GPB212 Lec 15 Pedigree & Bulk methdos.ppt

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1. Lecture 15. Pedigree breeding –
procedure – mass pedigree –
merits – demerits –
achievements; Bulk breeding –
procedure – merits – demerits –
achievements.

2. Breeding methods of SP crops with
involving hybridization
1.Pedigree method
2.Bulk method
3.Backcross method
Breeding methods for self pollinated crops
• Pureline selection selection without hybridisation
• Mass selection
• Pedigree selection
• Bulk method selection involving hybridization
• Backcross method
• Other approaches
 Multiline varieties
 Population breeding approach
 Hybrid varieties

3. PEDIGREE SELECTION
In pedigree method, individual plants are selected
from F
2
and the subsequent segregating generations,
and their progenies are tested.
During entire operation, a record of all the parent-
offspring relationships is kept; this is known as
pedigree record. Individual plant selection is continued
till the progenies become homozygous, and they show
no segregating.
At this stage, selection is done among progenies
because there would be no genetic variation within the
progenies.

4. Pedigree Record
In this method, a detailed record of the
relationships between the selected plants and their
progenies is maintained. As a result, each progeny in
every generation can be traced back to the F2 plant from
which it originated. Such a record of parent-offspring
relationships is known as Pedigree Record or simply
Pedigree.
The pedigree may be defined as a description of the
ancestors in the past. The pedigree is helpful in finding
out if two individuals are related by descent or not.

5. Maintenance of pedigree record
1.Designation based on the location of progeny rows in the
field

6. Maintenance of pedigree record
2. Designation based on serial numbers of selected plants

7. Applications of pedigree method
This method is the most commonly used method for
selection from segregating generations of crosses in
self-polllinated crops. This method is often used to
correct some specific weakness of an established variety
(Combining breeding).
Pedigree method is also useful in the selection of
new superior recombinant types. Some transgressive
segregants would be recovered (Transgressive breeding).
Thus the method is suitable for improving specific
characteristics, such as disease resistance, plant height,
maturity time, etc., as well as yield and quality.

8. Procedure for pedigree method

9. Merits of Pedigree method
1.This method gives the maximum opportunity for the
breeder to use his skill and judgement for the
selection of plants in the early segregating
generations.
2.It is well suited for the improvement of characters,
which can be easily identified and are simply
inherited.
3.Transgressive segregations for yield and other
quantitative characters may be recovered in addition
to the improvement in specific characters.

10. 4.It takes less time than the bulk method to develop a
new variety
5. The breeder may often be able to obtain information
about the inheritance of qualitative characters from
the pedigree record.
6. Plants and progenies with visible defects and
weaknesses are eliminated at an early stage in the
breeding programme; this saves resources and the
time of breeders.

11. Demerits of Pedigree method
1.Maintenance of accurate pedigree records takes
up valuable time. Sometimes it may be a limiting
factor in a large breeding programme.
2.Selection among and within a large number of
progenies in every generation is laborious and
time consuming; this limits the number of crosses
a breeder can handle.

12. 3. The success of this method largely depends
upon the skill of the breeder. There is no
opportunity for natural selection to influence
the populations
4. Selection for yield in F2 and F3 is ineffective.
If care is not taken to retain a sufficient
number of progenies, valuable genotypes
may be lost in the early segregating
generations.

13. Achievements
Wheat
Most of the NP wheats (NP52, NP80-5, NP120,
NP125, NP700 and 800 series of NP wheats, etc.) were
developed by the pedigree method.
K65 wheat is a tall variety isolated from the cross
C592 x NP 773.
K68 was developed from the cross NP773 x K13;
it has amber coloured grains and a very high chapatti
making quality.

14. WL 711 was selected from the cross (S308 x
Chris) x Kalyan Sona. It is a double dwarf variety and
is very high yielding, but highly susceptible to Karnal
bunt.
Malviya 12 wheat (developed from the cross
NP876 x Cno66) has amber, hard, medium bold grains
and is suitable for early as well as timely sown
conditions. It performs well even at low fertility with
restricted irrigation.

15. Rice
In rice breeding, Taichung Native 1 and
IR8 have contributed much in the development
of many high yielding popular varieties.
The cross TN1 x T141 produced two
outstanding rice varieties, jaya and Padma;
Padma has shorter duration and finer grains
than Jeya.
Some other varieties developed through
pedigree method are Bala, Cauveri, Karuna,
Krishna, Ratna, Sabarmati etc.

16. Tomato
Pusa Early Dwarf is a short statured
early maturing variety of tomato. It was
developed by pedigree selection from the
cross Meeruti x Red Cloud. Red Cloud is an
early dwarf variety introduced from USA. The
fruits of Pusa Early Dwarf are medium sized
and slightly flattish. It gives 30 per cent more
fruit yield than Pusa Ruby.

17. Basis of selection in Pedigree
method:
•Basis of selection in Pedigree method:
•Depending upon the objective, selection is to be made in
segregating generation.
•For insect and disease resistance part of the seeds may be
reserved in segregating generation and the rest may be
subjected to epiphytotic conditions.
•The families exhibiting resistance may be identified and the
reserve seeds may be used for further selection and testing.
•Early generation testing:
• If superior families are identified in F
3
or F
4
, they can be
tested for desirable characters and this is known as early
generation testing.

18. Shuttle breeding
•Shuttle breeding :
•This is followed especially in disease or insect resistance
breeding.
•For e.g. at Coimbatore YMV in blackgram is in epidemic form
during summer season only. Whereas at NPRC, Vamban
(Pudukkottai) the YMV is epidemic during kharif season. So
instead of waiting for next summer at Coimbatore the
materials can be tested at Vamban during kharif and thus one
season is saved.

