Self-Pollinating Breeding Methods Flashcards
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…
- Introduction
- Selection *
- Hybridization *
- = often used in conjuction
Discuss the steps of Mass Selection.
- Start with heterogeneous population of homozygotes.
- Subject population to selection pressure.
- 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.
Pure-line method!
Helps with low h traits… quick, easy, and hybridization isn’t necessary.
Steps:
- Select outliers.
- Perform yield test.
- Release selected line as a cultivar / germplasm
Bulk Method is aka…
Evolutionary Method
Discuss the steps of the Bulk Method.
- Create population -> Biparental / other, self.
- Grow F2, harvest in bulk.
- Plant random samples of F3 seed. Repeat for several generations (~6).
- Grow generations in intended area of adaptation -> poor genetics eliminated by natural selection.
- 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.
