Post on 16-Aug-2020
Do semi-dwarfing genes affect growth in temperate cereals?Tobias Wojciechowski1, 2 Luke Ramsay1 Mike Gooding2 Peter Gregory1
1SCRI, Invergowrie, Dundee DD2 5DA. 2University of Reading.
The aim of the project is to characterise the
effect of semi-dwarfing and dwarfing genes on
root development and growth in barley and
wheat. Although reduced height genes (Rht)
are associated with yield reduction and
reduced early vigour, a few of the genes
compensate for the reduced biomass with an
increase in the harvest index or lodging
resistance. About 90% of the semi-dwarf
wheat cultivars grown currently contain
Rht-B1b (formerly Rht1) and Rht-D1b (formerly
Rht2) genes, which cause a moderate
reduction in final crop height of approximately
15%.
The reduced height phenotype is mainly
caused by reduced sensitivity to gibberellic
acid (GA) by an interruption of GA
biosynthesis or signal transduction. The
effect of Rht genes on stem development and
growth is well documented, but little is known
about their effects on root growth. Whether
and how Rht genes affect the root systems of
temperate cereals is not clear, and there are
conflicting reports about their effects on roots.
The question is: Do semi-dwarfing and
dwarfing genes affect root development and
growth in temperate cereals?
To address the question, several near
isogenic wheat lines (cv Mercia) were grown in
gel chambers and soil. The root systems of
these Rht lines were analysed with “Winrhizo”
and Winrhizotron”.
Conclusion
The following near isogenic lines in wheat showed significant
differences in their total root length from the wildtype: Rht-B1c,
Rht-D1c and Rht12. These genotypes had an increased total
root length when grown in a gel chamber for 10 days but a
shorter root system in the soil experiment after 26 days.
Future work will test if root growth is influenced by the growth
media or plant developmental stage. Expression studies of
orthologous genes in barley should help to answer the
question: how do these genes affect root growth?
Results
Method
Near isogenic lines of wheat (cv
Mercia) containing semi-dwarfing
genes (Rht-B1b, Rht-D1b, Rht-B1c,
Rht8, Rht-D1c, and Rht12) were
grown in gel chambers and in soil.
Weighed seeds were individually
surface sterilised, pre-germinated on
filter paper and two seedlings planted
in a gel chamber. The plants were
grown at 15˚C for 10 d. The number of
seminal root axes was counted and root length and diameter recorded by
scanning with “Winrhizotron” at 2 d intervals. At final harvest, the plants
were removed from the chambers and the dry weight of roots and shoots
measured.
Seeds with a defined seed mass (40mg ± 1mg) were pre-germinated for the
soil experiment. The seedlings of each genotype were grown in columns
containing soil at either 27% or 18.5% volumetric water content. The water
content of columns at 27% was kept constant while those at 18.5% were
allowed to dry. After 26 days the root systems were washed and scanned
with “Winrhizo” to measure total root length, average diameter and surface
area.
d
of
y
Wild
type
Rht-B
1b
Rht-D
1b
Rht -B
1cRht
8
Rht-D
1c
Rht 1
2
Gel chamber experiment Soil experiment
Figure 3 shows total root length for each
genotype at harvest (26 days). The genotypes
compared to wildtype with a least significant
difference (p < 0.05) are marked (*). The root
systems of
Rht-B1c,
Rht-D1c, Rht12
differ from
wildtype with
the total root
length
significantly
reduced.
Figure 1 shows the increase of
total root length with time (two
days intervals)
Wild
type
Rht-B
1b
Rht-D
1b
Rht -B
1cRht
8
Rht-D
1c
Rht 1
2
2500
2000
1500
1000
500
0
[cm]
Average total root length
WWild
tdtype
Rht-B
1b
Rht-D
1b
Rht -B
1cRht
8
RhRhtht-D
1c
Rht 1
21222
255500
200000
155500
100000
55500
0
[cm]
Average total root leng
Figure 3: total root length after 26 days with standard error of difference
< 0.05) are marked ( ). The root
t12
h
t
gth
0
10
20
30
40
50
[cm]
0
10
20
30
40
50
[cm]
0
10
20
30
40
50
[cm]
Total root length (day 10)
0
10
20
30
40
50
[cm]
Wild
type
Rht-B
1b
Rht-D
1b
Rht -B
1cRht
8
Rht-D
1c
Rht 1
20
110
220
330
440
50
[c ]
00
11011
220220
3303
4404
505
[c ][
0000
10111
220220220220
3303
440444
550555555
[c ][[[
Total root length (day 10)
00000000000000
101001000010101010101010
2202200220000220220220220220220220
33033030330303030330330330330330330330
4040040000440440440440440440440
55055050550505050550550550550550550550
[cm][cm][ ][cm][ ][ ][ ][cm][cm][cm][cm][cm][cm][cm]
Wild
Wild
tyyppe
Rht-B
1b
RRht-D
1b
Rht -B
1cRht
8
Rhtht-D-D
1c
RRRht 1
22
Figure 2: Total root length at day ten with standard error of difference
Figure 2 shows the total root length at final
harvest. The genotypes with least significant
differences (p < 0.05) are marked (*). The
genotypes (Rht-B1c, Rht-D1c, and Rht12)
showed significant increase in total root length
from the wildtype by 8 d.
4.939.8916.8
21.9930.1
4.6410.4818.5927.4836.6
4.719.61
15.9424.8134.1
5.7812.9320.3130.6142.2
4.3310.3917.1927.1736.4
4.329.82
17.1428.7639
4.9212.9721.1234.1344.5
1.3232.6553.9996.1167.9
2468
10
Day Wild
type
Rht-B
1b
Rht-D
1b
Rht -B
1c
Rht 8
Rht-D
1c
Rht 1
2
lsd (5
%)
4 934.939.9.8916.8
2121.9930.1 30
4 644.6410.4818.5927.4836.6
4 714.719.61
15.9424.8134.1
5 785.7812.9320.3130.6142.2
4 334.3310.3917.1927.1736.4
4 324.329.82
17.1428.7639
4.9224.9212.9721.1234.1344.5
1.322332.655553.999996.111667.9
2468
110
DDaay WWild
tdtype
Rht-B
1b
RRht-D
1b
Rht -B
1c
Rht 8
Rht-D
1D1cc
Rht 1
222
lslslsdsd (5
%%)
%)
Table 1: Total root length with time
The table highlights significant differences between
the genotypes over time. The data were adjusted
for the seed mass covariant, as the seed mass had
a significant effect on root growth (p < 0.01).
Figure 1: Total root length with time