Advanced Plant Breeding PBG 650
Midterm 2, Fall 2015
Name
Please show your work.
1) A plant breeder is evaluating a random-mating population of Russian dandelion as a
potential source of natural rubber. She conducts progeny trials and estimates the breeding
values of genotypes segregating at a single locus that affects rubber production.
Frequency
A 1A 1
A 1A 2
A 2A 2
0.36
0.48
0.16
Genotypic Breeding
Value
Value
25
5.28
20
-1.32
11
-7.92
8 pts
a) What is the additive genetic variance for this trait at this locus in this population?
8 pts
b) She decides to cross an A1A1 genotype with an A1A2 genotype. What is the expected
breeding value of the offspring from this cross?
1
2) An experiment is conducted to estimate additive genetic variance from 200 half-sib families,
obtained from noninbred parents. Each plot represents a family, and the families are
replicated in four randomized blocks (r=4) and evaluated in two years (y=2).
Source
6 pts
df
MS
Expected Mean Square
Years
y-1
Blocks(Years)
r-1
Families
f-1
381
2
 e2  r FY
 ry F2
Families x Years
(f-1)(y-1)
183
2
 e2  r FY
Error
y(r-1)(f-1)
55
 e2
a) Calculate the genetic variance among families.
b) Calculate additive genetic variance for the reference population.
6 pts
6 pts
c) What is the heritability for this trait, assuming that selection would be based on half-sib
family means averaged across blocks and years? (Hint: 𝜎𝑃2 = 𝑀𝑆(𝑓𝑎𝑚𝑖𝑙𝑖𝑒𝑠)/𝑟𝑦)
2
10 pts
3) In the equation below, fill in the appropriate coefficients for the covariance of full-sibs when
two-locus epistasis is present.
2
2
2
CovFS   A2   D2   AA
  AD
  DD
8 pts
4) The mixed model equation that is used to estimate Best Linear Unbiased Predictors is
Y = X + Z + 
Briefly explain what X, ,
8 pts
Z and  in the model represent.
5) The benefits of using BLUP values for selection rather than the average performance of an
individual or family would be greatest when….(circle the best answer for each of the four
criteria)
Criteria
Heritability
Low
High
Parents
Related
Unrelated
Data
Balanced (genotypes are evaluated to
the same extent)
Unbalanced
Lifespan of the species
Short
Long
3
6) Heritability can be estimated from parent-offspring regression. Which statement about
parent-offspring regression is true?
6 pts
a) Heritability is expected to be higher when it is estimated from regression on midparent
values than it is for regression on a single parent.
b) Heritability is expected to be higher when we evaluate more offspring from each parent.
c) The slope for regression of offspring on midparent is expected to be twice as large as
the slope for regression on one parent.
d) The standard error of the heritability will be the same for regression on midparent
values as it is for regression on a single parent.
6 pts
7) A breeder selfs individual plants from a noninbred meadowfoam population in the
greenhouse. She harvests the seed from each plant and grows a row of 10 plants from each
parent plant in an outdoor nursery. She hires some honeybees to intermate all of the plants
in the nursery. Each row of 10 plants that came from a common parent is harvested in bulk
to create a half-sib family for progeny tests in the next cropping season. Can she assume
1
that the covariance for half-sib families is 4 𝜎𝐴2 , or will she need to make an adjustment for
inbreeding of the parents? Explain your answer.
8)
6 pts
A plant breeder has been hired to initiate a quinoa breeding program in Montana. He has
obtained some germplasm and plans to make diallel crosses using Griffing’s Method 4. He is
not sure how he should interpret his results.
a) List at least three questions that you would ask him to help him decide how to interpret
his data.
Question 8 continues on next page
4
8) continued
b) Describe (in general) how his answers would determine the inferences that can be made
from his experiment.
10 pts
9)
12 pts
Using 10 barley plants (A, B, C, D, E, F, G, H, I, and J), describe how you would make
1) Design I crosses (Nested)
2) Design II crosses (Factorial)
For each mating design, indicate how the crosses would form
1) A half-sib family
2) A full-sib family
Give an example for each mating design:
You don’t have to designate all possible
half-sib and full-sib families.
(Use the back of this page to answer this question if you need more space)
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