Clubroot Update

Jan 19/2016Red Deer

Photo courtesy of Dr. Ron Howard

J.P. Tewari

Lifecycle of Clubroot

• Strains of clubroot can overcome resistance. Over-reliance on resistant varieties in short rotationswill increase the risk of build up of various strains and should be avoided.

History teaches us but do we listen?

• Clubroot resistant cabbage in USA becomes susceptible (Seaman, U of Wisconsin,1960)

• Chinese cabbage clubroot resistance overcome in Australia (Donald et al., 2006)

• CR Chinese cabbage in Japan overcome about 10 years after introduction (Tanaka and Ito, 2013).

Canola Clubroot Resistance

• Most likely all western Canada current resistance in canola is from the European winter oilseed variety ‘Mendel’

Alberta Situation

Clubroot in Alberta 2003 to 2015

• First canola field reported in AB in 2003

• Over 2000 known fields infested in AB

• Fields in AB have been reported to have > 10m spores/gram in soil

• New strain of clubroot• 5x….

• This new strain was tested against all existing CR varieties• Most cases severity > 90%

2013 Situation

• Target survey on CR cultivars

• 16 fields of pathogen shift

• In addition to 5x, 9 distinct pathotypevariants

2014 Situation

Strelkov & Cao, unpublished

• Survey conducted on CR fields

• Found 32 new ‘suspicious’ fields in Central AB

• Samples to be pathotyped at UofA

2015 Survey

Classification of New Strains of Plasmodiophora brassicae: A Preliminary Assessment

S.E. Strelkov, S.F. Hwang, V.P. Manolii, and T. Cao

Pathogen

S S S R S

Pathogen isolates are grouped into strains based on the symptoms they

cause on a defined group of hosts

‘Pathotype 5x’Host variety Pathotype

3 5 5xJersey Queen (cabbage) + - -Badger Shipper (cabbage) - - -Laurentian (rutabaga) + - -Wilhemsburger (rutabaga) - - -Canadian ‘clubroot resistant’ canola

- - +

Pathotype designations as defined on system of Williams (1966)

Genotype

Field population

CDCN#2CDCN#4 CDCN#6 CDCS F1‐14 F175‐14 F3‐14

F183‐14

F184‐14

F185‐14

F186‐14

F187‐14

F188‐14

F189‐14 F331‐14 F41‐14

ECD 02 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐

ECD 05 + + + + + + + + + + + + + + + +

ECD 06 + + ‐ ‐ + + + + + + + + + + + +

ECD 08 + + + + + + + + + + + + + + + +

ECD 09 + + ‐ ‐ + + + + + + + + + + + +

ECD 10 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐

ECD 11 ‐ ‐ ‐ ‐ ‐ ‐ ‐ + ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐

ECD 13 ‐ + ‐ + + + + + + + + ‐ ‐ + + +

Brutor + + + + + + + + + + + + + + + +

Laurentian ‐ + ‐ ‐ + ‐ + + + + + + + + + +

Mendel ‐ ‐ ‐ ‐ ‐ + + + + + + ‐ ‐ + + ‐

Westar + + + + + + + + + + + + + + + +

45H29 ‐ ‐ + + + + + + + + + + + + + ‐

Pathotype designation:CCD (temporary) A B C D E F G H G G G I I G G B

Williams, 1966 5 3 5 6 3 6 3 2 3 3 3 8 8 3 3 3

Some et al., 1996 P2 P2 P3 P3 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2 P2

Nine distinct virulence phenotypes detected

• One variant of pathotype 3 was most common: 6 of 16 populations

• One variant of pathotype 2 also highly virulent (11 of 13 differentials)

Words of Caution

• Novel strains tested are ‘field’ populations

• May represent mixture of pathotypes – Masking of rarer strains– Antagonistic/synergistic

interactions

• Analysis of single-spore will be important

Characterizing P5x populations with B. napus lines at AAFC, Saskatoon

B. napus LG-01 LG-02 LG-03

BN-E-06 R S R

BN-E-08 S S S

BN-E-09 R R R

BN-I-01 R S S

Differential reactions were found in a set of B. napus lines at AAFC.

There are at least 3 races in P5x populations.

LG-2 is the most aggressive one.

BN-E-09 is resistant to all.

Clubroot Severity in B-Tolerant Lines

0

10

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50

60

70

80

90

100

Seve

rity

(DSI

)

UntreatedTreated

A fungal endophyte that induces resistance to clubroot in canola

y = 24.3x2 - 66.8x + 52R2 = 0.86

0

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20

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60

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Clu

broo

t sev

erity

(%)

Colonization of canola roots by Hc (ng/g)

qPCR