Flashcards in Self-Pollinating Breeding Methods Deck (19)
What are the major advantages of self-pollinated breeding methods?
** Drive to homozogosity!
- Genetic combinations can be "fixed" ... AA -> stabilized homozygote, no segregation. (Cultivars are true breeding!)
What is a disadvantage of self-pollinated breeding methods?
Can be difficult to get genetic recombination ("fixed" gene pool).
Name three types of self-pollinated breeding methods.
- Mass Selection
- Bulk Method
- Pedigree Method
Self-pollinated breeding methods involve...
- Selection *
- Hybridization *
* = often used in conjuction
Discuss the steps of Mass Selection.
1. Start with heterogeneous population of homozygotes.
2. Subject population to selection pressure.
3. Combine selected plants into new population.
How could you use Mass Selection for height traits in oat?
Trim to a uniform height (median range) to select outliers for next heterogeneous generation.
Types of Mass Selection
- Seed purification... population maintenance
- Rogue off-types... caused by mutation or contamination
When is the Mass Seletion method usually used?
To improve landrace varieties... oldest known method of plant breeding!
Discuss advantages of Mass Selection.
- Can be done in one year... fast!
- Maintains genetic variation.
- 'Anyone' (trained) can do it... easy!
- Few resources are required.
Discuss disadvantages of Mass Selection.
- Only work with easy to measure / observe traits.
- Can only be used where trait is expressed.
- Does not work well with traits that have low heritability.
Name a modification of Mass Selection and why it is necessary.
Helps with low h traits... quick, easy, and hybridization isn't necessary.
1. Select outliers.
2. Perform yield test.
3. Release selected line as a cultivar / germplasm
Bulk Method is aka...
Discuss the steps of the Bulk Method.
1. Create population -> Biparental / other, self.
2. Grow F2, harvest in bulk.
3. Plant random samples of F3 seed. Repeat for several generations (~6).
4. Grow generations in intended area of adaptation -> poor genetics eliminated by natural selection.
5. Three options: pursue pure-line selection, mass selection, or releasae population as germplasm / cultivar.
Discuss advantages of the Bulk Method.
- Easy way to homozygosity through natural selection.
- Can be used in conjuction with mass selection and pure-line selection.
- Little record-keeping is involved.
Discuss disadvantages of the Evolutionary Method.
- Not suitable for off-season nurseries (needs intended environment).
- Doesn't work well with populations with large maturity differences.
- Favors ONE particular yield component.
What is the main idea of the Bulk Method?
This is followed by several generations of natural selection in area of intended adaptation.
What is a crucial component of the Pedigree Method?
Plant performance during inbreeding generations.
Why is the Pedigree Method used?
To establish an elite line with the best genes from two [or more] parents.