Agriculture Reference
In-Depth Information
•
Greater than average controls plus one control
standard deviation
(11) Describe the main features of North Carolina I,
North Carolina II and Diallel crossing designs.
Explain the terms in the model for the analysis
of a diallel according to the method described by
Griffing:
•
Greater than the average control plus twice the
control standard deviation
Using the data presented above, how many clonal
lines would need to be raised from Cross 6 to be
90% certain of having one line which would have
a yield potential exceeding 3 standard deviations
from the control mean.
(8) A half diallel crossing design is carried out involv-
ing 30 homozygous parents. F
3
progeny from each
of the 435 possible cross combinations were raised
and grown in a two replicate yield trial (planting
F
3
and harvesting F
4
seed). Also grown within
the trial were all 30 parental lines. Based on the
yield results from the trial it was found that the
regression of mid-parent value (
x
) onto progeny
performance (
y
) was:
Y
ijk
=
µ
+
g
i
+
g
j
+
s
ij
+
e
ijk
and indicate the importance of these terms and
Griffing Analysis in selecting superior parental
lines.
(12) You have been appointed as Assistant Profes-
sor/Plant Breeder in the Crops Division of
McDonalds University in Frysville, MD. It
appears that the breeding programme has been try-
ing to select improved genotypes with decreased
sugar content in the tubers. However, in the 10
years previous to your appointment, there appears
to have been no genetic improvement resulting
from breeding. Outline three reasons that could
individually, or in combination, have caused this
non-response.
(13) In a series of properly designed experiments, a
team of plant breeders produced estimates of
narrow-sense heritabilities (
h
n
)
=
+
y
0.832
x
0.002
Also from this trial, the phenotypic variance of the
F
3
families was found to be
2
p
σ
=
65.216. What
would be the expected gain from selection if the F
3
families were selected at the 10% level (i.e. discard
90% of families) according to yield performance?
Would you expect the same response to selection if
the 43 selected F
4
families were further selected for
yield the following year? (Explain your answer).
(9) In chickpea breeding it is known that the corre-
lation between yield performance of F
4
families
in one year and F
5
families in the following year
is
r
for plant height
and plant yield from two different segregat-
ing families of spring barley (95.BAR.31 and
95.BAR.69). Both families were grown on two
farms (Moscow and Boise, in Idaho) in three suc-
cessive years (1993, 1994 and 1995). The
h
n
val-
ues from each year and site are summarized below.
=
0.57. 4000 F
4
breeding lines of chickpea
were evaluated for seed yield in a properly designed
field trial. All 4000 lines were re-evaluated at the
F
5
stage the following year. If the highest yielding
10% were selected based on F
4
performance and
the highest yielding 15% were selected based on
their F
5
performance, how many of the original
4000 lines would you expect to be selected both
on F
4
and F
5
performance. Explain what Type I
and Type II error means in the context of selection.
Estimate the Type I and Type II errors expected
by selecting F
4
families for yield at the 10% level
and selecting F
5
families at the 15% level.
(10) Parental selection can generally be divided into
two different types. List the types and, briefly,
indicate differences between them.
Character
Year
95. BAR. 31
95. BAR. 69
Moscow Boise Moscow Boise
Plant
1993
0.20
0.22
0.83
0.86
height
1994
0.01
0.21
0.31
0.74
1995
0.21
0.30
0.52
0.79
Plant
1993
0.11
0.25
0.52
0.57
yield
1994
0.02
0.15
0.12
0.46
1995
0.21
0.24
0.21
0.48
Which family is likely to give better responses in
a breeding programme, given equivalent selection
intensities, and why? In such a breeding pro-
gramme, which of the two characters (plant height
