Post on 16-Apr-2022
Biology Pillar, CRMIBiology Pillar, CRMIBiology Pillar, CRMIBiology Pillar, CRMIBruce D. Gossen 1
& Mary Ruth McDonald 2
1) AAFC, Saskatoon, SK, (2) Univ. of Guelph, Guelph, ON.
Clubroot Summit, March 7, 2012
- Breeding
- Disease management
- Surveillance
- Biology/Pathology
PillarsPillars
- Biology/Pathology
- Effect of temperature, pH, and moisture
- Effect of B and soil type
- Expression and timing of resistance
- Model crops and differential reaction
- Other (satellite imagery, inducers, RNAi, etc.)
Bruce Gossen and Gary Peng – AAFC, Saskatoon
Mary Ruth McDonald – University of Guelph- A. Deora, K. Sharma (post-docs)- K.K.C. Adhikari (MSc, graduated)- H. Kasinathan, T. Gludovacz (MSc students)
Research TeamResearch Team
Sheau-Fang Hwang – AARD, Edmonton
Stephen Strelkov – U of A, Edmonton
Denis Pageau – AAFC, Normandin
Fran Walley – U of S, Saskatoon
Anne Smith – AAFC, Lethbridge
• Examine the impact of temperature and seeding date on clubroot severity on canola and vegetable
Impact of Temperature
canola and vegetable Brassicas.
• Determine if pak choy is a good model system for clubroot reaction on canola.
Resting spores
Rhizosphere Plasmodium
SporangiumRoot hair infection
Primary zoospore
Cortical infection
Clubbed-root
Resting spores
Rhizosphere Plasmodium
SporangiumRoot hair infection
Primary zoospore
Cortical infection
Clubbed-root
Fig. 1. Life cycle of Plasmodiophora brassicae.
Secondaryplasmodia Secondary
zoospore
Sporangium
Dehisced sporangium
infectionResting spores
Secondaryplasmodia Secondary
zoospore
Sporangium
Dehisced sporangium
infectionResting spores
Clubroot Incidence and Severity
Correlation: Root Hair Infection vs. Severity
60
80
100
60
80
100
Roo
t hai
r inf
ectio
n (%
)
Dis
ease
sev
erity
inde
x (%
)
Root hair infectionDisease severity index
b
az
byy
5 10 15 20 25 30 350
20
40
0
20
40
Temperature (º C)
Roo
t hai
r inf
ectio
n (%
)
Dis
ease
sev
erity
inde
x (%
)
d
c
xx
Cortical Infection & Spore Production
30
40
50
60
Cor
tical
infe
ctio
n (%
)
2
3
4
SC
x108
Cortical infection
SC
Cortical infection: y = -0.04x2 + 1.84x -16.2; R2 = 0.88
SC: y = -0.01x2 + 0.50x -4.2; R2 = 0.92
0
10
20
30
10 15 20 25 30
Cor
tical
infe
ctio
n (%
)
0
1
2
SC
x10
Temperature (º C)
1.5
2
2.5
Dis
ease
sev
erity
(0-
3)
Effect of Seedling Age on Severity
aa
b
c c
0
0.5
1
1.5
0 days 1 week 2 weeks 3 weeks 4 weeks
Seedling age
Dis
ease
sev
erity
(0-
3)
c c
AA A
2.0
2.5
3.0Se
verity
(0-3)
St. AlbertLeduc
Impact of Seeding Date on Canola
b
aab
0.0
0.5
1.0
1.5
Sever
ity (0
Early Mid Late
a
bbA0.8
1.01.21.4
Seed
yield (
t/ha)
St. AlbertLeduc
Impact of Seeding Date on Canola
B
B0.00.20.40.60.8
Early Mid Late
Seed
yield (
t/ha)
Conclusions
• Low temperatures (≤ 17º C) reduce clubroot development and severity.
• Early seeding reduced clubroot severity and increased seed yield of canola.
• Impact was small relative to resistance.• Impact was small relative to resistance.• Shanghai pak choy would make a good
model system for temperature studies.
�� Clubroot confirmed in Clubroot confirmed in >800 fields in Alberta>800 fields in Alberta
��Most severe in black Most severe in black soil zone of central AB, soil zone of central AB, on heavy, acidic soils on heavy, acidic soils with abundant rainfallwith abundant rainfall
�� Confirmed (2 fields) in Confirmed (2 fields) in
Clubroot status, Clubroot status, 2011
�� Confirmed (2 fields) in Confirmed (2 fields) in Saskatchewan in 2011Saskatchewan in 2011
�� Crucial questionCrucial question --What is the clubroot risk What is the clubroot risk for other areas, e.g., on for other areas, e.g., on more alkaline or lighter more alkaline or lighter soils with lower rainfall?soils with lower rainfall?
Projects to Assess Clubroot Risk
�Turkington / Klein-Gebbinck – using projection (Climex) and modeling (Dymex) approaches to predict clubroot risk.
• Very little data available for canola (!)
�Strelkov et al. – annual survey provides info �Strelkov et al. – annual survey provides info on the impact of weather on clubroot severity.
�Gossen /McDonald et al. – impact of temperature x pH and soil type on clubroot.
Dis
ease
sev
erity
inde
x D
SI (
%)
60
80
100
Trial 2Trial 1
Temperature x pH
pH ranges
5.0 5.5 6.0 6.5 7.0 7.5 8.0
Dis
ease
sev
erity
inde
x D
SI (
%)
0
20
40 }25°°°° C}20°°°° C
→ 15°°°°C10°°°°C
40
60
80
100
Dis
ease
sev
erit
y in
dex
0-2020-4040-60 60-8080-100
Temperature x pH
0
20
40
15
20
256.0
6.5
7.0
7.5
8.0
Dis
ease
sev
erit
y in
dex
Temperatures
°CpH
Do dry conditions reduce clubroot?
