Agriculture Reference
In-Depth Information
Complete an appropriate analysis to explain
and interpret this segregation pattern.
(6) Assuming an additive-dominance model of inher-
itance is adequate to explain the variation in the
cross between two parents (P
1
and P
2
), both are
diploid and homozygous genotypes. In terms of
m
,
were grown in a replicated yield trial. Also shown
is the genotype of each inbred lines at the A-, B-
and C-locus (note that capital letters do not infer
dominant alleles, and lowercase letter do not refer
to recessive alleles). The analysis of variance of
yield is presented below. Determine whether these
three loci are located on the same chromosome
and whether any of the loci are linked to QTLs
for yield.
[
]
[
]
, what would be the expected per-
formance of each parent ( P
1
and
a
and
d
P
2
) and the
F
1
[
]
[
]
family? Also in terms of
m
,
, what
would be the expected values of the F
2
popula-
tion and the two possible backcrosses (B
1
and B
2
)
a
and
d
?
Using simple algebra, derive the expected values
you have listed for the F
2
family, above, in terms
of the frequency of segregating plant types in that
generation.
In a single cross between two homozygous bar-
ley cultivars (P
1
and P
2
)
Line
A-locus
B-locus
C-locus
Yield
1
AA
BB
CC
30.1
2
AA
BB
CC
20.8
3
AA
BB
cc
27.4
the yield of P
1
was
2642 kg/ha, the yield of P
2
was found to be
1290 kg/ha and the F
1
family showed a yield of
2308 kg/ha. Given that the additive-dominance
model is adequate to explain genetic variation for
yield in barley, what would the expected yield of
the F
2
, B
1
and B
2
families be?
(7) Cultivated potatoes (
Solanum tuberosum
spp.
tuberosum
) are all auto-tetraploids and there-
fore diploid segregation of qualitative traits is
not appropriate. A new single, completely dom-
inant, gene has been identified which con-
fers resistance to Colorado beetle. Given two
parental lines, each with a single copy of
this new gene, are inter-crossed and hybrid
seed produced. What proportion of the hybrid
family would you expect to be resistant to
potato Colorado beetle and what would be
the expected frequency of nulliplex, simplex,
duplex, triplex and quadruplex genotypes in the
progeny?
The aim of multiplex breeding is to develop
parental lines that have either three or four copies
of a single dominant gene of interest. Starting
with two simplex parents design a scheme to
develop either a triplex or quadruplex parental
line. Include in the scheme the frequency of geno-
types obtained at each stage and also include any
test crosses that may be necessary.
(8) The yield data were collected on 32 recombinant
inbred lines of barley from a cross between two
homozygous parents (
AABBCC
4
aa
bb
cc
13.7
5
aa
bb
cc
24.1
6
AA
BB
cc
21.8
7
aa
bb
cc
16.9
8
aa
bb
cc
13.5
9
AA
BB
CC
32.6
10
AA
BB
CC
33.0
11
aa
bb
cc
23.8
12
AA
BB
CC
26.7
13
AA
BB
CC
26.4
14
AA
bb
cc
11.1
15
AA
BB
CC
24.8
16
aa
BB
CC
31.9
17
aa
BB
cc
21.7
18
aa
bb
cc
22.1
19
aa
bb
cc
15.0
20
AA
BB
CC
25.4
21
AA
BB
CC
29.3
22
AA
bb
cc
20.8
23
AA
BB
cc
21.0
24
aa
bb
CC
19.7
25
AA
bb
CC
14.5
26
aa
bb
cc
17.0
27
AA
BB
CC
29.7
28
AA
BB
CC
32.0
29
aa
bb
cc
16.4
30
aa
bb
cc
14.0
31
aa
BB
CC
31.7
32
aa
bb
cc
16.9
×
aabbcc
), that
