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1. The main
directions of
selection
selection is an evolution guided by the will of man
(N.I.Vavilov)

2. 2
Breeding is a science that studies the biological basis and methods of
creating new breeds of animals, plant varieties, strains of
microorganisms, as well as improving existing forms.
Agricultural industry. production, which is engaged in the
breeding of varieties and hybrids of agriculture. cultures, breeds
of animals.

3. 3
From a methodological point of view, selection combines approaches
inherent, on the one hand, for genetics, on the other hand, for
population and evolutionary biology. Based on these approaches,
breeding develops specific techniques that are used in practice in
improving individual breeds and varieties.

4. 4
 The direction of theoretical and practical research in selection
is always determined by the specific needs of a person in
various aspects. The main one is the need to solve the food
problem, especially in those regions that, by their
climatogeographic characteristics, are unfavorable for food
production. This includes the creation of frost-resistant,
drought-resistant plant varieties, varieties resistant to lodging,
to the effects of sudden temperature changes, to soil salinity,
etc. Another example of the use of breeding developments is fur
farming, in which the needs of the market are of great
importance. There are many such examples.

5. The main directions of
selection are:
high yield of plant varieties, fertility and
productivity of animal breeds;
quality of products (for example, taste, appearance,
shelf life of fruits and vegetables, chemical composition
of grain - the content of protein, gluten, essential
amino acids, etc.);
physiological properties (precociousness, drought
resistance, resistance to diseases, pests and adverse
climatic conditions);
an intensive path of development (in plants -
responsiveness to fertilizers, watering, and in animals -
"payment" for feed, etc.).
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6. Models of breeds and varieties
Modern breeding, especially in developed
countries, has now achieved great success, and
the creation of new breeds and varieties and
the improvement of old ones are achieved with
great difficulty every year. Therefore, at
present, in breeding, more emphasis is placed
on modeling the so-called "ideal" breeds
(above) and varieties (bottom). When creating
such models, they usually take into account
their purpose and all those components from
which the productivity indicator will be
formed.
For example, when creating a model
of a modern variety of spring wheat, it
is assumed that there is a large
straight spiny spike, convenient to
process, a strong short stem, resistant
to lodging and convenient in
mechanized harvesting.
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(from S.G. Inge-Vechtomov, 1989)

7. Productivity
the main indicator that is most important from the point of
view of breeding is the productivity indicator. The
indicator of productivity includes, for example, the mass,
growth of animals, milkiness, egg production, coat
structure, yield, the presence of certain components in
fruits, seeds, etc.
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8. Features of productivity signs
First, an important feature of almost all elements of
productivity is their continuous variation,
characteristic of quantitative features.
The second main feature of these traits is the
dependence of their manifestation on a large number of
genes interacting with each other. Thus, we are talking
about the fact that most of the economically valuable
traits are inherited polygenically.
Finally, the third feature of these traits is that they are
affected by modificational variability, which further
eliminates the differences between phenotypes. Thus,
quantitative variability is continuous, not discrete.
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9. Factors of breeding success
the amount of variability of the selected trait;
the difference between the average size of the selected
trait in selected animals and the average value of the
same trait in the population (selection differential);
the proportion of genotypic variation in the total
phenotypic diversity of the trait, i.e. heritability;
the number of traits selected and the genetic
relationship between them;
the intergenerational interval, which is defined as the
average age of the parents at the birth of offspring
destined for the next generation.
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10. Heritability coefficient
It is known that variability can be due to the
action of environmental factors (paratypic
variability). On the other hand, there is
genotypic variation due to changes in the
genotype proper. To isolate the proportion of
genotypic variation, the heritability coefficient is
calculated, which is a specific characteristic of a
trait in a given group of individuals. This
indicator varies not only for different traits, but
also for different populations, depending on the
level of their heterozygosity. The higher the
heterozygosity, the greater the heritability
coefficient and the more effective the selection
for this trait will be.
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11. Artificial selection
The main methodological technique used in breeding
practice is selection. Artificial selection has many
similarities with natural selection, which is the main
factor in evolution, but there are also a number of
differences. First, artificial selection is always carried
out under certain conditions chosen by the breeder.
Conditions can be varied in such indicators as
temperature, humidity, illumination, feeding conditions,
etc. Secondly, artificial selection, unlike natural
selection, is not always carried out in the direction of the
manifestation of an adaptive trait, because it is aimed at
selecting signs that are beneficial only to humans.
Finally, thirdly, artificial selection is carried out with
strictly controlled crosses of a small number of
individuals, while natural selection mainly occurs in
conditions approaching panmixia.
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12. Mass selection
In breeding, there are two main types of
selection: mass and individual. Mass selection is
carried out according to external phenotypic
characteristics. It can be quite effective only
against traits controlled by one or a few genes –
qualitative traits. Qualitative signs include the
suit, color and shine of wool, blood groups,
horniness or comb, etc. An important role in
this case is played by the heritability coefficient
of the trait: the higher its indicator, the more
effective the selection will be.
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13. Individual selection
Selection of traits inherited polygenically is carried out
using an individual type of selection. It is based on a
comprehensive assessment of the genotype of a plant or
animal. Usually, the offspring of the selected organism are
obtained and its indicators are evaluated. In this case, the
population is divided into families or used by offspring
from self-pollination of individual plants (in cases where
possible).
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14. Types of crosses
Selection in breeding is combined with different
types of crosses. There are two main types of
crossbreeding: inbreeding – closely related
crossbreeding and outbreeding – unrelated
crossbreeding. A type of outbreeding is the so-
called crossbreeding - interlinear or interbreed
crossing. For example, crossing donkeys with
horses produces mules and horses; bison with
cows – cows; wheat with rye – triticale.
Interspecific crosses do not always lead to the
appearance of offspring. At the same time, the
descendants themselves are either sterile, like
mules, or their fecundity is sharply reduced, as in
cows. However, crossbreeding within one species
yields quite normal hybrids (mestizos).
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15. Inbreeding
- used to decompose a population into
homozygous lines in order to identify
the phenotypic effects of recessive
genes and to homozygotize
individuals by genes that control the
selectable trait.
As a rule, inbreeding is
accompanied by the so-called
inbred depression caused by a
homozygous state of unfavorable
recessive alleles.
On the other hand, inbreeding
leads to the alignment of lines,
making them more homogeneous in
most features and, therefore, more
convenient for further selection.
15
Inbred degeneration in corn; P –
variety before the start of
inbreeding, J1 –J7 – generations
obtained as a result of self-
pollination
(from S.M. Gershenzon, 1979)

