PB Ch 17. Pedigree Method
Definition
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Pedigree Method: Individual plants are selected from F2 and subsequent segregating generations, and their progenies are tested. A complete record (pedigree record) of all parent-offspring relationships is maintained throughout. Individual plant selection continues until progenies show no segregation. |
- The pedigree method is the MOST WIDELY USED breeding method in self-pollinated crops globally and in India.
- Almost all high-yielding varieties of wheat, rice, chickpea, and other self-pollinated crops were developed through the pedigree method.
Procedure — Generation by Generation
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Year |
Generation |
Action |
Selection criteria |
|
1 |
P1 x P2 |
Make crosses between parents with complementary characters |
Choose parents — diverse for transgressive breeding; one strong, one adapted for combination breeding |
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2 |
F1 |
Space-plant F1 for maximum seed production; harvest in bulk |
No selection — all F1 are identical heterozygotes; grow maximum plants |
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3 |
F2 |
Space-plant 2,000-10,000 F2 plants; grow parents as comparison |
Select 100-500 individual plants for simply-inherited characters (disease resistance, plant type, head type); pedigree number assigned to each |
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4 |
F3 |
Grow each F2 selection as separate progeny row (head-to-row) |
Select 50-100 best families; within each best family select 3-5 plants; discard diseased, segregating, off-type rows |
|
5 |
F4 |
Head-to-row; individual plants from best rows |
Select desirable plants from desirable rows; harvest separately |
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6 |
F5 |
3-row plots; ~25-50 families retained; check every 3-5 blocks |
Evaluate for yield; inferior rows rejected; plants per progeny bulked |
|
7 |
F6 |
Multi-row plots; ~96.87% homozygous |
Select superior progenies; bulk harvest per family; remove diseased plants |
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8 |
F7 |
Preliminary yield trial — 3+ replications with commercial check |
Select 2-5 outstanding lines for coordinated trials |
|
9-11 |
F8-F10 |
AICRP trials at several locations (IET, main yield trials) |
Line superior to commercial variety in yield, disease resistance, quality |
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11-13 |
F11-F13 |
Variety release through CVRC; seed multiplication |
DUS testing under PPV&FR Act 2001; official release |
Modifications of Pedigree Method
A. Early Generation Testing
- Replicated F2 or F3 tests used to identify superior crosses before advancing all of them.
- A good cross should have: high mean yield + high genetic variance + high expected genetic advance.
- Other crosses rejected early.
B. F2 Progeny Testing
- F2: Maximum single plant selections
- F3 to F6: Advance progenies in bulk — natural selection operates
- F6: Single plant selections within progenies
- Advantages: More crosses handled; natural selection operates from F3-F6
C. Mass Pedigree Method (Harlan's Method)
- Segregating material grown in bulk during unfavourable seasons (natural selection acts);
- individual plant selections made during favourable seasons.
- Combines advantages of bulk and pedigree.
- More crosses can be handled simultaneously.
4.4 Merits and Demerits
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Merits |
Demerits |
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Maximum opportunity for breeder to use skill and judgement — critical for success |
Valuable genotypes may be lost in early generations if breeder lacks skill |
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Well suited for simply inherited (qualitative) characters — disease resistance, grain type |
No opportunity for natural selection — breeder makes all selection decisions |
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Transgressive segregation for yield and quantitative characters can be recovered |
Difficult to handle many crosses simultaneously |
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Pedigree records provide information on inheritance — valuable for future crosses |
Maintaining thousands of pedigree records is time-consuming and laborious |
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Inferior plants/progenies eliminated in early generations — saves resources |
12-13 years to release a new variety |
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Quicker than bulk method |
Large number of selections from F2 to F5 requires substantial land and labour |
Achievements of Pedigree Method
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Crop |
Varieties |
|
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Wheat |
NP-52, NP-120, NP-125, NP-700 series; HD 2967, PBW 343, HD 2932 |
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Rice |
ADT-25, Jaya, Padma; IR-8, IR-36, IR-64 (IRRI) |
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Cotton |
Lakshmi, Digvijay |
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Sorghum |
CO 18, RS 610 |
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Chickpea |
JG 16, BG 372 |
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