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