�Drier conditions resulted in a small reduction in clubroot severity in ON.�Clubroot was severe
after drought delayed crop emergence, 2009.crop emergence, 2009.�Conclusion – Low mean
rainfall may make it more difficult for clubroot to establish, but once in place, severity could/would be high in wet years.
Does soil type affect clubroot?
To identify interactions among soil type, pathotype (P3 and P6), and biofungicide.
Background
• Clubroot reported to be severe in heavy soils.• Clubroot reported to be severe in heavy soils.• Several commercial biocontrol agents
showed promise against clubroot, but results not consistent, especially in field trials.
• P3 dominant in Alberta, P6 in Ontario.
Field trial, Chinese cabbage, Ontario, 2009(Rained shortly after seeding, P6)
30
40
50
60R hybrid S hybrid
Dis
ease
inde
x (%
)
0
10
20
30
Untrea
tedPre
-sto
pSer
enad
e
Allegr
oRan
man
Dis
ease
inde
x (%
)
Materials (3 trials, canola & pak choy)�Biofungicides
Prestop (Gliocladium catenulatum), root colonizer, mode of action is hyperparasitism
Serenade (Bacillus subtilis), root colonizer, mode of action is antibiotic production
�Soil�SoilMuck soil (pH~6.2, 70% o.m.)Mineral soil (pH~6.8, 3 % o.m.) Sand (pH~6.5, 0% o.m.) Soil-less mix (pH~6.0 )
�Inoculum sourcePathotype 6 (Ont.), P3 (Alta.) + non-inoculated check
60
80
100 Positive Serenade Prestop
aab
c
abbc bc
c
Dis
ease
sev
erity
inde
x (%
)Soil type x biofungicide
Soil Types
M uck M ineral Sand Soil-less m ix0
20
40
Dis
ease
sev
erity
inde
x (%
)
fef
ddefde
40
60
80
Inoculated control, soil typeD
isea
se s
ever
ity in
dex
(%)
a
abb
Soil Types
0
20
40
Muck Mineral Sand Soil-less mix
Dis
ease
sev
erity
inde
x (%
)
c
Results• High levels of clubroot in muck and mineral
soil, low in soil-less mix – generally more disease with higher bulk density.
• Clubroot more severe with P3 than P6.
• Efficacy of biofungicides was not consistent, • Efficacy of biofungicides was not consistent, and influenced by soil type.
• Efficacy of biofungicides even lower in companion trials with Shanghai pak choy, which is highly susceptible.
Conclusion• Clubroot severity on muck soil and sand was
surprisingly similar given the enormous difference in water-holding capacity. This would likely NOT occur under field conditions.
• Soil type is likely not an important factor in clubroot development when soils are saturated clubroot development when soils are saturated during crop establishment, but may have a large impact under drier conditions.
• Studies of biofungicides often use soil-less mix. Resistance assessments have also used soil-less mix. Tests of clubroot reaction in target soil types may be useful.
Host Resistance Study
Cultivar P3 P645H29
Moderately resistant
46A7645H21
Resistant Susceptible
0
20
40
60
80
Root
hair in
fectio
n (%) Dehisced sporangiaSporangiaPlasmodia
Root
hair in
fectio
n (%)
P3
80 P6
0
20
40
60
80
Root
hair in
fectio
n (%) Dehisced sporangiaSporangiaPlasmodia
Root
hair in
fectio
n (%)
P3
80 P6
Root
hair in
fectio
n (%)
4 DAI 12 DAI 4 DAI 4 DAI12 DAI 12 DAI
Susceptible Resistant8 DAI 8 DAI8 DAI
Moderately resistant0
20
40
60
P6
Root
hair in
fectio
n (%)
4 DAI 12 DAI 4 DAI 4 DAI12 DAI 12 DAI
Susceptible Resistant8 DAI 8 DAI8 DAI
Moderately resistant0
20
40
60
P6
100DSI DIb
ab aA
B
0
10
20
30
40
50
Corte
x infec
ted (%
)22 DAI 28 DAI
a
bb
cdd
ee
fg
100DSI DIb
ab aA
B
0
10
20
30
40
50
Corte
x infec
ted (%
)22 DAI 28 DAI
a
bb
cdd
ee
fg
P3 P6
0
20
40
60
80
Diseas
e level
(%) DSI DI
D
c
C
b
E
d
B
45H29 46A7645H21 45H29 46A7645H21P3 P6
0
20
40
60
80
Diseas
e level
(%) DSI DI
D
c
C
b
E
d
B
45H29 46A7645H21 45H29 46A7645H21
Conclusion
• Primary (root hair) infection - occurs in both resistant and susceptible lines, but the largest differences were between the moderately resistant line and all others.
• Cortical infection - resistance appears to inhibit secondary infection. Little or no cortical infection secondary infection. Little or no cortical infection developed in the highly resistant lines.
• Additional studies to assess other resistant lines of canola are nearing completion, and studies of other Brassicae spp. are underway.
Seed Transmission? Field No.Field No.
11 22 33 44 ++-- ++ --YY NN
Canola seed Barley seed
•• PCR tests PCR tests -- pathogen DNA is present on seed.pathogen DNA is present on seed.•• No evidence of seedNo evidence of seed--toto--seedling transmission seedling transmission
in trials in 2009 or 2010 (site in Ontario).in trials in 2009 or 2010 (site in Ontario).•• One clubrootOne clubroot--infected plant in 2011.infected plant in 2011.
Sustainable Management/StewardshipIPM
approaches
30
Prevent soil movement
Genetic resistance
CANOLA
PRODUCTION