Agriculture Reference
In-Depth Information
index and reduced lodging of
Rht-B1b/
Rht-D1b
+
Rht8
“double-dwarfs” in two wheat
backcross populations evaluated in multiple
environments. Despite their reduced heights,
coleoptile lengths of the doubled-dwarfs were not
different from the
Rht-B1b
or
Rht-D1b
semid-
warfs evaluated in the same study.
Transpiration effi ciency
Transpiration effi ciency (TE), or the ratio of net
photosynthesis to water transpired, is an impor-
tant component of crop water-use effi ciency
(biomass divided by water used during growth) in
environments where stored soil water accounts
for a major portion of crop water use (Condon et
al., 2004). Variation in TE at the leaf level is
negatively related to leaf intercellular CO
2
con-
centration (c
i
), but both TE and c
i
are diffi cult to
measure. Carbon isotope discrimination is posi-
tively associated with c
i
and therefore negatively
correlated with TE (Condon et al., 1990). Use of
CID has potential in breeding programs, as it
integrates TE over the period in which dry matter
is assimilated and is simple to measure on large
numbers of families (Condon et al., 2004). In a
breeding program targeting adaptation to water-
limited environments, indirect selection for high
biomass and yield via low CID can be more
2.8
2.6
2.4
2.2
2.0
1.8
1.6
Rht1 Rht2
Tall
Rht4 Rht5
Rht8 Rht12 Rht13
Genotype
Fig. 11.18
Mean grain yield for wheat sister lines containing
various dwarfi ng genes and representing a range of spring
wheat backgrounds. Yields were obtained from experiments
conducted in 2 years at up to 10 locations.
Table 11.3
Mean values for a range of traits measured on lines genotyped for presence or absence of different height-
reducing genes in two wheat populations.
Plant
Height
(cm)
Grain
Yield
(t ha
−1
)
Total
Biomass
(t ha
−1
)
Kernel
Number
(no.m
−2
)
Lodging
Score
(1-9)
Coleoptile
Length
(mm)
Population/Dwarfi ng
Genotype
Harvest
Index
CM18/Trident
Rht-D1b,Xgwm261
192
a
73
4.49
11.09
0.405
12,315
2.4
91
Rht-D1b,Xgwm261
208
78
4.48
11.85
0.378
11,947
2.4
90
Rht-D1a,Xgwm261
192
86
4.19
11.36
0.369
10,940
3.8
109
Rht-D1a,Xgwm261
208
97
3.84
11.71
0.328
10,159
3.9
112
cv. Trident
79
4.76
12.14
0.392
12,081
1.5
92
Chuan-mai 18
90
3.88
11.05
0.351
9,581
1.8
100
LSD
3
0.28
1.41
0.021
883
0.6
9
2*Chara/HM10S
Rht-B1b,Xgwm261
192
a
73
4.24
11.16
0.380
11,910
1.9
93
Rht-B1b,Xgwm261
165
79
4.17
11.30
0.369
12,157
2.2
91
Rht-B1a,Xgwm261
192
84
4.21
11.47
0.367
11,760
2.9
105
Rht-B1a,Xgwm261
165
90
3.97
11.71
0.339
11,474
3.0
107
cv. Chara
72
4.23
11.34
0.373
11,882
1.3
84
HM10S
69
3.97
10.61
0.374
11,507
2.0
125
LSD
5
0.37
1.81
0.022
1,389
0.8
11
LSD (
p
0.05) for statistical testing of differences among genotypic classes.
a
Rht-D1b
(syn
. Rht2
);
Rht-D1a
(
rht2
);
Rht-B1b
(
Rht1
);
Rht-B1a
(
rht1
);
Xgwm261
192
(
Rht8
);
Xgwm261
208
(
rht8
);
Xgwm261
165
(
rht8
).
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