16. Outbreeding, heterosis
 In contrast to inbreeding, outbreeding increases the level of
heterozygosity of the offspring and, accordingly, the level of
heterozygosity of the population. The consequences of outbreeding
include the phenomenon of heterosis (hybrid force), which is
manifested in the superiority of the hybrid over both parental
forms.
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Manifestation of heterosis in
different generations of
hybrid corn. 1,2 – original
parent forms, 3 – hybrids
F1, 4-10 – hybrids of
subsequent generations
(из Г.В. Гуляева, 1977)

17. Heterosis
- Is widely used in plant breeding, but its mechanism
remains unclear to date. There are several theories
that explain heterosis; including the theory of
"dominance", according to which heterosis is due to
the presence in hybrids of the selection of favorable
dominant alleles of different types interacting
according to the complementary type. Other theories
– "overdomination" explains heterosis due to the
advantage of the heterozygous state of the genotype
over the homozygous state; - the theory of
"compensatory complexes" - heterosis is provided by
a complex of genes that neutralizes the negative
effects of a high level of homozygosity and gives the
effect of hybrid force during hybridization. A feature
of heterosis, which complicates its use in breeding, is
the attenuation of its effect in a number of
generations. The ways of fixing heterosis are usually
associated with the transfer of hybrids to asexual
reproduction.
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18. Use of polyploidy
The next genetic effect that is used in breeding is
polyploidy. As you know, autopolyploidy leads
to an increase in the size of cells and the whole
organism. Polyploidy gives good results:
 – in plants with a small number of chromosomes;
 – in cross-pollinating plants;
 – in plants cultivated for the use of a mass of
vegetative organs.
 Widely known tetraploid varieties of cereals (rye,
buckwheat), triploid varieties of sugar beets, etc.

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19. Use of polyploidy
The effects of allopolyploidy are also used in breeding. This
is expressed in the method of distant hybridization
(interspecific and intergeneric). The limitation of this
method is the sterility of allopolyploids, but it is quite
applicable for forms that can be propagated vegetatively.
Remote hybridization is widely used in the production of
new forms of fruit plants, cereals.
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20. Use of polyploidy
For example, as a result of
hybridization of wheat and
rye, a number of new
forms were obtained,
united by the name
triticale. Triticales have
good winter hardiness,
disease resistance and
high yields.
Ears of wheat rye amphidiploid
triticale (2) and the original types
of wheat (1) and rye (3).

21. Using mutations
In breeding, a mutational process is also
used, both spontaneous and induced.
Spontaneous mutants are used mainly in
plant breeding (fruit forms, corn with a high
content of lysine, lupine, which does not
contain alkaloids, wheat varieties resistant
to yellow rust, etc.). Sometimes the mutation
affects only one shoot as a whole, and then it
is called kidney, or sport. As a result of such
a mutation, for example, the seedless
California orange Navel appeared. It, like
many other plants, does not need seeds for
reproduction: vegetative methods, in
particular cuttings or grafting, are enough.
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22. Using mutations
The use of radiation and chemical mutagenic
influences also allows breeders to obtain new
useful forms of plants, animals and
microorganisms.
For example, Gustafson's work on the production of
barley mutants with increased grain yield and a
shortened stem is known.
Radiation-induced rearrangements of chromosomes were
successfully used by V.A. Strunnikov in the selection of
silkworms. Strunnikov's method was based on obtaining
only male individuals in the offspring with the help of a
system of balanced lethals, since males in the silkworm
form cocoons 25-30% more productive than females.
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23. Using mutations
Especially intensively induced mutagenesis is used in the
selection of microorganisms. In particular, the Moscow
school of geneticists and breeders under the leadership of
S.I. Alikhanyan managed to obtain a number of forms that
actively produce antibiotics by treating actinomycetes with
various mutagens.
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24. 24
Thus, all the main traditional branches of genetics: hybridization,
mutational process, population genetics, etc. find their application in
selection.

25. Thank you for attention!
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