19. Off season nursery
•Off season nursery
•Some crops may be season bound. But it may be non -
season bound in certain agro - climatic zone.
•For e.g. Thalai virichan cholam. (S.roxburghii) is season
bound at Coimbatore. It has to be sown during July - August
and harvested during December - January.
•But this S.roxbughii is non - season bound in Yercaud. So to
save one season, the segregating material can be raised
during Rabi summer at Yercaud. This method is otherwise
known as rapid generation advancement (RGA).
• 

20. BULK METHOD
The bulk method of breeding was first used by
Nilsson-Ehle in 1908. This method is also known as the
mass method or Population method of breeding.
In this method F
2
and subsequent generations are
harvested as bulk to grow the next generation. The duration
of bulking may be 6 - 7 generations. Selection can be made
in each generation but harvest is done as bulk. This is
similar to mass selection . At the end of bulking period single
plant selection is made and tested for yielding ability.
If bulking period is long say 20 - 30 seasons, then
natural selection acts on the homozygous lines.
In this method the breeder uses his skill for selecting
the plants and at the same time there is no pedigree record.
This saves much time and labour

21. Applications of Bulk methods
1.Isolation of homozygous lines
2.Waiting for the opportunity for selection
3.To provide opportunity for natural selection to
change the composition of the populations

22. Waiting for the opportunity for selection
Mass-pedigree method of Harlan
Selection for resistance to diseases, lodging, cold, etc.
depends upon presence of suitable environments favouring
disease epidemic, severe lodging, cold-killing, etc. Such
environments do not occur every year. The segregating
generations may be carried in bulk until such environments
occur. Individual plants are then selected and handled as in
the pedigree method. The duration of bulking depends upon
occurrence of the concerned environment; it may end in F2
itself or may continue up to F6 or beyond. This method is
known as mass-pedigree method of Harlan.

23. PROCEDURE FOR BULK METHOD

24. PROCEDURE FOR BULK METHOD
•Hybridization:
Parents are selected according to the
objective of the breeding programme. A
simple or a complex cross is then made
depending upon the number of parents
involved.
•F
1
Generation:
The F
1
generations are space-planted
and harvested in bulk. The number of F
1

plants should be as a large possible;
usually more than 20 plants should be
grown.

25. •F
2
-F
6
Generation:
F
2
to F
6
generations are planted at
commercial seed rates and spacing.
These generations are harvested in
bulk. During this period,
environmental factors and disease
and pest outbreaks would change
the frequencies of different
genotypes present in the population.
Artificial selection is generally not
done. The population size should
be as large as possible, e.g.,
preferably 30,000-50,000 plants
should be grown in each generation.

26. •F
7
Generation:
About 30-50 thousand plants are
space-planted. About 1,000 to 5,000
plants with superior phenotypes are
selected and their seeds harvested
separately. Selection is based on the
phenotypes of plants, grain
characteristics, disease reaction etc.

27. •F
8
Generation:
Individual plant progenies are grown in
single or multi-row plots. Most of the
progenies would be reasonably
homozygous; therefore, each progeny is
harvested in bulk. Weak and inferior
progenies are rejected. Only 100-300
individual plant progenies with desirable
characteristics are saved.
Some progenies would show
segregation. Such progenies are generally
rejected unless they are of great promise.
In promising progenies, individual plants
may be selected; the preliminary yield trial
will be delayed by one year in all such
cases.

28. F
9 Generation.
A preliminary yield trial is
conducted in which standard
commercial varieties are included as
checks. The progenies are evaluated for
height, lodging resistance, maturity
date, disease resistance and other
important characteristics of the crop
species. The yield is used as a basis for
the selection of superior progenies.
Quality tests may be conducted to
further reject undesirable progenies.

29. F
10 – F
12 Generation:
Replicated yield trials
are conducted, under the
concerned coordinated project,
over several locations using
standard commercial varieties
as checks. The lines are
evaluated for important
agronomic characteristics in
addition to yield, diseases
resistance and quality. If a line
turns out to be superior to the
standard check varieties in
these yield trials, it would be
released as a new variety

30. •F
13
Generation:
Seed multiplication of the
newly released variety is
initiated for distribution to
the cultivators.

31. Merits of Bulk method
•The bulk method is simple, convenient and
inexpensive
•Natural selection increases the frequency of
superior types in the population. Progenies
selected from long term bulks are likely to be far
superior to those selected from F2 or short term
bulks
•Little work and attention is needed in F2 and the
subsequent generations. The breeder is free to
concentrate more on other breeding projects

32. •No pedigree record is to be kept, which saves time
and labour
•Since large populations are grown, transgressive
segregants are more likely to appear and increase
in frequency due to natural selection. Thus there
is a greater chance of isolation of transgressive
segregants than in the pedigree method
•Artificial selection may be practiced to increase
the frequency of desirable types
•It is suitable for studies on the survival of genes
and genotypes in populations

33. Demerits of bulk method
1.It takes a much longer time to develop a new variety.
Natural selection becomes important only after F8 or
F10 and bulking may have to be done up to F20 or
more.
2.In short term bulks, natural selection has little effect
on the genetic composition of populations. But short
term bulks are useful for the isolation of homozygous
lines and for specific objectives as in Harlan’s mass-
pedigree method
3.It provides little opportunity for the breeder to
exercise his skill or judgment in selection.

34. 4. A large number of progenies have to be selected
at the end of the bulking period
5. Information on the inheritance of characters
cannot be obtained, which is often available from
the pedigree method
6. In some cases, natural selection may act against
the agronomically desirable types

35. Achievements
Barley varieties viz., Arivat, Beecher,
Glacier and Gem originated from a bulk
population derived from the cross Atlas x
Vaughn; the bulk was maintained for 7
generations. More than 50 varieties have been
developed from composite crosses in barley
adapting bulk method.