Presentation on population improvement

1. COLLEGE OF
HORTICULTURE,CHIPLIMA
OUAT
COURSE TITLE : PRINCIPLE OF
PLANT BREEDING
COUSE NO. : PBG-122(HO)

2. 32 HO/16
SUBMITTED TO : DR. KAUSHIK PANIGRAHI
SUBMITTED BY : SIMILI MOHAPATRA

3. POPULATION IMPROVEMENT

4. INTRODUCTION
Accumulation of desirable alleles in a population through various
breeding techniques is known as population improvement and
those breeding procedures that are used for such work are
referred to as population improvement approaches . In plant
breeding following four approaches are used for population
improvement.
1.RECURRENT SELECTION
2.DISRUPTIVE SELECTION
3.DIALLEL SELECTIVE MATING
4.BIPARENTAL MATING

5. • To start this work in the project’s targeted areas, we chose
several populations with broad or narrow genetic bases still
available in the CIRAD/CIAT Rice Project. However, the possibility
of incorporating well-adapted local varieties into these
populations was considered in terms of contributing.
• For example, to adaptation to specific environmental conditions,
stable resistance to diseases, or a specific grain quality for
household consumption.
• These choices were based on the results of the diagnosis and the
preliminary in situ PVS trials of diverse lines and varieties.
• The incorporation of local varieties as contributors of local
adaptation genes into the exotic populations may be carried out
in two ways, according to the type of population and the time
needed to develop new varieties:

6. • Enhancement of populations with broad genetic bases for
population improvement and varietal development over the
medium and long term
• Development of new populations with narrow genetic bases
focused more on specific objectives for more rapid
improvement and extraction of lines.
In fact, for populations with broad genetic bases, population
improvement and amplification of the genetic base should
coexist permanently.
It should be emphasized that, when seeking a specific
adaptation or insect pest resistance, the direct incorporation
of new germplasm, whether landrace or exotic, into an existing
improved population could induce a setback in genetic
progress in productivity, plant height, earliness or grain quality,
thus moving away from the objectives as defined by Chaves
(1997).

7. Hence, new materials should first be incorporated through
intermediate populations and then, after several crosses between
these materials and the improved population, introduced into the
principal population (Gallais, 1990). Morais et al., (2000)
presented the alternative of crossing each new parent with the
population and evaluating the individual crosses, before mixing
the seeds of all individual combinations. Châtel et al., (1997)
describe an example this strategy being used to develop PCT-
4000.
The farmers involved in the participatory population
improvement schemes may intervene from the first phases of
selection (S0 plants). For this, however, the farmer-breeders
need training in several topics like reproduction biology,
genetics and plant improvement. They should be taught, for
example, how to perform crosses, what to expect from these
and the levels of heritability for the different traits under
selection.

9. SELECTION WITHOUT PROGENY
TESTING

10. Mass Selection:
1. It can be defined as selection of a number of
phenotypically superior plants heads or seeds from
the field population, harvesting and bulking their
produce together for sowing the next year’s crop and
repeating this process till desired characters are
achieved.
2. This is the simplest and oldest method of crop
improvement practiced by farmers. Mass selection is
based on phenotype (external characters) and the
harvested seeds are composited without progeny
testing.

11. Procedure:
1. Most vigorous plants from the mixed population
of a crop are selected. These plants are
thrashed together and a mixture of seeds is
obtained. This mixture of seeds is a mass, and,
therefore, it is known as mass selection.
2. The mixture so obtained is sown for raising the
new crop from which selection is made similarly
in the next year. This process of selection is
continued till the plants show uniformity in the
desired characters and they constitute a new
variety.

12. A GENERAL PRACEDURE FOR DEVELOPING NEW VARIETY
BY MASS SELECTION :

13. Merits:
1. It is more of an art than a science
because it needs no scientific
knowledge.
2. Simplest, easiest and quickest method
of crop improvement.
3. Pollination need not to be controlled to
provide a new variety.
4. To meet the need of the farmers, it is
the only method for improving the local
or wild varieties.

14. Demerits:
1. Importance is given to phenotypic characters only.
2. There is no control over pollination, which causes greater
heterozygosity and as a result the desirable qualities
gradually diminish.
3. It is not possible to increase the yield because:
(a) Importance is given to material characters only.
(b) Environmental effects cannot be separated out.
(c) Pollination may be both by superior and inferior pollens.
4. This method of crop improvement is not applicable to
self-pollinated crops (due to less amount of heterozygosity).
5. In cross pollinated crops variety produced is
heterozygous i.e., mixture of different genotypes.

