of his research, I. V. Michurin created several hundred new varieties of plants. New cold-resistant varieties of apple trees and berry crops were bred. These plants are characterized by high palatability and at the same time are perfectly adapted to local conditions. One of these species is the apple variety Antonovka six hundred grams, which yields up to 350 kg from one tree. The grapes bred by Michurin withstood the winter without powdering the vines, which is done even in the Crimea. At the same time, he did not reduce his commodity indicators.

I. V. Michurin, with his work, turned the idea of ​​​​human capabilities and laid a solid foundation for further research in plant breeding

Bibliography

Biology manual for university students. Minsk, I., Higher School, 1978

Encyclopedic Dictionary of a Young Naturalist. Moscow, I., Pedagogy. 1981