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Lecture 13
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What is Combining Ability?
the ability of parents to combine amongst each other so that favorable genes/alleles are transmitted to their progenies
What is Specific combining ability?
the deviation in performance of hybrids from the expected productivity based upon the
average performance of lines involved in the hybrid combination
Differences in SCA are attributed to
non-additive genetic variation
What is General combining ability?
—the average performance of a line in a series of crosses
Evaluates the additive portion of
genetic effects
Difference in GCA are due to additive
and additive x additive interactions in
the base population
Combining abilitiy concepts:
The higher the GCA value, the better
that parent will perform in a myriad of
crosses
The higher the SCA, the better hybrid
those lines will make
Used a lot in cross-pollinating species
where hybrid vigor is desired
Describe Population Improvement:
Population Genetics—change in the
genetic structure of a population of plants
Change the gene frequency such that
desirable genotypes predominate in the
population
Cyclical selection (recurrent selection)
increases the frequency of favorable
genes
What is Intrapopulation improvement?
—selection is practiced within a specific population for its improvement for a specific purpose
What is Interpopulation improvement?
—entails selection on the basis of the performance of a cross between two populations (used for hybrid production)
Describe Recurrent Selection:
Goal-improve the performance of a population
with respect to a trait such that the new
population is superior in mean performance
Population is improved without the reduction in
genetic variability
Population can respond to future improvements
Parents of the cross should be high performing
regarding the traits of interest
Parents should not be closely related
More rounds of mating increases the
opportunity for recombination
Key Features of Recurrent Selection:
Individual families are created for evaluation
Parents are crossed in all possible combinations
The plants/families are evaluated and new
parents selected
The selected parents are intermated to produce
a new population for future selection
Describe Ear to Row Selection:
Used to better manage G x E interactions
Genetic gain is both inter and intra family
selection
Often used with perennial species
Pros and Cons to Half-sib with progeny test
Advantages
Suited for improving traits of high
heritability
Good for plants with self-incompatibility or
male sterile
Disadvantages
Based on maternal plant selection, so
heritability estimates are reduced 50%
Less effective for low heritability traits
Pros and Cons to Half-sib with test cross:
Advantages
:
More precise evaluation of selected plant
Rapid to conduct
Disadvantages
:
Must be able to self-pollinate
Need a lot of seed for subsequent progeny
trials
What are the general advantages of half-sib methods:
Usually rapid to conduct
Increase frequency of desirable alleles
Progeny/test cross allows a more precise
evaluation of the genotype of selected
plants
What are the general disadvantages of half-sib methods:
Disadvantages-Half-sib methods
In some cases, a lot of seed is needed for
subsequent years testing
Trait should have high heritability
Some methods require self-pollination
Author
wsucoug12
ID
317415
Card Set
Lecture 13
Description
Plant Breeding
Updated
2016-03-23T03:48:55Z
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