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The Pedigree Method. 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. Nillson. Represented families by one or more plants

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Presentation Transcript
  • 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
  • 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”
begin with the f 2 generation
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
f 2 plant selection
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
f 2 selection
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
f 2 selection1
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?
selection pressure no of lines
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.
selection pressure no of lines1
Selection Pressure / No. of Lines
  • If you have selected only 5 - 10 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.
pedigree information
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
pedigree information1
Pedigree Information
  • Sister lines - what are they?
  • Pedigree information allows us to keep track of sister lines
  • E.g. 1) KY95C - 100 - 14 -23 - 8 - 6 - 0 and 2) KY95C - 100 - 14 -25 -2 - 2 - 0 and 3)KY95C - 100 - 14 -23 - 8 - 12 - 0
  • 1 and 2 are sisters at the F2:3 level and 1 and 3 are sisters at the F4:5 level
characters for selection
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.
choice of environments
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
  • 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
  • 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
pedigree selection
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)

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.

Pedigree of Compton Wheat