1. The Pedigree Method

2. History
Practice of the pedigree method predates rediscovery of Mendel’s work
Vilmorin used the pedigree method in France in the 1830’s
Institute at Svalof - used pedigree type breeding in the 1880’s

3. Nillson Represented families by one or more plants
Noted that when harvested seed came from only one plant, the progeny were much more uniform
Came to call this the “system of pedigree”

4. Begin with the F2 generation
May be space planted to provide maximum individual plant expression
May be planted at the same density as the crop normally is

5. F2 plant selection
Identify best plants, e.g. short, early, clean, vigorous
Tag or spray paint plants to signify selects
May tag at flowering to indicate traits that will not be readable at maturity
Historical - pull or dig up whole plants at maturity to provide plenty of F2:3seed

6. F2 Selection
To harvest (dig up) single plants or simply harvest single heads is a decision with several implications
Single head harvest is much quicker and easier, but it limits the amount of seed and thus the experimental unit that is grown in the F3

7. F2 selection Space-planted or solid seeded - another critical decision
Space planted populations allow for individual plant expression, maximum tillering (etc.), and maximum individual plant yield
But if it does not mirror the way the crop is grown, how “real” is it?

8. Variability Issues Generation Among Within F2:3 1 0.5 F3:4 1.5 0.25
1.75
0.125
F5:6
1.875
0.0625

9. Selection Pressure / No. of Lines
Maximize the number of F2:3 lines because the among line variation is greater than the within line variation
If you do not maximize the number of distinct F2:3 families, then you will be relying on within line variation, which is of diminishing magnitude as inbreeding progresses.

11. Selection Pressure / No. of Lines
If you have selected only plants from an F2 population, then you will be relying on variation within inbred lines that trace back to those few F2 plants.
The problem is that theory tells us that the within line variation will simply not be there.

12. Pedigree Information
The keeping of pedigree information is very tedious
One rationale for keeping it is to make sure that lines trace back to different F2 plants

13. Pedigree Information Sister lines - what are they?
Pedigree information allows us to keep track of sister lines
E.g. 1) KY95C and 2) KY95C and 3)KY95C
1 and 2 are sisters at the F2:3 level and 1 and 3 are sisters at the F4:5 level

14. Characters for Selection
High heritability desirable
Amenable to visual selection
Traits that can be evaluated in individual plants or progeny rows
Number of plants grown must be adequate for number of traits evaluated
Must maintain sufficient number of plants such that variability for low h2 traits like yield still remains.

15. Choice of Environments
Assume F2 will be grown in main nursery environment (ex. Lexington)
With pedigree selection, early generations will all be grown there because individual plant selection is practiced
Alternative is to grow a bulk version of a generation at another location

16. Pros Discard inferior types early
Each generation grown in different year which exposes material to different environments
Genetic relatedness of lines known, so variability among lines retained can be maximized

17. Cons
Can’t be used in environments where genetic variability for trait not expressed (off season nursery)
Tremendous record keeping
May need experienced person to select
Land and labor intensive

18. Pedigree Selection Most breeders use some aspect of it
Few breeders use very strict pedigree selection
Too expensive and labor intensive
May be most suitable for small program where quality considerations limit size and genetic variability (e.g., malting barley)

19. Pedigree of Compton Wheat
Fulhio / Purkof /3/ Trumbull // Hope / Hussar /5/ Fairfield /4/ PI94587 /3/ Hungarian // Fultz / Hungarian /8/ LaPorte /7/ Minhardi / Wabash /5/ Fultz / Hungarian // Illinois No. 1, W38 /3/ Wabash /4/ Fairfield /6/ Redcoat / Wisconsin 245 / Afghanistan /9/4* Knox /8/( Purdue 5127 ) Kawvale /5/ Fultz / Hungarian // Illinois No. 1, W38 /3/ Wabash /4/ Fairfield /6/3* Trumbull // Hope / Hussar /7/ Knox sib /5/ Fairfield /4/ PI94587 // Fultz / Hungarian /3/ Fultz / Hungarian / 10 /2* Knox / Frex // Riley sib.