Agriculture Reference
In-Depth Information
a wheat breeding programme. F
1
families along
with each of the parents were grown in a prop-
erly designed field trial. Yield (kg per plot) was
recorded and from the data, array means, within
array variances (
V
r
s) and between array covari-
ances (
W
r
s) were estimated. These statistics are
shown below. From this information determine
which three of the ten potential parents would
be best suited for use in a cultivar development
scheme designed to increase wheat yield? Explain
your choices.
Center. Briefly outline (using diagrams if neces-
sary) how you would screen these genotypes for
their potential as new parents in your breeding
programme.
(5) In a winter rapeseed breeding programme 3000
near-homozygous breeding lines were evaluated
for yield and oil content from a properly designed
field trial. The correlation coefficient between
yield and oil content was found to be
r
=
0.41.
Using independent culling you want to select the
highest yielding 10 per cent and select for oil con-
tent retaining the best 15 per cent. How many
genotypes would you expect to be: (1) selected for
high yield and high oil content; and (2) selected
for high yield but discarded for high oil content?
(6) Independent culling can be a very effective means
to select for two or more characters simultaneously
and can be easily applied to breeding data. Under
what circumstances would independent culling
not be very effective? If index selection is used list
two methods that could be used to weight variates.
(7) 50 progeny from ten potato crosses were evaluated
for yield in a properly designed field trial. From
the results the following cross means and genetic
variances (
Parent
Mean
V
r
W
r
1
32.3
234.0
215.2
2
15.2
45.2
19.2
3
21.3
150.4
298.1
4
24.5
17.3
19.2
5
29.3
100.1
90.1
6
17.4
210.9
250.3
7
16.3
199.0
99.1
8
19.1
26.9
15.6
9
17.1
292.8
211.2
10
22.3
379.5
403.1
2
σ
g
) were obtained:
g
Mean
σ
(3) In a bean breeding programme, it is desired to
produce new cultivars which are short (dwarf ) in
stature and that have oval bean shapes (rather than
round). Both bean shape and dwarfism are con-
trolled by single alleles at one locus. The allele for
oval beans is dominant to the alternative allele for
round beans. The dwarfing gene is recessive to the
non-dwarf (tall) gene.
A cross is made between two homozygous par-
ents where parent 1 is dwarf and with round
beans (
ttrr
) while parent two is tall with oval
beans (
TTRR
). A number of F
1
plants are selfed
to produce F
2
seeds from which 1600 F
2
plants
are grown. Assuming independent assortment of
genes, outline a selection scheme which will result
in harvesting F
4
seeds that are homozygous for
oval beans and dwarf stature. Indicate the number
of plants selected at each selection stage.
(4) You are a potato breeder working in a pub-
licly funded organization. Due to the break-up
of the former Soviet Union, you have inherited
500 potato lines from the Siberian Potato Research
Cross 1
25.60
27.34
Cross 2
19.33
19.40
Cross 3
27.71
13.31
Cross 4
12.06
10.39
Cross 5
13.11
15.63
Cross 6
26.56
14.21
Cross 7
27.45
25.69
Cross 8
19.21
15.21
Cross 9
23.21
39.13
Cross 10
19.32
17.31
Also grown in the same trial were ten commer-
cial cultivars. The average performance of the
commercial cultivars was 20.14 and the standard
deviation was 3.26. Using univariate cross pre-
diction procedures determine which three crosses
should be used in breeding for cultivars which
would have high yields. Rank your choices as first,
second and third and include the probabilities
used for your decision.