15. PROGENY SELECTION

16. INTRODUCTION
The genetics worth of an individual is assessed by progeny test.
The test of the genotypic value of an individual based on the
performance of its progeny is called progeny test. The progeny
test was developed by Louis de Vilmorin , hence it known as
Vilmorin principle. The progeny test is useful in two ways, viz
1. In understanding whether a plant is true breeding
(homozygous) or segregation (hetezygous)for a particular
character, and
2. In the assessment of the breeding value of a plant.
If the selection plant is really superior, its progeny will also exhibit
superior performance and vice-versa. Progeny selection is defined
as follows:

17. 1.A selection procedure in which superior plants are selected
from a heterogeneous population on the basis of the performance
of their progeny is referred to as progeny selection.
2.Selection of plants from a diverse population on the basis of
their progeny test is called progeny selection.
MAIN FEATURES
Main features of progeny selection are as follows:
1. Application : Progeny selection is commonly used in cross pollinated
and often cross pollinated species.
2. BASE MATERIAL : in cross pollinated species, three types of
materials,viz
i)Open pollinated seeds,
ii)Self seeds

18. SELECTION SCHEMES WITH PROGENY TEST
• Simplest form is Ear-to-Row Method.
• Developed by Hopkins in 1908.

19. iii)Top cross or test cross seeds of selected plants can be used
in producing the progenies for testing. Generally 10-50 seeds of
each selected plant are grown for progeny testing.
3. BASIS OF SELECTION : In this method, selection of plants is based
on the progeny performance(genotype). Those plants whose
progeny performance is superior for the character under
consideration are bulked together to produce the next
generation.
4. ADAPTATION : A variety developed by progeny selection has
wide adaptation and is more stable against environmental
changes due to heterogeneity which provide better buffering
capacity.
5. CONDUCT OF PROGENY TEST: Progeny Test should be conducted in
a replicated trial to get more reliable results. The
multilocational or multiseasonal test is considered ideal for
progeny testing. Finally , plants whose progeny performance is
good are selected and rest are discarded.

20. 6.GENETICS CONSTITUTION :A variety developed by progeny
selection is heterogenous because it consists of several homo
and heterozygous genotypes.
7.VARIATION : They are composed of several homo and
heterozygous genotypes. Hence there is heritable variation in
the varieties developed by progeny selection .The heritable
variation provides them good buffering capacity.
8. SELECTION : Future selection in a variety developed by progeny
selection may leadto inbreeding depression.
9.RESISTANCE : A variety developed by progeny selection is less
prone to the attack off new diseases due to genetics diversity.

21. 10. QUALITY : A variety developed by progeny selection is less
uniform in the quality of seed than pure lines due to presense
of heritable variation.
merits and demerits
Merits
1. Selection is based on progeny performance which is a
reliable technique.
2. This method is very simple and conveninent.

22. DEMERITS :
1. The main demerit of progeny selection is that there is
no control on the pollination.
2. The plant of the superior progeny are also pollinated by
the plants of inferior progenies.
3. If the progeny of each plant is tested in isolation, it
would require lot of area which is not practically
possible.

23. LINE BREEDING
• A system of breeding in which a number of
genotypes which superior performance for several
character are composited to form a variety is
known as line breeding.
• A breeding method of cross pollinated species in
which many genotypes with superior performance
for several characters are mixed together to form a
variety is called as line breeding

24. MAIN FEATURES
Main points related to line breeding are given below:
1. APPLICATION: Line breeding approach is commonly used
in animal breeding and less frequently in plant
breeding. In plant breeding it is used mostly in cross
pollinated species.
2. APPROACH: Line breeding can involve crossing between
closely or distantly related line ,but it does not
emphasize continuous breeding.
3. Purpose: The main purpose of line breeding is to transmit a
large proportion of desirable genes from generation to
generation without causing an increase in the frequency

25. Without causing an increase in the frequency of
undesirable traits upon associated with breeding.
4.Genetics constitution : In cross pollinated species, a variety
developed by line breeding approach consists of
several homo and hetero zygotes and thus has genetic
diversity.
5. ADOPTATION : A variety developed by line breeding
approach has wider adaptation due to presence of
genetic diversity.

26. MERITS AND
DEMERITS
1. Intensive breeding(and resulting increased
homozygosity) is often directly related to an increase
in the expression of many undesirable traits.
2. Line breeding is usually associated with little risk of
producing undesirable individuals.
3. Line breeding does not necessarily cause a rapid
increase in homozygous gene pairs. Consequently it
will not expose undesirable recessive genes as
extensively as inbreeding .For this reason line
breeding is generally a safer program for
improvement of cross pollinated species.

27. The main demerit of this approach is that there no
control over the pollination . The pollination is
affected by both superior and inferior pollen
producing plants.

28. REFERENCE
1. KWV, South Africa. (2005). Setting new global
standards for vine plant improvement. Vititec .
2. CHAHAL, G.S & GOSAL, S.S., 2002. Principles and
procedures of Plant Breeding, Alpha Science
International, United Kingdom.
3. FRISCH, M. & MELCHINGER, A.E., 2005. Selection
Theory for Marker-assisted Backcrossing. Genetics:
Published Articles Ahead of Print, published on March
31, 2005 as 10.1534/genetics.104.035451 .