Plant Breeding Methods (CS, GN, HS
741)
Exercise 3 - Quantitative Genetics Review
Give complete answers, but be brief and specific. Show your work.
20 points total
1. What is the mean and variance for a population (where only 1 locus
is segregating) consisting of the F2 of the cross BB x bb where BB yields
24, Bb yields 18 and bb yields 9 fruits per plot?
2. How could you measure directly all components of the epistatic variance
(s2I) of a population?
3. A population with a mean yield of 19 fruits per plant was intercrossed,
and 5 S0 plants were sampled from it with yields of 28, 21, 29, 16 and
19 fruits per plant each, respectively. The half-sib families derived
from the 5 S0 plants had yields of 25, 21, 24, 15, and 20 fruits per
plant, respectively. What is the breeding value (A) of the highest yielding
S0?
4. A quantitative genetic study was run for lodging resistance in a
population of sweet corn that had been wind-intercrossed several times
during development. Given the following analysis of variance, estimate
s2A, s2D, and h2N. Does the population have a high enough heritability
to warrant single-plant selection for the trait?
- 2 df Sets (S)
- 9 df Blocks / S
- 297 df Males / S MS=205
- 1200 df Females/M/S MS=45
- 4491 df Error MS=5
5. If the population in question 4 had a mean of 7 before selection,
what would it be after 2 cycles of selection where the best 5% of the
FS families in the population were intercrossed to form the next generation
(assuming the variances are not changed by selection)?
Given - k for selection percentage: 1%=2.64, 2%=2.42, 5%=2.06, 10%=1.76,
20%=1.40, 50%=0.80.
