Sustainability of continuous wheat sequences
in relation to crown rot in the low rainfall
Eastern Wheatbelt
Bob FrenchA and Shahajahan MiyanB
DPIRD AMerredin and BNortham
• Wheat after wheat is common in
WA, especially in low rainfall
areas and on loamy soils
• This is despite the well known
benefits of break crops for
system sustainability
• Can management of continuous
wheat prolong system
sustainability?
BACKGROUND
Where is crown rot in WA? – Stubble
plating survey 2012-2013
Crown rot incidence in
paddocks:
4 National crown rot project
(DAN00175)
Wheat yield loss – met-analysis 2014-2016
05
1015202530354045
Justica C
L
Wyalk
atc
hem
Mage
nta
Mace
Cob
ra
Calin
gir
i
Harp
er
Westo
nia
Yitpi
Cora
ck
Tro
jan
Sce
pte
r
Em
u R
ockYie
ld l
oss t
o c
row
n r
ot
(%)
Yield loss categories
0-10% Low
10-20% Medium
>20% High
Presented at Crop Updates – Feb 2017
Article in GroundCover Soilborne Diseases Supp. 2017
National crown rot project
(DAN00175)
(Huberli et al. Crop Updates 2017)
TRIAL DESIGN
2015 2016 2017 2018
Wheat Wheat Wheat Wheat
Canola Wheat Wheat Wheat
Fallow Wheat Wheat Wheat
Fallow Canola Wheat Wheat
Canola Fallow Wheat Wheat
Wheat Fallow Canola Wheat
2015 2016 2017 2018
Wheat Wheat Wheat Wheat
Canola Wheat Wheat Wheat
Fallow Wheat Wheat Wheat
Fallow Canola Wheat Wheat
Canola Fallow Wheat Wheat
Wheat Fallow Canola Wheat
2015 2016 2017 2018
Wheat Wheat Wheat Wheat
Canola Wheat Wheat Wheat
Fallow Wheat Wheat Wheat
Fallow Canola Wheat Wheat
Canola Fallow Wheat Wheat
Wheat Fallow Canola Wheat
Six sequences
Previous crop did not affect wheat yield in 2016
0
0.5
1
1.5
2
2.5
0.0
0.5
1.0
1.5
2.0
2.5
Gra
in y
ield
(t/
ha)
Emu Rock
Mace
Magenta
Average
Sequence did not affect wheat yield in 2017
0
0.5
1
1.5
2
0.0
0.5
1.0
1.5
2.0
Gra
in y
ield
(t/
ha)
Emu Rock
Mace
Magenta
Average
Initial crown rot levels were high
• In 2015 crown rot organism
isolated from ~12% of crowns
remaining from 2014*
• Predicta B: high levels of crown
rot DNA in soil, low or nil levels
of other soil borne diseases
* GRDC National Crown Rot Project (DAN00175)
Crown rot expression
0
5
10
15
20
25
30
35
40
45
50C
row
n r
ot
seve
rity
Emu Rock
Mace
Magenta
2016 2017
Sequence and cultivar both affect crown rot severity
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Cro
wn
ro
t D
NA
(lo
g(p
g/g
so
il +1
))
Emu Rock
Mace
Magenta
2016 2017
Sequence and cultivar both affect soil crown rot
DNA levels
Soil DNA levels are related to crown rot severity in previous
year
R² = 0.8582
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 20 40 60 80 100
20
17
Pre
dic
ta B
2016 crown rot incidence (%)
Magenta
Emu Rock
Mace
Sequence and crop competitiveness affect
ryegrass head numbers
2015 2016 2017
All cropped plots 18
Fallow <1 <1 <1
Canola 14
Wheat after wheat 2 9
Wheat after canola 20
Emu Rock – cont. wheat 45
Emu Rock – after canola 54
Mean ryegrass heads/m² in October 2015
18
<1
2 14
9 20 45
54
• Continuous wheat can be sustainable for at least 4 years on a loamy soil
with a crown rot background
• Emu Rock has lower crown rot expression than Mace or Magenta and
lower inoculum carry-over to the following season.
• Competitive crops are crucial in preventing weed blowouts
CONCLUSIONS
Grains Research and Development Corporation (GRDC)
A Level 4, East Building, 4 National Circuit, Barton, ACT 2600 Australia
P PO Box 5367 Kingston, ACT 2604 Australia
T +61 2 6166 4500
F +61 2 6166 4599
www.grdc.com.au
@thegrdc @GRDCWest #GRDCUpdates
Thank you
Merredin Research facility staff Shahajahan Miyan Bruce Haig Julia Tilli GRDC co-invested in this work as part of project DAW00249